Tensile Technical Publications

HOME

200. The Effect of Sintering Conditions and Composition on the Mechanical Property Response of Cr Containing PM Steels The desire for advanced ferrous PM materials has led to the development of alloys that more closely simulate wrought steel compositions. Traditional wrought steel alloying elements, such as Cr, are used to improve mechanical properties, hardenability and are cost effective. Chromium has historically been avoided in PM due to oxygen related issues, but newer PM alloy systems now contain this element. While providing good mechanical properties and overall product cost, proper sintering of these alloys is the critical challenge. This paper presents the role of sintering and composition on the mechanical properties and microstructure of a chromium containing PM steel.
199. Alloy Development of Sinter-Hardenable Compositions Market forces in the PM industry are challenging the traditional compositions typically used in PM alloys. Mo, Ni and Cu are the predominant alloying elements used in ferrous PM due to their low affinity for oxygen. In addition, Mo has little effect on compressibility and copper rapidly alloys by way of a liquid phase at sintering temperatures. All three elements also increase the hardenability of steels, allowing for sinterhardening of parts produced with a combination of the elements. Price pressures are causing a reevaluation of powder chemistries utilizing these elements, and the challenge of alloy development is to advance alloy systems that optimize the balance between mechanical properties and overall production cost. Sinter-hardenable compositions play a key role in this regard. This paper will evaluate and discuss alternative alloys to those primarily used in the European market.
194. Effect of Post Sintering Thermal Treatments on Dimensional Precision and Mechanical Properties in Sinter-Hardening PM Steels Dimensional precision is a critical parameter in net shape processing of ferrous PM components. PM parts producers continue to pursue larger parts, but absolute tolerances dictated by the end user generally do not scale with part size. Therefore, in larger parts, the variation in percentage change in size, or dimensional change, must be reduced. Beyond the dimensional changes associated with pressing and sintering of typical low alloy PM steels, sinter-hardenable alloys present some unique challenges and opportunities for PM part manufacturing. The ability to harden a part in the sintering furnace eliminates the need for a secondary quenching operation. The resulting microstructure of untempered martensite is, however, not ideal for dimensional stability and mechanical properties. Tempering hardened steels results in improved mechanical properties and dimensional shrinkage, as the martensite converts to a more stable ferrite and carbide microstructure of higher density. In addition, many sinter-hardening grades contain high Cu and C contents that result in relatively high amounts of retained austenite. Retained austenite can improve impact and ductility properties, but contributes to dimensional instability as it can transform to lower density bainite and/or martensite with thermal fluctuations. Proper thermal treatments of sinter-hardened steels are necessary to obtain the best combination of mechanical properties and dimensional control. This paper reviews the effects of different post-sintering thermal treatments on the dimensional, microstructural and mechanical property changes of sinter-hardened PM steels.
193. Chromium Steels for High Performance PM Applications Chromium steels have long dominated the landscape of the wrought industry because of their high performance capabilities at modest cost levels. Historically, chromium steels have had difficulty penetrating the powder metallurgy market because of oxidation issues. Recent powder manufacturing advances, however, have resulted in low-oxygen chromium steels such as Ancorsteel 4300, which enables the production of high performance parts with conventional processing techniques. The current work reviews the capabilities of this Cr-Si-Ni-Mo alloy and its derivatives. Static properties, dynamic properties, and dimensional stability data are reviewed with an emphasis on a sintering temperature of 1120 ºC (2050 ºF). Comparisons are made to traditional powder metallurgy materials in both the as-sintered and heat-treated conditions as well as to heat-treated wrought alloys.
192. Stainless Steel AISA Grades for PM Applications Applications requiring stainless steels are growing at a rate of about 5% annually. Opportunities for using powder metallurgy (PM) exist, but additional grades not covered by MPIF Standard 35 are required. The American Iron and Steel Institute (AISI) has standards for a broad range of stainless steels that can be used in many applications, but the compositions of these grades must be modified to be conducive to manufacture by conventional PM techniques. Several of these grades have been produced as standard press and sinter powders. The physical properties, mechanical properties and microstructures of these various grades are reviewed to serve as a guideline for PM parts manufacturers and potential applications of these grades are addressed.
191. Development of High Performance Stainless Steel Powders Advanced melting technology is now being employed in the manufacture of stainless steel powders. The new process currently includes electric arc furnace (EAF) technology in concert with Argon Oxygen Decarburization (AOD), High Performance Atomizing (HPA) and hydrogen annealing. The new high performance processing route has allowed the more consistent production of existing products, and has allowed enhanced properties, such as improved green strength and green density. This paper will review these processing changes along with the potential new products that are being developed utilizing this technology. These include high strength stainless steels such as duplex and dual phase as well as stainless steel powders used in high temperature applications such as diesel filters and fuel cells.
189. Capabilities of Two Chromium Powder Metallurgy Steel for High Performance Applications at Conventional Sintering Temperatures Ancorsteel 4300, a high performance Cr-Si-Ni-Mo steel, was unveiled two years ago as the first in a series of powder metallurgy alloys that will simulate wrought steel compositions. Advantages of this alloy include good compressibility, high hardenability, and excellent dimensional stability. More important, however, is that this alloy has the ability to be effectively sintered at 1120 °C and maintain oxygen contents below 500 ppm. This unique blend of performance and processing capabilities provides static and dynamic properties that exceed those of conventional powder metallurgy alloys and approach wrought gearing materials. A second Cr-Si-Ni-Mo alloy has now been developed that offers complimentary performance levels at a lower Mo content. This manuscript reviews properties of the two chromium steels with comparisons to traditional sinter-hardened and heat-treated powder metallurgy alloys.
188. Surface Densification Coupled with Higher Density ProcessesTargeting High-Performance Gearing This paper will describe a powder and processing method that facilitates single press-single sintered densities approaching 7.5 g/cm³. At this sintered density, mechanical properties of the powder metal (P/M) component are significantly improved over current P/M technologies and begin to approach the performance of wrought steels. High performance gears have the added requirement of rolling contact fatigue durability that is dependent upon localized density and thermal processing. Combining high density processing of engineered P/M materials with selective surface densification enables powder metal components to achieve rolling contact fatigue durability and mechanical property performance that satisfy the performance requirements of many high strength automotive transmission gears. Data will be presented that document P/M part performance in comparison to conventional wrought steel grades.
185. Precipitation Hardening PM Stainless Steels Applications requiring high strength stainless steels are growing rapidally. Precipitation-hardening stainless steels have seen limited use in powder metallurgy despite their high strength. Strengthening of these alloys is achieved by adding elements such as copper and niobium, which form intermetallic precipitates during aging. The precipitation-hardening grades exhibit corrosion resistance levels comparable with those of the chromium-nickel (300 series) grades. The physical properties and microstructures of two precipitation hardening PM stainless powders are presented: 17-4 PH, a high-chromium, martensitic precipitation hardening stainless steel, has been optimized for use in PM applications; and a new low chromium (12 w/o) alloy that utilizes copper in the precipitation reaction. This alloy (410LCu), is considered to be a cost-effective alternative in applications that require high strength and moderate corrosion resistance.
183. Performance Capabilities of High Strength Powder Metallurgy Chromium Steels with Two Different Molybdenum Contents The desire for advanced ferrous powder metallurgy materials has led to the development of alloys that simulate wrought steel compositions. A recently commercialized Cr-Si-Ni-Mo steel can be effectively sintered at conventional temperatures and provides good compressibility, high hardenability, and excellent dimensional stability while maintaining oxygen contents below 500 ppm. This alloy has demonstrated static and dynamic properties that exceed those of conventional powder metallurgy alloys and approach wrought gearing materials. A second Cr-Si-Ni-Mo alloy has now been developed to offer complimentary performance levels at a lower Mo content, while still providing excellent sinter-hardenability. The current work reviews static and dynamic properties of the two Cr steels with an emphasis on accelerated cooling rates after sintering at 1120 ºC (2050 ºF). Comparisons are made to traditional powder metallurgy materials processed in both the sinter-hardened and heat-treated conditions as well as to heat-treated wrought alloys.
182. Lower Molybdenum Steels for High Performance Powder Metallurgy Applications Molybdenum has long been known to be a useful alloying element in powder metallurgy steels because of its enhancement of hardenability at relatively modest alloying levels. Since their introduction to the industry two decades ago, hybrid alloys based on prealloyed Mo steels such as FLN2-4405 have often been used in the heat-treated state to provide high performance properties. However, as raw material prices have become increasingly unstable in the last few years, the economic benefit to such alloys has reduced, forcing parts manufacturers to seek alternative materials systems. The current work provides a comparative analysis of a recently developed 0.3 wt.% Mo steel with more conventional 0.85 wt.% Mo and Mo-free steels. Property data and metallography are presented for crankshaft sprockets processed in the as-sintered, oil quenched & tempered, and induction hardened conditions.
177. High Density Processing of Cr-Si-Ni-Mo Containing Steel Ancorsteel 4300, an iron alloy containing Cr-Si-Ni-Mo, was recently introduced and is capable of achieving high mechanical strength with exceptional dimensional stability. With the ability to be sintered at conventional temperatures, this alloy offers a unique blend of performance capabilities that can provide an economic advantage over alloy systems requiring high temperature sintering or secondary quench hardening. The current work discusses the performance of the new chromium steel at densities above 7.2 g/cm3 at various cooling rates using an advanced lubricant/binder system. Comparisons to a hybrid Ni-Mo steel and a diffusion alloyed Ni-Cu-Mo steel are presented.
175. Surface Densified P/M Steel - Comparison With Wrought Steel Grades The next major opportunity of P/M steels is in automotive transmission gears. The stress levels in these types of gears arise from rolling contact of gear teeth with certain amount of sliding. RCF studies have been undertaken to study the fatigue properties of powder metal gears using ZF test rig. AISI 8620 grade steel was also tested. Results of these investigations suggest that P/M gears are competitive with wrought steel grades.

172. Pre-Alloyed Boron in Powdered Metal (P/M) Stainless Steels The demand for high-density stainless parts continues to grow as P/M continues to battle conventional stainless. The compressibility and hence the final sintered density of P/M stainless steels are limited due to their high alloy content. The addition of boron allows P/M to produce nearly full density parts that achieve mechanical properties similar to wrought materials. By adding boron to the melt prior to atomizing, the segregation of boron is minimized leading to a more uniform microstructure and properties. The present work will examine the role of pre-alloyed boron in both austenitic and ferritic stainless steels. Experimental work will involve the measurement of green and sintered properties. Using the laboratory experiments as a guide, specimens will be sintered in production furnaces to determine the performance of various grades of boron containing stainless steels. The specimens will be evaluated for density distribution, dimensional stability and mechanical properties.

171. Development of a High-Strength-Dual-Phase P/M Stainless Steel Applications requiring high strength stainless steels are growing at a fast pace. Typical alloys used for these applications are either highly alloyed materials such as 17-4PH or materials that require a secondary heat treatment such as SS-410HT. A new dual-phase stainless steel has been developed as a lower cost option. The microstructure of the dual-phase stainless steel consists of a mixture of ferrite and martensite, the proportions of which are dictated by the chemical composition of the alloy. This unique microstructure results in high strength and hardness, while maintaining ductility. The mechanical properties of this new alloy are compared with those of competing materials such as 17-4PH, SS-409LE and SS-410HT. Potential applications for this new material are reviewed.

169. Rolling Contact Fatigue Performance Contrasting Surface Densified, Powder Forged, and Wrought Material Previous experimental work demonstrated that rolling contact fatigue durability of high-density powder metallurgy samples was influenced by depth of surface densification (achieved via roll densification), sintering temperature, and heat treat practice. One observation of the previous work was reduced rolling contact fatigue life at high Hertz stress levels relative to wrought machined steel samples. There were also some questions regards the influence of nickel rich regions and how they affected rolling contact fatigue performance. In an effort to understand the influence of elemental nickel additions, FLN2-4405 samples were sintered at 2050 °F (1120 °C) and 2300 °F (1260 °C) and subsequently powder forged to full density. This experimental work was designed to clarify the effects of elemental nickel additions on rolling contact fatigue durability. Additionally, wrought AISI 8620 carburizing steel was machined into rolling contact fatigue samples, carburized and tested. Additionally, the AISI 8620 was evaluated for tensile, impact and fatigue characteristics in the quench and tempered condition.

167. High Performance Applications of Chromium Steels Sintered at Conventional Temperatures To meet the rigorous demands of automotive gearing, sprocket and other power transmission applications, double-press / double-sinter (DP/DS) techniques are often used to achieve the desired level of static and fatigue performance. Ancorsteel 4300, a new Cr-bearing material, has shown improved strength levels compared to traditional P/M steels. By employing such an alloy, core property requirements can be met at densities around 7.0 g/cm3. Replacing the pre-sinter and secondary press operations with selective densification, which will ensure sufficient contact fatigue resistance, can provide an economic benefit. The current work demonstrates the viability of processing a sprocket for a power transmission application with this high performance alloy system sintered at 1120 °C (2050 °F) in a production furnace. Subsequent selective densification and surface carburization provides a wear resistant and durable case layer. The results are compared with those achieved using FLN2-4405 processed through the traditional route of DP/DS, heat-treat.

166. A New CR-Bearing Alloy for High Performance Applications  Ancorsteel 4300 was recently introduced to the marketplace and is the first in a series that will simulate wrought steel compositions. This new alloy represents a technological breakthrough with low sintered oxygen contents in a system that employs both chromium and silicon. Its main advantages include the ability to be effectively sintered at 1120 °C (2050 °F), good compressibility, high hardenability, and exceptional dimensional stability across a variety of processing conditions. These characteristics make this material an attractive cost-effective alternative to alloys that require secondary quench hardening treatments and enable the penetration of P/M into higher performance applications. The current work reviews the effects of density, cooling rate, and carbon content on the static and dynamic properties of this new product, along with comparisons to Q&T properties for wrought AISI grades 4340 and 8620.

165. High Density Processing of a New CR-Bearing Steel The application of P/M steels in highly stressed applications requires both high density processing and high performance alloys. Ancorsteel 4300, a new high performance alloy that contains Cr, Si, Mo, and Ni, utilizes the hardenability and mechanical property enhancement of chromium while maintaining low sintered oxygen contents. The elevated mechanical properties compliment the high compressibility of the powder allowing for use in high density applications. When combined with high density processing techniques such as the advanced lubricant/binder system AncorMax D, high densities and excellent properties can be achieved. This paper presents the effects of processing on density and mechanical properties with this new material, with a comparison to FLN2-4405 and FD-0405.

164. Full Density Properties of Low Alloy Steels Full density produces the best mechanical properties in a P/M or P/F component. Full density properties are available for traditional P/F materials, which are based on unalloyed base iron or low alloys with Ni and Mo additions. Additional base alloys have been developed which may be suitable for full density processing. This paper outlines the full density properties of these steels. Mechanical properties and microstructure will be presented.

163. Effect of Heat Treatment and Case Carburizing High-Density P/M Steels Recent advancements in high-density lubricants enable P/M steels to be processed to densities approaching 7.40 g/cm3 in a single compaction step using heated compaction tools via the AncorMax D® process. This broadens the number of suitable applications for P/M steels, including high performance gears. However, in addition to high-density, the microstructural and mechanical property requirements vary depending on the application. This objective of this paper is to quantify and understand the mechanical property differences obtained by subjecting high-density P/M steels to various heat-treatments. Mechanical properties, fatigue properties, and microstructural analysis will be presented in the as sintered, quenched and tempered, and carburized states.

162. Effect of Case Carburizing on Mechanical Properties And Fatigue Endurance Limits of P/M Steel Case carburizing has long been a basic technique for the improvement of the wear and fatigue resistance and of PM steel components. The key to the successful improvement in carburizing, however, is understanding, and interpreting the microstructure of the carburized case. The main area for growth in the PM industry is in the high performance gearing applications. The success of penetrating this area depends upon the ability to understand the key components that effect the fatigue endurance limits of PM materials. This paper will examine and illustrate how tensile properties and the fatigue endurance limits of a P/M hybrid alloy are affected by alloying additions and carburizing.

158. Chromium Containing Materials for High Strength-High Fatigue Applications  As the use of P/M in advanced applications continues to grow, the industry continues to encounter increasing demands for high strength-high fatigue alloys. Ancorsteel 4300, a developmental alloy, has been engineered for high performance applications and employs the use of silicon, chromium, and molybdenum. This alloy will be the first in a new line of engineered high performance binder-treated products that simulate wrought steel compositions and can be processed at conventional sintering temperatures. Advanced fabrication techniques prevent the alloy from being susceptible to the common oxygen-related problems that are often seen with chromium-containing P/M materials. The presence of chromium and silicon with a low oxygen content serves to increase hardenability, strength, and fatigue life. This manuscript presents the effects of compaction pressure, cooling rate, and sintering temperature on the performance of the developmental alloy.

156. Development of a High Performance Nickel-Free PM Steel   A developmental nickel-free P/M steel containing Cr, Mn, Si and Mo is being evaluated as a new high performance material. Bonded premixes with varying carbon contents were made with the AncorMax® D system and pressed to densities of 7.2 g/cm3. Sintering studies were performed at 1177°C and 1260°C. Higher strengths were achieved in the CrMnSiMo steel as compared to a Ni containing steel with a higher total alloy content. Ultimate tensile strengths over 1200 MPa and hardnesses of 70 HRA can be achieved in the sinter + temper condition. The effect of sintering temperature, cooling profile and carbon content on mechanical properties and microstructure will be discussed.

155. Single Pressed Single Sintered PM Products for High Density, High Performance Applications  Further improvements are being developed in binder and lubricant technology that makes it possible to reach green densities approaching 7.4 g/cm3 in some applications, without the need to heat the iron powder or to double press and double sinter. This paper outlines the progress of this research. The effect of die temperature and part length on ejection behavior and final properties has been studied. In addition, optimal processing parameters as well as mechanical data are presented.

154. A Review of Current Sinter-Hardening Technology Sinter-hardening has developed into a highly cost effective production method for the production of through hardened P/M parts without the need for additional heat-treatments. Over the last several years advances have been made in sinter-hardening material systems and furnace technology. This paper reviews these advances as well as some key processing parameters required to produce high quality sinter-hardened components. Specific topics included are proper alloy selection, mechanical and fatigue properties, microstructural development, optimization of furnace cooling rates, and proper tempering practices.

152. Production of Stainless Steel Powders by Advanced Steelmaking Technology Advanced melting technology is now being employed in the manufacture of stainless steel powders. The new process currently includes electric arc furnace (EAF) technology in concert with Argon Oxygen Decarburization (AOD), High Performance Atomizing (HPA) and hydrogen annealing. The new high performance processing route has allowed Hoeganaes Corporation to provide not only a more consistent product, but has allowed enhanced properties, such as improved green strength and green density. This paper will review the potential to use this processing route to provide products with improved properties and performance.

151. Properties of High Density Diffusion Bonded Alloys For P/M components, overall mechanical properties can be improved by increasing the density coupled with alloy additions. This can be seen by the excellent properties achieved for high performance applications with material compositions based on 1.75% Ni and 4% Ni diffusion bonded steel powders processed to high densities. Through the use of an advanced binder system, higher densities with subsequent increases in mechanical properties can be achieved in a single compaction step. Further densification can be achieved through the use of the double press, double sinter process coupled with the warm compaction process. The static and dynamic mechanical properties of warm compacted and double pressed, double sintered FD-0205 and FD-0405 with densities up to 7.5 g/cm3 are presented.

148. Higher Density and Higher Performance by Single Pressing and Single Sintering Further improvements were made in binder and lubricant technology that makes it possible to reach green densities approaching 7.4 g/cm3 in some applications, without the need to heat the iron powder or to double press and double sinter. The effect of die temperature and part length on ejection behavior and final properties will be studied. In addition, optimal processing parameters as well as mechanical data will be presented.
146. Sintering of Water Atomized PIM Fe-2Ni-0.8C The use of water atomized powders in powder injection molding processes has long been an area of interest because of the cost savings afforded by the water atomization process over gas atomization and chemical methods. In this study, water atomized Fe-2Ni powder is investigated for sintering response in the milled and as-received conditions. Variations in particle size, carbon content, heating rate, sintering temperature, and atmosphere were studied. The findings indicate that, aside from sintering temperature, the most important factors influencing the sintered density are the particle size, heating rate, and surface chemistry. Milling alters the surface chemistry and decreases the particles size, both of which serve to increase sintered density.
144. Unique Stainless Steel Materials and Processing for High Strength with Reduced Magnetic Performance A new automotive part was designed having property requirements incorporating high yield and tensile strengths with good ductility, while at the same time requiring reduced magnetic performance. This combination of properties precludes the use of iron and low alloy materials because of their intrinsic magnetic response. In an effort to satisfy both requirements, type 200 stainless steel powders were prepared and processed into both mechanical property test specimens and magnetic toroids. Processing of the compacted samples was optimized to give the required strength characteristics with required minimal magnetic response. This paper will detail the types of stainless materials utilized and unique processing developed to accomplish these conflicting requirements. The mechanical and magnetic properties will be presented.
143. Development of a High Performance Nickel-Free P/M Steel Chromium and manganese are used frequently in the wrought steel industry to improve mechanical properties and hardenability. However, these elements have been difficult to incorporate into P/M steels due to their high affinity for oxygen. A new nickel-free P/M steel containing Cr, Mn, Si and Mo is being developed for high performance applications. Sintering studies performed over a range of temperatures have shown that reasonable oxygen contents along with superior mechanical properties can be achieved with this new steel. The effect of sintering temperature and density on mechanical properties will be discussed.
142. Chromium Containing Materials for High Performance Components Recently developed silicon-bearing alloys were engineered to replace malleable and ductile cast irons, and have shown excellent property combinations at high sintering temperatures. A modification to these alloys merges the power of silicon and chromium in one system, and allows for extraordinary performance. The presence of chromium improves both static and dynamic properties with the added benefit of being close to die-size after sintering. The current work details extensive laboratory data that show the effects of compaction pressure on this modified alloy processed at high sintering temperatures. Also presented is a field experience on a heat-treated production component that combined the high performance alloy system with warm compaction technology. Static and dynamic properties are presented for samples sintered in both laboratory and production scale furnaces.
139. Effect of Microstructure on the Rotating Bend Fatigue Response of a Prealloyed and Two Hybrid P/M Steels The effect of microstructural inhomogeneities on the rotating bend fatigue response of a prealloyed (FL-4405) and two hybrid (FLC2-4405 and FLN2-4405) steels was evaluated. Different microstructures at a nominal density of 7.4 g/cm3 were developed by conventional sintering, high temperature sintering, quenching and tempering and sinter hardening followed by tempering. In previous studies on these steels, tensile and impact properties, hardenability, fatigue crack growth rates, pore characteristics and residual stress distributions were quantified. For each steel, the highest fatigue limit but the lowest fatigue ratio is obtained in the quenched + tempered condition. Sinter hardening of the steels containing copper and nickel increases the fatigue limit relative to the as-sintered condition. High temperature sintering reduces the fatigue limit relative to conventional sintering. The fatigue ratio is a function of microstructure and is lowest in the three steels in the quenched + tempered condition. The inferior fatigue behavior of the copper-containing steel is attributed to the large pores resulting from the coarse copper powder.
135. Improved Stainless Steel Processing Route Advanced melting technology is now being employed in the manufacture of stainless steel powders. The new process currently includes electric arc furnace (EAF) technology in concert with Argon Oxygen Decarburization (AOD), High Performance Atomizing (HPA) and hydrogen annealing. The new high performance processing route has allowed Hoeganaes Corporation to provide not only a more consistent product, but has allowed enhanced properties, such as improved green strength and green density. This paper will review these processing changes along with the potential new products that can be made with this technology.
133. Advanced Performance Alloys Processed by High Temperature Sintering Technique As the demand for improved performance of P/M components increases, requirements for selection of proper alloy composition as well as its processing routine continue to climb. Major areas of process improvement include utilization of high performance alloy systems, high temperature sintering to create more homogeneous diffusion throughout the alloy matrix, and higher final densities of the processed components. This paper demonstrates the benefits gained by combining all of these factors. Specifically, the properties of recently developed MD compositions compacted to high initial green densities by using an advanced binder system and subsequently subjected to high temperature sintering in a pusher furnace at full-scale production conditions are investigated.
132. High Density Processing of Ancorloy MDC Materials  Previous experimental work has shown that silicon containing steels exhibit high tensile properties and impact strength at relatively low densities ranging from 7.0 to 7.1 g/cm3. Higher densities via AncorMax D® processing has shown that sintered densities in excess of 7.3 g/cm3 are possible at compaction pressures ranging from 550 to 760 MPa. (40 to 55 tsi) This paper will examine the metallurgical and mechanical enhancements achieved through the AncorMax D process and high temperature sintering of the Ancorloy® MDC and Ancorloy® MDCL materials at densities ranging from 7.0 to in excess of 7.3 g/cm3.
131. Methods to Improve the Fatigue Life of Sinter-Hardened Components Previous experimental work showed that fatigue performance is affected by the alloy system, heat treatment method, and microstructural features of test specimens. The present study will present information concerning the effects of varying the sinter-hardening cooling rate (and subsequent microstructure features) on the mechanical properties sinter-harden steels and the Ancorloy MDCL™ material system. Emphasis will be given to the rotating bending fatigue performance of these systems and how this experimental data correlates with the fatigue performance of the actual component in accelerated life testing.
129. Effect of Cooling Rates During Sinter-Hardening Sinter-hardening is becoming a more widely used process for the production of high strength P/M parts. The ability to produce martensite directly from the sintering furnace enables the process to produce parts, with properties close to those of quenched and tempered steels, more efficiently by omitting a separate heat treatment operation. The success of sinter-hardening depends upon the ability to produce microstructures of high martensite content consistently during accelerated cooling after sintering. This paper will examine and illustrate the effects of changes in cooling rate from sintering temperature upon the microstructure, hardness and properties of a hybrid P/M steel. It will show how comparison of cooling curves of instrumented Jominy and sintering furnace can be used to improve the sinter-hardening process.
128. Chromium Additions to the Ancorloy MD Series Ancorsteel 41AB, introduced several years back, demonstrated the benefits of chromium and manganese additions to molybdenum steels. The more recently developed Ancorloy MD series provides enhanced ductility and strengths in P/M steels. This paper examines the mechanical properties achieved through the combination of high performance materials with chromium additions and high temperature sintering. Two chromium-modified materials were developed by replacing a portion of admixed nickel with a high carbon ferroalloy to improve dimensional properties and hardenability. Reviews of properties such as tensile, impact, transverse rupture, rotating bending fatigue, hardenability, and compressibility are presented.
127. Powder Metallurgy of High Density Helical Gears Powder Metallurgy is a proven technology to produce high strength gears for the automotive industry. Advances in powder production, compaction, and sintering combined with double pressing have enabled overall part densities up to 7.5 g/cm³ in spur gears. However, helical gears are more difficult to produce to these same densities because the geometry does not lend itself to the DP/DS process. Described in this paper is a P/M parts making technology capable of producing single pressed and sintered helical gears with core densities approaching 7.4 g/cm³. Description of a prototype run will be presented with the resulting sintered part densities and part-to-part variability. To further enhance the performance and geometry of these helical gears, they were subsequently surface densified via rolling. Improvements in the surface density and gear quality will be described.
125. Effect of Density on the Microstructure and Mechanical Behavior of Powder Metallurgy FE-MO-NI Steels The microstructure and mechanical properties of Fe-0.85Mo-Ni powder metallurgy (P/M) steels were investigated as a function of sintered density. A quantitative analysis of microstructure was correlated with tensile and fatigue behavior to understand the influence of pore size, shape, and distribution on mechanical behavior. Tensile strength, Young’s modulus, strain-to-failure, and fatigue strength all increased with a decrease in porosity. The decrease in Young’s modulus with increasing porosity was predicted by analytical modeling. Two-dimensional microstructure based finite element modeling showed that the enhanced tensile and fatigue behavior of the denser steels could be attributed to smaller, more homogeneous, and more spherical porosity which resulted in more homogeneous deformation and decreased strain localization in the material. The implications of pore size, morphology, and distribution on the mechanical behavior and fracture of P/M steels is discussed.
124. Properties and Applications of High Density Sinter-Hardening Materials  Sinter-hardening materials are characterized by their high hardenability which enables the formation of >80% martensite during accelerated cooling. However, these moderately alloyed materials often exhibit lower compressibility and the resulting lower density limits their use in potential high strength applications.

What is needed is a method to improve the green and sintered density of current sinter-hardening materials that will enable these materials to be utilized in new high strength applications. This paper describes how the green and sintered density of standard sinter-hardening alloys can be improved using new alloy systems coupled with advanced binder technology. The resulting improvements in mechanical properties will be presented as well as the potential use of high density
117. Properties of High Density Sinter Hardening P/M Steels Processed Using an Advanced Binder System Sinter-hardening P/M alloys offer an excellent opportunity for a part manufacturer to produce hardened components in an economical fashion by eliminating secondary heat-treatments. Unfortunately, sinter-hardening P/M base iron grades are prealloyed with substantial levels of Ni, Mn, and Mo which increase hardenability but reduce compressibility. Furthermore, Cu and graphite are added to further increase strength and hardness. These alloying additions all reduce compressibility limiting the maximum attainable green and sintered densities. This paper explores how processing sinter-hardening alloys with a new proprietary binder system can improve compressibility and lead to higher densities and mechanical properties. The data show green density increases of 0.05-0.15 g/cm3 and be achieved and can result in tensile strength and hardness improvements.
116. Advanced Sinter-Hardening Materials and Practices Sinter hardening is a well-established production technique utilized in the manufacture of P/M components with hardness and tensile strengths that approach the values of quench and tempered materials. The potential drawback of the sinter hardening process is the uniform carbon content of the case and core. This uniformity of carbon content does not promote a desirable compressive stress condition on the surface of the component leading to less than optimum fatigue strength. Experimental work was performed in which several sinter-hardening materials were produced with lower core carbons and subsequently carburized after the sintering process to produce a carburized case. Mechanical properties including tensile and fatigue of the non-carburized and carburized material will be presented plus the effect of the carburizing cycle on the carbon gradient of the new sinter hardening materials.
113. Effect of Small Additions of Boron on Mechanical Properties & Hardenability of Sintered P/M Steels Low levels of boron (0.01-0.15w/o) may induce sufficient hardenability and strength in powder metallurgy steels to permit a decrease in the level of the alloying elements, increase powder compressibility and reduce the as-sintered hardness. These lean alloys may be sufficiently ductile to coin and be hardened by subsequent heat treatment. The goal of this study was to identify the boron level in FLN2-4400 (Fe + 0.85w/oMo, 2.0w/oNi, 0.3w/oC) which yields the optimal combination of strength, ductility, and hardenability. Tensile, transverse rupture, hardness, and Jominy end quench tests were performed on this alloy with six different levels of boron added Sintered strength and ductility increase up to 0.05w/oB, but decrease beyond this level, even though sintered density increases significantly. Jominy hardness traces show that the hardenability is not increased substantially until the concentration of boron reaches 0.05w/o. The microstructures of the Jominy bars show that with an increase in boron level, the depth to which martensite is retained increases, but that grain boundary segregation occurs. A level of boron ~ 0.05w/o gives the optimum combination of strength, ductility, and hardenability in FLN2-4400.
112. Processing of Hybrid Alloys to High Densities  Premixes containing prealloy molybdenum, such as Ancorsteel 85HP, nickel and graphite have exceptional mechanical properties. This presentation will highlight the properties of these materials processed to densities of 7.25 to 7.45 g/cm3 by single press, single sinter techniques. The exceptional green strength of these materials in combination with density provides a unique opportunity to convert more automotive components to P/M.
111. Economics and Benefits of High Temperature Sintering of High Performance Alloys Today’s global economy has produced an extremely competitive marketplace. Design engineers constantly compare the economics and benefits of powder metallurgy (P/M) with those of stamping, casting and wrought machining. While parts manufacturers have traditionally exploited the near net shape cost savings of conventional P/M compositions, many have turned to higher performance alloys and elevated temperature sintering in an effort to optimize the metallurgical and mechanical properties of their products. Powder producers and furnace manufacturers have continued to support these endeavors through new product and process development.

This study will examine the metallurgical and mechanical enhancements achieved through the combination of high performance alloy systems and high temperature sintering. In addition, it will show how these benefits can be exploited to produce superior parts economically. High performance silicon-containing P/M steels sintered at 1150 to 1343 °C (2100 to 2450 °F) will be used to explore these property enhancements. These silicon-containing P/M steels yield excellent properties when sintered above 1260 °C (2300 °F) and are capable of attaining high apparent hardnesses .
110. Enhanced Processing of Silicon-Containing High Performance Materials In 2001, an extensive program was initiated to evaluate new silicon-containing materials designed to compete with various grades of ductile and malleable cast irons. These bindertreated, press-ready premixes were compared to a standard FLN4-4405 in a production environment on a complicated, high volume application. This year’s work investigates both double pressed / double sintered and heat-treated performance of the new silicon-containing materials. Mechanical properties and dimensional stability information are presented and compared to several standard material candidates containing no silicon.
108. Effect of Microstructural Inhomogeneties on the Fatigue Properties of a Prealloyed & Two Hybrid P/M Steels In the first phase of this study, the effect of microstructural inhomogeneities on the tensile and impact response of a prealloyed (FL-4405) and two hybrid (FLC2-4405 and FLN2-4405) P/M steels based on prealloyed Ancorsteel 85 HP was evaluated. In phase two we assess crack propagation response. The base powder and additions were mixed with 0.75 w/o Lonza Acrawax in 227 kg (500 lb) batches. A density of 7.4 g/cm3 was obtained by double pressing (550/550 MPa). Sintering temperatures of 2050 °F(1120 °C) and 2300 °F (1260 °C ) were utilized. A group of sintered compacts of each alloy was heat treated by quenching from 1650 °F (900 °C) into warm oil at 160 °F (70 °C) followed by tempering at 375 °F (190 °C) for 1 h. Two groups of sintered compacts of the FLC2-4405 and FLN2-4405 alloys were sinter hardened and tempered at 375 °F (190 °C) for 1 h. Experimental data showed that the P/M steels exhibit comparable fatigue crack growth rates (1.1207E-4 to 3.0185E-4 mm/cycle) at a stress intensity range of 1000 MPa (mm)1/2. Quenched and tempered microstructures resulted in the highest fatigue crack growth rate. Sinter hardening of FLC2-4405 and FLN2-4405 lowered the fatigue crack growth rate. High temperature sintering reduced the fatigue crack growth rate in FL-4405 but increased it in FLC2-4405 and FLN2-4405.
107. Effect of Copper and Nickel Alloying Additions in the Tensile and Fatigue Behavior of Sintered Steels (Axial Fatigue Behavior of Sintered Ferrous P/M Alloys: Experiments and Modeling) The influence of Cu and Ni on tensile and fatigue behavior of Fe-0.85Mo prealloy with 0.6% graphite addition was investigated. The transient liquid phase formed by the presence of Cu resulted in more rounded pores in the Fe-Ni-Cu alloy compared to Fe-Ni. While the total porosity was similar in both alloys, a larger fraction of secondary pores was present in the Fe-Ni-Cu. The addition of Cu resulted in an increase in proportional limit stress, ultimate tensile strength, and fatigue strength over the Cu-free alloy. The higher fatigue resistance was attributed to the enhanced solid solution strengthening provided by Cu in Fe, and the higher proportional limit in the Fe-Ni-Cu alloy, caused by the more rounded nature of the pores, and stronger Fe-Ni-Cu matrix surrounding the pores. The proportional limit stress appears to be a good indicator of fatigue strength, since it quantifies the onset of localized plasticity in these materials.
106. Materials Solutions for Converting Cast Iron Applications to Powder Metal In the last several years, powder metallurgy (P/M) materials have been developed to rival the properties of cast iron and screw machined grades utilized in both automotive and non-automotive applications. These materials offer the P/M industry a momentous opportunity to dramatically increase its market by replacing some of the cast iron volume utilized today. While the inherent net shape capabilities of P/M and the potential cost savings of conversion to P/M offer customers distinct advantages, previous materials have not offered property combinations comparable to many cast iron grades. This work will explore the common grades of cast iron and propose P/M materials as possible replacements for each.
105. Advances in P/M Gear Materials Powder Metallurgy is an efficient manufacturing process for the production of gearing and similar net shape components. Because of limitations arising from the inherent porosity and limited alloy systems available, the traditional uses for P/M gearing was in relatively low stress applications. The recent introduction of new compaction techniques and new alloy materials has produced P/M components with significantly higher yield and tensile strengths approaching the strength levels of wrought gearing materials. This paper will review the new P/M processes and materials and their suitability for gear type applications. Mechanical property comparisons will be made to the common automotive gearing materials including ductile and malleable cast irons and wrought low alloy steels.
104. Application of Sinter-Hardenable Materials for Advanced Automotive Applications Such as Gears, Cams, and Sprockets  Recent demands within the automotive industry have been for applications requiring high apparent hardness, high hardenability, and increased mechanical performance. These often-conflicting requirements necessitated the development of new materials that offer high as-sintered apparent hardness and good static/dynamic mechanical properties without the added expense of a secondary heat treatment. Traditionally, sinter-hardening materials have offered acceptable apparent hardness but at the expense of mechanical properties and sintered density. This paper will document the mechanical properties of a series of sinter hardening materials that offer good compressibility, high apparent hardness and enhanced mechanical properties. The discussion will focus on utilization of these materials in automotive applications (within both the engine and transmission) such as gears, cams and sprockets that are currently produced by either the press, sinter, and heat treat process or by conventional machining of a casting or wrought material. Enhanced processing through high temperature sintering also will be discussed.
103. The Development of Engineered Binder-Treated Alternatives to Duffusion-Alloyed Powders Engineered binder-treated premixes have been developed as alternatives to diffusion alloyed powders. The binder-treated materials meet the chemical composition limits for the diffusion alloyed materials listed in MPIF Standard 35, Materials Standard for P/M Structural Parts.

At  an equivalent combined carbon content the binder-treated materials exhibit higher strength than the diffusion alloyed materials. When the combined carbon content of the binder-treated materials is reduced, to provide an equivalent strength level, the binder-treated materials match the tensile ductility and impact energy of the diffusion alloyed products.

The as-sintered and the quench-hardened and tempered performance of the new materials is reviewed and compared with diffusion alloyed materials of similar chemistry. These recently developed materials represent the first in a new family of high performance ferrous P/M materials.
101. Fatigue Crack Initiation and Propagation in Ferrous Powder Metallurgy Alloys Many of the targeted applications for powder metallurgy materials, particularly in the automotive industry, undergo cyclic loading. It is, therefore, essential to examine the fatigue mechanisms in these materials. The mechanisms of fatigue crack initiation and propagation in ferrous powder metallurgy components have been investigated. The fatigue mechanisms are controlled primarily by the inherent porosity present in these materials. Since most, if not all, fatigue cracks initiate and propagate at the specimen surface, surface replication was used to determine the role of surface porosity in relation to fatigue behavior. Surface replication provides detailed information on both initiation sites, and propagation path of fatigue cracks. The effect of microstructural features such as pore size, mean pore spacing, as well as the heterogeneous microstructure on crack deflection was examined and is discussed. Fracture surfaces were examined to elucidate a mechanistic understanding of fatigue processes in these materials.
99. Effect of Microstructural InHomogeneities on The Mechanical Properties of Hybrid P/M Steels The effect of microstructural inhomogeneities on the tensile and impact response of a prealloyed (FL-4405) and two hybrid (FLC2-4405 and FLN2-4405) P/M steels was investigated. Tensile and impact response, microstructures, pore characteristics and fracture modes were determined in the sintered, quenched + tempered and sinterhardened conditions. Sintering temperatures of 1120°C (2050°F) and at 1260°C (2300°F) were utilized anddensities in the range 7.0 - 7.4 g/cm3 were achieved by single and double pressing and sintering. Over this sintered density range, tensile strength increases by >30%. In the quenched + tempered condition tensile strength exceeds 1000 MPa. Tensile properties are rationalized in terms of the attendant microstructures and modes of fracture.
96. P/M High Strength Magnetic Alloys Sintered P/M magnetic materials are characterized by good DC magnetic performance with relatively low yield and tensile strengths, typically the tensile strengths are less than 50,000 psi. This inherently low strength of the common magnetic alloys results from the use of pure iron or iron phosphorus alloys. This low strength often limits the potential applications for sintered P/M magnetic materials. Described in this paper are P/M alloys that have tensile strengths approaching 70,000 psi (480 MPa) in the as sintered condition with tensile ductility approaching 10% and having magnetic properties equal to the pure iron and / or iron phosphorus alloys. These alloys are intended for higher strength, magnetic applications. A comparison to the standard P/M magnetic alloys will be made.
94. Silicon Containing High Performance Alloys - Machinability and Mechanical Properties With the introduction of several silicon-containing materials, the potential for replacing ductile and malleable cast irons with P/M alloys has never been greater. These materials exhibit extremely competitive property combinations when conventionally compacted and sintered at 1260 °C (2300 °F). However, additional opportunities exist if advanced densification processes such as double press / double sinter or warm compaction are employed. This paper investigates several important manufacturing processes including advanced densification techniques, vacuum sintering, and machinability.
93. High Performance Materials - Ancorloy MD Series New silicon-containing materials were recently introduced to compete with various grades of ductile and malleable cast irons. These binder-treated, press-ready premixes offer extremely good physical and mechanical property combinations. This work focuses on the evaluation of these materials in a production environment. Properties such as impact energy, tensile strength, elongation, dimensional change and apparent hardness are presented.
90. Advanced Processing of Sinter-Hardening Materials The sinter-hardening process has been shown to provide excellent mechanical properties and part-to-part size control. Previous work has indicated that exceptional mechanical properties and high apparent hardness values can be achieved by sinter hardening in a high temperature furnace with standard cooling. This work focuses on combinations of advanced techniques intended to optimize mechanical properties for stringent applications. While warm compaction is utilized to increase density, various material alloy combinations are blended together in an effort to study green density variables. Where applicable, specific market opportunities are identified.
89. Newly Developed P/M Materials to Replace Malleable and Ductile Cast Irons  Malleable and ductile cast irons are used extensively in automotive applications such as clutches, gears, carriers, shafts, bearings, cam, racers, hubs, etc. Recently developed P/M materials can be processed cost efficiently to replace malleable and ductile iron castings. An UTS in excess of 1240 MPa and a YS in excess of 825 MPa can be achieved with one of these new materials. These tensile properties can be coupled with elongations over 2% and impact energies over 25 Joules. This presentation will cover processing routes for these new materials and will identify parts that may benefit from this new technological advancement.
88. Advances in High Performance PM Alloys For Automotive Applications The as-sintered and the sintered and tempered transverse rupture and tensile properties of seven recently developed high performance PM compositions are reviewed. Two are improved versions of the well known diffusion alloyed grades according to MPIF Standard 35. Two others are likewise improved versions of more highly alloyed analogs of the latter that have only recently been introduced. The remaining three are all new compositions that take advantage of the powerful alloying effects of silicon. The silicon is added by a proprietary method that greatly reduces its susceptibility to oxidation during sintering, an effect that has heretofore limited its use.
86. The Development of Binder-Treated Alternatives to Diffusion Alloyed Powders Engineered binder-treated premixes have been developed as alternatives to diffusion-alloyed powders. One family of binder-treated materials meets the chemical composition limits for diffusion-alloyed materials listed in MPIF Standard 35, Materials Standards for P/M Structural Parts. A second family of engineered binder-treated premixes has been developed as an alternative to high performance diffusion-alloyed materials that are based on prealloyed low-alloy steels containing 1.5 weight percent molybdenum. The as-sintered and the quench-hardened and tempered performance of the new materials will be reviewed and compared with diffusion-alloyed materials of similar chemistry.
85. New High Performance P/M Alloy Substitutes for Malleable and Ductile Cast Irons Ferrous P/M alloys generally do not exhibit a good combination of strength, ductility, and impact toughness. A series of new P/M alloy systems has been developed to match the performance characteristics of malleable and ductile cast irons. The new materials maintain excellent tensile ductility at high strength levels while possessing good impact resistance. The performance characteristics and benefits of the new P/M materials will be presented.
83. New High Performance Ferrous P/M Materials for Demanding Automotive Applications Diffusion-alloyed powders have been used for many years in automotive applications such as synchronizer hubs where there is a need for a combination of tensile strength, ductility, and impact energy. Recently, engineered binder-treated premixes have been developed as alternatives to diffusion-alloyed powders including those based on a prealloyed powder (1.5 w/o molybdenum). The engineered binder-treated materials will be compared with their diffusion-alloyed counterparts.
82. New Higher Performance Materials Through the use of enhanced atomization, annealing, and binder treatment technologies, several new silicon-containing alloy grades have been introduced for high performance automotive applications. This presentation will include data on compacts produced from these new grades using conventional compaction, warm compaction, and double press / double sinter processing. With these new material systems, single compaction can achieve ultimate and yield strengths in excess of 1200 MPa and 800 MPa with elongation over 2%. Such tensile properties can be developed in conjunction with apparent hardness values over 65 HRA and impact energies exceeding 25 Joules.
81. Opportunities for Conversion of Powertrain Components from Malleable/Ductile Cast Irons to Powder Metallurgy Malleable and ductile cast irons are used extensively in gearing and high strength applications within automotive power train applications. Advantages of malleable and ductile cast irons are low material cost with mechanical properties that meet or exceed the requirements of the intended application(s). One disadvantage of the malleable cast iron is the extensive heat treating required to obtain the proper microstructure and mechanical properties. Both malleable and ductile iron components require extensive machining to produce the finished component. The combination of heat treating and extensive machining often results in a component that is costly to manufacture. Recent advances in the Powder Metallurgy (P/M) process including high strength material systems and high density processing have achieved mechanical properties that meet or exceed the level achieved with the current malleable and ductile cast iron materials. This paper will present an evaluation and comparison of the mechanical properties of malleable cast iron with selected P/M material systems and processing parameters. This property discussion will demonstrate the suitability of the P/M process in replacing these cast and machined components. Examples of specific parts will be cited and discussed.
80. Application of Sinter-Hardenable Materials for Advanced Automotive Applications such as Gears, Cams, and Sprockets Recent demands within the automotive industry have been for applications requiring high hardness, high hardenability, and increased mechanical performance. These often conflicting requirements necessitated the development of new materials that offer high as-sintered hardness and good static/dynamic mechanical properties without the added expense of a secondary heat treatment. Traditionally, sinter-hardening materials have offered acceptable hardness but at the expense of mechanical properties and sintered density. This paper will document a series of sinter hardening materials that offer good compressibility, high hardness and enhanced mechanical properties. The discussion will focus on utilization of these materials in automotive applications (within both the engine and transmission) such as gears, cams and sprockets that are currently produced by either the press, sinter, and heat treat process or by conventional machining of a casting or wrought material.
79. New High Performance P/M Alloy Substitutes for Malleable and Ductile Cast Irons To advance applications of powder metallurgy (P/M) into areas where current products do not have the desired performance characteristics, a series of new alloys has been developed. These new materials exhibit mechanical properties comparable to those of malleable and ductile cast irons. Some possible applications include ring gears, pinion gears, and carriers. The tensile and impact properties of the new materials are presented for compaction pressures of 415, 550, and 690 MPa and comparisons are made with current high performance P/M materials as well as with various cast irons.
78. Binder-treated Analogs of Diffusion Alloyed Compositions Based On Ancorsteel 150 HP The powder, green and sintered properties of binder-treated analogs of two diffusion alloyed steels based on Ancorsteel 150 HP are presented. These new additions to the binder-treated family of compositions are made according to a proprietary practice that does not include diffusion alloying. It is shown by direct comparison that these new premixes offer significantly improved compressibility and otherwise generally similar powder, green and sintered properties to compositionally similar premixes of the diffusion alloyed steels. The sintered property comparisons presented include the TRS, tensile, and impact properties of the subject compositions in the as-sintered and sintered and tempered conditions.
77. Field Experience on a New Sinter-Hardening Material Traditionally, the processing of sinter-hardening materials has been limited to conventional sintering temperatures. Hence, very little sinter-hardening research has been conducted at higher sintering temperatures. However, the superior hardenability of Ancorsteel® 737 SH allows for sinter-hardening at temperatures in excess of 1180 ºC (2150 ºF) without the need for accelerated cooling.

This paper will both present field experience on conventional sinter-hardening processes and investigate the effect of copper, nickel, and graphite additions on the properties of Ancorsteel 737 SH sintered at 1260 ºC (2300 ºF) utilizing conventional cooling. Particular attention will be paid to dimensional change characteristics, mechanical properties, apparent hardness values, and martensite content in sintered parts.
76. New High Performance P/M Alloys for Replacing Ductile Cast Irons Improvements in atomizing technology and binder treatment technology have allowed Hoeganaes to develop unique alloy systems with high strength, ductility, and impact energy. These systems, material MDD (currently experimental) and AncorloyÒ MDA (commercial product), have been shown to be extremely competitive with numerous ductile cast iron grades. This paper presents the powder, green, and sintered properties of the new materials and compares their performance with existing material systems.
74. Improved Efficiency by Use of Sinter-Hardened P/M Automotive Components  Sinter-hardening, accelerated cooling, of P/M components directly from the sintering furnace is an increasingly popular production process. Sinterhardened P/M steels possess similar macrohardness and strength to heat treated P/M steels processed by quenching and tempering. Where design permits, sinter-hardening enables P/M fabricators to improve process efficiencies by omitting a separate heat treatment operation. This paper examines the interaction of material selection and process conditions required to develop a sinterhardened P/M component for an automotive application.
69. The Effect of Microstructure and Pore Morephology on Mechanical and Dynamic Properties of Ferrous P/M Materials The objective of this study was to quantify and understand the combined role of microstructure and pore characteristics on the transverse rupture strength (TRS), tensile properties and rotating bend fatigue response of conventional and ANCORDENSE processed FLN2-4405 premixes. To this end, the premixes were made with samples using fine (4µm) and coarse (50µm) nickel powder to promote differences in pore size and diffusion characteristics. Compacts were sintered in synthetic DA (75 v/o H2 / 25 v/o N2) at 2050°F (1120°C) or 2300°F (1260°C) to densities in the range of 6.8 g/cm³ - 7.2 g/cm³. Pore size and spacing, cumulative pore size and number of pores per unit area were determined by stereological analysis, and the crack path was monitored by means of optical microscopy. The static and dynamic properties of the materials made from the two premixes are interpreted in terms of the attendant microstructures and pore characteristics, as dictated by the premix type, sintering temperature and sintered density.
68. Performance Characteristics of a New Water-Atomized Prealloyed Powder (0.5 weight % Molybdenum  A new prealloy material containing 0.50 w/o Mo was introduced recently. This medium hardenability material can be admixed with a variety of alloying ingredients to produce superior tensile properties. Results of admixing this prealloyed powder with nickel, copper, manganese, and graphite will be presented. In addition, quench and temper properties will also be discussed.
67. A Comparison of ANCORDENSE Processed Materials with Malleable Cast Iron  A study was conducted that compared the mechanical properties of a series of ANCORDENSE prepared materials with malleable cast iron. This paper will present the mechanical properties (TRS, tensile, impact, and fatigue) of various ANCORDENSE prepared premixes in the as sintered condition compared with a malleable cast iron. The objective of this investigation was to demonstrate that an engineered P/M material coupled with ANCORDENSE processing can replace a malleable cast iron component giving equivalent mechanical property performance and potentially equivalent gear performance.
66. A Superior Sinter-Hardenable Material  Sinter-hardening technology has been assisting the P/M parts fabricator by improving processing efficiencies and reducing costs. Furthermore, the barriers to attaining good sinterhardenability and part performance have been reduced through improvements in materials and equipment developments. Recent material advances have focused on new alloys with increased hardenability and compressibility.

A new sinter-hardenable alloy has been introduced which provides improvements in hardenability and compressibility over the well-established FLC-4608 composition. These improvements will allow fabricators to reach higher densities and mechanical performance under typical compaction and sintering conditions. Mechanical performance and material capabilities are investigated as a function of density and admixed composition. Additional processing to achieve higher green densities and mechanical performance will also be reviewed.
65. Ancorloy Premixes: Binder Treated Analogs of the Diffusion Alloyed Steels  The properties at two carbon levels of binder treated analogs of the diffusion alloyed steels are presented. These Ancorloy premixes are made according to a proprietary practice that does not include diffusion alloying. It is shown by direct comparison with compositionally similar premixes of the diffusion alloyed steels that the Ancorloys generally exhibit similar powder, green and dimensional change properties and significantly enhanced mechanical properties. Tensile, impact and fatigue property data in the sintered, sintered and tempered and quenched and tempered conditions are presented.
60. Application of High Performance Materials and Processes - Alloy Systems  Significant advances have been made in the past several years in developing Low alloy materials for highly stressed applications. A review of these material and processing developments will be made. Recent material developments focus on developing high apparent hardness and tensile strength in P/M parts without the need for a secondary quench-hardening operation. The effect of alloy type, alloy content, and cooling rate on hardness and other properties will be discussed.
55. The Effect of Service Temperature on the Properties of Ferritic P/M Stainless Steels  An area of current development for P/M stainless steel applications is automotive exhaust systems. Recent work in this area has proven the potential application of ferritic stainless steel P/M materials for exhaust flanges to be viable. Lacking in this work, however, is a sufficient database for P/M stainless steels and, in particular, elevated temperature mechanical properties.

A study was undertaken to investigate the effect of service temperature on the mechanical properties of several ferritic P/M stainless steel grades including 410L, 409Cb, 434L and 434Cb. In particular, tensile properties were generated for these alloys and compared with their wrought equivalents. The effect of process conditions and the subsequent microstructure was also considered.
54. Sinter-Hardening P/M Steels  The use of P/M structural parts is growing in part due to the use of the sinter-hardening process which utilizes high performance materials in combination with an accelerated post sintering cooling rate. The sinter-hardening process offers improved mechanical properties over conventional sintering without a separate heat treatment operation. Thus, where the part design permits, sinter-hardening offers considerable economic benefits to the part producer.

Sinter-hardening typically requires that the P/M steel substantially transform to martensite during cooling. A variety of microstructures and properties can be obtained by varying the post sintering cooling rate. By controlling this rate, the microstructure can be manipulated to produce the required amount of martensite to obtain the desired mechanical properties.

Alloying elements such as molybdenum, nickel, and copper promote hardenability in P/M parts. By increasing the hardenability of the material, the parts can be cooled at slower rates and still produce large amounts of martensite. The ability to increase the amount of martensite, leading to increased strength and hardness, through the use of proper alloy selection and accelerated cooling rate will be discussed.
53. The Application of Warm Compaction to High Density Powder Metallurgy Parts  The warm compaction process (ANCORDENSE®) has been shown to provide increased density in ferrous powder metallurgy parts. This improvement in density contributes significantly to mechanical properties and thus the overall performance of the part. The combination of increased density with high performance material selections, provides parts that can exceed the performance of forged or cast material counterparts while taking advantage of powder metallurgy's net shape forming capabilities.

Turbine hubs for automatic transmission torque converters have proven to be ideal candidates for the powder metallurgy (P/M) process. The complex shape of turbine hubs is costly to produce via conventional forging and machining operations. However, increases in engine size and torque requirements in several automotive designs have required that turbine hubs possess higher levels of mechanical properties. High density P/M manufacturing techniques, in combination with high performance ferrous materials produces components capable of replacing a forged and machined turbine hub.

This paper will review the conversion of a conventionally forged and machined turbine hub used in a high torque automatic transmission to a single pressed and single sintered P/M turbine hub. The material used for the P/M hub was an FD-0405. This diffusion alloyed material was evaluated in the laboratory and mechanical properties are reported at several density levels. Warm compaction processing achieved high overall sintered densities in the highly stressed internal spline region. Extensive mechanical and part specific testing was conducted to verify the suitability of the P/M part.
52. The Effect of Microstructure on Fatigue Properties of Ferrous P/M Materials  Fatigue testing (rotating bending fatigue) was performed on several materials in order to evaluate the effect of several microstructural elements. Metallographic analysis was performed to characterize the microstructures of the materials and attempt to identify failure mechanisms.

Previous work indicated that predicting the fatigue strength of P/M materials is a complex relationship between the grain size of the material, the type and strength of the microstructural constituents present and, primarily, the mean pore spacing. [1,2] This study examines these relationships in more depth.
50. Effect of Process Conditions Upon Sinter-Hardening Response of FLC-4608 Materials Sinter-hardening provides for improved efficiency and competitiveness by eliminating a separate, secondary heat treatment operation. Materials options, process flexibility, and application requirements demand a better understanding of process, microstructure, and mechanical property relationships in order to fully capitalize on the opportunity afforded by sinter-hardening.

This study investigates the effect of cooling rate on the material properties of an FLC-4608 material processed under production conditions. Variables used to control accelerated cooling are related to componet microstructure and mechanical properties. Production cooling rates and microstructural comparisons are made with a laboratory developed Continuous Cooling Curve (CCT) for the FLC-4608 alloy.
49. The Effect of Nickel Content, Sintering Temperature, and Density on the Properties of a 0.85 w/o Molybdenum Prealloy  The combination of molybdenum prealloyed steel powders and admixed nickel provides sintered steels that are used in structural parts requiring strength, wear resistance, and impact toughness. The properties of these materials, like all P/M steels, are dependent on density, microstructure and composition. This work discusses the effect of admixed nickel content, sintering temperature, and density on the properties of a 0.85 w/o molybdenum prealloy. Samples were prepared with 0, 2, 4 and 6 w/o nickel additions. The materials were warm compacted at 30, 40, 45, and 50 tsi (415, 550, 620 and 690 MPa) and sintered at 1900°F, 2100°F and 2300°F (1040°C, 1150°C, and 1260°C). Mechanical properties were determined and related to the density, microstructure, and composition.
45. The Development of High Performance P/M Steels  Ferrous powder metallurgy has continued to displace competing cast or wrought technologies in automotive applications. This required the development of materials systems with higher, more consistent performance than those available previously. However, competing technologies are not static. The paper examines the materials development and microstructural control required to meet the challenges and opportunities offered by the development of new P/M parts.
43. Single Compaction to Achieve High Density in Ferrous P/M Materials in Automotive Applications  The continued growth of ferrous powder metallurgy in automotive applications is dependent on the development of higher density and improved dynamic properties. New powder metallurgy applications also must be cost effective through the continued use of the process's, net shape forming capabilities and a reduced number of manufacturing steps. The processes utilized to manufacture some of these new parts also must provide the ability to produce thin walled parts with complex geometries.

The use of the warm compaction process (ANCORDENSE™) will be shown to develop high density levels with a single compaction process. The process also provides increased green strength and reduced ejection forces. The dependence of mechanical properties on density will be demonstrated.

An example of a potential application of the warm compaction technology is an output shaft. The capability of manufacturing this part with the warm compaction process is outlined and compared with the same part made by the double press/double sinter (DPDS) process. Part density and performance from both processes are compared.
42. The Effect of Microstructure on Fatigue Properties of High Density Ferrous Materials  Fatigue testing (rotating bending fatigue) has been performed on several high performance ferrous P/M material systems. Detailed metallographic analysis was performed to determine differences in the failure mechanisms for various material and process combinations. A variety of material compositions were single compacted to high density via the ANCORDENSE™ compaction system. This was followed by conventional and high temperature sintering and testing in the as-sintered and heat treated conditions. The analysis provides information as to the relationships between density, structure and composition with fatigue life.
41. Properties of Several ANCORDENSE Processed High Performance Materials  The effect of powder and compaction temperature on the ANCORDENSE™ warm compaction system is evaluated. Detailed property analysis is presented on several warm compacted high performance materials systems. Properties evaluated include density, tensile, and impact performance. A detailed assessment of the microstructure resulting from various alloy compositions and processing techniques is performed. The materials involved in the tests were conventional and high temperature sintered and tested in the as sintered and heat treated condition.
33. An Investigation Into the Effects of Processing Methods on the Mechanical Characteristics of High Performance Ferrous P/M Materials  The mechanical properties of high performance ferrous P/M materials are influenced by the material composition and processing method. This paper investigates the effects of the ANCORDENSE™ process, a new, high density, single compaction method, on the mechanical properties of Distaloy® 4800A based materials. The results of this study are discussed with a comparison to the mechanical properties for the same materials developed through single-pressed and double-pressed, doublesintered processing methods. In addition, a case study is performed on a component produced via the ANCORDENSE method.
32. Properties of Diffusion Bonded Alloys Processed to High Densities  Diffusion bonded alloys have been shown to exhibit excellent properties. Recent advancements in compaction technology have allowed these materials to reach green density levels of over 7.3 g/cm3 in a single compaction process. Various capabilities of this new compaction system will be demonstrated utilizing diffusion bonded alloys. Properties of several diffusion bonded materials will be investigated at these high density levels. A variety of processing techniques will be utilized including high temperature sintering and heat treatment to demonstrate the flexibility of these materials.
31. Advanced Properties of High Density Ferrous Powder Metallurgy Materials  The introduction of the ANCORDENSE™ system has provided significantly higher density levels than previously possible in a single press/single sinter operation. This paper will explore the role that higher density has on mechanical properties. Various properties will be evaluated, including transverse rupture strength, tensile strength, and impact. Additionally, the effect of other processes, such as high temperature sintering and heat treatment, will be addressed.
27. Recent Developments in Ferrous Powder Metallurgy Alloys  A systems approach to engineered ferrous powder metallurgy (P/M) materials is described. The approach encompasses the use of high compressible, high performance powders in premixes produced using proprietary mixing technology that employs patented binders. To ensure that an appropriate microstructure is achieved to suit the functional requirements of a particular application, alloys are formulated based on knowledge of the compaction and sintering cycle that will be used to make the P/M parts. These premixes have improved flow and die filling characteristics that result in greater consistency throughout the entire P/M part manufacturing process. In addition, the use of binder treated premixes leads to reduced dusting and segregation of alloy additions. Binder treated premixes produced using high compressible, prealloyed molybdenum steel powders are shown to be particularly well suited for quench-hardening, sinter-hardening, and high temperature sintering. They also form the basis for a series of chromium, manganese, and chrome-manganese P/M 'Steels. The systems approach will be augmented during 1994 by the introduction of new material and process technology that enables part densities of 7.3 to 7.5 g/cm3 to be achieved through single compaction processing.
26. High Performance Ferrous P/M Materials For Automotive Applications  The majority of automotive components (transmission, chassis, suspension, and engine) for which parts with densities up to about 7.0 g/cm3 are suitable have already been converted to P/M and there are few opportunities for growth in this density range. In order to meet the requirements of more demanding applications there has been a trend toward higher densities through the use of infiltration, double pressing/double sintering, or powder forging (l - 4) to produce parts such as synchronizer hubs, crankshaft sprockets, chain sprockets, gerotors, steering column tilt levers, planetary gear carriers, parking gears shift levers, and connecting rods. While powder forging has been shown capable of producing parts, which are superior to wrought, or cast products process economics have limited market penetration by this technology (5). The double press and sinter route also adds process costs and is probably too expensive for other than premium applications. There is a real need for a systems approach that will permit double pressed and sintered or infiltrated performance characteristics to be achieved by means of single compaction processing. The mechanical properties of P/M materials are directly related to their microstructure and the size, distribution, and morphology of the porosity they contain. Alloying additions are made to develop specific material performance characteristics. However, the manner in which the alloys are constituted has a significant effect on the porosity and microstructure of the final product (6).
24. Properties of High Density Ferrous P/M Materials, A Study of Various Processes  Several methods of achieving higher density in ferrous P/M parts are possible. Double press/double sinter allows densities in excess of 7.3 g/cm3 but is limited by cost and geometry considerations. A new method of single processing high performance materials is evaluated and compared to other methods of processing. The comparison is performed utilizing Ancorsteel 85HP and Distaloy 4800A base materials. Various green and sintered properties are evaluated including; green strength, transverse rupture strength, tensile properties and impact values.

The data clearly demonstrates that the patented (1) ANCORDENSE™* process offers performance comparable to double press/double sinter processing. Green density values of approximately 98.5% of the pore free density limit are achieved with a single compaction step.
23. High Density Processing of High Performance Ferrous Materials  Density is an predominant factor in the performance of powder metallurgy components. Methods such as double press/double sinter, copper infiltration and powder forging have been employed to provide higher densities than traditional single press and sinter operations; however, their widespread use is constrained by cost and geometry considerations.

A commercially proven method for obtaining single compaction/single sinter densities in the 7.25 to 7.55 g/cm3 range by means of the patented ANCORDENSE™ technology is introduced. Conventional compaction pressures and sintering temperatures, typically not exceeding 50 tsi or 2300°F, respectively, are utilized. Resulting properties for several high performance materials are presented.

Test results indicate that the ANCORDENSE process is a cost effective method of providing high density parts with outstanding physical properties. The process is shown to be applicable to a wide variety of high performance materials. Additionally, significant improvements in green strength and ejection forces are realized.
22. High Density Processing of CR-Mn P/M Steels  The use of chromium and manganese as alloying elements in P/M steels offers several potential advantages over copper and nickel that are used in conventional P/M alloy steels. The paper will illustrate how the principles used to improve the hardenability and performance of wrought steels can be applied to P/M chromium and manganese alloy steels using a systems approach. The use of chromium-manganese for P/M applications was made possible by binder-treated premix technology of a highly compressible prealloyed low alloy base material. The flexibility of alloy design will be illustrated by examples of through hardening, high strength low alloy steels.
18. Properties of Heat Treated P/M Alloy Steels  Further development of ferrous P/M technology into highly stressed applications will require the development of P/M steels with mechanical properties approaching those of cast or wrought products. The P/M process offers many routes to improve mechanical properties through alloy design, increased density and high temperature sintering. The paper will present the results of a study into the effects of density and composition upon the microstructure and properties of quenched and tempered P/M alloy steels.
17. Sinter-Hardening Low-Alloy Steels The availability of prealloyed steel powders employing molybdenum as the major alloying element offers new levels of compressibility and mechanical properties. When the prealloyed powders are combined with conventional P/M additives such as copper, nickel and graphite, it is possible to develop high strength martensitic microstructures directly from the sintering cycle. The impact and tensile properties of copper, nickel, graphite premixes based upon the prealloyed molybdenum steels are compared under controlled cooled conditions. The ability to balance tensile strength, toughness and hardness by control of alloy chemistry is illustrated.
16. High Performance Ferrous P/M Materials Utilizing High Temperature Sintering  Several new and more challenging P/M applications require materials that exhibit higher strength along with improved dynamic property characteristics. To meet these requirements, development efforts focused on material grades capable of achieving high performance properties when sintered at elevated temperature. Several elements, specifically nickel and copper, were admixed to the water atomized, prealloyed low-alloy steel powders Ancorsteel® 85 HP and 150 HP using the patented ANCORBOND® process. Tensile and impact performance of the resulting materials have been reviewed along with quantitative metallography of selected as-sintered samples. The results indicate the type and amount of each admixed element plays an important role in achieving specific characteristics. In addition, the overall performance values are greater for the single press and sinter technique used in this investigation than could previously be achieved using a double press - double sinter process.
15. Surface-Hardenable Heat Treated P/M Steels The addition of fine particles (< 20µm) of high-carbon ferroalloys to the high compressible prealloy powders, Ancorsteel® 85 HP and Ancorsteel 150 HP, has been shown to be a practical way of producing ferrous low-alloy steels containing chromium and manganese. Increased sintering temperatures improved the mechanical properties of the materials and the effect was particularly noticeable at 2350°F.

The ferroalloy additions significantly enhanced the hardenability of the base low-alloys. Materials based on the low-alloy powder containing 1.5% molybdenum were more hardenable than those based on the 0.85% molybdenum alloy. These materials are well suited for plasma nitriding and should find use in gears and cams that require a hard wear-resistant surface coupled with a strong, tough core.
12. Improved Dimensional Control and Elimination of Heat Treatment for Automotive Parts The automotive industry has expressed concern about the general quality of heat treatment (austenization and quenching) and the desire to reduce or eliminate dependence upon this process whenever possible. Therefore, in a continuing effort for improvement during the past year, a process has been developed that eliminates the conventional heat treating operation for some applications. Some of these finished parts require both a high impact strength and a hardened wear resistant surface. The Charpy impact, tensile and TRS properties of a binder treated premix based on a partially alloyed powder have been evaluated utilizing a variety of processing conditions. These include various carbon contents, sintering temperatures and sintering times. Quantitative metallography was used to evaluate the pore size, pore shape and microstructural constituents present as a result of the various materials and processes. These factors were then correlated with the measured properties.
11. Tensile, Impact and Fatigue Performance of New Water Atomized Low-Alloy Powder - Ancorsteel 85 HP  A new water atomized, prealloyed powder has been developed containing 0.85% molybdenum as the alloying addition. The as-sintered and heat treated tensile, impact and fatigue performance have been determined for a range of graphite additions using both single and double pressing techniques. Results indicate that the new powder, Ancorsteel 85 HP, has a unique ability to be compacted and repressed to densities not attainable with existing prealloyed nickel-molybdenum powders. The higher densities achieved produce performance equivalent to or better than Ancorstee12000 or Ancorstee14600V using conventional single compaction techniques. However, the additional density increment achieved during repressing results in mechanical properties in excess of what is possible with the existing low-alloy steels. It is expected that the new prealloyed powder will be used in high-density applications requiring good hardenability. It will also provide a base for our high performance ferrous material development program.
7.  High Performance Ferrous P/M Materials: The Effect of Alloying Method on Dynamic Properties  A comparison has been made between fully prealloyed, partially prealloyed, and elementally admixed alloys in the "as sintered" condition in order to assess the influence of microstructural and chemical homogeneity on the tensile, impact, and fatigue properties. Elementally admixed and completely prealloyed powders were prepared with chemistry similar to that of the diffusion bonded Distaloy 4600A (nominally 1.8 wt. % Ni, 1.6 wt. % Cu, and 0.55 wt. % Ho). An addition of 0.6% graphite was made to each of these materials. In one series of experiments, test pieces were prepared from each of the materi`1als pressed to a green density of 6.9 g/cm3. Sintering was carried out at 2050°F for 30 minutes at temperature in a dissociated ammonia atmosphere. A second series of experiments was carried out in which a fixed compaction pressure of 45 tsi was applied to each of the materials. Sintering was carried out in a similar manner to the first series. An additional prealloyed material, Sumiron 4100S, was included in this second series of experiments. However, this material was sintered at 2300°F to reduce the tendency for oxidation of this chromium and manganese steel alloy. For the samples pressed to a fixed green density of 6.9 g/cm3, the tensile strength of the partially prealloyed material was significantly higher than the other materials. The impact energy of the partially prealloyed material was also higher. A similar trend was found for the samples pressed at a fixed compaction pressure of 45 tsi. The partially prealloyed product, sintered at 2050OF, was even superior to the Sumiron 4100S; sintered at 2300°F. The differences in the tensile and impact properties were significant at the one percent level. The rotating bending fatigue performance of the partially prealloyed material was superior to that of the Sumiron 4100S.
4.  Ferrous Powders - How Alloying Method Influences Sintering  The mechanical properties of P/M materials are directly related to their microstructure and the size, distribution, and morphology of the porosity they contain. Alloying additions are made to develop specific material performance characteristics. However, the manner in which the alloys are constituted has a significant effect on the porosity and microstructure of the final sintered product (1,2).
3.  Fatigue Properties of P/M Materials  The tensile properties and fatigue endurance limits of several widely used P/M steels have been tested. Statistical estimates of the 99.9% survival stress have shown that fatigue endurance ratios can vary from 0.16 to 0.47. Thus the use of 0.38 as a rule of thumb for estimating the fatigue endurance limit from static tensile property data can result in large errors. The single most effective method of improving fatigue properties is to increase the part density. Fractographic observations were made on some of the fatigue failures, including stable and unstable crack growth.
1.  Impact and Fatigue Characterization of Selected Ferrous P/M Materials  Dynamic property data on pressed and sintered ferrous powder metallurgy materials have come under increasing demand as the P/M industry has grown into areas of application involving more highly stressed components. Data collected from relatively simple dynamic property tests will provide new avenues for P/M alloy development. Un-notched Gharpy impact energy and rotating bending fatigue tests have been used to characterize commonly used P/M steels. The endurance ratios of porous steels have been found to be relatively insensitive to processing, with higher strength materials giving proportionally higher endurance limits. Since impact energy was not strongly affected by varying the carbon content up to the eutectoid composition, increasing the carbon content of low alloy steels is a viable way of increasing endurance limit. Impact energy transition temperature has been found to be a factor in carbon-free phosphorus steels, but not in conventional low alloy steels. As has been indicated in the literature, sintered density is crucial to both impact energy and fatigue endurance limit. Metallographic examination of the fatigue cracks has provided some insight into the nature of the R.B.F. test.


Home | Structural Parts | Chemical | Atomized Unalloyed Steel | Atomized Low Alloyed Steel | Public Technical Seminars | MPIF Conference | SAE | Press Releases | Technical Library by Topic | F.A.Q. | Related Resources | Sitemap

© 2010 Hoeganaes Corporation. All Rights Reserved.

1001 Taylors Lane • Cinnaminson, NJ 08077-2017 • USA • 856-829-2220