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Development of new PM materials and processes during the last decade has led to an increased use of PM components in automotive applications. To maintain its competitiveness towards other manufacturing techniques, the PM industry must continue to combine high demands on mechanical properties with maintained or even improved close tolerances of the sintered components in a robust, reliable and cost effective way. As the PM technology offers a wide selection of alloys that can be processed under a variety of conditions it is of outmost importance to know the influence of each on the both performance and robustness of the PM part to secure a reliable function in the final application. In this paper the influence of material and processing conditions on dimensional tolerances and reliability are discussed. A case study is presented describing results from manufacturing of belt pulleys in a state-of-the-art hydraulic press.

The past decades have seen a continuous growth of the use of PM parts in automotive applications. However, the performance requirements the components must meet are more and more demanding. Transmission gears for automotive applications are complex in shape and require both very high geometrical accuracy in terms of gear quality and very high mechanical performance in terms of durability of tooth flank and root. Powder metallurgy is very cost effective for complex shaped parts and by adding a selective densification of the teeth the accuracy and mechanical performance requirements can be met at a very low added cost. In this paper a process route consisting of compaction, sintering, surface densification by rolling and finally heat treatment have been studied to assess the feasibility of producing transmission gears by powder metallurgy. Helical and spur gears were used in the study where the densification as well as the resulting gear quality and durability were tested.

Planetary gears in heavy truck gearboxes are normally manufactured by forging a blank, turning, hobbing, shaving and heat-treatment followed by grinding. Due to the size of the gear the net shape capability of PM methods can be cost effective alternatively to conventional manufacturing. Warm compaction and surface densification are two PM methods to reach high density and thereby high strength and fatigue properties. Typical characteristics for PM gears manufactured by these methods are outlined.

Powder Metallurgy (P/M) is an increasingly viable alternative for applications requiring high material performance. Continuous advances in alloy systems and processing techniques, combined with powder metallurgy's ability to produce complex net shapes, have made it possible for powder metallurgy to compete with other technologies in engine and transmission applications. This paper will focus on new alloy systems and advanced processing techniques. The properties achievable with currently available materials, such as chromium containing materials, combined with advanced processing techniques, such as warm compaction and surface densification, will be presented. Additionally, a case study where a warm compacted synchronizing latch cone in a heavy duty truck transmission was found to have equal or superior performance to precision forged and powder forged latch cones.

Warm Compaction of Densmix™ powders provides means to produce P/M parts with densities in the range of 7.1 to 7.4 g/cm3. As most properties are improved by increased density, the warm compaction method offers possibilities to increase the competitiveness of P/M compared to other manufacturing techniques. In this paper a comparison of material properties obtained by two different manufacturing routes is presented. Heat treated properties of some P/M steels after double pressing/sintering are compared with properties obtained with sinterhardening and conventional heat treating of warm compacted Densmix™ powders. Additionally, the single tooth static rupture force and the single tooth bending fatigue strength will be presented.

High performance P/M prototype gears made by high velocity compaction (HVC) and sinter-hardening has been experimentally investigated with respect to mechanical properties. Experiments were conducted on high density sinter-hardened planetary gears made of Astaloy CrM and D. DH-1. The high velocity compacted prototype gears, compacted to a density of 7.5 g/cm3, were compared to reference gears representative for conventional processing routes that leads to densities up to 7.1 g/cm3. As a result of increased density, the high velocity compacted and sinter-hardened planetary gears showed significantly improved hardness and static tooth strength compared with conventionally compacted and hardened planetary gears.