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This paper presents the progress in Powder Metallurgy (PM) Gears, including examples of how to combine the disciplines of materials-, design- and process technology to push the limits towards increased performance, reduced weight, energy consumption and total manufacturing cost. Advancements in materials and manufacturing technology for PM gears will be presented as well as the result from simulations and reverse engineering work on existing automotive transmissions. The results from this work show that the amount and type of load on the individual gears in auto transmissions are very different and this gives room for optimized selection of material and manufacturing process.

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.

Ferritic stainless steel 409L and ferritic-martensitic stainless steel 409LNi, made via powder metallurgy (P/M) process, are being increasingly used for the manufacture of automotive exhaust flanges and oxygen sensor bosses. High temperature, hydrogen sintering is most commonly utilized for the manufacture of these components, with an aim to achieve a minimum sintered density of 7.25 g/cm3. Alloy 409L is a fully ferritic material, exhibiting a hardness in the range of 55 to 62 HRB. Alloy 409LNi, on the other hand, possesses a 50/50 ferritic-martensitic microstructure, and exhibits a hardness in the range of 85 to 92 HRB. Some amount of machining, such as thread cutting, drilling and turning, is often required in the processing of these components. This study evaluates the effects of adding a machinability enhancing agent, namely manganese sulfide, on the machinability, as well as on the corrosion resistance and mechanical properties of these alloys.

Conventional forged and powder forged connecting rods (con-rods) for automotive engines have been a successful application for an appreciable amount of time. In recent years several powder metallurgy (P/M) processes have been proposed to eliminate the need for forging, for example heat treatment after sintering or double compacting - double sintering./1/ A new P/M alloy which achieves a density of nearly 7.2 g/cm3 using a Warm Compaction process has been developed. This alloy has high fatigue strength, and high Young's modulus as compared to conventional P/M alloys and processing (single press - single sintering). The new alloy also has machinability as good as wrought steel as determined by a drilling test. Con-rods made from this alloy, employing the Warm Compaction processes, were evaluated. Weight was almost the same as compared to conventional forged con-rods intended for three-cylinder engines.