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The P/M industry is being challenged with increasingly demanding applications requiring high mechanical strength as well as very high dimensional stability. Synchronizer hubs, sprockets and gears are examples of such applications in the automotive industry. The dimensional stability of P/M sintered parts is influenced by a number of factors including the powder mix formulation, the selection of additives, the blending procedures, the handling, compaction, sintering and post-sintering operations. A study was conducted to evaluate and quantify the effect of a few of these factors, namely the mix formulation and type of additives on the dimensional stability of parts made with high performance materials. Statistical tools were used to identify the significant parameters affecting the dimensional stability and quantify their effects.

Although powder metallurgy (P/M) is a cost attractive route to manufacture near net shape complex parts, many P/M components require machining to meet tight dimensional tolerances or accommodate design features that cannot be molded during compaction. With the development of high performance materials having high strength and apparent hardness in the as-sintered condition, green machining is becoming an important issue to maintain the competitiveness or extend the use of P/M technology. Machining of green P/M parts can be made feasible if the strength of the part is high enough to enable the clamping and machining of the component. Therefore, the use of specific techniques to improve strength and allow machining of un-sintered P/M parts are worthy avenues to reduce machining costs. This paper describes various routes that increase green strength of P/M components and make feasible green machining.