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Powder Metallurgy (P/M) stainless steel automotive exhaust flanges are in volume production. However competing technologies continue to improve and may threaten the anticipated increase in applications of P/M stainless steel flanges. This paper examines improvements in powder propeties that should improve the processing and perfomance of P/M stainless steels.

Several applications for powder metallurgy (P/M) produced stainless steel exhaust components have been approved and are in production today. Many more stainless steel parts, both ferritic and austenitic, are in the final qualification stages. This paper will review the performance and economic criteria employed by automotive companies and exhaust manufacturers in sourcing exhaust coupling flanges and oxygen sensor bosses. Also, the performance record of the components in service to date will be reviewed. Finally, the advantages of P/M steel parts versus competing metal working industries (i.e. cold stamping, cold heading, screw machining) will be detailed.

Due to recent developments in ferrous powder metallurgy, production of high performance parts has become more cost competitive. Advances in high performance materials have provided high strength in as-sintered components. With recent technological developments, high density parts (>7.3 g/cm3) can be fabricated with a single compaction process that also provides green strengths significantly higher than obtained with traditional processes. Properties obtained with these materials are described and the use of Mn and Cr as alloying elements are reviewed. Machining high performance P/M materials is difficult. A method of green machining P/M components by taking advantage of the material's high green strength is introduced.