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Requirements for automotive exhaust system components include room temperature and elevated temperature mechanical integrity, oxidation resistance, corrosion resistance, and weldability. Powder metallurgy offers sufficient flexibility with material and process selection to meet these challenges. This presentation will cover the effects of alloy composition, density, and process parameters on the performance of P/M S.S. components in O.E.M. specified thermal, mechanical, and corrosion tests.

Evaluation of commercial high temperature H2-sintered 410L ABS sensor rings, after use for over 10 years and/or over 100,000 miles in various automobiles and in various locations across the USA and Canada, showed only small amounts of rusting; less than which results in a 100-hour Salt Spray Test (ASTM B117); and no loss of their mechanical strength and ductility. Although sensor rings made of 434L and 434L-Modified (18 Cr, 2 Mo) show even lesser amounts of rusting and pitting, 410L sensor rings made by the above process are deemed adequate for this application. The 1000-hour Salt Spray Test is found to be much too severe for this application. A 100-hour test is considered to be more suitable in this regard.

Powder Metallurgy (P/M) offers a cost-effective and design-friendly option for the manufacture of stainless steel hot exhaust gas oxygen sensor (HEGO) bosses for automotive exhaust systems. The critical requirements for this application include high temperature mechanical strength, good corrosion resistance, weldability, machine-ability for thread tapping, and resistance to thread galling when exposed to temperatures as high as 1000°C (1832°F). Optimally processed P/M 400-series stainless steel oxygen sensor (HEGO) bosses meet these critical requirements, and are comparable to those made from wrought stainless steel, either cold headed or machined.