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The use of P/M stainless steel components in automotive exhaust systems continues to grow rapidly. These P/M components have met the stringent requirements demanded for these applications which were formerly only provided by wrought materials. These high density components are being required to pass specific qualification tests designed by OEM's and Tier 1's - Galling, Hot Vibration Leak and High Temperature Oxidation/Corrosion Tests. This paper discusses the performance of P/M stainless steel exhaust flanges and HEGO bosses in a number of OEM and Tier 1 specified performance tests.

Property test data shows 434 stainless steel material, with and without nickel additions, to be a desirable material for exhaust system component applications. The material provides a good balance of corrosion and oxidation resistance, impact strength, and tensile strength compared to other 400 series stainless steel powder metal (P/M) materials. Addition of nickel to standard 434 greatly improves many physical properties with a slight increase in cost. Parts with densities between 7.2 and 7.5 g/cc offer the best combination of properties versus process economics. The processing costs to achieve high densities are minimized when the parts are sintered at temperatures at or above 2400°F, thus eliminating the need for a secondary operation such as coining or heat treating.