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.