16.05.2007 Pressing & Sintering

Optimization of Corrosion Resistance and Machinability of PM 316L Stainless Steel

Austenitic stainless steels offer significantly superior corrosion resistance, when compared to ferritic and martensitic stainless steels. Austenitic stainless steels are however difficult to machine. Austenitic alloy 303L is formulated with a small sulfur addition, which leads to the formation of MnS precipitates in the matrix. Presence of MnS in the alloy does lead to improved machinability. Alternately, it is possible to add a machinability enhancing additive, such as MnS or MoS2 to a standard grade of stainless steel in the powder form in order to improve its machinability. Unfortunately, the presence of a sulfide in an austenitic stainless steel significantly lowers its corrosion resistance. Hence, neither of these options makes it possible to combine good corrosion resistance with good machinability.  This study evaluates a sulfur free additive for enhancing machinability of PM 316L, along with its effect on the corrosion resistance of the alloy. Two currently popular additives, namely MnSE and MoS2, are also included in the study for comparison. The new additive is found to offer enhanced machinability without any adverse effect on the alloy’s corrosion resistance. All sintering was carried out under conditions that maximize corrosion resistance. Machinability was determined by drilling.