Mechanical Properties and Corrosion Resistance of PM High Nitrogen Stainless Steel Consolidated by Hot Extrusion

Abstract

High nitrogen stainless steels (HNSS) were produced through powder metallurgy (PM) route by hot extrusion, using nitrided stainless steel powders which had the original chemical compositions corresponding to TP410 and TP316L. Low pressure nitriding was given to powders put in a can, which was followed by encapsulation. The capsules were successfully hot extruded to straight bars by the Ugine-Sejourne method. An alternative experiment was conducted to study the characteristics of low pressure nitriding along with the production of HNSS. Consequently, it was found that nitrogen contents of martensitic and austenitic stainless steels can be controlled by the Sieverts raw up to the nitrogen contents for precipitation of Cr nitrides. The consolidated TP410 with nitrogen content of 0.34 % showed better mechanical properties and corrosion resistance than conventionally produced TP410, while austenitic TP316L with nitrogen content of 0.56 % including Cr nitrides exhibited poor pitting corrosion resistance. It was, however, demonstrated that excellent corrosion resistance could be achieved by employing solution temperatures higher than the conventional ones.