Active screen plasma nitriding of austenitic stainless steel

Abstract

Active screen (AS) plasma nitriding is a new surface engineering technique which provides many advantages over conventional dc plasma nitriding. In this study the AS technique has been used to nitride austenitic stainless steel (AISI 316). The morphology, composition and properties of the AS plasma nitrided layers have been characterised and compared with those of the normal dc plasma nitrided layers. AS nitriding can achieve similar hardening effects for austenitic stainless steel when compared to conventional dc nitriding, and does not have the common problems associated with the dc technique such as ‘edging effect’. AS nitriding at a lower temperature of 420° C can also produce a precipitation free layer, the S phase, on a 316 stainless steel surface. The AS nitrided S phase exhibits not only high hardness and wear resistance but also very good corrosion resistance.