RF Plasma Nitriding of AISI 304 Stainless Steel

Abstract

Austenitic stainless steel AISI 304 was nitrided in a low-pressure RF plasma using pure nitrogen. With a treatment of time of 4.0h at 400oC, the nitrogen-rich layer on the sample was 3 mm thick and had a hardness of approximately 4.4 times higher than that of untreated material. XRD data showed that as the process temperature rose from 350~450oC, the expanded austenite peaks became more prominent while the austenite peaks became weaker. Expanded austenite was transformed to ferrite and CrN at the treatment of 500oC. Langmuir probe measurements showed that electron density decreased above 450oC.