Material condition tailored to plasma nitriding process for ensuring corrosion and wear resistance of austenitic stainless steel

Abstract

Austenitic stainless steel is equipped with an excellent corrosion resistance, whereby plasma nitriding of austenitic stainless steel principally results in a high hardness associated with an excellent wear resistance. Whenever a high wear resistance accompanied by the existing corrosion resistance of austenitic stainless steel is required, the application of plasma nitrided stainless steel is restricted. The research goal is maintenance of the wear resistance with the least possible loss of corrosion resistance. In the present study AISI 304 austenitic stainless steel was plasma nitrided in a range of temperature from 325°C to 550°C. Examinations revealed that in addition to treatment temperature, time, pulse ratio and the ratio of gas mixture affected the corrosion resistance of plasma nitrided austenitic steel. Results of microhardness tests and potentiodynamic polarization tests showed that an enhancement of corrosion resistance in addition to preservation of hardness is possible. A reduction of plasma power as well as the addition of argon to the process gas induced an increase of the corrosions resistance with just a slight drop in hardness. Characterization of the chemical composition was determined by glow discharge optical emission spectroscopy (GDOS). Phases of expanded austenite were detected by XRD analysis.