The Effect of Ion Nitriding on the Residual Stress of the Nitrided Layer on Austenitic Stainless

Abstract

Low-temperature ion nitriding has an excellent performance in improving the surface hardness and wear-resistant of stainless steel by forming the nitriding layer, which can strike a balance between corrosion resistance and wear resistance. In the case of a common treatment temperature of 430°C, for example, after applying ion nitriding for 24 hours in this experiment, the surface hardness of stainless steel increased from 330-360 HV to 1250-1330 HV, and the thickness of the formed nitrided layer was approximately 11-15 μm. Since the nitriding process generated compressive stress on the surface of the material, the residual stress was measured from the surface of nitride layer to the substrate in thickness direction using the Pulstec μ-X360n Residual Stress Analyzer. The residual stress value decreased from -913MPa to -124MPa. When the nitriding temperature exceeded 450°C, the lattice expansion was caused by structural changes. This change would result in the generation of chromium nitride on the surface. The residual stress increased significantly, leading to the rupture of the nitrided layer on the surface. This behavior decreased the corrosion resistance. Furthermore, in this study, the effect of the nitrided layer on the abrasion and residual stresses was investigated. Here, the nitride layer was formed on the surface of 304 and 316 austenitic stainless in different temperatures and treatment times with fixed gas ratios.