Effect of nitrogen on the plasma (ion)-carburized layer of high nitrogen austenitic stainless steel

Abstract

Austenitic stainless steel or high nitrogen austenitic steel are used extensively as structural non-magnetic materials. The former, because of their low surface hardness, have low wear resistance. Recently developed plasma (ion)-carburizing improves the surface of austenitic stainless steel by removing the oxide scale. In contrast, high nitrogen austenitic stainless steel are expected as wear-resistance material because the hardness is higher than that of conventional austenitic stainless steel.In this study, two kinds of austenitic stainless steel were plasma (ion)-carburized in an atmosphere of CH4+H2 plasma at 1303 K for 14.4 ks. The metallurgical characteristics were then investigated using XRD (X-ray diffraction method), OM (optical microscopy), hardness testing, glow discharge optical emission spectroscopy (GDOES) and a scanning electron microscopy (SEM).The results show that the plasma (ion)-carburized low nitrogen austenitic stainless steel had the layer with structure similar to the common austenitic stainless steel. The plasma (ion)-carburized high nitrogen austenitic stainless steel had the carbide layer at the top surface, carbide dispersed layer in the matrix, and then lamellar structure of carbides toward the inner layer.