2017 Volume 56 Issue 6 Pages 352-360
A low temperature plasma carburizing process can produce an expanded-austenite layer (generally called the S phase), which has high hardness and corrosion resistance at the surface of austenitic stainless steels. We have investigated S phase formation behaviors by using a combined process of active screen and DC plasma carburizing for austenitic stainless steels such as JIS SUS304 and 316 with the aim of developing a highly effective and efficient production technique. The influence of carburizing parameters (processing temperature, time, gas atmosphere, etc.) on the formation of the S phase was studied in terms of thickness, hardness, carbon concentration, lattice constant, and residual stress. The mechanical properties and corrosion resistances of the obtained S phases were also evaluated by using a ball-on-disk test and a salt spray test (SST). The results show that S-phases produced efficiently by the combined process under a condition of 733 K and a 10.5 vol% of CH4 gas ratio have both excellent wear and corrosion resistances.
