Effects of Heat Treatment Conditions on Formation of Expanded-Austenite Phase in Austenitic Stainless Steels by Combining Active Screen and DC Plasma Carburizing Processes

Abstract

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 ef cient production technique. The in uence 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 ef ciently by the combined process under a condition of 733 K and a 10.5 vol% of CH 4 gas ratio have both excellent wear and corrosion resistances.

Study of the Thermochemical Surface Treatment Effect on the Phase Precipitation and Degradation Behaviour of DSS and SDSS

“…For instance, DSS corrosion behaviour can be adversely affected under high temperature processes such as welding. As a result, microstructural rearrangement can significantly decrease corrosion resistance and some mechanical properties relevant for specific applications [2,[7][8][9][10][11].…”