[en] Special environment requires the parts in the core of water-cooling nuclear power reactors to have good corrosion resistance and high surface wear resistance. Stainless steel and nickel base alloys have good corrosion resistance but their hardness and wear resistance are low. This technical challenge can be addressed by low temperature nitriding or carburizing to produce carbon and/or nitrogen supersaturated expanded austenite (i.e. S-phase) with high hardness, high wear resistance and good corrosion resistance. This paper mainly overviews the development, the microstructure, the unique combination of attractive properties and the application prospect of low temperature S-phase surface treatment of stainless steel using gas, plasma and salt bath mediums. The microstructure, hardness, wear resistance and corrosion resistance of S- phase are analyzed and evaluated. (authors)