Surface engineering of austenitic stainless steel

The inherent poor tribological behaviour of austenitic stainless steels has been a barrier to their wider application under corrosion wear conditions. Therefore, researchers have long dreamt of developing new technologies to enhance the wear resistance of stainless steel surfaces without loss of their attractive ‘stainless’ characteristics. For example, the discovery of low temperature plasma nitriding in the mid 1980s allowed a new phase with a high hardness and good corrosion resistance to be produced on austenitic stainless steel surfaces. Since then much research and development has aimed to combine improvements in wear, corrosion and fatigue properties. This has been demonstrated by various low temperature surface alloying processes (including plasma, ion beam, gaseous and salt bath methods) and increasing numbers of academic publications, reflecting rapidly expanding niche markets in the food, chemical, nuclear and medical sectors. In this paper, the historical evolution and development of low temperature thermochemical surface alloying processes are overviewed. The research and development of low temperature surface alloying of austenitic stainless steels in an attempt to combine improvements in wear, corrosion and fatigue properties are also assessed. Finally, new directions and key areas for future development are identified and discussed.