Surface modification of austenitic thermal spray coatings by low-temperature nitration

Thermal spray coatings of austenitic materials are mainly used under corrosive conditions. The relatively poor wear resistance strongly limits their use. A selective enrichment of the surface layer region with nitrogen by means of thermochemical heat treatment improves the residual stresses and increases the wear resistance. The interstitially dissolved nitrogen causes the expression of strong compressive residual stresses and high surface hardness. The low process temperature of the thermochemical heat treatment avoids the precipitation of chromium phases. Increases in the service life of existing applications or new material combinations with face-centred cubic friction partners are possible. In the absence of dimensional change, uniform as well as partial nitrogen enrichment of the thermal spray coating is possible. The influence of the nitrogen enrichment on the coating properties and the microstructure was investigated. Nitrated coatings demonstrate a significant improvement in adhesive wear resistance and extremely high surface hardness.