Improvement of Wear and Corrosion Resistance of Austenitic Stainless Steel by Combined Treatment using Electron Beam Cladding and Subsequent Gas Nitrocarburizing

The high passivation capacity of austenitic stainless steels results in excellent corrosion resistance in a wide variety of corrosion media. However, the tribological properties of these steels are insufficient due to their low hardness and high susceptibility to adhesive wear. To improve the wear behavior of austenitic steels while maintaining corrosion resistance, thermochemical processes such as nitriding or nitrocarburizing can be used. Such processes can be carried out as single procedures or in combination with coating techniques. Herein, the results of a new combination treatment consisting of the electron beam cladding (EBC) of a Co-based alloy with subsequent gas nitrocarburizing (GNC) are presented. The effects of the beam deflection technique on the microstructure and phase formation of the cladded wear protection layer, the resulting hardness as well as the dilution ratio and the bonding of this layer to the base material are demonstrated. The subsequent gas nitrocaburizing leads to the formation of an approximate to 10 mu m-thick surface layer enriched with nitrogen and carbon. The significant improvement in wear resistance compared with the untreated base material is demonstrated by abrasive and adhesive-abrasive wear tests. Corrosion resistance is investigated by recording current density-potential curves and long-term tests in corrosive media.