Plasma diffusion treatment and duplex treatment recent development and new applications

Plasma diffusion treatment (PDT) is one of the most promising methods for improving both the surface and the near-surface properties. The duplex treatment combining the plasma diffusion with PVD or PACVD provides an excellent method for achieving optimal properties of the surface and the near surface and allows the design of a layer system to meet the increased demands of functional surfaces. In the present review, recent investigations of the plasma diffusion treatment of ferrous and non-ferrous materials are reported. For austenitic steel, Ti alloys, Co base alloys and Cr coating, plasma diffusion treatment has been carried out. In the case of austenitic steel, processes are optimized to achieve improved wear resistance, retaining the excellent corrosion resistance of the steel. While the wear resistance and the friction properties were mainly of interest for stellite 6B, in addition the corrosion resistance has been investigated for Cr coating on steels after plasma diffusion treatment. The Ti alloy TiA16V4 showing a gradient layer system after plasma nitriding has been duplex treated by adopting PACVD. The microstructure, wear and friction as well as corrosion behaviour have been investigated and the results of biocompatibility testing are presented briefly.