Thermal stability and wear resistance of hard TiN/TiCN coatings on plasma nitrided PH15-5 steel

In the present work, we performed a case study of the wear resistance of 3μm thick film systems consisting of TiCN single-layer and TiN/TiCN double-layer structures deposited by electron beam evaporation onto plasma-nitrided PH15-5 steel. We particularly focused on the wear resistance of the duplex-treated (nitriding+deposition) coatings before and after annealing at 1123±3K using a ball-on-disk tribometer. We found that the plasma-nitrided layer prepared in a dual-mode microwave-radiofrequency discharge improved the wear resistance by nearly one order of magnitude compared to untreated steel (wear volume of 0.9±0.2×10−6mm3 compared to 8.7±0.2×10−6mm3). In addition, the experiments showed that the nitrided-layer between the steel and the hard coating acts as a diffusion barrier which maintains the wear resistance of the duplex-treated coatings composed of TiCN or TiN/TiCN layers.