Effect of Si and Cr Doping on Microstructure and Tribological Properties of TiAlN-Based Coating

With Ti_0.5Al_0.5, Ti_0.5Al_0.4Cr_0.1 and Ti_0.5Al_0.4Si_0.1 as target materials, TiA1N coating, TiAlSiN coating and TiAlCrN coating were prepared by arc ion plating technique. The effects of doping of Si and Cr with almost the same amount on the microstructure, mechanical properties and tribological properties of TiAlN-based coatings were investigated. The results show that the TiAlN coating, TiAlSiN coating and TiAlCrN coating had compact structure, well combined with the substrate, grew in columnar crystal, and exhibited a preferential orientation of (200) plane. Si and Cr doping made the grain of the coating finer. Si₃N₄ amorphous phase formed by Si doping inhibited the growth of (Ti,Al)N nanocrystals, and the TiAlSiN coating had the smallest grain size. The Si and Cr doping could improve the hardness and internal stress of the coating, and the Si doping had a higher improvement effect. The Si and Cr doping reduced the ratio of hardness to elastic modulus and adhesion force of the coating, and the reduction degree was larger after Si doping, indicating that TiAlSiN coating had the worst toughness. The doping of both Si and Cr could reduce the friction coefficient and wear rate of TiAlN coating.The friction cofficient decrease degree after Si doping was higher than that after Cr doping, and the wear rate decrease degree was lower than that after Cr doping.