Thin TiN coating on NiTi substrate through PVD method: improvement of the wear resistance

The preparation of a thin hard coating is the main challenge in the coating of NiTi articles. To achieve a thin coating of titanium nitride (TiN) on NiTi substrate, physical vapour deposition (PVD) was proposed in this study. Deposition of TiN coating was carried out at the nitrogen flows of 0.79 and 0.93 Pa. Phase composition, thickness, porosity, adhesion strength, hardness, and tribological properties of the TiN coatings were evaluated. The adhesion of the coating to the substrate was acceptable. Increasing of the gas flow resulted in a higher thickness (1 & mu;m), lower porosity and higher adhesion strength. On contrary, the samples prepared with the lower gas flow showed higher hardness and elastic modulus. The coated samples showed smaller width of wear, lower wear rate and lower friction coefficient in comparison to the substrate. The delamination and adhesive wear mechanisms govern the wear process.