Effects of tungsten doping on mechanical properties and tribological behavior of TiB2 coatings in contact with titanium alloy counterballs

Abstract

Element doping serves as a crucial strategy for surface modification of TiB₂ coatings, improving the toughness, mitigating the residual stress and reducing the coefficient of friction of the coatings. Tungsten(W)-doped TiB₂ coatings were deposited by magnetron sputtering with adjusting the working current of W target. The chemical compositions, microstructure, mechanical properties and tribological performance of the coatings were systematically investigated using EPMA, SEM, XRD, XPS, TEM, indentation tests and ball-on-disk tribometer. The results reveal that W doping weakens the crystallization of the TiB₂ coatings. As the concentration of W increases, the content of TiB₂ phase in the coatings decreases and that of WB₂ phase increases. However, when the W concentration increases to 15.1 at.%, the content of WB₂ in the coatings decreases again. The W element in the coatings mainly exists in the form of amorphous WB₂ phase. The 10.7 at.% W-doped TiB₂ coating demonstrates an optimal toughness and a moderate adhesion strength. W doping exhibits no statistically significant improvement in adhesive wear performance of the TiB₂ coating at room temperature. However, the W-doped TiB₂ coatings exhibit an improved anti-adhesive wear resistance at 600 °C, which is correlated with the presence of amorphous WB₂ phase.