Effect of Al target power density on tribological properties of (Ti, Al)N coatings

(Ti, Al)N coatings with different Al target power densities on the surface of M2 high-speed steel were deposited by magnetron sputtering to study the tribological properties. The phase composition, microstructure, and element distribution of coatings were characterized by x-ray diffraction, field emission scanning electron microscopy, x-ray photoelectron spectroscopy, and energy dispersive spectrometry. The results showed that the tribological properties of the coatings were closely related to the power density of the Al target. With a gradual increase in the Al target power density, the microhardness increased from 1324.7 to 2819.2 HV. Meanwhile, when Al target power density was 7.9 W/cm2, the coatings exhibit the lowest coefficient of friction (COF = 0.23). By comparison, it was found that (Ti, Al)N coatings exhibited a smooth surface, uniformly dense columnar structures, and smaller grain sizes due to the addition of Al atoms. (Ti, Al)N coatings showed a unique microstructure that determined their excellent tribological properties.