Influence of the Al content on mechanical properties of CVD aluminum titanium nitride coatings

Fcc-AlTiN coatings deposited by PVD are widely used in the market. Fcc-AlTiN is a metastable phase with excellent properties such as high hardness, high oxidation resistance and high cutting performance. The deposition of single phase fcc-AlxTi(1 − x)N with higher than x = 0.7 by PVD have not been reported, because AlTiN coatings with higher x-values contained softer hexagonal wurtzite phase. Al-rich fcc-AlxTi(1 − x)N(x > 0.7) coatings deposited by thermal CVD process have been developed in the last decade. It was reported that these fcc-AlxTi(1 − x)N(x > 0.7) coatings were much superior to PVD-AlTiN coatings in cutting tests. In this work, influence of x value (x = 0, 0.31, 0.62, 0.73, 1.0) on mechanical properties of AlxTi(1 − x)N coatings by thermal CVD process was investigated. The deposited CVD-AlxTi(1 − x)N coatings were characterized by X-ray diffraction, scanning electron microscopy, nano-indentation and adhesion measurements. Except for CVD-AlxTi(1 − x)N with x = 1.0, CVD-AlxTi(1 − x)N coatings (x = 0, 0.31, 0.62, 0.73) with single phase fcc-AlTiN were obtained and every deposited coating was composed of fine-grained granular structure. CVD-AlxTi(1 − x)N with x = 0.73 showed the highest hardness and adhesion property.