Studies on mechanical properties of titanium aluminium nitride coatings

Vickers and Knoop microhardness studies have been carried out on titanium aluminium nitride (TiAlN) hard coatings deposited on WC-12Co substrates. The microhardness test has been studied as a function of applied loads varying from 0.49 to 9.8 N. The normal indentation size effect has been observed in Vickers and Knoop microhardness test. It follows that increase in microhardness at lower loads (up to 9.8 N) depends inversely on elastic modulus of the hard coatings. Knoop microhardness test shows that microhardness values decrease with increase in applied load. The elastic stiffness constants have been calculated using Wooster's empirical relation. Young's modulus is found to be 378.18 GPa. Also hardness anisotropy has been performed with respect to the orientation of the TiAlN coatings from Knoop microhardness test. Morphology of indented imprints of the coatings has been examined using scanning electron microscopy. (author)