Effects of TiN sublayers on the response of TiSiN nanocomposite coatings to nanoidentation and scratching contacts

The effects of introducing thin-TiN sublayers into TiSiN nanocomposite coatings on the deformation mechanisms imparted by both uni-axial indentation and scratch contacts were evaluated by examining cross-sections of the deformed samples. Nanoindentation testing shows that the monolithic TiSiN coating is much harder than the monolithic TiN. The indentation hardness of the multilayer samples increased with the thickness of the TiSiN sublayer in the TiSiN/TiN multilayer coatings. The density of catastrophic cracks in the coatings was largely reduced when relatively ductile TiN sublayers were introduced to form the TiSiN/TiN multilayers, as a larger portion of deformation is accommodated within them. It was observed that some of the TiN grains extended into the neighboring TiSiN sublayers. The orientation of these grains helped to inhibit the growth of cracks. To summarize, the TiN sublayers helped to maintain the structural integrity by reducing the degree of catastrophic damage in the harder TiSiN sublayers.