Synthesis and Optimization of Ti–TiN multilayered protective nanocoatings on Zr-based bulk metallic glass

Monolithic TiN and Ti–TiN multilayer nanocoatings with a period thickness Λ in the range of 5–60 nm have been deposited on Silicon substrate by means of RF sputtering technique at room temperature. The influence of nitrogen partial pressure on the microstructural and morphological properties of TiN coatings has been monitored by grazing X-ray reflectivity and atomic force microscopy. We have observed that an increase of nitrogen partial pressure decreases the roughness and the grain size of TiN deposited coatings. For the multilayer with a period of Λ = 5 nm, we have found a significant improvement of the hardness (32 GPa) and the elastic modulus (263 GPa). Moreover, the friction coefficient value decreased, while the normal load necessary to be in the ploughing regime increased with decreasing Λ. Ti–TiN multilayer films with an optimised Λ value were deposited on Zr60Ni10Cu20Al10 bulk metallic glass. These coated samples show a significant enhancement of both the hardness and elastic modulus and a decrease of the friction coefficient. The Bhowmick model description was used to deduce analytic expressions of the shear stress τ. This allows us to predict the variation of τ as a function of the tip penetration depth. The effect of film total thickness was studied.