Effect of Ti/TiN multilayer protective nanocoatings on Zr-based metallic glasses mechanical performance

Abstract : Ti/TiN multilayer and monolithic TiN nanocoatings have been deposited on Zr-based metallic glass substrates by means of RF sputtering technique at room temperature. Nanoindentation and nanoscratch tests are used to characterise the mechanical and tribological properties of coated samples. In addition, a Vickers indentation tests and scanning electron microscopy observation have been carried out to explore the deformation mechanism. When coated with the TiN and Ti/TiN multilayers, Zr₆₀Ni₁₀Cu₂₀Al₁₀ bulk metallic glass shows a significant enhancement of both apparent hardness and elastic modulus with a decrease of the friction coefficient. The Vickers indentation shows a fragile behaviour of TiN coatings compared to the Ti/TiN multilayer one. Based on Bhowmick model description, experimental nanoindentation approach is taken to determine the variation of shear stress as function of the penetration depth. It is found that the shear stress developed in the TiN coatings is higher than that observed in the Ti/TiN multilayer. A correlation between finite-element analysis results and experimental data has been proposed. The monolithic or multilayer type of coatings is found to have an influence on the stress and plastic deformation distributions.