Influence of Ti-TiN multilayer PVD-coatings design on residual stresses and adhesion

Multilayer systems can offer an efficient way of controlling residual stress, improve adhesion and enhance toughness of coated systems. This work aims at the development of multilayer coating with improved adhesion, based on numerical design approach. The numerical model of titanium-titanium nitride (Ti-TiN) multilayer has been formulated with multi-physics FEM, to find the optimal thickness of individual layers in a multilayer that can decrease interfacial axial and in-plane shear stress. These coatings configurations are experimentally produced to quantitatively evaluate the scratch adhesion, in-plane residual stresses, nanoindentation hardness and elastic-modulus. Analytical modeling with FilmDoctor (R) was performed for accurate adhesion evaluation. The multilayer in comparison with bi-layer shows significant improvement (22%) in adhesion under decreased interfacial stress conditions without any affect on overall coating stiffness and hardness. The multilayer coating in comparison with different configurations was also investigated. Result shows an increase in scratch adhesion of 18% and 27% for the optimal position and thickness of interlayers respectively. Qualitative comparison of in-plane residual stress shows higher stress in bi-layer and lower stress in multilayer with optimal thickness of interlayer. The approach in the study could be used to develop stress-optimized coatings for wear resistance applications. (C) 2015 Elsevier Ltd. All rights reserved.