A Method to Extract the Elastoplastic Properties of the Constituent Layers of Multilayer Coatings

Abstract

This paper presents an approach to characterize the elastoplastic properties of the distinct layers, constituting multilayer coating. The proposed procedure utilizes nanoindentation load-displacement (P-h) curves and a non linear least squares fitting analysis to extract the elastoplastic properties of each layer in the multilayer coating. The accuracy of the optimization results is achieved by choosing initial guess parameters closer to the target values using the modified Jönsson and Hogmark model. The methodology is validated on a CrN/CrAlN multilayer coating systems with varying layer thicknesses from 1 to 0.5 μm, from which the optimal elastoplastic properties: Young’s modulus (E), yield stress (σy), and strain hardening exponent (n) of each individual layer were determined. The results show good agreement between the simulated and the experimental (P-h) curves. Furthermore, the results revealed a reduction in the material parameters (E, H and σY) of the constituent layers when the layer thickness decreases. These findings suggest that decreasing the coating layer thickness lead to an increase in the plastic deformation within the coatings, which reduces the stress concentration in this area and improves the adhesion properties of CrN/CrAlN multilayer coatings.