Influence of bi-layer period thickness on the residual stress, mechanical and tribological properties of nanolayered TiAlN/CrN multi-layer coatings

Abstract

TiAlN/CrN nanoscale multi-layered coatings have been deposited using cathodic arc evaporation system. The coatings were deposited using one Ti 50Al 50 alloy target and one Cr target with a fixed target power in all the processes, while the bi-layer thickness was varied by various rotation speeds of the substrate holder in order to produce different nanoscale multi-layered period thickness. The texture structure, residual stress, and nanoscale multi-layer period thickness of the coatings were determined by X-ray diffraction using both Bragg–Brentano and glancing angle parallel beam geometries. Hardness and adhesion strength of the coatings were measured by Nano-indentation and Rockwell-C indentation methods, respectively. It has been found that the structural and mechanical properties of the films correlate with nano-scaled bi-layer thickness and crystalline texture. The maximum hardness of nano-scaled TiAlN/CrN multi-layered coatings was approximately 36 GPa with highest residual stress of −6.2 GPa, for a bi-layer thickness ranging from 6 to 12 nm.