Mechanical Properties of High-Entropy Coatings of the (TiZrVCrAl)N System of Different Architectures Deposited by the Arc-PVD Method on the Surface of Ti-6Al-4V Alloy

In this work, for the first time, we applied and determined the mechanical characteristics of protective coatings made of high-entropy alloy (TiZrVCrAl)N with different architectures onto the surface of Ti-6Al-4V alloy with the initial coarse-grained and ultrafine-grained structure using arc physical vapor deposition. We designed and prepared three coating architectures: a monolayer nitride coating (TiZrVCrAl)N, a multilayer coating consisting of nine alternating layers of TiZrVCrAl and (TiZrVCrAl)N, and a multilayer coating consisting of 720 alternating layers of (TiZrVCrAl)N and TiN, with a total thickness not exceeding 2 microns. We evaluated their protective performances by nanoindentation and scratch tests. Importantly, the effect of the substrate microstructure on the coatings’ performance is investigated by comparing their mechanical behavior on coarse-grained and ultrafine-grained Ti-6Al-4V. Our experimental results show that the coating performance improves with increasing number of layers in the coating, and this effect is even more pronounced for the multilayer coating deposited on the ultrafine-grained titanium alloy substrate. We also find that the (TiZrVCrAl)N/TiN (720 layers) multilayer coating deposited on the UFG Ti-6Al-4V alloy substrate exhibits the highest H/E- and H3/E2-values, indicating the coating’s high innovative potential for performance in extreme conditions. The origins of this phenomenon are analyzed and discussed.