Effect of bias potential on the phase composition, structure and properties of CrAlYN/CrAlYO vacuum-arc multilayer coatings

Abstract

The article presents the results of a study of multilayer (32 layers) CrAlYN/CrAlYO coatings obtained by vacuum-arc plasma-assisted deposition on a VK8 (WC + 8% Co) hard alloy substrate. The effect of the substrate bias potential (Ucm: –50, –75, and –100 V) on the phase composition, crystal structure parameters, thickness, roughness, surface morphology, and mechanical properties has been studied. X-ray diffraction analysis revealed that the resulting multilayer coatings have a multiphase structure consisting of phases of nitrides (CrN and AlN) and oxides (Cr2O3 and AlYO3). With an increase in the negative bias potential from 50 to 75 V, a decrease in Cr2O3 from 52 to 18 % and an increase in CrN from 26 to 39 % were observed, which led to the lowest microvoltages for both phases (Δd/d×10–3 = 1.9). The size of the CSR of all phases was in the range from 15 to 19 nm and practically did not depend on Ub. It was found that an increase in the bias potential from 50 to 100 V led to a decrease in the thickness of the formed coating and a decrease in the roughness according to the Rz criterion, which indicated a decrease in the droplet phase, confirmed by optical microscopy. It was found that increasing Ub from 50 to 100 V led to an increase in the hardness (H) of the coatings from 17.2 to 19.9 GPa, however, the coating obtained at 75 V had the highest values of H/E and H3/E2. Using X-ray phase analysis using synchrotron radiation, it was found that the resulting CrAlYN/CrAlYO multilayer coatings retained thermal stability during heating in air to a temperature of ~1020 °C.