Tribological Behaviors and High-Temperature Oxidation Resistance Properties of Wtavcr Alloy Coating

Abstract

Tungsten based refractory high entropy alloys (RHEAs) are potential candidate for high temperature applications owing to their remarkable mechanical properties. However, the oxidation resistance of W based RHEAs at high temperature is problematic, and it received less attention. Moreover, there is still a lack of research on the evaluation of room temperature wear on tungsten-based alloy coating. In this work, several WTaVCr alloys were fabricated by double glow plasma surface alloying (DGPSA) technology at different temperatures and different source ratios. The microstructure of the WTaVCr alloys exhibited a single BCC solid solution, while the WTaVCr (the source ratio is 1:1:3:3) showed some extent of intermetallic compounds along with the BCC phase. The structure and composition of the coatings were confirmed by SEM, XRD and EDS, respectively. The micro-hardness tester was adopted to measure the surface hardness of the coatings. The coatings were dense, uniform and compact, encompassing a complete structure of deposited layer, interdiffusion layer and sputtering-affected zone. The morphology of the WTaVCr coatings were typical coatings formed by DGPSA, with their structure consisting of uniform submicron-sized grains. The surface hardness of the samples increases significantly after alloying, which is 5 times that of the substrate. In addition, the oxidation characteristics of the coatings and the substrate were examined at 800°C using a muffle furnace. The coatings (1-1000) showed a lower oxidation rate, approximately a quarter of the substrate, which was protected by a continuous Cr 2 O 3 scale layer. Sliding wear tests under dry friction conditions were performed on the coating as well as the W substrate. The fairly low specific wear rate of the coating proved its excellent wear-resisting property (The wear rate was as low as 8×10 -7 mm 3 /N∙m, which is two orders of magnitude lower than that of the W substrate), and the dominant wear mechanism evolved from abrasive wear and slight oxidative wear to oxidative wear slight abrasive wear.

Keywords: refractory high entropy alloys, double glow plasma surface alloying technology, microstructure, oxidation characteristics, Wear