Effect of microwave heating on microstructure and elevated temperature adhesive wear behavior of HVOF deposited CoMoCrSi-Cr3C2 coating

Abstract

This research reports the improvement of high-temperature sliding wear resistance of a grade 15 titanium alloy protected by an HVOF sprayed CoMoCrSi-Cr<inf>3</inf>C<inf>2</inf> coating. The coatings have been tested in as-sprayed condition and after a post-deposition microwave heating step. The powder feedstock has been manufactured by high energy ball milling. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) equipped with the Energy Dispersive Spectroscopy (EDS) methods were used for coatings characterization. Surface roughness, microhardness, adhesion strength, and porosity of coatings were also measured. The wear test was conducted at an applied load of l0 N and 20 N with varying temperatures of 200 °C, 400 °C, and 600 °C under dry sliding conditions. Co<inf>3</inf>Mo<inf>2</inf>Si, Co<inf>7</inf>Mo<inf>6</inf>, Mo<inf>3</inf>Si, Co<inf>3</inf>Mo, and Co<inf>2</inf>Mo<inf>3</inf> were the intermetallic laves phases generated in the CoMoCrSi feedstock during HEBM process. The microwave-fused coating exhibited metallurgical bonding, homogeneous structure, less porosity, and greater hardness as compared to as-sprayed coating. Microwave-treated coating revealed better wear property than an as-sprayed coating. This was mainly due to the intermetallic formation and metallurgical bonding in coatings. The fused coatings exhibit tribo-oxide layers during sliding action which was the main phenomenon of improving the wear resistance of the fused composite coatings. © 2019 Elsevier B.V.