Effect of Microwave Hybrid Heating on High-Temperature Adhesive Wear Behavior of High-Velocity Oxygen Fuel-Sprayed WC-CrC-Ni and WC-Co/NiCrFeSiB Coatings

HVOF-processed coatings are chemically inhomogeneous and are not metallurgically bonded to the substrate. As a result, components coated with HVOF experience considerable material degradation during sliding wear. Microwave hybrid heating (MHH) is a novel surface modification technique for modifying the as-sprayed properties of the coating. Hence, this paper investigates and compares the wear and frictional behavior of HVOF as-sprayed coatings against MHH samples of WC-CrC-Ni and WC-Co/NiCrFeSiB coatings at elevated temperatures. MHH had a significant impact on wear rate and coefficient of friction by optimizing the porosity, integrated oxide phases and intersplat cohesion strength of the coatings. A modified domestic oven was used to perform MHH on HVOF-coated samples for 5 min at 1200 °C. Wear tests were performed using a pin-on-disk tribometer from room temperature to 200, 400, and 600 °C with Al₂O₃ disk as a counterface. SEM/EDS and XRD were utilized to examine the microstructural characterization of the coatings and substrate. Both the coatings showed higher wear resistance than the substrate at all temperatures. The WC-Co/NiCrFeSiB coating produced an oxide layer on the worn surfaces and integrated WC, CoWO₄, and Fe₂SiO₄ splats, enhancing wear resistance. The MHH WC-CrC-Ni coating formed Cr₂O₃ and NiWO₄ phases on the worn surfaces, increasing the intersplat cohesion strength between matrix and carbide splats, lowering the overall wear rate. After MHH, the wear rate of a substrate and WC-CrC-Ni coating was 3.5 and 1.12 times more at room temperature and 8.07 and 2.92 times more at 600 °C than WC-Co/NiCrFeSiB coating.