This study investigates the influence of cobalt content on the microstructural characteristics, mechanical properties, and erosive wear behavior of HVOF-sprayed WC–Co–Cr cermet coatings deposited on Inconel 718 superalloy. Three coating compositions, namely WC–8Co–2Cr, WC–11Co–2Cr, and WC–14Co–2Cr, were deposited using the high-velocity oxy-fuel (HVOF) process and characterized through scanning electron microscopy (SEM), energydispersive spectroscopy (EDS), X-ray diffraction (XRD), porosity analysis, microhardness testing, and high-temperature erosion testing at 550°C. The coatings exhibited dense microstructures, strong coating–substrate adhesion, and uniform distribution of WC particles within the Co–Cr matrix. Quantitative analysis revealed that increasing cobalt content reduced porosity from 0.9% to 0.6% and improved coating compactness. The average coating thickness ranged from 220 to 230 μm. XRD analysis confirmed WC as the dominant phase along with secondary phases such as W 2 C, Cr 7 C 3 , CoCr, and Co 3 W 3 C, which contributed to enhanced structural stability and erosion resistance. Microhardness increased from 890 HV for WC–8Co–2Cr to 935 HV for WC–14Co–2Cr due to improved microstructural homogeneity and binder phase continuity. Erosion testing conducted at impact angles of 45°, 60°, and 90° showed that maximum material loss occurred at 45° because of dominant micro-cutting and ploughing mechanisms, while the minimum erosion rate was observed at 90° due to deformationcontrolled wear. Among the investigated coatings, WC–14Co–2Cr exhibited the lowest volume loss and erosion rate owing to its lower porosity, stronger splat cohesion, enhanced fracture toughness, and improved carbide retention. SEM analysis of eroded surfaces identified microcutting, ploughing, crater formation, and localized brittle fracture as the primary erosion mechanisms. The results demonstrate that optimizing cobalt content significantly improves the densification, hardness, and erosion resistance of WC–Co–Cr coatings, making WC–14Co–2Cr a promising protective coating for high-temperature aerospace and gas-turbine applications.
Harish et al. (Tue,) studied this question.