Effect of thermal exposure on the wear and phase stability of HVOF-deposited WC-17Co coatings

Wear-induced material loss is a major concern in industrial applications, driving the development of wear-resistant surface coatings. High-velocity oxy-fuel (HVOF) spraying is widely used to deposit coatings with high bond strength, low porosity, and improved wear resistance. Among these, WC–Co cermet coatings exhibit excellent hardness and tribological performance; however, wear behaviour can change significantly at elevated temperatures. The present study investigates the dry sliding wear behaviour of HVOF-deposited WC–17Co coatings from RT to 600 °C under constant load, sliding velocity, test duration, and sliding distance. The coatings were characterized before and after wear testing using SEM, EDS, XRD, and 3D surface profilometry to evaluate changes in morphology, elemental distribution, phase composition, and wear-track geometry. The coating showed a thickness of ~268.99 µm, 1.53% porosity, and an average surface roughness (Sa) of 10.2 µm. The coating showed favourable wear resistance at 200–400 °C, with minimum wear and friction at 400 °C likely due to a protective tribo-oxide layer and compacted debris. Above 400 °C, particularly at 500 and 600 °C, the wear rate increased markedly because of Co binder-phase degradation, intensified oxidation, and reduced adherence of the oxide layer, and the optimal operating range is 200–400 °C.