Tribological Behaviour of Atmospheric Plasma and High Velocity Oxy-Fuel Sprayed WC-Cr3C2-Ni Coatings for High Temperature Applications

The thermally sprayed coatings are extensively used in high temperatures applications such as power generation, automotive, oil and gas aerospace industries. The comprehensive tribological performance of WC-Cr₃C₂-Ni coatings deposited on SS 316L by atmospheric plasma spray (APS) and high velocity oxy-fuel (HVOF) techniques have been relatively investigated as per ASTM G99. The unidirectional dry sliding wear of coatings against Al₂O₃ counter body was studied from room temperature to 800 ºC using ball-on-disc high-temperature tribometer. The worn surface morphology, oxide content and phase transition were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray analyzer (EDX) and Raman spectroscopy. The result findings revealed that, the specific wear rates of both coatings decrease after 500 ºC . The relationships linking between wear and oxidation of coatings were studied which suggests that the oxidation of HVOF coatings inhibits wear above 500 ºC , due to the development of tribo-film and well retained hard WC phase on the surface even at high temperature. The WO₃, NiWO₄ and CrWO₄ phases attributed to form a tribo-oxide film which resulted into superior wear resistance up to 800 ºC. Nevertheless, specific wear rates for both coatings are in mild regime which recommend that WC-Cr₃C₂-Ni coatings could be more durable in the oxygen enriched environments under a diverse range of temperatures.