Effect of HVOF method spraying parameters on phase composition and mechanical and tribological properties of 86WC-10Co-4Cr coating

Abstract

Valve components used in the petroleum industry are subjected to intense wear during operation, which leads to a sharp decrease in their durability. Usually, the often subjected to the wear process surface of the valves is treated by tungsten carbide cladding to improve its durability. Because of the difficulty in applying tungsten carbide using conventional surfacing techniques, high velocity oxyfuel (HVOF) spraying technology is recommended. In this work, the mechanical, tribological properties and phase composition of 86WC-10Co-4Cr composition coatings obtained by HVOF Termika-3 high-velocity gas-fuel spraying were investigated. Varying the technological parameters of spraying was carried out by changing the spraying distance, which led to differences in the thickness of the coatings. The phase composition, microstructure and distribution of elements were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) methods. The hardness of the samples was measured on a microhardness tester using the Vickers method, the friction coefficient and the wear rate were investigated using a friction and wear tester. It was determined that the surface of the coatings had developed character and high roughness. The results of X-ray phase analysis showed the predominance of hexagonal WC as the major phase, with a small amount of hexagonal tungsten carbide W2C as the minor phase, and the minor presence of cobalt oxide CoO. It was found that the increased wear resistance and low friction coefficient of 86WC-10Co-4Cr coatings are explained by the high volume fraction of hard and stable WC grains with high resistance to wear.