Abstract:Due to high hardness, great wear resistance and good corrosion resistance, WC-based coatings are widely used in industry to increase the wear resistance and corrosion resistance of components. As the development of industry, the properties of WC-based coatings are demanding higher and higher. In thermal spraying processes, Atmospheric plasma spraying (APS) has unique advantages due to large range of temperature and highest tens of thousands of temperature, which can melt refractory materials. The high-velocity-oxy-fuel (HVOF) is widely used in thermal spraying with its high velocity of flame and kinetic energy of powders. With the cooling by N2 during spraying, the coatings sprayed by HVOF show better property. This paper focused on the microstructure and properties of WC-10Co-4Cr, WC-17Co coatings sprayed by HVOF/APS on AISI 1045 steel. The hardness, metallographic structure, adhesion with substrates, decarburization during spraying of two coatings was investigated separately. The results showed that the powders of HVOF coatings melted incompletely and had high kinetic energy, resulting in more smooth coating. The adhesion with substrates of HVOF coatings was higher than APS coatings according to metallographic structure. Furthermore, porosity of all coatings sprayed by HVOF was much higher than APS sprayed coatings and the WC-17Co coating sprayed by HVOF had lowest porosity (0.65%). Besides, the hardness of coatings sprayed by HVOF was higher than APS sprayed coatings. Due to lowest binder content, the WC-10Co-4Cr sprayed by HVOF had highest hardness. From XRD, the coatings sprayed by HVOF had very slight decarburization with the existence of little W2C. However, the decarburization of APS sprayed coatings was more serious. There existed a large amount of W2C and little Co3W3C, Co6W6C (η phase) due to its higher temperature and lower velocity of flame during spraying. Accordingly, HVOF was more suitable to spray WC-10Co-4Cr, WC-17Co coatings.