Numerous studies have been made to enhance the wear resistance of WC-Co coatings deposited by HVOF during the last few years. Spherical WC-30WB-10Co powders were firstly fabricated by agglomeration and sintering process, which were then employed to deposit coating by HVOF. The morphologies, phase composition, hardness, as well as sliding wear performance of the as-deposited coatings were explored. The same experiments were carried out on traditional WC-12Co coatings with the purpose of making the comparison. The results showed that the CoWB compound was formed through the reaction between Co and WB in the sintering process of the WC-30WB-10Co powders. The diffraction peaks of W₂C, Co₃W₃C and Co₆W₆C were found in the XRD patterns of both coatings, implying that oxidation and decarburization happened in the spraying process of both powders. In relative to the traditional WC-12Co coating, the microhardness and wear resistance of the WC-30WB-10Co coating were greatly enhanced. Obviously, with the microhardness of the WC-30WB-10Co coating being elevated by 34.1%, the wear rates were only 49.3% of that of WC-12Co coatings. This was resulted from the existence of the superhard CoWB phase in the WC-30WB-10Co coating. The wear mechanisms of both coatings were abrasive wear and oxidative wear.

Keywords: Coating, Microstructure, Wear, High velocity oxy-fuel spraying.