Microstructure and high-temperature friction and wear behavior of WC-(W,Cr)2C-Ni coating prepared by high velocity oxy-fuel spraying

WC-(W,Cr)2C-Ni coating was prepared by high velocity oxy-fuel spraying (HVOF). The microstructure and phase composition of the as-sprayed coating and that after oxidation at high temperature were analyzed by means of scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The oxidation behavior of as-sprayed coating and starting powders was evaluated by thermogravimetry. Dry sliding friction and wear behavior of the WC-(W,Cr)2C-Ni coating sliding against Si3N4 ball at different temperatures (room temperature 20 °C and elevated temperature of 700 °C and 800 °C) was evaluated using an oscillating friction and wear tester. Besides, the microhardness and fracture toughness of the coating was also measured. Results show that sintering agglomerated WC-20 wt.%Cr-7 wt.%Ni powder is an effective method to prepare agglomerated and sintered WC-(W,Cr)2C-Ni composite powder. The excellent oxidation resistance of WC-(W,Cr)2C-Ni coating is mainly resulted from a double-decker shell-core microstructure formed in the coating. The composition of the outer shell is (W,Cr)2C phase and that of the inner shell is Cr3C2. During high-temperature friction and wear test, well remained hard WC phase in the WC-(W,Cr)2C-Ni coating can guarantee its good mechanical properties and wear resistance, and newly generated nano NiWO4, CrWO4 and Cr2WO6 particles can further improve these properties significantly.