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)(2)C-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)(2)C-Ni coating sliding against Si3N4 ball at different temperatures (room temperature 20 degrees C and elevated temperature of 700 degrees C and 800 degrees 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)(2)C-Ni composite powder. The excellent oxidation resistance of WC-(W,Cr)(2)C-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)(2)C phase and that of the inner shell is Cr(3)C2. During high-temperature friction and wear test, well remained hard WC phase in the WC-(W,Cr)(2)C-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. (C) 2011 Elsevier B.V. All rights reserved.