Tribology and corrosion properties of HVOF-sprayed WC coatings on surface of screw pump rotor
1.School of Mechanical and Electrical Engineering, Xuzhou University of Technology, Xuzhou, Jiangsu 221018, China； 2.School of Mechatronic Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China
Abstract：The WC-12Co and WC10Co4Cr coatings were deposited on the surface of screw pump rotor substrate (45 steel) by high velocity oxygen fuel (HVOF) technology. The micromorphology, porosity, phase structure and Vickers hardness of the coatings were characterized by SEM, EDS, XRD and microhardness tester. The wear and corrosion mechanisms of the coating were discussed based on friction and wear test and electrochemical test. The results show that the microstructure of WC12Co coating and WC10Co4Cr coating is compact, and the porosity values are 0.58% and 0.48%,respectively. The average Vickers hardness values are respective 1 38587 HV03 and 1 26862 HV03, and the wear mass loss are 19.5% and 21.8% of the substrate, respectively. The wear resistance of WC12Co coating is better. The wear mechanisms of the two coatings are mild abrasive wear, while the substrate is dominated by abrasive wear and supplemented by adhesive wear. The corrosion current densities of WC12Co coating and WC10Co4Cr coating are 21.1% and 128% of that of the substrate, respectively. The passivation film formed by Cr oxide makes the WC10Co4Cr coating have good corrosion resistance. Microgalvanic corrosion occurs between WC and metal bonded phase in both coatings, leading to the dissolution of bonded phase and shedding of some WC particles, and the corrosion products can protect the coating.
