Microstructure And Properties Of Wear-cavitation Resistance Cemented Carbide Coating Fabricated By Electrospark Deposition

Wear and corrosion problems exist universally in all industries. The wear and abrasionphenomenon of water conservancy machinery parts is very serious, which consume tens ofmillions on repairing hydraulic machinery. Under this situation, this paper undertakes theexperiments of making the cladding coating by electrospark deposition technology on thesurface of hydraulic machineries. The influence was systematically studied by the fivediffenent parameters of voltage, power, discharge frequency, cladding efficiency and theargon flow. The best process parameters were determined through the contrast test: the outputpower is3000W, the output voltage is200V, the discharge frequency is1800Hz, the claddingefficiency is2min/cm², the protective gas of argon flow is6L/min.The microstructure and properties of the coating were investigated by scanning electronmicroscopy （SEM）, X-ray diffraction （XRD）, coating thickness gauge of TT260,microhardness tester and ball-disc configuration wear tester. The results show that theelectrospark cladding coating bonded metallurgically with the substrate, and the organizationof the coating is no obvious defects, uniform and compact. The thickness of the claddingcoating on the surface of ZG0Cr13Ni5Mo is40μm, and the thickness of transition layer andthe heat affected zone is140μm. The main phases of the coating consisted by Co₃W₃C,Fe₃W₃C, Fe₃Mo₃C, W₂C and Fe₇W₆C. The hardness of the coating is about5.5times higherthan the0Cr13Ni5Mo cast steel substrate, and the coating improves the wear resistanceperformance and the average wear resistance rate is3.4times of that of the ZG0Cr13Ni5Mocast steel substrate. The thickness of the cladding coating on the surface of1Cr18Ni9Ti caststeel is30μm, and the thickness of transition layer and the heat affected zone is120μm. Themain phases of the coating consisted by Co₃W₃C, Fe₃W₃C,（CrFe）₇C₃, Cr2N and Ni-Cr-Fe.The hardness of the coating is about6times higher than the1Cr18Ni9Ti cast steel substrate,and the coating improves the wear resistance performance and the average wear resistance rate is3.75times of that of the1Cr18Ni9Ti cast steel substrate.The highest hardness is white layer, and then is transition area and heat affect zone inelectrospark cladding coating which are higher than the hardness of substrate. The elementsbetween electrode materials and basis materials diffuse mutually during the process ofelectrospark cladding. A large number of amorphous fine grain carbide hard phases areformed and disperse distribution among the cladding, which improve significantly thehardness, strength and wear resistance on the surface of the workpiece. The wear mechanismof the coating is mainly adhesion wear, abrasive wear and oxidization wear.