Investigation on Characterization of GGG 60 Coated with WC/Co by ESD Technique

Abstract

Hard surface coatings are necessity when the surface of a metallic materials are required to perform better during the service and lower the cost of replacement and labour. In this study, WC/Co coatings were deposited on GGG60 ductile (spherical graphite) cast iron with Electro Spark Deposition technique. The ductile cast iron specimens were non heat treated, heat treated for hardening the surface and subsurface prior to coating. Optimum coating parameters were determined as 132 V and 1230 Hz. Coating characterization was investigated by SEM/EDS and XRD. The surface hardness value of the substrate sample increased from 270 ± 5.6 HV_0.2 to 1330 ± 12.5 HV_0.2. Surface hardness value increased 5 times. The presence of W₂C, W and WC_{1 – x} phases in the coatings increased the possibility of decarburization. WC ratio was calculated more in heat treated coated samples compared to other coatings. The mechanical properties of the coatings were tried to be determined by tensile and three-point bending tests. The tensile stress of the heat-treated coated samples was calculated as 780 MPa and the maximum bending stress was calculated as 1581 MPa. The decrease in the C ratio in the coating in the heat treated coated samples made the samples more resistant to thermal stresses.