Characterization of WC-%XCo-%XCr coatings applied on stainless steel 316 by HP/HVOF and investigation the behavior of the coating in molten zinc bath

In this study, the effect of cobalt percentage on WC-Co coating properties was investigated. Corrosion behavoiur of coatings was evaluated after immersion in molten zinc. For this purpose, various compositions of WC-Co powder (WC-12Co, WC-17Co and WC-10Co-4Cr) were coated on 316 stainless steel by means of HP/HVOF method. To determine the phases produced during the process of spraying, thickness, porosity and hardness of the coatings, X-ray diffraction (XRD), scanning electron microscopy (SEM) and microhardness tester were used. The XRD patterns showed negligible amount of W2C and Co6W6C brittle phases, which indicates very low decarborizing of WC phase. WC-17Co coating showed the highest hardness (1280 Hv). Pin on disk wear test was used at 450 ° C and then wear surfaces were examined by electron microscopy. WC-10Co-4Cr coating showed highest wear resistance. Main wear mechanism of coatings was adhesive wear. Evaluation of corrosion behaviour of coatings and phases produced during immersion in molten zinc was done by electron microscopy and energy spectrometer. Unlike WC-17Co coating, on the cross section of WC-12Co and WC-10Co-4Cr coatings some cracks were observed which penetrating element to these cracks was aluminum and lead to destruction of these two coatings.