Abstract
WC-12Co thermally sprayed coating, formed by high velocity oxygen-fuel spraying, is widely used in industry for its high wear resistance properties. Unfortunately, WC-12Co coatings are plagued by low corrosion resistance in aqueous solutions. Previous studies have shown that adding Cr to the coating improves corrosion resistance, but the effect on corrosion fatigue fractures remains unknown.In this study, first, two kinds of coatings (WC-12Co & WC-10Co-4Cr) were deposited on SS400 steel by high-velocity flame spraying. Second, fracture behavior was investigated through corrosion fatigue testing in an Na2SO4 aqueous solution (R=0, f=14Hz). The cause of the corrosion fatigue fractures was found to be corrosion pits formed at the interface between the coating and the substrate. The corrosion fatigue life for WC-10Co-4Cr was longer than that for WC-12Co in low cyclic stress areas (stress amplitude σa<75MPa). This extended corrosion fatigue life is assumed to be due to decreased corrosion response, because the passivation film on the surface of the WC-10Co-4Cr coated materials was quickly restored, even after it had been mechanically broken.
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