The corrosion-wear mechanisms of S-phase (nitrogen supersaturated austenitic stainless steel) and CrN coatings applied to 316L substrates have been evaluated under unidirectional sliding contact corrosion-wear situations. The S-phase coating reduced corrosion-wear compared to untreated 316L, but despite exhibiting the most electrochemically passive behaviour, proved inferior to CrN. It is proposed that the difference in passivity between the test pin and the coating (ΔP{sub}(P,S)), and between the coating and the substrate (ΔP{sub}(C,S)) is important in driving the corrosion and corrosion-wear rates of the test pin and disc. For tests conducted on S-phase coated 316L discs both ΔP{sub}(P,C) and ΔP{sub}(C,S) were larger compared to the CrN coated 316L. From a design point of view, in order to minimise corrosion-wear, ΔP{sub}(P,C) and ΔP{sub}(C,S) must be minimised whilst retaining sufficient hardness and toughness in the coating to mitigate mechanical wear mechanisms.
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