Wear and corrosion resistance of CoCrNi composite coatings by laser cladding

Two kinds of CoCrNi composite coatings, CoCrNiMo and CoCrNiMoBC, were prepared by laser cladding on the base metal of 304 stainless steel. The wear and corrosion properties of the coatings were studied by wear tests and electrochemical tests. Results show that the addition of B4C promotes the generation of the ceramic phase, and therefore improving the microhardness of the coating and enhancing its wear resistance, while simutaneously keeps its excellent corrosion resistance. Energy dispersive X-ray spectrometry analysis shows that the chromium distribution in the two coatings is relatively uniform, which is beneficial for corrosion resistance. Scanning Kelvin probe microscopy results reveal that the potential difference between dendrites and interdendrites is only 20 mV, which leads to a relatively low driving force for galvanic corrosion. Observation through the atomic-scale high-resolution transmission electron microscopy shows that the fundamental reason for the high wear and corrosion resistance of the coating is the excellent coherent interface between the two phases, which reduces the interface energy and potential difference and thus improving its corrosion resistance.