Effect of Cu additions on the microstructure, wear resistance and corrosion resistance of Fe-based/B4C composite coating by vacuum cladding

Fe-based/B4C composite coatings with different Cu contents were prepared on the surface of ASTM 1045 steel by vacuum cladding. The influence of Cu contents on the microstructure, hardness, wear behavior and corrosion resistance of coatings was investigated. The results demonstrated that the microstructure was finer owing to the dissolution and dispersion of Cu, although the type of boride M2B and carboboride M23(C, B)6 in Cu-free and Cu-added coatings did not change. Since the Cu additions improved the hardenability of coating matrix and transformed its microstructure into martensite, the microhardness of coating matrix reached over 600 HV, and the macrohardness also increased and reached the maximum of 57.85 HRC for 5Cu sample. The wear volume of Cu-added coating was significantly lower than that of Cu-free coating, and the wear rate of 5Cu sample decreased by 50.40 %. The number of spalling pits on the worn surface decreased, showing the best wear resistance, and the main wear mechanism was fatigue spalling. Furthermore, the coating with high Cu contents possessed higher Ecorr, lower Icorr and higher Rct, which was attributed to the composite oxide passive film formed on the corrosion surface effectively isolated the coating from corrosive medium and greatly improved the overall corrosion resistance of coating.