Superior compound coatings prepared by low-temperature vanadium-nitrocarburizing duplex treatment

Superior compound coatings were prepared on CK45 steel surface by vanadium-nitrocarburizing duplex treatment in low-temperature salt bath. In this study, the microhardness, the phase constitution and the compositional distribution in the coatings prepared under different conditions were systematically characterized. The results indicated that the reactions among activated vanadium, carbon and nitrogen atoms occurred on the steel surface, leading to the formation of compound coatings composed of outermost and compound layers. The mechanism for the formation of compound layer as well as the growth kinetics of the layer was also discussed. Upon the duplex treatment, the wear and corrosion resistances of steel surface were significantly improved. It was found that the growth kinetics of compound layer obeyed the parabolic law, with the activation energy of 122.82 kJ·mol⁻¹.