Microstructure, phase composition and wear properties of iron-based gradient coatings by laser cladding on 65Mn steel

Abstract

Iron-based coatings with high wear resistance were prepared on a 65Mn substrate using a laser cladding technique. The coatings were characterized and compared with the substrate in terms of microstructure, phase composition, hardness distribution and friction-wear properties. The coatings had a gradient microstructure consisting of a working layer and a transition layer with different compositions. The working layer contained (Cr, Fe)7C3 carbides as the hard phase, which improved the hardness and wear resistance of the coatings. The transition layer had a higher soft phase amount due to the higher Ni content, which enhanced the bonding strength between the coating and the substrate. The coatings showed a uniform and dense surface morphology, free of cracks and pores, and a fine and uniform grain size. The average hardness of the coatings was 721 HV1, which is more than three times that of the substrate. The friction coefficient and wear loss of the coatings were 0.42 and 0.0018 mg/m, respectively, lower than those of the substrate (0.48 and 0.036 mg/m). The coatings demonstrated excellent wear resistance and durability in soil tank tests, exhibiting an 81.15 % reduction in mass loss when utilized on rotary tiller blades. The results present an effective method for surface modification of agricultural machinery components and provide valuable insights for the further development of unique gradient coatings.