Wear resistance of nickel-based alloy coating formed by multilayer laser cladding

Different thickness coatings formed by multilayer laser cladding are widely employed in laser repairing and the wear resistance of them are concerned. Multilayer nickel-based alloy were fabricated on the surface of low alloy steel by laser-induction hybrid cladding. Orthogonal analysis was used to evaluate the influence of the number of coating layers, load and relative velocity on the wear resistance of the coating. Wear loss and friction coefficient were set as the evaluate indexes. Microstructure, element distribution and phase composition were investigated by optical microscope, energy dispersive spectrometer (EDS) and x-ray diffractometer (XRD). Microhardness and worn surface of coatings were also tested.

The results showed that the number of coating layers had an effect on the wear resistance of nickel-based coating. With the increase of coating thickness, more uniform was happened to the crystal grain. The nickel-based alloy coating was mainly composed of Cr₂₃C₆, Cr₇C₃, CrB, FeNi₃ and Fe₂₃(C, B)₆. The lowest hardness was shown in the single-layer coating with an average value of 818.0 HV0.2. The average hardness of the two-layer coating and three-layer coating was 6.88% and 16% higher than that of the single-layer one, respectively. The cross-sectional area of the worn surface was (0.64 ∼ 2.3) × 10⁻³ mm² and the distribution of them was consistent with the distribution of wear loss. The wear mechanism of nickel-based coating in this friction system was abrasive wear. The good wear resistance of the nickel-based alloy coating was mainly due to the presence of dense fine crystal grain and hard phase. (paper)