Microstructure and Wear Resistance of NbC‐Reinforced Ni35 Composite Coatings on Low Carbon Structural Steel by Laser Cladding

Low carbon structural steel, valued in industry for its low cost and adequate strength, exhibits limited hardness and poor wear resistance. In this study, NbC‐reinforced Ni35 coatings are fabricated on low‐carbon structural steel by laser cladding. The influences of NbC content on microstructure and properties are analyzed. The large NbC particles are effectively retained within the coatings, while fine NbC particles precipitate between these large particles. In addition, various solid solutions, carbides, and borides are also present in the coatings. Higher NbC additions increase the volume fraction of precipitates and the dilution ratio. The coating achieves a maximum hardness of 783 HV 0.1 at a 50 vol% NbC content. A further increase to 70 vol% NbC lowers hardness because excessive dilution enlarges the heat‐affected zone. The friction coefficients of the coatings are lower than those of the steel, exhibiting a minimum value of 0.52. Steel substrate experiences severe plowing and brittle spalling. Elevated NbC contents progressively improve the wear resistance of coatings by suppressing plowing, but the cracks caused by fatigue and the subsequent brittle spalling remain quite serious. At 70 vol% NbC, the wear volume is only 4.55% of that of the substrate.