High-temperature tribological properties of coatings repaired by laser additive manufacturing on railway wheel tread damage

Heavy-duty train wheels can easily cause local damage. Laser additive manufacturing technology has obvious advantages in repairing local damage to train wheels. The high temperature sliding condition caused by tread braking is a severe test for the coating of damaged wheels repaired by laser additive. In this study, three self-fluxing alloy powders, Fe-, Ni-, and Co-based, which are the most widely used in laser cladding, were selected as repair materials. The sliding friction wear performance at high temperatures was evaluated with an HT-1000 ball-disk wear tester, and the wear mechanisms of the repair area, substrate, and counterpart surfaces of the specimens were analyzed. The results show that the microstructure of the coating after the surface damage of the wheel is repaired by laser additive is mainly composed of dendritic structure and eutectic structure. Compared with the base material, the hardness of Fe-, Ni-, and Co-based alloy cladding coatings is significantly improved. At the same time, the wear resistance of the repaired wheel steel samples was improved to different degrees. The wear mechanism of the repaired area of the Fe-based alloy sample is mainly adhesive wear, and the wear mechanism of the repaired area of the Ni-based alloy sample is adhesive wear and oxidation wear. However, the surface of the wear scar of the Co-based alloy repaired sample is relatively smooth, the damage is slight, and the friction reduction effect is the best.