Effect of Y on microstructure, mechanical performance of Ni based coatings by multi-layer laser cladding

To improve the wear and impact resistance of mechanical components, Ni45 and Y powders were used to prepare the coatings via laser cladding. The microstructure and elemental composition of the coatings were characterised via scanning electron microscopy and energy-dispersive X-ray spectroscopy, while molten pool morphology during cladding was observed with a high-speed camera. Wear and impact resistance were evaluated using a wear and impact testing machine. The oxidation of Y in the molten pool released a large amount of thermal energy, accelerating molten pool flow. When the Y content was ≤ 0.8 wt.%, the flow rate increased rapidly: at 0–0.4 wt.% Y, the flow velocity increased by 0.003 m/s, and at 0.4–0.8 wt.% Y, the flow velocity increased by 0.0065 m/s. At Y > 0.8 wt.%, the flow rate of the melt pool increased more slowly. Y inhibited crystal grain growth and acted as a heterogeneous nucleation particle, increasing nucleation rates. The microstructure of the coating containing 0.8 wt.% Y was significantly refined. Y addition also promoted the precipitation of Cr-rich hard phases and intermetallic compounds, thereby enhancing wear resistance and impact toughness. Compared with the Ni45 coating, the 0.8 wt.%-Y coating showed a 31.97% reduction in wear rate and an 11.01% improvement in impact toughness.