Effect of Y₂O₃ on Microstructure and Corrosion Resistance of Ni45 Coating by Laser Cladding with Different Flow Rates of Carrier Gas

Laser cladding can create a protective coating on metal. In this study, Ni45 coatings were fabricated on 42CrMoA alloy steel by laser cladding using a CO₂ laser-processing system. Numerical analysis of the carrier gas was conducted in FLUENT software. The microstructure was evaluated by SEM and XRD analyses. The effects of Y₂O₃ on the microstructure and corrosion resistance of composite coatings made under carrier gas flow rates of 500-700 L/h were investigated. The powder concentration at the convergence point increased and then decreased, with the maximum powder concentration and molten pool brightness obtained at 600 L/h. The Ni45 cladding layer and Ni45 + 0.4 wt.% Y₂O₃ coatings were mainly composed of γ-Ni, M₂₃C₆, and Ni₃B. The solidification types were planar, cellular crystal, columnar crystal, and equiaxed dendritic. When the carrier gas flow rate is from 500 to 600 L/h, the grains are refined and the corrosion resistance of the coating is enhanced.