A 5 kW CO2 laser was used for the preparation of pure Ni45 alloy coating and Ni45+0.4wt％Y2O3 coating on 42CrMoA steel substrate.Numerical simulation of the carrier gas flow rate was conducted using FLUENT software.The macroscopic morphologies and microstructure of the two coatings with different carrier gas flow rates were characterized using optical microscopy,scanning electron microscopy and XRD tester.The results show that as the carrier gas flow rate is increased from 500 L/h to 700 L/h,the powder deposition efficiency initially increases and then decreases.The solidification types of the two coatings consist of planar grains,cellular grains,columnar dendritic grains,and equiaxed grains,and with γ-Ni,M23C6,and Ni3B phases.The microstructure refinement is most prominent when using a carrier gas flow rate of 600 L/h.The corrosion resistance increases initially,then decreases with the increase of carrier gas flow rate,and the coating produced with 600 L/h carrier gas flow rate has the best corrosion resistance.
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