Study on laser remelting NiCrAlY coating

The bond coatings of NiCrAlY powder was coated on the substrate material of IN718 nickel alloy by air plasma spraying (APS), and then it was remelted by 5 kW CO₂ laser. The microstructure of the bond coatings was characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and X-ray diffraction (XRD). The experimental results show that with the optimized remelting process, the bond coating displays superior metallurgical bonding with its substrate, and the mechanical bonding and layer structure of coatings by plasma spraying are changed, which is good for improving the mechanic performance of the coatings. Typical dendritic structure growing in cladding zone in the direction perpendicular to the substrate could strengthen the bond coating with its substrate. The dendritic structure is primarily made of metal Ni and Ni₃Al compounds, while some impurities and oxides such as Al₂O₃, Cr₃O₄ survived in flake exist in interdendritic structure. A dense oxide layer formed on the bonding surface can avoid O₂ diffusion, and effectively prevent the further oxidation of coatings and substrate, and improve the oxidation resistance of bond coatings.