激光重熔NiCrAlY涂层研究

Study on laser remelting NiCrAlY coating

采用空气等离子喷涂技术(APS)将NiCrAlY粉末作为粘结层材料喷涂在IN718镍基合金上,再用5 kW CO2连续激光器对其进行激光重熔处理,利用扫描电镜(SEM)、能谱分析(EDX)和X射线衍射(XRD)等手段对等离子喷涂层和激光重熔层的微观组织与成分进行了比较分析。结果表明:应用优化激光重熔工艺进行重熔后,涂层与基底形成冶金结合,改变了等离子喷涂层与基底的机械结合以及层状结构,有利于提高涂层的力学性能。重熔区组织为垂直基底向内部发散生长的树枝晶,加强了涂层与基底的结合。涂层中的树枝晶内部组织为Ni和Ni3Al,晶间则是被树枝晶凝固生长时排出的Al2O3,Cr2O3等呈片状生长的氧化物和杂质。涂层表面形成一层致密的氧化物,将会阻碍O2的内扩散,有效延缓粘结层和基底元素的进一步氧化,有利于提高涂层的抗氧化性能。

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.