一种无机盐铝涂层涂覆镍基粉末高温合金的高温氧化组织分析

High temperature oxidation microstructure analysis of Ni-based P/M superalloy coated with an inorganic aluminum coating

使用TWL12+TWL20无机盐铝涂层喷涂于镍基粉末高温合金表面,采用XRD、SEM、EPMA和TEM研究无机盐铝涂层与粉末高温合金经700、750、800℃高温氧化后的组织变化。结果表明:高温氧化后涂层表层结构出现剥落,涂层中的铝与基体合金发生扩散,形成由氧化区、扩散区、互扩散区组成的过渡层,其中氧化区为最外层,该区域主要富集O、Al元素,形成Al_(2)O_(3)层;随之的扩散区主要含有Ni、Al元素,形成NiAl相及在其中弥散分布的α-Cr相;最后是富集Ti、Cr、Co、Ta等元素的互扩散区,存在于扩散区与基体之间,主要由Ni_(2)AlTi相基体及在其中弥散分布的σ相组成;分析表明过渡层厚度随着氧化温度升高而变化,主要表现为互扩散区宽度增加,扩散区中的α-Cr相与互扩散区的σ相尺寸增大,且σ相沿垂直过渡区方向生长的趋势加剧;氧化增重曲线表明,涂层表层结构脱落后,过渡层在750、800℃高温氧化过程中表现出良好的抗氧化性能,说明TWL12+TWL20无机盐铝涂层具有为航空发动机用先进粉末高温合金提供高温氧化涂层保护的潜力。

In this paper,TWL12+TWL20 inorganic salt aluminum coating was sprayed on the surface of Ni-based P/M superalloy.The microstructure changes of inorganic salt aluminum coating and P/M superalloy after high temperature oxidation at 700,750℃and 800℃were studied by XRD,SEM,EPMA and TEM.The results show that after high temperature oxidation,the surface structure of the coating peels off,and the aluminum in the coating diffuses with the substrate to form a transition layer composed of oxidation zone,diffusion layer and interdiffusion zone.The oxidation zone is the outermost layer,where is mainly enriched with O and Al elements to form Al_(2)O_(3) layer.The diffusion layer mainly contains Ni and Al elements,forming NiAl phase andα-Cr phase dispersed in it.Finally,the interdiffusion zone rich in Ti,Cr,Co,Ta and other elements exists between the diffusion zone and the matrix,which is mainly composed of Ni_(2)AlTi phase matrix andσphase dispersed in it.The analysis shows that the thickness of transition layer changes with the increase of oxidation temperature,it is mainly manifested by the increase of the width of the interdiffusion zone,the increase of the size ofα-Cr phase in the diffusion layer andσphase in the interdiffusion zone,and the growth trend ofσphase along the vertical transition zone is intensified.The oxidation weight gain curve shows that the transition layer exhibits good oxidation resistance during high temperature oxidation at 750℃and 800℃after the surface structure of the coating falls off,it indicates that the TWL12+TWL20 inorganic salt aluminum coating has the potential to provide high temperature oxidation coating protection for advanced P/M superalloy used in aeroengines.