真空热处理对钛合金基体/NiCrAlY涂层组织结构及元素扩散行为的影响

采用电弧离子镀(AIP)技术在钛合金基体表面沉积制备了NiCrAlY涂层。通过SEM与能谱分析、XRD分析研究了真空热处理钛合金基体/NiCrAlY涂层界面显微组织的变化和元素扩散行为。结果表明: 从650 ℃开始, NiCrAlY涂层和钛合金基体就有明显的界面反应, 随着温度的升高, 界面分层并加厚, 同时出现Kirkendall空位带, 导致涂层退化。NiCrAlY涂层在650 ℃真空热处理后发现析出γ'-Ni₃Al相, 在1 050 ℃时发现只有CrTi₄相。在750 ℃温度下主要发生了Ti, Ni元素的扩散, Cr元素在870 ℃开始扩散并参与界面反应, 当温度升高到950 ℃时, Ni、Ti、Al、Cr各元素的扩散现象都很明显, Ni元素在涂层聚集的现象消失。

Effect of Vacuum Heat Treatment on Microstructure and Elements Diffusion Behavior of NiCrAlY Coating on Titanium Alloy

NiCrAlY coating was deposited on Ti6Al4V substrate by arc ion plating (AIP). SEM、EDS and XRD analysis were used to characterize microstructure and morphology of the NiCrAlY coating. And the influence of vacuum heat treatment on the elements diffusion behavior was studied. The results show that there were obvious interface reactions after vacuum heat treatment at above 650 ℃.With heat treatment temperature increasing, the interface became several layers with Kirkendall voids belts, which resulted in the degradation of the coating. γ'-Ni₃Al phase was precipitated in the coating after vacuum heat treatment at 650 ℃, and only CrTi₄ phase could be found at 1 050 ℃. Ti and Ni were the major diffusion elements at 750 ℃ while the diffusion of Cr occurred when the heat treatment temperature increased up to 870 ℃. At 950 ℃, Ni、Ti、Al and Cr elements all diffused significantly and Ni did not gather at the coating layer.