NiCrAlY涂层与镍基单晶高温合金基体的互扩散行为

Interdiffusion behavior between NiCrAlY coating and Ni-based single-crystal superalloy

采用多弧离子镀技术在镍基单晶高温合金基体表面制备NiCrAlY涂层,并利用XRD、SEM/EDS、EPMA等表征方法研究试样在1100℃热暴露100 h过程中涂层/基体之间互扩散引发的微观结构演变与各组元的成分分布。基于所测定的各组元成分−距离曲线,采用基于数值回归方法框架的HitDIC软件获得各组元沿整个扩散通道的主互扩散系数。研究结果表明:在1100℃热暴露初期,NiCrAlY涂层和基体界面处形成了互扩散区(IDZ)和二次反应区(SRZ),而且IDZ和SRZ的厚度随热暴露时间不断增大;在SRZ中析出的颗粒状和针状拓扑密堆相(TCP)主要由Re,Cr,W等元素组成,且与合金基体界面成特定角度;在热暴露过程中NiCrAlY涂层与基体间主要发生Cr元素向基体的内扩散和Ni,Al,Ta,Re,W等元素由基体向涂层的外扩散,且随着热暴露时间的延长,涂层与基体界面处元素的浓度梯度逐步减小;采用数值回归法获得的模拟结果与实测成分−距离曲线吻合较好,且Al,Co和Cr成分变化对所得各组元主互扩散系数的影响较大。

A NiCrAlY coating was deposited on Ni-based single crystal superalloy by arc ion plating technology.The microstructure evolution and element interdiffusion behavior caused by the interdiffusion between the coating and substrate during thermal exposure at 1100℃for up to 100 h were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM)equipped with energy dispersive spectroscopy(EDS),electron probe microanalyze(EPMA),and so on.Based on the experimental composition profiles,the main interdiffusion coefficients of each composition along the entire diffusion channel were obtained by HitDIC(high-throughput determination of interdiffusion coefficients)software,which has been developed in the framework of numerical inverse method.The results show that the interdiffusion zone(IDZ)and second reaction zone(SRZ)are formed at the interface between coating and substrate at the initial stage of thermal exposure at 1100℃,and both widths increase with the extension of thermal exposure time.The precipitated granular and needle-like topologically close-packed(TCP)phases in the SRZ are inclined by a certain angle to the coating/substrate interface and are mainly composed of Re,Cr and W etc.During the thermal exposure process,the inward diffusion of Cr from the coating to the substrate are accompanied with the outward diffusion of Ni,Al,Ta,Re and W caused the decrease of concentration gradient of components at the interface of coating/substrate.Besides,the numerical inverse method is conducted,and the simulation results are in good agreement with the experiment composition profiles.The main interdiffusion coefficients of each composition are mainly affected by Al,Co and Cr components.