元素扩散对热障涂层/DZ125合金组织与显微硬度的影响

Effect of the element diffusion on the microstructure and micro-hardness of thermal barrier coating/DZ125 superalloy

为研究元素扩散对CoCrAlY涂层与Ni基高温合金DZ125显微组织和显微硬度的影响,采用电子束物理气相沉积法在Ni基高温合金基体上制备了8YSZ/CoCrAlY热障涂层。运用Boltzmann-Matano算法以及X射线衍射(X-ray diffraction,XRD)、电子探针(electron probe micro-analyzer,EPMA)等方法对氧化前后涂层基体的元素质量浓度分布曲线、相转变及显微硬度进行分析。研究结果表明:在1 050℃热氧化中,Co的互扩散系数在10-16 m2/s量级;元素扩散引起黏结层β-CoAl相退化,且涂层与基体界面处会形成互扩散区(inter-diffusion zone,IDZ)与二次反应区(second reaction zone,SRZ);IDZ的组织主要为富含Al的β相和富含Cr与W的γ相;SRZ中的拓扑密排相(topologically close-packed phase,TCP)削弱了γ'的位错阻碍作用,导致SRZ的显微硬度远低于合金基体硬度。

To investigate the effect of the interface element diffusion on the microstructure and micro-hardness of CoCrAlY coating/Ni based DZ125 superalloy,8YSZ/CoCrAlY thermal barrier coatings was deposited on Ni-based superalloy DZ125 using the electron beam physical vapor deposition（PVD）technology.The element diffusion,phase constituent and micro-hardness were characterized by Boltzmann-Matano method,X-ray diffraction（XRD）,and electron probe micro-analyzer（EPMA）.The results showed that the diffusion coefficient of Co element annealing at 1 050 ℃ was in the magnitude of 10^-16 m^2/s.Elements diffusion resulted in the depletion ofβ-CoAl phase in CoCrAlY coating.Also,the inter-diffusion zone（IDZ）and second reaction zone（SRZ）were formed at the interface of the coatings and substrates.The composition of the inter-diffusion zone was Al-richedβphase and Cr/W richedγphase.The micro-hardness of SRZ was much lower than that of the substrate since the dislocation blocking effect ofγ′phase was weakened by the topologically close-packed phase（TCP）in SRZ.