热冲击环境下涂层/基底界面的微观形貌及元素扩散规律研究

Study on Microstructure of Coating/Substrate Interface and Law of Element Diffusion in Thermal Shock Environment

针对热障涂层在高温环境中长期服役的需求,研究热障涂层在热冲击环境下涂层/基底界面形貌演变及元素扩散规律。通过自主搭建的石英灯加热平台对热障涂层进行热冲击试验。利用SEM和EDS对热冲击后涂层/基底界面的微观形貌及元素分布进行分析,利用Boltzmann-Matano扩散模型计算了涂层/基底界面Al元素的扩散系数。结果表明,沉积态的热障涂层中黏结层(BC)主要由β和γ相组成,并且在涂层/基底界面已经出现扩散区;随着热冲击试验的进行,Al元素快速消耗致使BC层和基底间Al元素浓度梯度转变,Al元素开始向外扩散,部分拓扑密堆(TCP)相中富集的难熔元素可以重新固溶到基底中,最终各元素在界面区的分布逐渐均匀;Al元素的扩散系数在热冲击试验开始前为正值,到600次热冲击循环后为负值,且扩散系数的最大值均出现在涂层/基底界面处,距离界面越大,扩散系数就越低。

In order to meet the requirement of long-term service of thermal barrier coatings(TBCs)in high temperature environment,the morphology evolution of coating/substrate interface and the laws of element diffusion of TBCs in thermal shock environment were studied in this paper.The thermal shock tests of TBCs was carried out by the quartz lamp heating platform.The microstructure and element distribution of the coating/substrate interface after thermal shock were analyzed by SEM and EDS,and the diffusion coefficient of Al element at the coating/substrate interface was calculated by Boltzmann-Matano diffusion model.The results show that the BC layer was mainly composed ofβandγphases,and the diffusion zone has appeared at the coating/substrate interface.With the thermal shock tests,the rapid consumption of Al element caused the gradient shift of Al element concentration between BC layer and substrate,and Al element began to diffuse outward.Some refractory elements enriched in the topologically close-packed(TCP)phase could be solidly dissolved into the substrate again.Finally,the distribution of all elements gradually uniform in the interface region.The diffusion coefficient of Al element was positive before the thermal shock tests and negative after 600 cycles.The maximum diffusion coefficient appears at the coating/substrate interface.And the greater the distance from the interface,the lower the diffusion coefficient.