热障涂层TGO界面应力分布及裂纹扩展行为的研究进展

Progress on Stress Distribution and Crack Propagation Behavior at the TGO Interfaces of Thermal Barrier Coatings

热障涂层以其优异的抗氧化、隔热、耐腐蚀性而广泛应用于热端部件表面。在超过1000℃高温的服役环境下,外界的氧元素通过陶瓷层扩散到粘接层界面,与其中的金属元素发生氧化反应生成一层热生长高温氧化物(TGO)。随着服役时间的增加,TGO不断生长,TGO界面产生较大的热应力,导致裂纹的萌生与扩展,使得涂层大面积剥落,因此TGO氧化失效的研究既是难点也是热点问题。总结了研究TGO界面建立的主要几种模型,例如同心圆界面模型、曲线弦界面模型和真实界面模型,其中曲线几何结构通常只需要振幅和波长即可很好地描述界面,因此大多数模型建立采用了曲线模型。在此基础上,重点综述了界面形貌、界面粗糙度和TGO厚度对应力分布的影响,以及从应变能释放率和裂纹路径两个角度探讨了界面损伤行为。上述研究很好地阐明了TGO生长过程,但是仅考虑了形态特征对应力分布的影响,接下来的研究应考虑真实TGO界面并完善模拟的准确性,同时发展有限元技术实现在实际条件下裂纹扩展路径和使用寿命的预测。

Thermal barrier coatings(TBCs)has been widely used on the surface of hot end components because its excellent high temperature oxidation resistance,adiabatic performance and corrosion resistance.In service environments with temperatures in excess of 1000℃,external oxygen elements will diffuse through the toping coating to the interface of the bonding coating,and reacts with the metal elements in it to form a layer of thermal growth oxidation(TGO).With the increase of service time,the TGO interface generates high thermal stress during the continuous growth of TGO leads to crack initiation and propagation,which results in the peeling off of large areas of the coating.Therefore,the study of TGO oxidation failure is both a tough and a popular problem.This paper summarizes the main models used in the study of TGO interface establishment,such as concentric circle interface model,curved string interface model and real interface model.The curve string geometry generally requires only amplitude and wavelength to describe the interface well,so most modeling are established by the curve model.Based on this,the influence of interfacial topography,interfacial roughness and TGO thickness on stress distribution are summarized,and the interfacial damage behavior is discussed from both the strain energy release rate and the crack trajectory.The mentioned studies have provided a sound illustration of the TGO growth process,but only the influence of morphological features on stress distribution has been considered,therefore further research should consider the real TGO interface and refine the accuracy of the simulation results,and develop FEM techniques to achieve predict crack propagation trajectory and service life under realistic conditions.