MCrAlY涂层高温氧化界面扩散行为研究进展

Recent Advances for Interface Diffusion Behavior in MCrAlY Coatings at Elevated Temperature Oxidation

摘要:

MCrAlY涂层在保护基体高温氧化和腐蚀方面发挥着重要作用，可在基体表面形成致密连续的氧化层，阻止阳离子和氧的扩散。随着氧化铝层的生长，导致涂层/氧化层界面处铝浓度降低，抑制了连续的Al2O3层的生长，导致混合氧化物和裂缝以及空隙的形成，使得涂层过早失效。在涂层和基体界面，真空热处理提高了界面的结合强度，改善了涂层与基体的粘附性。然而在高温下的界面扩散过程将对基体产生有害的影响。基体的难熔强化元素，如Ti，W，Mo，可以扩散到涂层中。而且相互扩散过程可在基体形成二级反应区（SRZ），析出拓扑密堆相（TCP）相，如σ，μ和Laves相等，降低高温合金的高温疲劳寿命。在本文中，详细介绍了涂层/基体的界面扩散过程，以及总结了当前对界面扩散效应的理解以及对减少界面扩散所做的努力。

Abstract:

MCrAlY coatings are playing an important role in protecting the substrate from oxidation and corrosion at high temperature, which can form dense and continuous oxide scales on the surface to retard the diffusion of cations and oxygen. With the depletion of Al for the growth of alumina layer, the concentration of aluminum in the coating near coating/oxide scales interface decreased, which further suppresses the consecutive Al₂O₃-scale growth, causing the formation of mixed oxide compounds and cracks as well as voids. This process can cause premature failure of the coating. Between the coatings and the superalloy, the interdiffusion process after vacuum heat treatment is beneficial, which can improve the adhesion of the coating and the substrate. However, because of its thermally activated nature, the interface diffusion process will make deleterious effects at elevated temperature. The elements of the substrate, like Ti, W, Mo, can diffuse into coating. Furthermore, the interdiffusion process in the coating/substrate will form a secondary reaction zone (SRZ), which mainly consists of high density of topologically close-packed (TCP) phases, such as σ, μ and Laves phases. These TCP phases in the matrix may reduce the high-temperature fatigue life of the superalloy.