MCrAlY (M=Ni and/or Co) overlay coating is widely used as a protective coating against high temperature oxidation and corrosion. However, due to its big difference in chemical composition with the underlying superalloy, elements interdiffusion occurs inevitably. One of the direct results is the formation of interdiffusion zone (IDZ) and secondary reaction zone (SRZ) with a high density of fine topological closed-packed phases (TCPs), weakening dramatically the mechanical properties of the alloy substrate. It is by now the main problem of modern high-temperature metallic coatings, but there are still hardly any reports studying the formation, growth and transformation of IDZ and SRZ in deep, as well as the precipitation of TCPs. In this work, a typical NiCrAlY coating is deposited by arc ion plating on a single-crystal superalloy N5. Elements interdiffusion between them and its relationship on microstructure were clarified. Cr rather than Al from the coating diffuses into the alloy at high temperatures and segregates immediately beneath their interface, contributing largely to the formation of IDZ. Simultaneously, diffusion of Ni from the deep alloy to IDZ leads to the formation and continuous expansion of SRZ.

中号CrAlY（中号（Ni和/或Co）覆盖涂层被广泛用作抗高温氧化和腐蚀的保护涂层。但是，由于其与下层超合金的化学成分差异很大，因此不可避免地会发生元素相互扩散。直接结果之一是形成相互扩散区​​（IDZ）和二级反应区（SRZ），它们具有高密度的精细拓扑密堆积相（TCP），大大削弱了合金基材的机械性能。到目前为止，这是现代高温金属涂层的主要问题，但几乎没有关于深入研究IDZ和SRZ的形成，生长和转变以及TCP沉淀的报道。在这项工作中，典型的NiCrAlY涂层是通过电弧离子镀在单晶高温合金N5上沉积的。阐明了元素之间的相互扩散及其与微观结构的关系。涂层中的Cr而不是Al会在高温下扩散到合金中，并在其界面下方立即偏析，这在很大程度上有助于形成IDZ。同时，Ni从深合金扩散到IDZ导致SRZ的形成和连续膨胀。