Generally, CMAS corrosion is a key factor leading to the spalling failure in thermal barrier coatings (TBCs). Figuring out the component-dependent failure mechanism is the premise to improve the service life of TBCs. Here, CMAS corrosion behaviors with different Ca/Si components have been investigated through analyzing microstructure evolution in 8-YSZ coatings by EB-PVD. Capillary force from the gap between columnar crystals could accelerate the infiltration speed of the molten CMAS, leading to a fully populated coating with lower strain tolerance in 4 h. Subsequently, CMAS infiltration in the coatings led to preferential dissolution of yttrium ions and precipitation of yttria lean YSZ, and secondary CMAS phases. The corrosiveness of CMAS could be further tailored by optical basicity and viscosity. TBC failure could be enhanced in high-Ca case, resulting in the morphology evolution from columnar crystals to coarsening grain structures. Raman spectra indicates CMAS corrosion with high-Ca content will facilitate the phase transformation of t-YSZ to harmful monoclinic phase. In addition, DFT calculation demonstrates Ca doping into 8-YSZ will make monoclinic phase more stable and generate a 4.1 % volume expansion from the view point of energy. Consequently, the combination of the above low strain tolerance, new phases and volume expansion will accelerate the harmful morphology evolution. This work provides direct insight into the failure mechanism of CMAS corrosion and paves the way to design of new TBCs.

通常，CMAS 腐蚀是导致热障涂层 (TBC) 剥落失效的关键因素。弄清楚组件相关的失效机制是提高TBC使用寿命的前提。在这里，通过 EB-PVD 分析 8-YSZ 涂层的微观结构演变，研究了不同 Ca/Si 组分的 CMAS 腐蚀行为。来自柱状晶体之间间隙的毛细管力可以加快熔融 CMAS 的渗透速度，从而在 4 小时内形成具有较低应变耐受性的完全填充涂层。随后，涂层中的 CMAS 渗透导致钇离子优先溶解和氧化钇沉淀精益 YSZ 和二级 CMAS 阶段。CMAS 的腐蚀性可以通过光学碱度和粘度进一步调整。在高 Ca 情况下，TBC 失效会增强，导致形态从柱状晶体演变为粗化晶粒结构。拉曼光谱表明具有高 Ca 含量的 CMAS 腐蚀将促进t的相变-YSZ 为有害的单斜晶相。此外，DFT 计算表明，Ca 掺杂到 8-YSZ 中会使单斜晶相更加稳定，并且从能量的角度来看会产生 4.1% 的体积膨胀。因此，上述低应变容限、新相和体积膨胀的结合将加速有害形态的演变。这项工作提供了对 CMAS 腐蚀失效机制的直接洞察，并为设计新的 TBC 铺平了道路。