Effect of microstructure evolution and crystal structure on thermal properties for plasma-sprayed RE2SiO5 (RE = Gd, Y, Er) environmental barrier coatings

Microstructure and property evolution of high‐entropy rare‐earth silicate T/EBCs during thermal aging

“…that can reduce heat conduction. The thermal conductivities of the as‐sprayed coatings increased with the increase of test temperature, especially above 800°C, which might be resulted from the microstructural changes because of sintering effects, as well as the recrystallization of the amorphous phase at about 1000°C 35 . It can be seen that the thermal conductivities of the thermal‐aged 4HES and 5HES coatings were 1.45–1.97 and 1.35–1.77 W/(m K), respectively.…”

“…that can reduce heat conduction. The thermal conductivities of the as-sprayed coatings increased with the increase of test temperature, especially above 800 • C, which might be resulted from the microstructural changes because of sintering effects, as well as the recrystallization of the amorphous phase at about 1000 • C. 35 It can be seen that the thermal conductivities of the thermal-aged 4HES and 5HES coatings were 1.45-1.97 and 1.35-1.77 W/(m K), respectively. The thermal diffusivities and thermal conductivities significantly increased after thermal aging, F I G U R E 1 4 Thermal conductivities and thermal diffusivities of as-sprayed and thermal-aged monosilicate coatings: (A and B) 4HES and 5HES coatings; (C) single-component coatings which was caused by the crystallization of amorphous phase as well as reduction in defects.…”

“…The appearance of HEO second phase was related to the decomposition of 4HES and 5HES powders, whereas the formation of the amorphous phase was mainly due to the rapid cooling of the molten particles during the spraying process. 35 The contents of the amorphous phase, which were calculated by MDI Jade 6.0 software in the as-sprayed 4HES and 5HES coatings, were about 30.67% and 37.24%, respectively.…”

Evaluation of environmental barrier coatings: A review

“…Thermal stress of a coating on substrate is strongly related to their CTEs as shown in the following equation 61 :…”

Molten Salt Corrosion Behaviors and Mechanisms of Ytterbium Silicate Environmental Barrier Coating

“…Key words: environmental barrier coating; ytterbium silicate; Na 2 SO 4 +25% NaCl molten salt; corrosion mechanism 硅基非氧化物陶瓷及其复合材料具有低密度、 高比强度、耐高温、抗氧化和优异的高温力学性能 等特点, 可部分取代高温合金应用于航空发动机的 热端部件 [1] 。 在干燥环境中, 硅基非氧化物陶瓷材料 与氧气发生反应生成 SiO 2 保护层, 可以避免其继续 氧化。然而, 航空发动机的服役环境包含多种腐蚀 介质(如高温水蒸气、熔盐等), 会与 SiO 2 保护层反应 生成挥发性的 Si(OH) 4 , 导致材料性能迅速退化 [2][3] 。 环境障涂层(Environmental Barrier Coating, EBC)涂 覆于硅基非氧化物陶瓷材料表面, 能够将基体与发 动机中的腐蚀性介质隔离开来, 从而有效提高材料 在发动机环境中的性能稳定性 [4] 。 稀土硅酸盐材料具有良好的相稳定性、优异的 耐蚀性能、与基体匹配的热膨胀系数等特点, 是最 具应用潜力的环境障涂层材料。王京阳等 [5] 结合第 一性原理和实验表征系统研究了不同稀土硅酸盐块 体材料的力学与热学性能。王一光等 [6][7] 针对稀土硅 酸盐块体材料的耐蚀性能开展了相关研究工作, 发 现 X2-RE 2 SiO 5 比 X1-RE 2 SiO 5 具有更好的耐蚀性能。 近年来, 通过高熵化设计优化稀土硅酸盐材料的性 能也引起了研究者的关注 [8][9] 。这些工作为 EBC 的选 材和结构优化设计提供了可靠的理论依据。稀土硅 酸盐用作涂层材料时, 其结构、性能与块体材料相 比会产生差异。本研究团队 [10][11][12][13][14][15] 针对不同稀土硅酸盐 涂层材料的显微结构、热学力学性能和耐蚀性能开 展了系列研究, 发现稀土硅酸盐涂层在制备过程中 易形成孔隙和裂纹等缺陷, 并分解产生氧化物第二相, 从而影响涂层的抗热震和耐蚀性能。为提高 EBC 的 服役性能, 研究者 [16][17] 开发了稀土硅酸盐/Si 和稀土 硅酸盐/Mullite/Si 等涂层体系。张小锋等 [18][19][20][21] 采用等 离子喷涂-物理气相沉积技术(Plasma Spray-Physical Vapor Deposition, PS-PVD)制备了 Yb 2 SiO 5 /Mullite/Si 环境障涂层体系, 探讨了涂层沉积机制及其在高温环 境下的显微结构演化过程, 并提出了通过表面镀 Al 来 提高 EBC 耐蚀性的新方法。 Hu 等 [22] 设计了 Lu 2 Si 2 O 7 -Lu 2 SiO 5 /Mullite 双涂层体系, 该体系可有效提高服 役温度(1450 ℃), 但热循环过程中因产生贯穿裂纹 而失效。本研究团队 [10,23]…”