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首页> 外文期刊>DVS-Berichte >Mechanical Properties and Behaviour of BSAS/mullite-based Environmental Barrier Coatings Exposed to High Temperature in Water Vapour Environment
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Mechanical Properties and Behaviour of BSAS/mullite-based Environmental Barrier Coatings Exposed to High Temperature in Water Vapour Environment

机译：水蒸气环境中暴露于高温下的BSAS /莫来石基环境屏障涂料的力学性能和行为

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摘要

Si-based ceramics (e.g., SiC and Si_3N_4) are known as promising high-temperature structural materials in various components where metals/alloys reached their ultimate performances (e.g., advanced gas turbine engines and structural components of future hypersonic vehicles). To alleviate the thickness recess that Si-based ceramics undergo in a high-temperature environmental attack (e.g., H_2O vapour), appropriate refractory oxides are engineered as environmental barrier coatings (EBCs). Presently, the state-of-the art EBCs comprise multilayers of silicon (Si) bond coat, mullite (A_l6Si_2O_(13)) intermediate layer and BaO-SrO-Al_2O_3-SiO_2 (BSAS) top coat. Evaluating and understanding their mechanical properties, such as, the elastic modulus (E) and the strain-stress relationship is essential for their practical application and reliable employment. It was investigated via depth-sensing indentation the role of high-temperature treatment (1300℃), performed in H_2O vapour environment (for time intervals up to 500 h), on the mechanical behaviour of air plasma sprayed Si/mullite/BSAS layers deposited on SiC substrates. Laserultrasonics was employed to evaluate the E values of as-sprayed coatings and to validate the indentation results. The fully crystalline, crack-free and near crack-free as-sprayed EBCs were engineered under controlled deposition conditions. The (i) absence of phase transformation and (ii) stability of the low elastic modulus values (e.g., ～60-70 GPa) retained by the BSAS top layers even after harsh environmental exposures provides a plausible explanation for the almost crack-free coatings observed. The measured mechanical properties of the EBCs and their microstructural behaviour during the high-temperature exposure are discussed and correlated.
机译：硅基陶瓷（例如SiC和Si_3N_4）被公认为在金属/合金达到其最终性能的各种组件（例如高级燃气轮机和未来超音速飞行器的结构组件）中具有前景的高温结构材料。为了减轻硅基陶瓷在高温环境（例如H_2O蒸气）中遭受的厚度降低，将适当的难熔氧化物设计为环境屏障涂层（EBC）。当前，最先进的EBC包括硅（Si）粘结涂层，莫来石（Al_16Si_2O_（13））中间层和BaO-SrO-Al_2O_3-SiO_2（BSAS）面涂层的多层。评估和了解它们的机械性能，例如弹性模量（E）和应变-应力关系，对于它们的实际应用和可靠使用至关重要。通过深度感应压痕研究了在H_2O蒸气环境中（时间间隔长达500 h）进行的高温处理（1300℃）对空气等离子喷涂Si /莫来石/ BSAS层的力学行为的影响。在SiC衬底上。激光超声技术用于评估喷涂后的涂层的E值并验证压痕结果。在受控的沉积条件下设计了全结晶，无裂纹和几乎无裂纹的喷涂EBC。即使在苛刻的环境暴露后，BSAS顶层仍能保持（i）没有相变和（ii）低弹性模量值（例如〜60-70 GPa）的稳定性，这为几乎无裂纹的涂层提供了合理的解释观测到的。讨论并关联了在高温下测量的EBC的机械性能及其微结构行为。

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