硅酸镱环境障涂层抗熔盐腐蚀行为与机制研究

稀土硅酸盐环境障涂层(EBC)是应用于新一代高推重比航空发动机热端部件的重要材料, 但其在高温熔盐环境的腐蚀行为与机制尚不明晰。本工作采用真空等离子喷涂技术(VPS)制备了Yb₂SiO₅/Yb₂Si₂O₇/Si环境障涂层, 并研究了该涂层体系在900 ℃、Na₂SO₄+25% NaCl(质量分数)熔盐环境中的腐蚀行为与机制。研究发现, 所制备的Yb₂SiO₅/Yb₂Si₂O₇/Si涂层体系结构致密, 各层之间结合良好; 涂层体系腐蚀240 h, 熔盐组分渗透Yb₂SiO₅涂层, 在Yb₂Si₂O₇中间层发生富集。涂层中Yb₂SiO₅相具有良好的稳定性, Yb₂O₃第二相与熔盐发生反应, 且随腐蚀时间延长, Yb₂O₃含量减少。中间层Yb₂Si₂O₇相与熔盐反应生成磷灰石相NaYb₉Si₆O₂₆和钠硅酸盐, 并产生Cl₂和SO₂等挥发性物质, 从而影响服役寿命。硅黏结层中未发现熔盐渗透现象, 保持完整。该涂层体系具有良好的抗熔盐腐蚀性能。

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

Environmental barrier coating (EBC) is essential for protection of ceramic matrix composite hot-sections in future gas turbine engines with high thrust-to-weight ratio. Rare-earth silicates, such as Yb₂SiO₅ and Yb₂Si₂O₇, have been developed for potential application as EBC. However, the corrosion behaviors and mechanisms of EBC in molten salt environment such as Na₂SO₄ at high temperature are not clear. In this work, the Yb₂SiO₅/Yb₂Si₂O₇/Si coating was prepared by vacuum plasma spraying (VPS). The molten salt (Na₂SO₄+25% NaCl, in mass) corrosion behaviors and mechanisms of the coating at 900 ℃ for 60-240 h were investigated. Results showed that the Yb₂SiO₅/Yb₂Si₂O₇/Si coating exhibited dense structure with good bonding between the triple ceramic layers. The molten salt of Na₂SO₄+25% NaCl penetrated the Yb₂SiO₅ top layer and enriched in the Yb₂Si₂O₇ interlayer, while the interfacial bonding between the coating and substrate still remained good after corrosion for 240 h. The Yb₂SiO₅ phase in the top layer exhibited good stability, while the second phase of the Yb₂O₃ reacted with molten salt. The content of the Yb₂O₃ decreased with the increase of corrosion time. The Yb₂Si₂O₇ phase in the interlayer reacted with molten salt to form apatite phase of NaYb₉Si₆O₂₆ and sodium silicate as well as volatile species such as Cl₂ and SO₂, which might shorten the service life of the coating. Moreover, there was almost no molten salt in the silicon bond layer, which remained intact. The Yb₂SiO₅/Yb₂Si₂O₇/Si coating exhibited good resistance to molten salt corrosion.