二硅化钼改性硅酸镱环境障涂层的高温抗氧化行为及机理

High-temperature Antioxidant Behavior and Mechanism of Ytterbium Silicate Environmental Barrier Coatings Modified by MoSi_(2)

新一代高推重比航空发动机的发展对环境障涂层(EBCs)的服役寿命和温度提出了苛刻的要求。稀土硅酸盐作为EBCs材料应用于面层,在服役过程中易产生纵向裂纹,为腐蚀性介质的侵蚀提供通道,严重影响EBCs的寿命。二硅化钼(MoSi_(2))具有优异的高温性能,有望改善稀土硅酸盐EBCs体系的高温性能。采用MoSi_(2)改性Yb_(2)SiO_(5)面层,通过真空等离子喷涂技术(VPS)分别制备了Yb_(2)SiO_(5)-XMoSi_(2)(X=0,5%和10%,体积分数)为面层,Yb_(2)Si_(2)O_(7)为中间层,Si为黏结层的三种环境障涂层体系。研究了涂层在1350℃长时间氧化前后显微结构演化过程。结果发现,掺杂MoSi_(2)涂层体系在高温氧化500 h后仍能保持结构完整且面层裂纹减少。原因在于,MoSi_(2)可消耗氧化剂,减缓涂层内部TGO的增长速率,反应产物Yb_(2)Si_(2)O_(7)与中间层成分一致,具有较好的化学相容性,有效改善了涂层体系的高温性能。

The development of new generation of high thrust-to-weight ratio aero-engines places severe demands on the service life and temperature of environmental barrier coatings(EBCs).As a material for EBCs,rare-earth silicate applied to the surface layer is prone to longitudinal cracks during service,which providing channels for corrosive media to invade and seriously affecting the lifespan of EBCs.MoSi_(2)has excellent high-temperature properties and is expected to improve the high-temperature stability of rare-earth silicate EBC systems.In this work,MoSi_(2)was used to modify the Yb_(2)SiO_(5)top layer,and three types of EBC systems were prepared by vacuum plasma spraying(VPS),with Yb_(2)SiO_(5)-XMoSi_(2)(X=0,5%and 10%,volume fraction)as the top layer,Yb_(2)Si_(2)O_(7)as the intermediate layer,and Si as the bonding layer.The microstructural evolution of the coatings before and after long-term oxidation at 1350℃was studied.The results show that the MoSi_(2)-doped coating system maintains structural integrity with reduced cracks in the top layer after high-temperature oxidation for 500 h.MoSi_(2)can consume the oxidizer and slow down the growth rate of TGO inside the coating.The reaction product Yb_(2)Si_(2)O_(7)is consistent with the composition of the intermediate layer,which has better chemical compatibility and effectively improves the high-temperature performance of the coating system.