高熵稀土单硅酸盐环境障涂层局域结构的原子对分布函数解析  

Neutron Pair Distribution Function Analysis to the LocalStructure of High-Entropy RE2SiO5 EnvironmentalBarrier Coating

作　　者：王浩宇 吕熙睿 陈琦 熊瑛[3] 罗志新 张洁 王京阳[1] WANG Haoyu;LÜXirui;CHEN Qi;XIONG Ying;LUO Zhixin;ZHANG Jie;WANG Jingyang(Shenyang National Laboratory for Materials Science,Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China;School of Materials Science and Engineering,University of Science and Technology of China,Hefei 230000,China;AECC Shenyang Liming AERO-ENGINE Science and Technology Co.Ltd.,Shenyang 110043,China)

机构地区：[1]中国科学院金属研究所沈阳材料科学国家实验室,沈阳110016 [2]中国科学技术大学材料科学与工程学院,合肥230000 [3]中国航发沈阳黎明航空发动机有限责任公司,沈阳110043

出　　处：《金属学报》2024年第8期1130-1140,共11页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目Nos.U21A2063,52372071,52302076,92360304。

摘　　要：调控稀土单硅酸盐(RE_(2)SiO_(5))环境障涂层热膨胀系数,优化其与碳化硅纤维增强碳化硅(SiC_(f)/SiC)陶瓷基复合材料基体热膨胀系数匹配性,是其应用于高推比航空发动机的关键。本工作基于RE_(2)SiO_(5)/Yb_(2)Si_(2)O_(7)/Si三层结构涂层体系,对比研究了采用与基体热膨胀系数匹配优的(Y_(1/4)Ho_(1/4)Er_(1/4)Yb_(1/4))_(2)SiO_(5)面层与典型Yb_(2)SiO_(5)面层涂层体系的抗热冲击性能,发现Yb_(2)SiO_(5)面层热膨胀系数偏大造成的应力累积,是导致三层结构涂层失效的主要原因。依据中子衍射数据,分析中子对分布函数,对2种单硅酸盐局域结构特征进行解析。结果表明,高熵稀土单硅酸盐中多种稀土元素协同作用,降低了[ORE_(4)]四面体畸变程度,表现为热膨胀系数减小。提出通过合理选择稀土元素组合,扰动[ORE_(4)]局域结构畸变,有望实现稀土单硅酸盐热膨胀系数的定向调控。Environmental barrier coatings(EBCs)enable SiC_(f)/SiC ceramic matrix composites(CMC)to operate under high-temperature combustion conditions.They reduce the oxidation rate of SiC_(f)/SiC,the volatilization of the composites due to reaction with water vapor,and the surface temperature of the composites.Rare-earth monosilicates(RE_(2)SiO_(5)),owing to their excellent high-temperature durability,low thermal conductivity,and good phase stability,are used as the top layer of EBCs.However,they exhibit a high coefficient of thermal expansion(CTE),leading to thermal mismatch and inducing tensile residual stress(with a magnitude of several hundred MPa)in the coating,resulting in the formation of vertical cracks,which act as extremely-high-diffusivity paths for oxidation species transportation and silica volatilization.Therefore,regulating the CTE of RE_(2)SiO_(5) EBCs and minimizing the CTE mismatch among constituent RE_(2)SiO_(5) layers with SiC_(f)/SiC CMCs are critical for multilayered EBCs.Through atmospheric plasma spraying,a typical Yb_(2)SiO_(5)/Yb_(2)Si_(2)O_(7)/Si coating system and a tri-layer structured multicomponent(Y_(1/4)Ho_(1/4)Er_(1/4)Yb_(1/4))_(2)SiO_(5)/Yb_(2)Si_(2)O_(7)/Si coating system with better matched CTEs were manufactured.Both the coatings remained adhered to the substrate during deposition and after annealing,and no mud cracks that would compromise the coating gas-tightness quality and delamination cracks were observed at any of the coating interfaces.In thermal cycling tests,(Y1/4Ho1/4Er1/4Yb1/4)2SiO_(5)/Yb_(2)Si_(2)O_(7)/Si coatings showed a lifetime that is three times longer than that of conventional Yb_(2)SiO_(5)/Yb_(2)Si_(2)O_(7)/Si coatings.The failure mechanisms in thermal cycling were investigated via the finite element simulation of stress.It was found that the stress in the substrate was low,and the residual thermal stress was mainly concentrated on the top,inter,and bond layers and increased with an increase in temperature.Compared with that of the(Y1/4Ho1/4Er1/4Yb1/4)2SiO_(5) top

关 键 词：中子衍射 原子对分布函数 稀土硅酸盐 环境障涂层 燃气热冲击 

分 类 号：TG174.4[金属学及工艺—金属表面处理]