为研究真空等离子喷涂Si/Yb_(2)Si_(2)O_(7)/Yb_(2)SiO_(5)环境障涂层试样在涂层受压、涂层受拉时的室温弯曲强度及失效原因,采用超景深三维显微镜、SEM(Scanning Electron Microscope)等方法对喷涂后的试样进行了表征,并测量了涂层孔隙...为研究真空等离子喷涂Si/Yb_(2)Si_(2)O_(7)/Yb_(2)SiO_(5)环境障涂层试样在涂层受压、涂层受拉时的室温弯曲强度及失效原因,采用超景深三维显微镜、SEM(Scanning Electron Microscope)等方法对喷涂后的试样进行了表征,并测量了涂层孔隙率;采用拉伸法测试了涂层的结合强度,并采用三点弯曲试验测试了裸材、涂层受压和涂层受拉时的室温弯曲强度。结果表明:Si/Yb_(2)Si_(2)O_(7)/Yb_(2)SiO_(5)涂层与SiC_(f)/SiC复合材料的结合强度为10.13 MPa,拉伸断裂主要在复材表层发生。计算涂层厚度时,涂层受压样的弯曲强度(503.21 MPa)与裸材(506.79 MPa)基本一致;不计算涂层厚度时,涂层受拉样的弯曲强度(499.77 MPa)与裸材一致;EBC涂层整体具有一定的压缩强度,其整体抗拉强度比复材自身抗拉强度小很多。压涂层时,在载荷增加至接近最大载荷时,复材层间发生破坏,并逐步失效,随后涂层发生飞崩,载荷迅速下降,试验停止;拉涂层时,在载荷很小时(约64 N)涂层就被拉开,随着载荷增加,直至接近最大载荷时,层间发生破坏并逐步失效。弯曲试验时复材的主要失效模式是SiC纤维断裂、复材的SiC基体开裂和复材层间撕裂,复材受拉面产生复材厚度方向的纵向裂纹;复材表层沉积的SiC膜层失效模式主要是开裂和剥落;EBC涂层在受压时的主要失效模式是整体飞崩和开裂,在受拉时,涂层在最大应力处断裂为2部分。本研究对含EBC涂层的SiC_(f)/SiC复材的最大弯曲载荷设计具有参考意义.展开更多
Model composites consisting of Si C fiber embedded inβ-Yb_(2)Si_(2)O_(7) matrix were processed by Spark Plasma Sintering method and the feasibility of tunable Si Cf/Yb_(2)Si_(2)O_(7) interface in Si C-based CMCs were...Model composites consisting of Si C fiber embedded inβ-Yb_(2)Si_(2)O_(7) matrix were processed by Spark Plasma Sintering method and the feasibility of tunable Si Cf/Yb_(2)Si_(2)O_(7) interface in Si C-based CMCs were estimated.Weak and strengthened Si Cf/Yb_(2)Si_(2)O_(7) interfaces were achieved by adjusting sintering temperatures.The indentation crack test and fiber push out experiments clearly demonstrated the different debonding mechanisms in the samples.Weak interfaces sintered at 1200 and 1250℃exhibited crack deflection at interface in indentation test.Their low debond energy at the interface,which were comparable to those of Py C or BN,satisfied the well-recognized interfacial debond and crack deflection criteria for CMCs.The interface was strengthened by atomic bonding in model composite sintered at 1450℃,leading to crack penetrating into Si C fiber and high debond energy.The strong interface may be promising in Si Cf/Si C CMC to withstand higher combustion temperature,because Yb_(2)Si_(2)O_(7) will provide plastic deformation capacity,which would serve as weak interphase for crack deflection and energy dissipation.Therefore,it is possible to design the capability of Si C_(f)/RE_(2)Si_(2)O_(7) interface for different requirements by adjusting interfacial strength or debond energy to reach optimal mechanical fuse mechanism in SiC_(f)/SiC CMC.展开更多
基金supported by the National Key R&D Program of China under Grant No.2017YFB0703201Natural Science Foundation of China under Grant No.51772302CAS International Cooperation Key Program under Grant No.174321KYSB20180008。
文摘Model composites consisting of Si C fiber embedded inβ-Yb_(2)Si_(2)O_(7) matrix were processed by Spark Plasma Sintering method and the feasibility of tunable Si Cf/Yb_(2)Si_(2)O_(7) interface in Si C-based CMCs were estimated.Weak and strengthened Si Cf/Yb_(2)Si_(2)O_(7) interfaces were achieved by adjusting sintering temperatures.The indentation crack test and fiber push out experiments clearly demonstrated the different debonding mechanisms in the samples.Weak interfaces sintered at 1200 and 1250℃exhibited crack deflection at interface in indentation test.Their low debond energy at the interface,which were comparable to those of Py C or BN,satisfied the well-recognized interfacial debond and crack deflection criteria for CMCs.The interface was strengthened by atomic bonding in model composite sintered at 1450℃,leading to crack penetrating into Si C fiber and high debond energy.The strong interface may be promising in Si Cf/Si C CMC to withstand higher combustion temperature,because Yb_(2)Si_(2)O_(7) will provide plastic deformation capacity,which would serve as weak interphase for crack deflection and energy dissipation.Therefore,it is possible to design the capability of Si C_(f)/RE_(2)Si_(2)O_(7) interface for different requirements by adjusting interfacial strength or debond energy to reach optimal mechanical fuse mechanism in SiC_(f)/SiC CMC.
