SiC/BN层状陶瓷的抗热震性能研究

Study on Thermal Shock Behavior of SiC/BN Laminated Ceramic Composites

采用水中急冷法研究了SiC/BN层状陶瓷的抗热震性能,并同SiC块体陶瓷作比较。实验结果表明SiC/BN层状陶瓷的热震断裂临界温差ΔTc为300℃,略低于SiC块体陶瓷的抗热震断裂临界温差。当热震温差ΔT>ΔTc时,SiC/BN层状陶瓷的热震剩余强度的下降趋势明显比块体陶瓷的下降趋势缓慢。这同热震断裂和热震损伤理论计算的热震参数R和R的结果相一致。这表明:与SiC块体陶瓷相比,SiC/BN层状陶瓷的热震裂纹形核阻力略有降低,但热震裂纹扩展阻力却大大提高。分析认为BN弱界面对裂纹的吸收和偏转是材料断裂能提高的主要原因,断裂能的提高有利于材料热震阻力的提高。

In this paper, the thermal shock resistance behavior of SiC/BN laminated ceramics was investigated by water quench test, and compared with that of SiC monolithic ceramics. The experimental results show that the thermal shock resistance critical temperature, △Tc, was 300℃ , which was less than that of SiC monolithic ceramics. When △T 〉 △Tc, the bending strength of SiC/BN laminated ceramics slightly decreased with increasing △T, while the bending strength of SiC monolithic ceramics decreased steeply with increasing △T. The experimental result coincided with the thermal shock parameter R and R′″ calculated values based on thermal shock fracture and thermal shock damage. The results reveal that the thermal shock crack initiation resistance of the materials was slightly less than that of SiC monolithic ceramics, but while the crack propagation resistance was much higher than that of SiC monolithic ceramics. SiC/BN laminated ceramics show excellent thermal shock behavior due to the high fracture energy resulting from crack deflection and crack absorbing at the BN weak interface.