SiC/BN层状陶瓷耐损伤性能

采用压痕法在SiC/BN层状陶瓷试样的表面引入不同尺寸的表面裂纹,利用三点弯曲测量含裂纹试样的极限断裂应力,研究了不同尺寸的表面裂纹对层状陶瓷断裂强度的影响;根据压痕载荷-强度实验结果,测定层状陶瓷的阻力曲线,并与单相SiC陶瓷对比。结果表明,层状陶瓷的压痕强度对压痕裂纹深度的变化不敏感,阻力曲线呈上升型;而单相SiC陶瓷的压痕强度随压痕裂纹深度的增加急剧下降,阻力曲线呈平稳型,说明层状陶瓷具有优异的耐损伤性能和升值R-曲线行为。分析认为,裂纹在弱界面处发生偏折是层状陶瓷具有优良耐损伤性能和升值R-曲线行为的主要原因。这为陶瓷材料在含有一定的制备和加工缺陷以及承受冲击、磨损等接触损伤的条件下保持高强度提供了可能。

DAMAGE RESISTANCE OF SiC/BN LAMINATED CERAMICS

The surface flaws of different sizes were introduced into SiC/BN laminated ceramics by Vickers indentation method. The specimens were fractured by three-point bending. The effect of the surface flaw size on strength of SiC/BN ceramics was studied. The R-curve of SiC/BN laminated ceramics was evaluated using the indentation-strength method and compared with that of the monolithic SiC. The results show that the fracture strength for monolithic SiC decreases steeply with increasing indentation load, while for SiC/BN laminated ceramics reducing slightly with increasing indentation load, suggesting an exceptional damage resistance. Moreover, a rising R-curve behavior was demonstrated from the strength-indentation load method for SiC/BN laminated ceramics, a plateau R-curve behavior for monolithic SiC. The excellent damage resistance of SiC/BN laminated ceramics should be attributed to the crack deflection at the SiC/BN weak interfaces. The results show that SiC/BN laminated ceramics can retain a significant fraction of its strength under contact damage conditions; this should allow it to exhibit superior resistance to impact- or abrasion-induced damage in service.