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.