FRACTURE-TOUGHNESS AND THERMAL-SHOCK BEHAVIOR OF SILICON NITRIDE-BORON NITRIDE CERAMICS

Fracture toughness behavior, stress-strain behavior, and flaw resistance of pressureless-sintered Si3N4-BN ceramics are investigated. The results are discussed with respect to the reported thermal shock behavior of these composites. Although the materials behave linear-elastic and exhibit no R-curve behavior, their flaw resistance is different from that of other linear-elastic materials. Whereas the critical thermal shock temperature difference (DELTA-T(c)) is enhanced by adding BN, the content of BN has no influence on the strength loss during severe thermal shocks.