High temperature fracture and creep fatigue characteristics for structural design of silicon nitride
Murata Masato; Takahara Wataru; Sato ichi; Deguchi Takeshi
Abstract:High temperature creep and creep fatigue fracture behavior were investigated in air on two kinds of silicon nitride with different additives of MgO + Y2O3 and Al2O3 + Y2O sub . Fracture elongation was almost identical in the both cases of creep and creep fatigue tests at 1673K in air for the two kinds of silicon nitride. The fracture surface was rough in the creep test specimens, while it was relatively smooth in the creep fatigue test specimens. In the creep fatigue tests, fracture lifetime was shorter than that of the creep tests. However, for the silicon nitride with MgO + Y2O3 the fracture lifetime in the creep fatigue tests approached to the level of creep tests with increasing the hold time under no stress in the wave pattern. It seems that some intelligent function of the self-repairing of materials damage occurs in silicon nitride with MgO + Y2O3. Key Words:silicon nitride, additive, creep, creep-fatigue, fracture lifetime, fracture surface, self-repairing, intelligent function