1991 年 40 巻 453 号 p. 695-699
Fractographic analysis was carried out on the fracture surfaces of two kinds of sintered silicon nitride fractured under static or cyclic loads. The main results obtained are as follows.
(1) As for the final fracture surface, 80% to 90% of the whole area was intergranular fracture, regardless of kinds of materials, loading stress mode or temperature. It was concluded that the strength of grain boundary of the materials used in this study was very low as compared with the strength of columnar beta silicon nitride crystal.
(2) Although the percentage of transgranular fracture was low, it varied with the crack velocity. It was higher on the final fracture surface than on the slow crack growth surface.
(3) Debris of the fractured grains and wear marks were observed only on the fracture surface of CT specimens under cyclic load.