1303 Crack-healing behavior of silicon nitride/silicon carbide composite at low oxygen partial pressure
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The crack-healing behavior of Si_3N_4/20 wt% SiC composite sintered with 8 wt.% Y_2O_3 was investigated under low oxygen partial pressure (pO_2=50, 5000, 21000Pa). A semi-elliptical surface crack with length of about 100 μm was introduced on the tensile surface by Vickers indentation. The specimens were healed at various conditions using the tube furnace with gas flowing system. After crack-healing, the bending strengths were tested at room temperature and at high temperatures ranging 800℃ to 1400℃. Even under pO_2=50Pa, the crack was completely healed at 1300℃ for 10h heat-treatment. Also, the high-temperature strength of crack-healed specimens at pO_2=50Pa showed almost constant bending strength of about 900MPa up to 1400℃.
