Crack healing behaviour and high-temperature strength of mullite/SiC composite ceramics

Mechanical properties of sintered mullite/SiC ceramics related to its significant crack healing behavior are discussed in this paper. This investigation was made on four kinds of specimens such as as-received smooth, heat treated smooth, pre-cracked and pre-crack healed. Pre-crack sizes were 100 and 200 μm and they were semi-elliptical in shape. The main conclusions were obtained as follows: (a) mullite/SiC composite ceramic has ability to heal crack, (b) the best healing condition was found to be 1300 °C in air for 1 h, (c) maximum crack size able to be healed is semi-elliptical crack of 200 μm in diameter, (d) crack-healed zone has enough strength up to 1200 °C and most specimens failed outside the crack-healed zone.