Alumina-based crucibles with enhanced thermal shock resistance via reinforcement of mullite fibers

Abstract

Crucible is the indispensable vessel in smelting of superalloy, and the service life of crucibles is quite important to the development of superalloy. In order to extend the service life of crucible for superalloy smelting, alumina-based crucibles are prepared by slip casting, and mullite fibers are used as reinforcement phase. The effect of mullite fibers on the microstructure and property of the crucibles was studied. The appropriate content of mullite fibers are beneficial to the comprehensive performance of the crucibles. The reinforcement mechanism of mullite fibers includes crack deflection, fiber extraction, and fiber bridging, through which fibers hinder the initiation and propagation of cracks in ceramics. For the crucible samples with 3 wt% of mullite fibers, the values of flexure strength are 22.47 MPa and 19.14 MPa at room temperature and high-temperature, respectively. After thermal shock for 5 times, the residual room-temperature flexural strength is 16.65 MPa and the strength retention rate is 74.1%. It is confirmed that, the 3 wt% of mullite fibers improves the thermal shock resistance of the crucible, which is beneficial for extending the service life of the crucible for superalloy melting.