Maximum compressive strain at high temperature was introduced as a new quality indicator of ceramic foam filters used in metal casting. Maximum compressive strain at high temperature, number of thermal cycles before failure, room temperature compressive strength and bulk density of SiC-based ceramic foam filters with the same pore size produced by four manufacturers were measured. The best quality product exhibited the highest number of thermal cycles before failure and minimum strain at high temperature. Differences in properties were elucidated based on X-ray diffraction and scanning electron microscope microstructural characterization. The best quality filter has less glass phase and more quartz phase, while lower quality filters have more glass and cristobalite phases. The glass phase increases the maximum strain at high temperature, while both glass and cristobalite phases reduce the number of thermal cycles before failure. The maximum compressive strain at high temperature can be utilized as the main indicator for evaluating the quality of ceramic foam filters.

Keywords: Engineering ceramics, Sintering, Thermal, Microstructure.