THERMAL-SHOCK BEHAVIOR OF ADV ANCED CERAMIC/COMPOSITE HOT-GAS FILTERS

摘要

The thermal shock/fatigue behavior of monolithicand composite hot-gas candle filers obtained from variousmanufacturers was evaluated. The composite filters were madeof both oxide and nonoxide materials; the monolithic filterswere made only of nonoxide materials.During single cycle thermal shock tests, composite filters showlittle or no strength degradation when quenched fromtemperatures between 900 and 1000 deg C. At higher quenchingtemperatures, slow strength degradation was observed. Regularmonolithic SiC filters showed no strength degradation whenquenched from temperatures up to ≈700-900 deg C, whereas athigher quenching temperatures, the strength decreased at arelatively sharper rate. On the other hand, recrystallizedmonolithic SiC filters showed higher initial strength andretained this strength to higher quenching temperatures whencompared with regular SiC filters. This finding may be relatedto the difference in the strength of grain boundary phases in thetwo filters. For thermal cycles between room temperature and800-1000 deg C, composite filters show little (18-24%) strengthdegradation up to three cycles, beyond which the strengthremains unchanged. Similar behavior, with an initial strengthdrop of 15-28%, was observed for monolithic filter specimensthat were thermally cycled between room temperature and 800 deg C.