Hot-Salt Induced Degradation of a High Strength Silicon Nitride

The maintenance of mechanical strength to very high temperatures renders advanced non-oxide ceramics good candidates for developing and future elevated temperature applications. Unfortunately, high temperature service environments contain a number of species that can act in an aggressive manner toward structural components and cause significant damage. The corrosion behavior of a high strength, hot-pressed Si sub 3 N sub 4 was studied in a burner rig combustion environment. In the temperature range 1000-1150 deg C, the corrosion process was influenced by the presence of sodium and sulphur, derived from impurities in the gas stream. In the paper, corrosion product morphologies are related to the temperature of exposure and measured reaction kinetics. A limited study on the effects of corrosion on mechanical properties is also reported.