Degradation of Silicon Nitrides in High Pressure, Moisture Rich Environments

Abstract

This paper provides a review of a recent study undertaken to examine the long-term reliability of silicon nitride and silicon carbide ceramics exposed to a representative gas turbine environment. A typical test exposure consisted of 500 hours at 1204°C and 1.5 atm of water vapor carried in an air environment at 10 atm of total pressure. Following each exposure specimens were weighed, measured, and then sectioned for optical and scanning electron microscopy. The total exposure duration was 1500 h for the silicon nitride and 2500 h for the silicon carbide.