Environmental Effects Upon the Time-Dependent Fracture of Silicon Nitride and Silicon Carbide.

摘要

The great advantages, in terms of economy and performance, to be gained by using high performance ceramics in applications such as the gas turbine engine have spurred development efforts in the non-oxide ceramic area and in hardware applications. However, relatively little effort has been devoted to examining in detail the factors which may limit lifetimes in the above applications in which long lifetimes have been traditionally demanded. The purpose of this research project was to use a fundamentally based fracture mechanics approach to examine the susceptibility of Si3N4 and SiC ceramics to stress-corrosion in water and various gaseous environments over a range of temperatures. Further, the fundamental mechanism(s) which contribute(s) to the observed slow crack growth were to be elucidated. In addition, an effort was initiated to investigate the mechanism(s) by which molten salt environments may limit strengths and lifetimes of these materials. (Author)