Special Seminar: Oxygen Embrittlement and Time-Dependent Grain Boundry Cracking in Ni-Base Superalloys

Abstract

Embrittlement of grain boundaries by oxygen or other deleterious species can take place in a wide variety of Nickel – base superalloys when exposed to an aggressive environment. This leads to a complete change in failure mode from a ductile transgranular fracture to a macroscopically brittle intergranular fracture with very low ductility. It has also recently been shown that moisture level in the test atmosphere may play a significant role in the grain boundary embrittlement process. The degree of susceptibility to time – dependent intergranular cracking is highly dependent upon microstructure as well as composition. Microstructures which are susceptible to grain boundary embrittlement will be presented and discussed. Methods to enhance the materials resistance to brittle grain boundary fracture will also be discussed. Fracture characteristics have been studied using SEM. Microstructures are characterized using optical metallography and TEM.

This talk is not part of the MSE or WE 795 seminar series.