Comparison of K sub J sub IC and K sub IC values from tests on a single crystal nickel-base superalloy

Single crystal superalloys are being used in advanced gas turbine engines to exploit their superior creep strength at high temperatures. However, creep resistance alone is an insufficient selection criterion for some applications, and resistance to crack propagation can be an important property at all temperatures. Potential use in hydrogen-fueled engines, such as the Space Shuttle Main Engine, introduces the further concern of reduced toughness due to hydrogen embrittlement processes. While several nickel-base alloys have been screened in the past for such applications using fracture toughness testing, little is known concerning the effects of hydrogen on the fracture toughness of high {gamma} volume fraction superalloys. The work presented in this paper is part of a broader program to study hydrogen effects and embrittlement mechanisms in single crystal superalloys.