The fatigue and fracture of turbine blade alloys in high pressure hydrogen

In June 1995, the NASA space shuttle Discovery lifted off for the first time with an improved high-pressure oxidizer turbopump fitted to one of its three main engines. In 1997, an advanced high-pressure fuel turbopump will enter service as well. Both systems will make extensive use of nickel-based superalloy microstructures specially tailored for improved resistance to hydrogen embrittlement. This article reviews a study on cast single-crystal and equiaxed nickel superalloys and the subsequent approach used to improve their hydrogen resistance.