Comprehensive effect of grain boundaries and grain boundary carbides on the hydrogen embrittlement of GH3536

In this work, the effects of the grain boundaries (GBs) and GB carbides on the hydrogen embrittlement (HE) of GH3536 superalloy were investigated. The GBs and (Cr, Mo)-enriched M23C6 carbides at GBs would lead to the dominating intergranular brittle fractures after electrochemical hydrogen pre-charging. The GBs and GB carbides act as hydrogen traps to promote the hydrogen-assisted crack initiation and further propagation at the interfaces between the GB carbides and matrix, which ultimately leads to the brittle fracture. With decreasing the solid solution temperature from 1150 degrees C to 950 degrees C, the average grain size refined from 23.9 +/- 1.3 mu m to 14.5 +/- 0.3 mu m, resulting in the superior HE resistance and less brittle fracture region. The study may be instructive for designing HE-resistant superalloys for hydrogen-fueled gas turbines in the future.