Mechanism of hydrogen cracking in carbides of directionally solidified cast nickel-based superalloy

The study investigates the effect of carbides on hydrogen embrittlement in a directionally solidified cast nickel-based superalloy. Most of the microstructures of the specimens are γ - γ ΄ network structures, and there is also a large amount of carbide precipitation. The presence of hydrogen reduces the binding force at the carbide interface, leading to a change in the fracture mode from preferential cracking within the carbide to preferential cracking at the carbide interface. Then, as the stress increases, the crack expands rapidly along the dislocation slip bands, eventually leading to fracture of the material. Hydrogen cracking at the carbide interface is the result of the synergistic action of multiple hydrogen embrittlement mechanisms. This study provides reference values for failure analysis of directionally solidified cast nickel-based superalloy materials for future hydrogen-fueled gas turbines.