Solute-hydrogen segregation and interaction at γ/γ′ interface of nickel-based single crystal superalloys

The effects of alloying elements on hydrogen embrittlement (HE) resistance of nickel-based single-crystal superalloys (Ni-SXs) are investigated through first-principles calculations and macro-mechanical experiments. The segregation of hydrogen at the γ/γ′ interface leads to the degradation of interfacial cohesive strength and vacancy formation energy. Analysis of bonding charge density reveals that hydrogen-induced decohesion stems from the weakening of interatomic bonds between the first-nearest-neighboring atoms. The tensile-fracture morphology demonstrates that the growth and coalescence of micro-voids near crack tips promote hydrogen-assisted crack propagation. Among the investigated alloying elements, Re preferentially segregates at the interface and exerts pronounced inhibition of hydrogen-enhanced decohesion and vacancy formation through the formation of strong Ni-Re bonds. Consequently, Re improves the HE resistance of Ni-SXs by inhibiting hydrogen-induced cracks and micro-voids. The current work extends the understanding of HE mechanisms in Ni-SXs and provides theoretical guidance for designing superalloys with exceptional HE resistance.