Hydrogen-induced damage in Ni-based superalloys at elevated temperatures.

The urgent need to decarbonize the energy and transport sectors motivates the use of hydrogen-containing fuels in gas turbines for power generation and aviation applications, exposing safety-critical components to hydrogen environments at elevated temperatures. Ambient-temperature hydrogen embrittlement has long been interpreted through the physical interactions between hydrogen and microstructural defects like interfaces and dislocations. Here we show that this understanding does not fully capture the behaviour at elevated temperatures, where vacancy-driven chemical reactions between hydrogen and specific microstructural constituents can markedly intensify embrittlement compared with ambient conditions. In a prototypical face-centred cubic Ni-based superalloy, our near-atomic-scale characterization and ab initio calculations reveal strong trapping of hydrogen atoms in carbon vacancies in carbides, driving their partial decomposition while simultaneously triggering localized methane formation at the carbide-matrix interface. As a result, the heterointerfaces are weakened, rendering them vulnerable to deformation-induced damage. Our work provides a physical foundation for mechanistic modelling of elevated-temperature hydrogen embrittlement in Ni-based alloys, an emerging area critical to hydrogen-fuelled turbines and related high-temperature technologies.