Hydrogen-induced damage in Ni-based superalloys at high temperatures

The urgent need to decarbonize society and industry motivates the use of hydrogen-containing fuels in gas turbines for power generation and aviation applications. This exposes safety-critical components to hydrogen at high-temperatures, but embrittlement effects under such conditions remain unexplored. Ever since the first report almost 150 years ago, mechanistic studies of hydrogen embrittlement have primarily emphasized the physical interactions between hydrogen and microstructural defects like interfaces and dislocations: a framework successfully exploited to rationalize numerous embrittlement phenomena at ambient temperature. Here, we show that this widely accepted understanding of hydrogen embrittlement breaks down at elevated temperatures, where vacancy-driven chemical reactions between hydrogen and specific microstructural constituents lead to embrittlement at least four times as severe as under ambient conditions. In a face-centered cubic (FCC) Ni-based superalloy that is the global backbone material for high-temperature applications, 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 substantially weakened, rendering them vulnerable to deformation-induced damage. Our work provides a physical foundation for developing mechanistic models of high-temperature H embrittlement in Ni-based alloys—a previously uncharted but critical step toward ensuring the safe deployment of H-fueled turbines and other high-temperature components in similar H-rich environments.