Hydrogen uptake and embrittlement in nickel-base superalloys during hydrogen flame charging

Abstract Adopting hydrogen as fuel is one of the most promising solutions to eliminate carbon emissions in aviation. However, hydrogen is known to degrade the properties of structural alloys––a phenomenon known as hydrogen embrittlement. Here, we show that the environmental response of nickel-base superalloys in hydrogen combustion environments contrasts with the existing understanding of hydrogen embrittlement in metals. We demonstrate that direct flame exposure, i.e., flame charging, leads to significant hydrogen absorption, with oxidation strongly affecting hydrogen mass flow. Pre-existing oxides increase total hydrogen uptake during combustion, yet oxides also hinder hydrogen desorption. These effects reveal complex behaviour not observed in other hydrogen introduction methods, such as electrochemical hydrogen charging, with embrittlement being more extensive and showing distinct fracture behaviours. The study identifies key factors controlling hydrogen uptake and highlights critical differences between combustion and other hydrogen environments. Our findings can inform future alloy development, testing and certification for safe, sustainable hydrogen-powered jet engines.