Hydrogen Embrittlement Threatens Hydrogen-Fueled Gas Turbines

The transition to a hydrogen economy, which could reduce global carbon dioxide emissions by 15%, faces a significant hurdle in its application to gas turbines. These machines, responsible for roughly 22% of the world's electricity generation, are being considered for hydrogen fuel in both power plants and aviation. However, the impact of hydrogen on the materials within these turbines, especially under extreme operating conditions, requires deeper understanding.

While hydrogen's effects on metals at ambient temperatures are well-documented, its behavior at the elevated temperatures found inside gas turbines is less understood. An international research team has now examined how hydrogen affects nickel-based superalloys, the standard materials for gas turbines, at high temperatures. Their findings indicate that hydrogen-induced embrittlement can be more than twice as severe under these conditions, presenting a critical safety and reliability concern.

Researchers discovered that at temperatures between 400°C and 1,000°C, hydrogen migrates to carbon vacancies within carbides in the superalloys. This process leads to the partial decomposition of carbides and the formation of methane. The resulting high internal pressure from the methane weakens the material's interfaces and promotes damage. This degradation mechanism is particularly pronounced around 400°C, with methane formation ceasing at higher temperatures.

This discovery is especially relevant for gas turbines that cycle on and off, such as those in aircraft, as they experience a wider range of temperatures and loads where embrittlement can occur. The research pinpoints carbides as the primary entry points for hydrogen-induced cracking. Future efforts will need to focus on redesigning alloy microstructures by either replacing carbides or finding a balance between their strengthening effects and hydrogen embrittlement resistance. Developing temperature-specific models to predict this damage is crucial for enabling the safe implementation of hydrogen-fueled turbines.