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

Area of Science:

• Materials Science
• Hydrogen Embrittlement
• Nickel-Based Superalloys

Background:

• Decarbonization efforts necessitate hydrogen fuels in gas turbines for power generation and aviation.
• Existing models of hydrogen embrittlement focus on ambient temperatures and physical interactions with defects.
• Elevated temperatures introduce new mechanisms of hydrogen-material interaction.

Purpose of the Study:

• To investigate the mechanisms of hydrogen embrittlement in nickel-based superalloys at elevated temperatures.
• To understand how hydrogen interacts with microstructural constituents beyond simple physical trapping.
• To provide a mechanistic basis for modeling high-temperature hydrogen embrittlement.

Main Methods:

• Near-atomic-scale characterization of a face-centered cubic Ni-based superalloy exposed to hydrogen at elevated temperatures.
• Ab initio calculations to model hydrogen-vacancy interactions and chemical reactions.
• Analysis of carbide decomposition and methane formation at the carbide-matrix interface.

Main Results:

• Hydrogen atoms are strongly trapped in carbon vacancies within carbides.
• This trapping drives partial decomposition of carbides and localized methane formation at the carbide-matrix interface.
• Weakened heterointerfaces become susceptible to deformation-induced damage, intensifying embrittlement.

Conclusions:

• Elevated-temperature hydrogen embrittlement is significantly influenced by vacancy-driven chemical reactions, not just physical interactions.
• Carbide decomposition and methane formation are key mechanisms weakening interfaces in Ni-based superalloys under hydrogen exposure.
• This research provides critical insights for developing robust hydrogen-fuelled turbines and high-temperature technologies.