Mechanisms and Analysis Techniques of Hydrogen Embrittlement in Metals

This study examines hydrogen embrittlement (HE) in metals, focusing on its mechanisms, evaluation, and analytical methods. HE occurs when hydrogen interacts with microstructural defects―dislocations, grain boundaries, precipitates, and vacancies―reducing ductility and toughness and leading to premature fracture. The primary mechanisms include Hydrogen-enhanced decohesion, Hydrogen-enhanced localized plasticity, Adsorptioninduced dislocation emission, and Hydrogen-Enhanced Strain-Induced Vacancy formation. Hydrogen charging methods such as electrochemical and high-pressure gas charging, along with evaluation tests including Slow strain rate test, constant load, bending, and Crack tip opening displacement, are discussed. Analytical approaches―Thermal desorption spectroscopy, silver decoration, Atom probe tomography, and hydrogen permeation testing―enable quantification and visualization of hydrogen trapping and diffusion behaviour. The findings indicate that diffusible hydrogen predominantly governs embrittlement sensitivity and that controlling trap-site distribution through microstructural design is essential. Developing standardized testing protocols and integrated analysis systems under hydrogen conditions will be essential for advancing hydrogen-resistant structural materials.