Advanced synchrotron-based X-ray diffraction and tomography techniques were used to capture 3D images of microscopic cracks in nickel alloy caused by hydrogen embrittlement. Source: Dharmesh Patel/Texas A&M University College of Engineering

Hydrogen embrittlement causes microfractures in metal alloys that spread when exposed to hydrogen, resulting in structural problems and failures in bridges, nuclear plants and hydrogen storage containers. Researchers have used synchrotron-based X-ray diffraction and tomography techniques to investigate hydrogen-assisted cracks in nickel alloy and to produce the first 3D images of microscopic cracks in metal caused by hydrogen embrittlement.

Analysis of these images revealed 10 orientations of microscopic structures called grain boundaries that can deflect cracks and prevent damage caused by hydrogen. The data gleaned could be used to improve materials processing methods aimed at blocking cracks from further propagation, strengthening metals and leading to longer lifespans for structures and components.

To perform the nondestructive analysis required for the project, researchers took samples of cracked nickel alloy. The samples were assayed by the Advanced Photon Source beamline at Argonne National Lab (ANL) by illuminating them with high-energy X-ray beams, after which a camera picked up diffracted and transmitted beams. By testing hundreds of thousands of orientations, analyzing millions of points and matching the data with physical models, the researchers were able to convert diffraction spots into a 3D microstructure image. The resulting image highlighted which grain boundary types can deflect cracks and indicated that boundaries with low index plains, or BLIPs, were especially resistant to damage.

The information could be used to promote stronger grain boundaries and to eliminate detrimental ones in metal alloys to engineer more obstacles for cracks and stop them from spreading. Engineers could design microstructures to extend the life of materials, potentially saving on repair costs or replacement of metal components regularly exposed to water or hydrogen. Microstructures might be designed with more BLIPs to extend material service life and reduce repairs or replacement of components regularly exposed to water or hydrogen.

In addition to scientists from ANL, researchers from MIT, Johns Hopkins University, Carnegie Mellon University, Lawrence Livermore National Laboratory and Texas A&M University contributed to this development, which is reported in Nature Communications.