Synchrotron Tools Used to 3D Image Microscopic, Hydrogen-Induced Cracks in Metals for the First Time
Siobhan Treacy | August 23, 2018Texas A&M University researchers have, for the first time, 3D imaged microscopic cracks in engineering metals from hydrogen wear and tear. In the past, these types of cracks have been impossible to study without destroying the metal. This imaging of the cracks before they destroy the metal completely, allows the team to study why these cracks happen, how to prevent them and what happens at the beginning of the cracks.
"Hydrogen gets into the metal and causes it to fracture unexpectedly in a process called hydrogen embrittlement," said John P. Hanson, a reactor engineer at Oklo and first author of the paper.
"As a result, engineers have to overdesign with additional material to cover any sudden failure and that costs a lot," said co-author Peter Kenesei of Argonne, who operates the instruments used in the work. "So a better understanding of this behavior could have a huge economic impact."
During the testing and research, the A&M researchers used two Argonne National Laboratory’ Advanced Photon Source (APS) tools. The tools were high-energy diffraction microscopy and an x-ray absorption tomography tool. The tools were used to analyze the structure of cracks in nickel.
Fractures in nickel happen between the grains to make the metal. With the tools, the researchers were able to see the grains around a crack caused by hydrogen. This helped the team find ten microscopic structures in metals that make the metal stronger and less vulnerable to hydrogen exposure.
"We were able to show not only which grain boundaries are stronger, but exactly what it is about them that improves their performance," Hanson said.
The tools could also be used to image the microstructures of all metals. They could even be used to predict when a metal is going to fail so engineers can find the best metal for their needs. They are already being used to do this kind of research in other materials.
"It's highly encrypted in the form of streaks and dots, or diffraction patterns, that must be analyzed by a supercomputer," said Robert M. Suter from Carnegie Mellon University (CMU), an expert on the analysis.
A paper on this research was published in Nature Communications.