Researchers at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg are studying hydrogen-induced embrittlement to find materials and manufacturing processes that are compatible with hydrogen.
Hydrogen can make metals such as steel, aluminum and magnesium brittle; the ductility of the metal becomes reduced and its durability deteriorates. This can lead to sudden failure of parts and components.
Hydrogen can permeate the materials of which a fuel cell vehicle is made not only when filling the tank, but also through various manufacturing processes. Hydrogen can infiltrate the metal lattice through corrosion, or during chromium-plating of car parts. Infiltration may likewise occur during welding, milling or pressing.
With our new special laboratory, we are investigating how and at which speed hydrogen migrates through a metal. We are able to detect the points at which the element accumulates in the material, and where it doesn’t.
—Nicholas Winzer, researcher at IWM
Since the risk potential mostly emanates from the diffusible, and therefore mobile, portion of the hydrogen, it is necessary to separate this from the entire hydrogen content. Researchers can release and simultaneously measure the movable part of the hydrogen by heat treatment, where samples are continuously heated up.
In addition, the experts can measure the rate that hydrogen is transported through the metal while simultaneously applying stress to the material samples mechanically. They can determine how the hydrogen in the metal behaves when tension is increased. For this purpose, the scientists use special tensile test equipment that permit simultaneous mechanical loading and infiltration with hydrogen. Next, they determine how resistant the material is.
The researchers use the results from the laboratory tests for computer simulation, with which they calculate the hydrogen embrittlement in the metals. In doing so, they enlist atomic and FEM simulation to investigate the interaction between hydrogen and metal both on an atomic and a macroscopic scale.
Through the combination of special laboratory and simulation tools, we have found out which materials are suitable for hydrogen, and how manufacturing processes can be improved. With this knowledge, we can support companies from the industry.
—Dr. Wulf Pfeiffer, head of the process and materials analysis business unit at IWM