Dr.-Ing. Christoph Bleicher - He is Head of the Qualification of Cast Components Group at Fraunhofer LBF, Darmstadt
Interview: Heinz Käsinger
Mr. Bleicher, hydrogen is becoming increasingly important as an energy source. Doesn't this also increase the demands on materials?
Yes, even small amounts of hydrogen can lead to the embrittlement of components. Specifically, the effect of hydrogen leads to a significant reduction in the fatigue strength of materials, both in the time and long-term strength range.
How do you arrive at an assessment of hydrogen-related influences on components?
We try to describe the quasi-static and cyclic material behavior - depending on the application. This is the only way to prevent premature failure of parts and system components due to a lack of knowledge. With the help of the individual analysis and testing concepts at Fraunhofer LBF, materials and components for the hydrogen economy can be reliably evaluated in terms of their resilience and service life. We have been doing this for several years with special test facilities for carrying out force- and strain-controlled tests under pressurized hydrogen with gas pressures of 10 to 50 bar.
Can you give us a specific example?
Let's take stainless steel components. In a research project, the influence of compressed hydrogen on the cyclic material behavior of stainless steel 1.4521, X2CrMoTi18-2, was investigated. For this purpose, strain-controlled tests were carried out under 50 bar hydrogen pressure. The evaluation of the determined cyclic deformation curves makes it clear that the failure under the medium of pressurized hydrogen occurs rather abruptly and without a pronounced cracking phase compared to the test in air.
"Failure of components can have fatal consequences for users"
That is, without advance warning due to certain technical indications?
Correct. Without a recognizable drop in stress, the material sample will fail abruptly with a significantly reduced service life. This change in material properties, in particular an increase in brittleness, is caused by the penetration and storage of hydrogen in the metal lattice, known as hydrogen embrittlement. Under certain circumstances, this can have fatal, even dramatic consequences for the user. Incidentally, hydrogen is not alone in these effects. Biogenic and synthetic fuels also contribute to corrosive environmental conditions.
What are the consequences of your research results?
Our investigations can identify relevant damage mechanisms and determine characteristic values for modeling and deriving suitable design concepts for components exposed to hydrogen.
ABOUT THE PERSON
Dr.-Ing. Christoph Bleicher has proven in his experiments that the influence of compressed hydrogen leads to a considerably shorter service life of a material.
