As a result of agreements to achieve climate neutrality such as the European Green Deal, interest in hydrogen as a climate-neutral energy carrier has risen sharply in recent years [1]. Therefore, the Federal Ministry for Economic Affairs and Energy (BMWi) is funding the joint project AdHyBau as part of the first call of the sixth civil aviation research program. In this project, additive processes and fiber composite metal hybrid construction methods for electric motors cooled with low temperature hydrogen gas are developed to increase efficiency and power density.

It has been known for many years that hydrogen can deteriorate the mechanical properties of metallic materials [2]. In order to carry out mechanical experiments in a hydrogen atmosphere, expensive and time-consuming experiments in autoclaves are usually used, where possible test temperatures are often strongly limited. The tubular specimen technique offers an alternative. It is a simple test method for hydrogen embrittlement with low risk, due to a small amount of hydrogen. Furthermore, it gives the possibility of directly cooling or heating the sample from the outside.

In this work, different materials considered for a hydrogen cooled electric motor are examined at room temperature and 77K. Slow strain rate tensile tests are carried out on tubular specimen to investigate hydrogen embrittlement. Therefore, specimen are filled with 10 bar or 100 bar hydrogen gas. For the low temperature tests, specimen are cooled in a liquid nitrogen bath during testing.

[1] European Commission, “The European Green Deal,” Eur. Comm., vol. 53, no. 9, p. 24, 2019, doi: 10.1017/CBO9781107415324.004.

[2] William H. Johnson, “On some remarkable changes produced in iron and steels by the action of hydrogen acids.” Nature 11, 393, 1875, doi: https://doi.org/10.1038/011393a0.