The activity aimed to extend the material characterization capacity at ET CRYOLAB for high pressure testing at temperature down to 20 K. The main objective was to develop and validate a service for in-situ material characterization in cryogenic media under high pressure. Proof of concept was demonstrated with a first study on hydrogen embrittlement as a function of pressure and temperature.

For current and future ESA projects there is a strong need to use new materials to increase launchers and spacecraft performance. For most of the new materials properties and performance data under hydrogen at high pressure and/or low temperatures are missing. The very limited available data do not cover the real operational conditions. To get access to the missing data the capabilities of the existing material characterization laboratory at ET were extended.

Material characterization at the combination of high pressure conditions and cryogenic temperature / media is now available opening up studies at realistic conditions. Two methods were developed to study material susceptibility to hydrogen:  Tensile test method: A hollow test specimen or component is pressurized from inside and is conditioned at the target temperature from outside. Different test types are available: tensile test, slow strain rate or fatigue test.  Single Sided pressurization method: Disc shaped test specimens are slowly pressurized until they burst. For both methods the tests are performed with the defined medium - in general hydrogen - and an inert gas like helium. The material compatibility of a material with a medium is characterized by the comparison with the test results in helium. A study of the hydrogen embrittlement of EN 1.4301 was performed to proof the concept.

With the smart technical approach developed under the activity the combination of high pressure conditions and cryogenic temperature / media is now available for material testing. Especially studies on hydrogen embrittlement are now possible with different methods at temperature down to 20K combined with pressure up to 100 MPa.

The flexible set-up allows for further adaption of capabilities to customers needs - e.g. extension of the temperature range or introduction of other media of interest