The Effect of High-Pressure Hydrogen Gas at Room and High Temperature on the Mechanical Performance of Conventional and Additively Manufactured Ni-base Alloys

Additively manufactured (AM) metallic materials have high potential for structural components in various applications. This is especially valid where the freedom to design complex geometries is vital to the optimization of the component performance. AM is a key enabler for the design of efficient hydrogen gas (H 2 ) combustion systems. Conventionally manufactured solid solution strengthened Ni-base alloys are generally known to have a low susceptibility towards hydrogen embrittlement. There is however a lack of knowledge on how AM materials behave when used in high-pressure H 2 environment. This is of crucial importance for many applications where AM materials can be considered as potential candidates to replace the conventional ones in different hydrogen gas technologies. In this work the behaviour of a conventionally manufactured, hot-rolled Hastelloy X was compared with respective AM alloy as relevant candidate for manufacturing components in gas turbines for power generation fuelled on H 2 . To reveal the effect of H 2 on the mechanical performance, slow strain rate testing (SSRT) was performed using hollow specimen method at 200 bar in H 2 environment at room temperature (RT) and 800 °C compared with inert gas (Ar) as a reference. The hydrogen content was analysed using thermal desorption spectroscopy with mass spectrometry (TDMS) in the SSRT tested specimens to reveal the absorption and potential interaction of hydrogen with the materials. Moreover, to validate whether hydrogen embrittlement occurred a fractographic analysis on the tested specimens was also carried out. The test results indicated no significant deterioration of mechanical properties due to H 2 exposure at any of the test temperatures either for AM or hot rolled material. TDMS analysis showed notable hydrogen uptake for the specimens tested in H 2 at high temperature as compared to the ones tested at room temperature for both conventionally and AM alloys.