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High-entropy alloys (HEAs) are characterized by a solid solution of minimum five and medium-entropy alloys (MEAs) of minimum three principal alloying elements in equiatomic proportions. They show exceptional application properties, such as high-strength and ductility or corrosion resistance. Future HEA/MEA-components could be exposed to hydrogen containing environments like vessels for cryogenic or high-pressure storage where the hydrogen absorption and diffusion in these materials is of interest. In our study, we investigated the HEA Co20Cr20Fe20Mn20Ni20 and the MEA Co33.3Cr33.3Ni33.3. For hydrogen ingress, cathodic charging was applied and diffusion kinetic was measured by high-resolution thermal desorption spectros-copy using different heating rates up to 0.250 K/s. Peak deconvolution resulted in high-temperature desorption peaks and hydrogen trapping above 280 °C. A total hydrogen concentration > 40 ppm was identified for the MEA and > 100 ppm for HEA. This indicates two important effects: (1) delayed hydrogen diffusion and (2) considerable amount of trapped hydrogen that must be anticipated for hydrogen assisted cracking phenomenon. Local electrochemical Volta potential maps had been measured for the hydrogen free condition by means of high-resolution Scanning Kelvin Probe Force Microscopy (SKPFM).
High-entropy alloys (HEAs) are innovative high-performance materials that have attracted more and more research attention. HEAs are characterized by a solid solution of typically five equiatomic metallic elements. In addition, medium-entropy alloys (MEA, with three elements) are of interest and become more and more important. Depending on the alloy concept, HEAs and MEAs show exceptional mechanical properties, especially high-strength and ductility combinations at both cryogenic and elevated temperatures combined with excellent corrosion resistance. Future structural HEA/MEA components can be exposed to potential applications with hydrogen containing environments like high-temperature water in pressurized nuclear reactors or aerospace structures. Other potential applications could be in materials for vessel walls in the field of cryogenic and high-pressure hydrogen storage. So far, the susceptibility of HEAs/MEAs to hydrogen assisted cracking (if any) and the hydrogen diffusion is not investigated in detail yet and can limit or extend possible applications of HEA/MEA as structural materials. In our work, we focused on the hydrogen absorption, diffusion, and distribution in a HEA (CoCrFeMnNi the original Cantor-alloy) and a MEA (CoCrNi). Cathodic hydrogen charging was carried out for the hydrogen ingress, and thermal desorption analysis (TDA) revealed complex hydrogen trapping in both alloy types up to 300 °C. The absorbed total hydrogen concentrations were > 100 ppm for the HEA and > 40 ppm for MEA. In addition, the assessment of the peak deconvolution is not trivial and must consider both experimental and microstructure influences.