The work deals with two types of high entropy alloys (HEAs) of Fe4CrCuMnNi and Fe4CrCuMnNi type, which were laboratory synthesized by vacuum arc-melting method. Much cheaper Fe of higher portion replaced cobalt in high entropy alloy of CoCuCrMnNi type. Tensile tests and micro-hardness for both HEAs and a susceptibility to hydrogen induced cracking for Fe4CrCuMnNi were carried. Reached results in as cast state of both HEAs were compared each other. Mechanical properties were more favourable in case of Fe4CrCuMnNi. On average, yield stress was by 29 % higher, strength insignificantly lover by 14 MPa, while ductility by 2 % higher. Micro-hardness HV0.5 showed higher level in case of alloy with higher Fe content. Regarding hydrogen induced cracking of Fe4CrCuMnNi alloy under conditions in accord with NACE Standard TM0284-2013, Item No. 21215 the exposed samples were without any defects, even when length of sample was approx. 15 mm and diameter 3 mm only. Using Ni and Cr equivalents FCC+ BCC and/or BCC solid solution structures were found out. Microstructure, segregation and micro-fracture investigations were part of solution.Keywords: High entropy alloy, tensile test, hardness, hydrogen induced cracking, microstructure
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