Investigation of the Oxidation Behavior of Cr(20)Mn(17)Fe(18)Ta(23)W(22) and Microdefects Evolution Induced by Hydrogen Ions before and after Oxidation

The oxidation behavior of body-centered cubic (bcc) structure Cr(20)Mn(17)Fe(18)Ta(23)W(22) refractory high-entropy alloy (RHEA) and the microdefects induced by hydrogen ions before and after oxidation were investigated. The results revealed that compared with oxidizing Cr(20)Mn(17)Fe(18)Ta(23)W(22) at 800 °C (6.7 °C/min) for 4 h (ST3, Ar:O(2) = 3:1), the heating procedure of oxidizing Cr(20)Mn(17)Fe(18)Ta(23)W(22) at 300 °C (6 °C/min) for 2 h and then increased to 800 °C (5 °C/min) for 4 h is more conducive to the production of oxides without spalling on the surface, i.e., HT1 (Ar:O(2) = 1:1), HT2 (Ar:O(2) = 2:1) and HT3 (Ar:O(2) = 3:1) samples. The oxidation of Cr(20)Mn(17)Fe(18)Ta(23)W(22) RHEA is mainly controlled by the diffusion of cations instead of affinities with O. Additionally, HT1 and HT3 samples irradiated with a fluence of 3.9 × 10(22) cm(−2) hydrogen ions (60 eV) were found to have a better hydrogen irradiation resistance than Cr(20)Mn(17)Fe(18)Ta(23)W(22) RHEA. The microdefects in irradiated Cr(20)Mn(17)Fe(18)Ta(23)W(22) mainly existed as hydrogen bubbles, hydrogen-vacancy (H-V) complexes and vacancy/vacancy clusters. The microdefects in irradiated HT3 were mainly vacancies and H-V complexes, while the microdefects in irradiated HT1 mainly existed as vacancies and vacancy clusters, as large amounts of hydrogen were consumed to react with oxides on the HT1 surface. The oxides on the surface of the HT3 sample were more stable than those on HT1 under hydrogen irradiation.