Rational design of doping strategy for stable α-Fe2O3 passive films of high-strength steel against hydrogen ingress

Hydrogen embrittlement critically limits the reliability of high-strength steels, where α-Fe2O3 within passive films serves as the primary barrier against hydrogen ingress. Elemental doping is an effective approach to tune the hydrogen resistance of α-Fe2O3, yet the dopants selection criterion is absent. Here, the spin-polarized density functional theory (DFT) is employed to estimate the doping formation characteristics of 24 types of elements and elucidate how the doping elements influence the vacancies characteristics and hydrogen dissolution behaviors in α-Fe2O3. The 24 types of substitutional doping elements are classified according to their formation energies of dopants, oxygen vacancies, and iron vacancies in α-Fe2O3. The orange-group elements (Al, Cr, Y, Mn, and Ga) are selected as promising dopants to effectively resist the hydrogen and maintain the integrity of oxide film. The effects of strain on the hydrogen dissolution behaviors in doping α-Fe2O3 are also analyzed and the Y doped α-Fe2O3 shows the weakest strain sensitivity. At last, the linear regression models based on seven atomic descriptors are proposed, which could accurately predict the Edoping, EOv, EFev, and Ediss (R2 = 0.70–0.88), respectively. These descriptor-property relationships provide the guidance to design doped α-Fe2O3 passive films with desired hydrogen resistance.