Hydrogen adsorption and diffusion on the surface of alloyed steel: First-principles studies

The investigation into the impact of alloying element doping on material properties is one of the major research problems of materials science and engineering. Alloying elements such as Cr, Mn, Si, and Ni is commonly employed to improve mechanical properties of materials, such as strength and hardness. However, the incorporation of these elements affects hydrogen adsorption and diffusion behavior by altering crystal structure and electron distributions. In this study, simulations were systematically conducted on the binary alloy system Fe-X (Cr, Mn, Si, Ni), employing first-principles calculations based on density functional theory to investigate the effects of alloying elements on the hydrogen adsorption and diffusion. The interaction mechanisms between the alloying elements and hydrogen are also investigated. The results show that Cr doping increases the adsorption energy by 2.9 eV and decreases the adsorption stability of H atoms compared to the pure Fe surface. Conversely, doping with Si and Mn increases the interaction between H and the surface, reduces the adsorption energies by 2.87 eV and 1.32 eV respectively, and improves the adsorption stability. On the other hand, Ni has the minimal effect on H adsorption, with its adsorption energy decreasing by 0.55 eV. In terms of diffusion, Cr doping increases the diffusion energy barrier by 5.32 kJ/mol, which is hindering H diffusion, while Mn decreases the diffusion energy barrier by 3.88 kJ/mol. Si and Ni have comparatively less influence on H diffusion. Cr doping improves the hydrogen embrittlement resistance of the alloy, whereas Si and Mn may have the opposite effect. These theoretical findings may serve as useful guidelines for various engineering and research applications by designing hydrogen embrittlement-resistant surfaces.