Cr-V Microalloying Suppresses Hydrogen Embrittlement in L245 Pipeline Steel: A DFT Study

Hydrogen-enriched compressed natural gas represents a promising strategy for low-carbon energy transportation; however, hydrogen embrittlement remains a critical challenge for pipeline safety. This study employs density functional theory (DFT) to investigate the atomic-scale mechanisms by which Cr, V, and interstitial C regulate hydrogen adsorption and diffusion on the Fe(100) surface of a ferritic pipeline steel model relevant to L245. Seven representative doping configurations with different concentrations were constructed to evaluate the effects of electronic structure modification and local lattice distortion on hydrogen behavior. The results demonstrate that Cr/V doping effectively weakens hydrogen adsorption by inducing a downward shift of the d-band center and reducing Fe–H orbital hybridization. The destabilization of adsorption configurations further promotes hydrogen migration from top sites to neighboring hollow sites, decreasing the probability of stable surface adsorption. Among all configurations, Cr1V1 exhibits the strongest adsorption suppression, making the adsorption energy 9.26% less negative. In addition, Cr/V-containing dopants enhance hydrogen diffusion resistance along the modelled surface-to-subsurface pathway by reducing the octahedral interstitial volume and restricting migration pathways. Within the DFT model, the Cr1V1 and C1Cr2 configurations increase the hydrogen diffusion barriers by 37.89% and 39.27%, respectively. A tentative concentration trend emerges, suggesting an intermediate (5.6–8.3%) doping range may be the most effective. Excessive or insufficient doping concentrations may induce lattice expansion and accelerate hydrogen transport. These findings should be regarded as model-specific predictions that provide atomic-scale insights into the design of microalloyed pipeline steels, rather than direct predictions of the performance of commercial L245 steel under service conditions.