Atomic-scale design of Fe3C/α′C interfaces in carburized steels: First-principles insights into alloying doping for interfacial cohesion

• Thermally stable Fe 3 C/α′ C interface identified with superior adhesion strength of 1.94 J/m 2 . • Cr and Co are typical doping elements that enhance and weaken interfacial adhesion, respectively. • Cr strengthens bonding through synergistic Fe-Fe metallic and Cr-C covalent bonds. • Atomic design rules enable fatigue-resistant carburized steels for aerospace gearings/bearings. The Fe 3 C/α′ C phase interface in carburized steels/layers serves as a potential preferential site for fatigue crack initiation under cyclic loading, yet atomic-scale mechanisms underlying doping-induced modifications of interfacial properties remain unresolved. To address this, we systematically investigate alloying effects on interfacial bonding characteristics in Fe 3 C(001)/α′ C ( 11 2 ¯ ) heterostructures using first-principles calculations. The thermodynamically stable Fe-SB-LB configuration exhibits a maximum work of adhesion (1.94 J/m 2 ), with alloying elements ranked by interfacial adhesion enhancement efficacy as Cr > Nb > V > Ti > Mo > Fe > Al > Si > Mn > Ni > Cu > Zr > Co. Analysis of electronic structures and bonding properties reveals that Cr doping enhances interfacial cohesion via synergistic reinforcement of Fe-Fe metallic bonds and Cr-C covalent interactions, resulting in a 40–56 % increase in Fe-Fe bond strength and approximately sixfold stronger Cr-C bonds compared to Co-C counterparts. In contrast, Co doping degrades interfacial stability due to weakened bonding interactions and the emergence of positive embrittlement energies up to 4.0 eV. These results establish atomic-scale guidelines for optimizing carburized steels and deliver valuable insights for developing advanced doping strategies to enhance fatigue resistance under extreme mechanical loading conditions.