Interfacial Crack Initiation Mechanisms and Fatigue Life Modeling via Energy Dissipation in Carbide‐Containing High‐Strength Steels

Fatigue failure in high‐strength gear steels under cyclic loading is critically influenced by microstructural inhomogeneities. This study combines crystal plasticity finite element (CPFE) simulations, ultrasonic fatigue testing, and electron microscopy to investigate carbide‐induced crack initiation and life prediction. Carbides are identified as primary crack initiation sites, where carbides arise from dislocation pile‐ups and stress concentration at triple junctions formed by carbides and twin boundaries. A CPFE model, calibrated with experimental grain topology and cyclic responses, demonstrates that slip localization and geometrically necessary dislocation accumulation near carbide‐matrix interfaces amplify strain gradients and energy dissipation. A nonlinear fatigue life prediction framework, linking the incremental plastic energy dissipation (Δ D dis ) to fatigue cycles, is established. The model achieves 70% of predictions within a twofold scatter band, validated across stress amplitudes from 500 to 530 MPa. This work bridges crystal‐scale mechanisms to structural fatigue performance, offering insights for designing fatigue‐resistant components in aerospace and automotive industries.