FEM Modeling of Cementite Spheroidization Under Cyclic Heat Treatment for Precision Manufacturing Applications

Control of carbide morphology during heat treatment plays a decisive role in achieving stable dimensions, improved cutting performance, and reliable mechanical properties in precision steel components. In this work, a computational approach is developed to analyze the spheroidization behavior of cementite in eutectoid Fe-0.8 wt.% C steel subjected to cyclic thermal processing. The model, implemented within a finite element method (FEM) framework, links the transient local temperature history to temperature-dependent spheroidization kinetics. The kinetic formulation is physically motivated by established mechanisms of cementite spheroidization, including carbon diffusion and curvature-driven reduction of interfacial energy; however, carbon concentration and interface curvature are not explicitly solved as independent FEM field variables. Instead of relying on empirical correlations, the transformation kinetics are described through physically based rate equations that account for temperature dependence and accumulated thermal exposure. A morphology evolution parameter is introduced to quantitatively represent the transition from lamellar pearlite to spheroidal carbide particles during repeated heating cycles. Numerical predictions indicate that cyclic reheating enhances the transformation rate due to progressive lamella fragmentation and increased interfacial stability, leading to accelerated approach toward equilibrium morphology. The simulated evolution trends are consistent with reported experimental behavior, confirming the validity of the modeling strategy. This study demonstrates the feasibility of integrating microstructural kinetics into process simulation platforms, providing a practical tool for optimizing heat-treatment schedules in precision manufacturing applications while minimizing experimental iterations.