This study presents an integrated scientific and engineering framework for multi-track laser surface hardening of gears and rotating mechanical components operating under severe contact loading conditions. Conventional surface strengthening methods are often associated with bulk heating, dimensional distortion, and limited adaptability to complex geometries. In contrast, laser-based surface modification enables localized,
high-energy-density treatment with minimal thermal distortion. The physical mechanisms of laser–material interaction, transient heat transfer, rapid thermal cycling, phase transformation behavior, and residual stress evolution are systematically analyzed. A multi-track scanning strategy with controlled overlap is proposed to ensure thermal field uniformity and optimized residual stress distribution across complex surface geometries. Numerical simulations were performed to establish quantitative relationships between laser power, scanning speed, absorptivity, and hardened layer depth. Virtual experiments demonstrate the nonlinear dependence of peak temperature and layer thickness on linear energy density. The predicted trends are consistent with experimental findings reported in the literature. The proposed integrated hardening concept enhances surface hardness, wear resistance, and contact fatigue performance while preserving the mechanical integrity of the substrate. The results provide a theoretical and engineering basis for advanced laser hardening technologies applicable in high-reliability mechanical transmission systems.