INTEGRATED MULTI-TRACK LASER SURFACE HARDENING OF GEARS AND ROTATING COMPONENTS: THERMAL FIELD CONTROL AND RESIDUAL STRESS ENGINEERING

Abstract

A complete scientific and engineering analysis of multi-track laser surface hardening, commonly for gears and rotating mechanical elements subject to high contact stresses, is presented in this study. Traditional, bulk heating-intensive surface hardening techniques can cause dimensional changes and make them suitable for mostly simple geometries. Surface modification with lasers for example enables selective treatment at high-energy density and reduced thermal distortion. For the purpose of enhancing thermal field uniformity and effectively establishing a desirable residual stress distribution on comprising surface morphologies, it is proposed to apply a multi-track scanning technique with controlled overlap. Quantitative correlations between laser power, scanning speed, absorptivity and hardened layer depth were determined through numerical simulation. Modeling and experiments confirm that the peak temperature and layer thickness both vary nonlinearly with linear energy density. The expected trends are consistent with previous experimental results. An approach for integrated hardening was presented to improve the surface hardness, wear resistance and contact fatigue performance without damaging the mechanical properties of substrate. These results corroborate advanced laser hardening technologies, theoretically and practically, which are applicable to the highly reliable mechanical transmission system.