Numerical analysis and experimental validation of hardness and microstructural changes during laser transformation hardening of low alloy steel plates

Abstract

Laser transformation hardening is used to obtain the localized microstructural change, improve wear resistance and hardness to the desired area without affecting the bulk properties. In this study, laser transformation hardening of EN25 steel is performed using a 2 kW continuous wave solid-state neodymium yttrium aluminium garnet laser system. Numerical simulation of laser transformation hardening is carried out by finite element method considering the thermo-physical properties of the material. Based on the numerical simulation the temperature, hardness distribution, hardened depth and width and the phase proportions are determined. The simulation is performed by varying the travel speed of the workpiece. The simulation results are verified with the experimental data and are found to be satisfactory with less than 5% error. It is observed that almost 97% of the phases in the hardened zone is converted into martensite phase with increased hardness about two fold compared to the base material.