Studies on residual stress developed in laser surface irradiated 0.6% carbon steel

Laser surface hardening is a process of microstructural modification of the near surface region of iron-based component by inducing martensitic transformation with a high power laser beam as a source of heat. The process is aimed at introducing a hard and wear-resistant layer on the surface, thereby increasing the service life of the component. Due to a rapid rate of heating and cooling and a large thermal gradient associated with the process, a measurable amount of residual stress is developed in the laser irradiated region. In the present investigation, an attempt has been made to surface harden medium carbon steel (0.6% Carbon) using 2.5 kW continuous wave CO2 laser as a source of heat using Ar as shrouding gas. The microstructure and phase analysis of the irradiated region have been carried out in details. Residual stress developed in the laser-irradiated region has been carefully measured. Effect of laser parameters on microhardness and wear resistance has been studied. Finally, the processing zone for the surface hardening has been derived following a detailed structure-property correlation.