A complete residual stress model for laser surface hardening of complex medium carbon steel components

A numerical model is presented for evaluation of residual stresses following laser surface treatment of mechanical components with arbitrary geometry. Following on from previous temperature and microstructural models, stress evaluation is performed by considering the resulting deformation from thermal expansion, elastic and plastic deformation, and microstructural changes. A 3.3 kW diode laser with wavelength of 930 nm and 34 mm × 2 mm rectangular spot is utilized to perform heat treatment experiments on an AISI 9810 steel cam, with x-ray diffraction measurements performed before and after laser exposure to determine circumferential and axial surface stresses. Verification of model accuracy is performed by comparing calculated stresses with the measured values. The influence of incident laser fluence and scanning velocity on the hardened depth and residual stress state is then investigated numerically for the same component. It is found that higher laser fluence, or an increase in exposure velocity at constant fluence, leads to an increase in the hardened depth and a reduction in compressive residual stresses.