Experimental and Simulative Studies on Residual Stress Formation for Laser-Beam Surface Hardening*

Abstract

Abstract The results of high spatially resolved X-ray diffraction (XRD) analyses of residual stresses in laser-line hardened 42CrMo4 tempering steel samples are comparedwith the results of numerical process simulations and carefully discussed. Samples were locally line hardened at different maximum temperatures (950 °C, 1150 °C) and with different laser-beam feeds (200 mm/min, 800 mm/min) for the investigations. In addition to X-ray diffraction analyses, the effect of the process parameters on the formation of local microstructures was also examined. The results show that experimentally determined compressive residual stresses in process zones transverse and parallel to the laser track increase as temperatures decrease and feed increases. The dimensions of hardened zones (width, depth) affected by laser hardening at lower maximum temperatures are clearly smaller than those affected by laser hardening at higher temperatures, whilst the impact of laser-beam feed is less pronounced. A new model was developed for numerical simulation of laser-line hardening processes, showing good agreement between numerically calculated and experimentally determined microstructures in the process zones. The results of residual stresses calculated by simulation also exhibit good qualitative and largely also quantitative agreement with experimentally determined residual stresses. Partly, the simulation predicts some local deviations in the distribution of residual stresses.