Non-destructive characterisation of laser hardened steels. Pt.2: Metallography and residual stresses

Surface laser hardening of steels is a well-established industrial technology. The surface of the specimen is scanned with a high-power laser beam along the trace to be hardened. The rapid cooling due to the non-heated surroundings of the laser-treated zones leads to local hardening of the material. Non-destructive evaluation of some mechanical properties (hardness, residual stresses, etc) of the hardened region and the heat-affected zone are of technological importance. A previous paper reported non-destructive testing (NDT) experiments (by scanning of the specimens) made with the 3MA-II (Multiparameter Micromagnetic Microstructure and Stress Analysis) equipment developed by the Fraunhofer Institute for Non-Destructive Testing (IZFP), Saarbrücken. This contribution presents an X-ray diffraction evaluation of the residual stresses in laser-hardened SAE 1045 steels and metallographic studies of the affected areas. The results are compared with the previously reported 3MA-II output.