Influence of partial laser beam hardening with low pulse repetition frequency on the fatigue behavior of steel

In comparison to conventional heat treatments, laser beam hardening has some specific advantages, /is a result of the local limited heat input, the distortion of the material is essentially reduced. Because of the self-quenching process, it is possible to abandon cooling agents and additionally laser hardening is well qualified for the integration in automated manufacturing systems. In the field of transformation hardening, Nd:YAG lasers are superior to CO2 lasers due to higher energy impact into the material and their greater flexibility. By using pulsed mode, case hardness and case hardening depth are increased. The aim of the examinations is a quantitative description of the microstructure, the distributions of hardness and residual stress and the resulting fatigue limit of the steels 42CrMo4 (EN 10038) and lOOCro (SAE 52100) after hardening with a pulse frequency of 25Hz. Flat bending specimens were locally hardened by single and overlapping tracks in the longitudinal direction. In addition to that the influence of a mechanically remove of the heat affected zones besides the tracks on the fatigue limit was investigated. © 2000 Carl Hanser Verlag. All rights reserved.