Loading optimized laser transformation hardening

With regard to fatigue strength improvement of components with stress concentrations the local hardening of the highly stressed surface areas by laser beam is of interest. For circumferential-notched bars from steel C45 it has been shown, that by adjusting the hardening depth and the surface hardness to the notch geometry and the applied load an increase in fatigue limit of about 200 per cent can be obtained. The local concept is useful for such optimization and for fatigue limit assessment. In addition to the hardness and the hardening depth an explicit influence of the prior austenite grain size on the fatigue limit exists. The fatigue limit increases with decreasing grain size. Finally conclusions for the loading optimized laser transformation hardening of real components has been drawn.