EFFECT OF DISCONTINUOUSLY LASER HEAT-TREA TED SURFACE ON FATIGUE BEHAVIOR OF CARBON-STEELS

The influence of laser surface treatment with no overlapping beads on the S-N curves of three carbon steels was studied. The fatigue behavio ur was discussed on the basis of microhardness tests, metallographic o bservations, and fractographic analysis. The decrease of fatigue stren gth due to the applied laser treatment mode and high sensitivity on pr ocessing parameters is significant for the steel with the highest carb on content and relatively slight in the steels with lower carbon conte nt. The reasons for lower fatigue resistance of laser treated material without overlap beads might be partly both local tensile residual str esses and susceptiblity of martensitic structure to intergranular frac ture.