Fatigue crack behaviour in carburized and laser-hardened components made of 18 HGM steel

Fatigue strength and fatigue crack behaviour in the carburized and laser-hardened 18HGM steel under reversed bending were studied. The structure, microhardness and residual stresses in the hardened zone were investigated. The Wohler's diagram, the plots of crack length and crack growth rate versus numbers of cycles are presented in this paper. Characteristic features of a mechanism of crack initiation and propagation have been established on the basis of observations made under the SEM and TEM microscopes.