No abstract

The fatigue life of aged 18Ni300 maraging steel was investigated in two different surface conditions: polished and grit-blasted. Axial fatigue tests results, plotted in the form of S-N curves were used to correlate the fatigue performance and the surface characteristics, carefully characterized using a combination of experimental techniques, including X-ray diffraction (XRD), contact profilometry, microhardness testing, scanning electron microscopy (SEM), and stereo optical microscopy (S-OM). The results show that turn-machining of round fatigue samples forms a thin recrystallized layer over the steel surface, which remains after polishing. Roughness increases significantly after grit-blasting, but strain hardening and compressive residual stresses developed after blasting outweigh the deleterious increase of roughness and the fatigue life increases in comparison to the polished condition. Both crack initiation and propagation are retarded under the effects of blasting.