Effect of severe shot peening on microstructure and fatigue strength of cast iron

Effect of nanocrystalline surface obtained by severe plastic deformation on fatigue strength of nodular cast iron has been studied in the paper. Surface nanocrystallization has been applied by means of standard air blast shot peening equipment with particularly severe parameters compared to the usual ones used for similar classes of material. Microscopy observation, microhardness, surface roughness and X-ray diffraction measurements were carried out to characterize the treated surface of differently shot peened specimens. Rotating bending fatigue tests were performed to investigate the effects of process parameters on fatigue behaviour. The results indicate a sensible fatigue strength improvement obtained through application of severe shot peening with respect to conventional shot peening, notwithstanding the specimen’s very high surface roughness due to high energy impacts. The obtained results are critically discussed.