Fatigue behavior of a low-alloy steel with nanostructured surfaceobtained by severe shot peening

Severe shot peening aimed to generate a nanograined layer over specimens’ surface has been applied by means of standard air blast equipment but using peening parameters essentially different from typical ones. Different experimental processes including microscopy observation, microhardness, roughness and X-ray diffraction measurements have been performed to characterize the treated surface of specimens. The results confirm the generation of a nanocrystallized surface layer. Rotating bending fatigue tests are then performed on smooth specimens to evaluate the effect of the nanocrystallized layer on fatigue strength. The results indicate improvement of fatigue life notwithstanding the specimen’s very high surface roughness: a refinement of the treatment parameters aimed at reducing the roughness is proposed.