Low carbon steel with nanostructured surface layer induced by high-energy shot peening

Abstract

The materials used in this work is a low carbon steel plate of 1.5 mm thick, its chemical compositions contain (mass, %) 0.11C, 0.24Si, 0.35Mn, 0.018P and 0.014S. The initial grain size of the low carbon steel is in the range of 20 ; 40 mm. Samples of 100 3 100 mm 2 were prepared for the HESP treatment. The principle of the HESP treatment used in the present work is similar to that of the USP method (9), but with a lower frequency (3 kHz) and bigger shots (diameter of 8 mm). The entire surface of the sample to be treated is peened by the flying shots with a high energy. The processing durations are 30, 60, 90 and 180 min, respectively. Surface structure of peened samples and structural evolution along the depth of the sample peened for 180 min were studied using X-ray diffraction (XRD) with CuKa radiation in a Rigaku D/max-2400 X-ray diffractometer. The average grain size and the mean microstrain were calculated from XRD line