Metal surface swelling by heavy charged particle irradiation

Abstract

Austenitic stainless steel specimens of Type 316SS were irradiated with 200 keV He + or N + ions, and the irradiated specimen surfaces were observed by atomic force microscopy (AFM). At the ion irradiation in high temperatures the specimens show surface step-up. In case of He +, the surface swelling is remarkable and increases linearly with He ion fluence, which indicates the swelling is due to formation of He bubbles. The irradiated surface is sometimes in irregularity, especially at and near grain boundary, remarkable ridging is observed. In case of N +, the surface step-up is less remarkable compared with He +. The swelling shows a so-called bi-linear behavior, i.e. a threshold of N + fluence appears and beyond the threshold the swelling increase is almost linearly presumably due to evolution of voids induced by the N + irradiation in high temperature. Denudation of void formation adjacent to grain boundary is recognized.