Surface Growth, Inner Defects and Interface Mixing of the Cr Coating on Zr Alloy Irradiated by 5 Mev Protons at 400 °C

Abstract

Arc-ion plated Cr coatings were irradiated by 5 MeV protons. Surface, inner and interface damages of the irradiated coatings were characterized by XRD, SEM, TEM and nanoidentation in this work. After irradiation, porous and polycrystalline Cr layers and grain refinement were formed on the surface due to the irradiation-enhanced diffusion. Irradiation-induced defects in the Cr coatings were voids, dislocations, and bubble-vacancies complexes. Importantly, the surface and inner changes resulted into irradiation softening in the coatings. At the coating-substrate interface, C14 ZrCr2 crystals, a multilayered interface and Cr preferential diffusion were found, which indicate that the diffusion of Cr atoms might be driven in forms of chains or layers when passing though the interface. Also, the surface and interface effects were found to be crystal-orientation dependent. For reasons, irradiation-enhanced diffusion is a main mechanism in driving surface and interface atoms by thermal spikes of highly energetic protons. The results show that the irradiation resistance of the Cr coating is still dependent on technical processes in preparation.

Keywords: irradiation effect, arc ion plating, chromium coating, defect, Laves phase