Surface condition, structure and phase composition of carbon steel irradiated with an intense pulsed ion beam

Abstract

The effect of irradiation with an intense pulsed ion beam of hydrogen (30%) and carbon (70%) at accelerating voltage of 250 kV and an energy density of 0,6 and 1,6 J/cm2 with a single pulse of 100 ns duration on the surface condition, structure, phase composition, elastoplastic and tribomechanical properties of carbon steel 65 was studied. Atomic force and scanning electron microscopy revealed smoothing of the surface relief and the formation of craters on it, while the average surface roughness decreases by 2-3 times compared to the initial one, and an increase in energy density leads to an increase in the average diameter of craters from 4 to 6 μm and their surface density from 2×108 to 8×108 m-2. X-ray diffraction studies conducted in the grazing incidence diffraction geometry and Bragg-Brentano identified a change in the predominant orientation of crystallites in the near-surface layer, comparable in magnitude to the projective range of ions, and to a change in the phase composition in a wider layer, significantly exceeding it: the appearance of new phases and an increase in their volume fraction with increasing energy density. Instrumental indentation revealed changes in hardness and elastic-plastic characteristics of the near-surface layer of the samples. After IPIB exposure the friction coefficient decreased by 1.5 times. The observed changes are caused by rapid heating, melting, and solidification of the near-surface layer of the target and are caused by the processes of redistribution of elements, accumulation of defects, the course of structural and phase transformations, and the local stresses growth in the modified layer.