Effect of Long-Range Interaction in the Modification of Surface Layers of WC–Co Samples by a Pulsed Ion Beam

Abstract

The results of modification of WC–Co samples by a pulsed beam of nitrogen ions (200–300 keV, 120 ns) with an energy density of 7–8 J/cm2 are presented. It is shown that the change in the structure occurs in the near-surface layer with a thickness of 20–30 µm, which significantly exceeds the range of ions in the target (≈0.5 µm) and the depth of propagation of the thermal front during the pulse (≈1 µm). The analysis of various mechanisms of the long-range effect is carried out: the formation of a shock wave, the generation of primary radiation defects, etc. It is shown that the long-range effect is associated with the charge exchange of ions and the formation of fast atoms. The simulation of the charge exchange of ions in the gaseous layer of desorbed molecules is performed. It was found that the probability of ion charge exchange in the processes N+ + N2 → N0 and N+ + O2 → N0 significantly exceeds 100%, which indicates that the effect of irradiation by atoms was not taken into account while calculating. In contrast to ions, when the target is irradiated with atoms, the efficiency of the formation of radiation defects is much higher.