THE THERMAL EVOLUTION OF TARGETS UNDER PLASMA-FOCUS PULSED ION-IMPLANTATION

Pulsed ion beam implantation with plasma focus has proved to be an eff ective method of metal surface treatment for tribological purposes. Ne vertheless, the pulsed nature and the continuous energy spectrum of th e ion beams differ from those of the standard ion implantation process es. In this paper a model of the thermal evolution of the surface laye rs of stainless steel, titanium and copper, during and after nitrogen and argon ion beam incidence, is presented using the finite-difference method. In the calculations, the geometry and physical characteristic s of the ion beams, the single-ion-solid interaction process and the t hermal properties of the materials were used. The results showed a str ong thermal effect consisting in the generation of transitory heating slopes and heating speeds as high as similar to 3600 K mu m(-1) and si milar to 40 K ns(-1) respectively, with maximum temperatures that can reach even the material evaporation point at the surface layers. The c ooling down process, through the thermal conduction mechanism at the t arget bulk, turns out to be fast enough to produce the complete therma l relaxation of the target in only a few microseconds after the end of the ion beam incidence. The results presented are contrasted with exp eriments performed in similar conditions to those used in the numerica l model.