EQUIPMENT AND METHODS OF SURFACE MODIFICATION OF THE MICROSTRUCTURE AND PROPERTIES OF METALS BY ADSORPTION ASSISTED ION-IMPLANTATION

Data on phase and structural transformations in the surface layers of metallic alloys as a function of the conditions of ion implantation ar e reviewed. It is noted that the ion mixing of the surface-absorbed ac tive elements from the implantational gas medium plays an important ro le in the formation of the element and phase composition of the ion-do ped layers. The most important treatment parameters determining the re lative role of ionic mixing in structural-phase transformations in the ion-doped layer are: the elementary composition and pressure of the i mplantational gas medium, the target temperature, the atomic weight of the implanted ions, and the reactivity of these ions and the target i ons to the absorbed elements (C, N, O). The formation of high-energy d efect structures and the dispersion of the implanted-layer crystal str ucture in the strong internal-stress fields generated by the highly no nequilibrium solid solutions and in the course of phase transformation are considered. New possibilities for microstructural modification du ring high-dose implantation are identified with the formation of high- energy defect (including nanocrystalline) structures; heterophase, com pletely amorphized and other phase-structural states and their combina tions in ion-doped layers of metallic alloys. Taking advantage of thes e possibilities makes it possible to reduce by an order of magnitude t he implanted dose necessary to upgrade the performance of the surface, and to raise the productivity and lower the cost of the ion-beam tech nological treatment. (C) 1997 Elsevier Science S.A.