Advanced surface treatments by plasma ion implantation

Plasma ion implantation techniques have emerged recently as non-line-of-sight alternatives to ion beams for surface modifications in the energy range 10–100 keV. Experimental work performed over the last 7 years is reviewed, pointing out the progress that has been made in both the physical understanding of the process and the technological developments necessary for its implementation. Improvements in the surface properties of a wide range of alloys have been obtained by the implantation of nitrogen while field test results for industrial tools and components from a diverse range of applications have been positive. Although the process has been extended to the implantation of other gaseous and metal ions, it is in the combination of the technique with other surface treatments such as ion-assisted deposition and ion nitriding that the most interesting developments have been taking place. For deposition, it has been demonstrated that, for certain coating/substrate systems, increasing the ion energy can result in improved film properties. Treatment at elevated temperatures, particularly in steels, has shown that a substantial diffusion zone can be produced supporting the implanted layer. Some of the results of these advanced surface treatments involving high energy ion bombardment from a plasma are presented and the advantages and limitations of the process are discussed.