Ion Implantation of Metal and Non-Metal Surfaces

Abstract

For material surface modification, the ion implantation process has been found to have beneficial effects on surface-sensitive properties such as hardness, wear, coefficient of friction, fatigue, aqueous corrosion, oxidation, adhesion, optical characteristics and catalytic activity. These are in part due to the fact that ion implantation is inherently a non- equilibrium phenomenon which can substantially alter surfaces of metals and non-metals to impart new characteristics. From the chemistry standpoint, conventional alloys can be formed on the surface without affecting the bulk material. More importantly, since elements can be introduced in concentrations far beyond equilibrium solid and compound solubility limits, the process may be used to form unusual alloys, metastable phases, and morphologies which are impossible to prepare by other methods. The technique involves directing a beam of high energy ions, in the one hundred kilo electron volt and higher range in energy, at a substrate surface, under vacuum. An analyzing magnet is used to separate the ion or ions of interest, and thus, a pure isotope species is energetically injected into the surface to a depth up to several thousand angstroms. Recent variations in direct beam implantation include ion beam mixing, simultaneous deposition and implantation, and ion cluster beam deposition. These processes result in thicker alloy deposits and higher additive concentrations, along with implantation. Discussion of applications of implantation will be limited to friction and wear and general corrosion. Results in the literature document wear improvement factors of between two and twelve times for treated cutting tools and dies. In corrosion, one program has shown substantial improvement of M50 steel bearings in resistance to chloride in lubricating oil. Applications of implantation to non-metal is much more limited. Investigators have examined effects of implantations on silicon carbide, aluminum oxide and titanium diboride. Miscellaneous investigations on non-metal include studies on polymers and polymer films, and on glasses.