Applications of ion implantation in metals

The author considers the development of ion implantation as a means of improving wear resistance in metals. The first commercial machines developed specifically for industrial applications are now in routine operation; the chief areas of use are for the treatment of tools employed in the moulding of plastics, industrial knives, punches and dies. The simple process of nitrogen implantation has proved effective not only in steels but also in cemented carbide, titanium, chromium and aluminium. Mould tools typically last ten times longer after treatment. The low temperature of the process, the lack of surface degradation and the absence of any interface account for its success, but costs are still relatively high (approximately equal to that of coatings obtained by chemical vapour deposition). More powerful sources of ions are being developed, however, and it seems feasible to gain a further order of magnitude in throughput, which would improve the economics considerably. In addition, the more novel concept of ion beam mixing of a thin deposited coating (e.g. of tin, silicon etc.) by energetic ion bombardment extends greatly the versatility of equipment developed solely for gaseous ion beams. Dual implantations of metallic and gaseous ion species can now be done by sputtering ion sources. Applications relating to improved oxidation resistance thus become practicable. Ion beam mixing is also discussed as a pretreatment before coating (e.g. by ion plating, electrodeposition or spray coating). The scope for tailoring the surface composition and structure is very wide. (Auth.)