Modification of metallic materials and hard coatings using metal ion implantation

Ion implantation, with doses in the range 10(16) to 10(18) ion cm(-2), modi fies the surface properties of many metallic and ceramic materials. Whilst gas ion beams are currently employed extensively, metal ion implantation (M II) systems have been developed based on the vacuum metal are and a brief r eview of these systems is presented. Examples of industrial applications ar e given using, primarily, Mo ions which harden the surface of steel, increa se its corrosion resistance and lower the coefficient of friction of the al loyed (or implanted) zone, IZ. Extending well beyond this zone, a dislocati on network is developed which hardens the material in depth. Termed the lon g-range effect, this occurs in alloys and in low ductility materials such a s TiN. Microstructural studies of TiN coatings after MII are presented toge ther with a model for the development of this effect. The results show that the stress field in TiN made by PVD is modified by implantation but no eff ect on the grain structure is found, whereas in TiN made by CVD the residua l stress is not changed but growth of fine grains within the original grain structure is observed. (C) 1999 Elsevier Science Ltd. All rights reserved.