Hybrid processes - a versatile technique to match process requirements andcoating needs

The properties of thin hard coatings and consequently their functionality a re influenced by microstructural characteristics such as phase composition and grain size distribution. Recent studies indicate that microlaminated hy brid coatings offer an opportunity to establish unique and controllable mic rostructural characteristics. A variety of interlayers has been used in hyb rid coatings for various purposes: (1) to enhance the adherence between coa tings and substrates, (2) to prevent crack initiation, (3) to give good sho ck resistance, (4) to tailor the thermal expansion characteristics, which l eads to good interfacial strength, (5) to prevent diffusion of substrate sp ecies into coatings or vice versa during annealing, (6) to enhance corrosio n protection of coating and substrate, and (7) to enhance sliding wear resi stance or lower sliding friction. In order to obtain the above mentioned pr operties, various surface modification techniques such as (1) electrodeposi tion, (2) thermal treatment, (3) ion plating, (4) ion implantation, and (5) sputtering can be used to prepare hybrid coatings. This review includes a discussion on surface modification techniques and properties of different h ybrid coatings. (C) 1999 Elsevier Science S.A. All rights reserved.