Hybrid processes — a versatile technique to match process requirements and coating needs

Abstract

The properties of thin hard coatings and consequently their functionality are influenced by microstructural characteristics such as phase composition and grain size distribution. Recent studies indicate that microlaminated hybrid coatings offer an opportunity to establish unique and controllable microstructural characteristics. A variety of interlayers has been used in hybrid coatings for various purposes: (1) to enhance the adherence between coatings and substrates, (2) to prevent crack initiation, (3) to give good shock resistance, (4) to tailor the thermal expansion characteristics, which leads to good interfacial strength, (5) to prevent diffusion of substrate species into coatings or vice versa during annealing, (6) to enhance corrosion protection of coating and substrate, and (7) to enhance sliding wear resistance or lower sliding friction. In order to obtain the above mentioned properties, various surface modification techniques such as (1) electrodeposition, (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 hybrid coatings.