Development of tailored coating concepts for CVD and PVD deposition of multifunctional coatings - A review

In thin films technology the engineering design and the application of adva nced coating concepts is getting more and more important. This can clearly be seen in the development of new materials with multifunctional character in properties suitable to fulfil various technical requirements of specific problems in practice. For example protective coatings for applications in tribology and wear problems should combine high hardness values, high tough ness, low friction coefficients as well as corrosion and oxidation resistan ce and high-temperature strength and stability. A PVD-coating concept, the multilayer concept, consisting of 10 and up to 5000 single layers with a to tal film thickness of 5 mu m, now is well-established in industry and has s hown a great potential fur designing new thin film materials with tailored properties. This paper reviews the development and realization of the multi layer concept for wear-resistant coatings and gives an outlook on advanced coatings based on this concept. The principle is a strong separation of int erface properties, volume and surface properties of the coatings in an engi neering manner with respect to the development of protective multilayer mat erials with optimized mechanical and tribological properties. For various m ultilayer coating systems prepared by magnetron-sputtering results on mecha nical and tribological properties are presented, e.g. for 1) materials with different bonding characteristics, 2) solid-solution strengthened material s, 3) metastable materials, 4) nanocrystalline materials, 5) nanocomposite materials, 6) superhard materials, 7) crystalline and amorphous materials, 8) nano-graded coatings, 9) coatings with interface modifications, 10) mate rials with nanostabilization, 11) nanomodulated superlattice structures and , finally, multilayers designed of different combinations of these systems.