Multifunctional nanolaminated PVD coatings in the system Ti-Al-N-C by combination of metastable fcc phases and nanocomposite microstructures

The design and manufacture of multifunctional, wear resistant and lubricious nanocomposite coatings by simultaneous growth of nanocrystalline hard phases and amorphous carbon is an ambitious objective of current R&D in thin film engineering. This paper presents a concept of advanced nanolaminated PVD coatings combining the advantages of both the concepts of carbon-based nanocomposite coatings and those of multilayer coatings. in the past, mainly thermodynamically stable binary phases like TiC were used as hard phases to synthesize carbon-based nanocomposite protective and solid-lubricant coatings. The development of such coatings and basic results on magnetron-sputtered TiC/a-C coatings are reviewed briefly. New nanoscale single-layer composite coatings composed of coexisting metastable hard phases like fcc (Ti,Al)(N,C) and amorphous carbon were grown by magnetron sputtering. The microstructure, properties and performance of these coatings is presented and discussed versus the carbon concentration of the coatings. A five-step growth model of these coatings is suggested. The main focus is on the presentation of concepts for innovative nanolaminated composite coatings: these coatings have a special nano-architecture and are composed of the different carbon-based nanocomposite layers described previously. For example, a nanolaminated composite coating with a stacking sequence of each 50 layers of TiC/a-C and (Ti,Al)(N,C)/a-C shows promising properties and performance in tribological testing and in tool testing as well. The scale-up of such coatings was also successfully demonstrated and a new route towards industrial manufacture by applying new ceramic composite targets for magnetron sputtering is reported. (c) 2005 Elsevier B.V. All rights reserved