Structures and properties of hard and superhard nanocomposite coatings

Various approaches to creating multicomponent nanocomposite coatings of high and superhigh hardness (from $\le 30$ to 100–120 GPa) are reviewed with particular emphasis on mechanisms underlying the increase in hardness in thin ($\le 10\mu$m) coatings. The deposition techniques considered include magnetron, ion-assisted and vacuum arc sputtering. A classification of hard and superhard coatings of high thermal stability is given. Possible applications of such coatings are discussed and prospects for the field are outlined.