Hard Nanocomposite Films Prepared by Reactive Magnetron Sputtering

Abstract

The paper (1) reviews the present state of the art in magnetron sputtering of hard and superhard nanocomposite coatings and (2) reports on recent advances in this field. In the first part of this article, it is shown that nanocomposite coatings represent a new generation of materials, which exhibit new unique properties. A main attention is devoted to the enhanced hardness. It is shown that (1) the hardness H of the nanocomposite film can be more than two times higher than H of its hardest component, (2) there are two groups of hard and superhard nanocomposites: (i) nc-MeN/hard phase and (ii) nc-MeN/soft phase, (3) H correlates well with the film structure and (4) there are three possible origins of the enhanced hardness: (i) dislocation-dominated plastic deformation, (ii) cohesive forces between atoms and (iii) nanostructure of materials. In spite of these findings, there are, however, two fundamental questions: (1) The enhanced hardness of the sputtered film is due to its high intrinsic macrostress σ, induced by the ion bombardment used in their formation, or to its nanostructure? and (2) What is the origin of the hardness in single-phase films? The second part of the paper reports on results of an investigation of last two problems. At the end, trends of next development are outlined.Keywordsnanocompositefilmstwo-phasesingle-phasehardnessphysical propertiesmechanical propertiesmagnetron sputtering