GROWTH, STRUCTURAL CHARACTERIZATION AND PROPERTIES OF HARD AND WEAR-PROTECTIVE LAYERED MATERIALS

Even though layered materials grown by chemical vapour deposition have been used as hard wear protective films for a long time, e.g. TiN/Al2O3/TiC structures on cemented carbide tools, it is only recently that layered structures grown by a physical vapour deposition techniques have attracted attention in this field. In this paper we address questions concerning growth mechanisms, characterization and properties of such materials. Examples are given in which layered structures are uses (i) to increase the matching between the film and the substrate in order to increase the adhesion, (ii) to improve the oxidation properties of wear-protective films and (iii) to increase the strength and hardness of the deposited films. The emphasis is placed on the growth of superlattice structures by dual-target magnetron sputtering. Both pure metallic (Mo/V) and refractory metal nitride (TiN/VN) superlattices are discussed and it is shown, using a combination of X-ray diffraction and high resolution transmission electron microscopy, that films with interface widths less than +/- 1 atomic layer can be grown. Also microhardness values of superlattices, which can show extreme high values for certain layer thicknesses, are discussed. For example, in the case of single-crystal TiN/VN structures, values of more than twice the hardness of the individual materials have been measured.