Superhardness Effect in TransitionMetal Diborides Films

Abstract

The structure, composition, and properties of transitionmetal diboride films have been studied. It was shown that they are characterized by a wide range of structural states, namely from amorphouslike to nanocrystalline with crystallite sizes of 1–50 nm. The characteristic peculiarity of the structure of film transitionmetal diborides with high physical and mechanical properties is the formation of a nanocrystalline (columnar) structure with the growth texture in plane [00.1] and a nanocrystallite size of 20–50 nm. The element composition of a superhard highly textured film transitionmetal diborides was studied by ion mass spectrometry and Auger electron spectroscopy. The overstoichiometry effect in nanocrystalline transition metal diboride films is explained. It was shown that this effect is related to the formation of an additional B⎯B covalent bond, which is realized at subgrain boundaries and leads to the appearance of superhardness in the formed coatings. Keywo