STRUCTURE AND PROPERTIES OF TIB2 BASED COATINGS PREPARED BY UNBALANCED DC MAGNETRON SPUTTERING

TiB2 coatings with thicknesses of 3 to 4 mu m were deposited by means of non-reactive unbalanced direct current (DC) magnetron sputtering us ing a TiB2 target. The intensity as well as the energy of ion bombardm ent of the growing film was varied systematically by varying the exter nal magnetic field supplied via a Helmholtz coil system and the bias p otential. Deposition conditions with less intense ion bombardment resu lted in the formation of fine-grained coating structures consisting of the TIB2 phase with (100) texture and hardness values of 2200 HV0.01. Increases in the energy and intensity of ion bombardment caused grain refinement and a shift of the preferred orientation to (001). Maximum hardness values of up to 6900 HV0.01 were observed for intense bombar dment with energetic argon ions. The friction coefficient during dry s liding against carbon steel was determined to vary between 0.50 and 0. 65 as a result of the formation of coating chips acting as abrasive pa rticles. (C) 1998 Elsevier Science S.A.