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 using a TiB2 target. The intensity as well as the energy of ion bombardment of the growing film was varied systematically by varying the external magnetic field supplied via a Helmholtz coil system and the bias potential. Deposition conditions with less intense ion bombardment resulted 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 bombardment with energetic argon ions. The friction coefficient during dry sliding 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 particles. (C) 1998 Elsevier Science S.A.