TiB2 coatings were prepared on steer and silicon substrates by d.c. ma
gnetron sputtering at different bias voltages. After deposition part o
f the coatings was vacuum annealed at 400 degrees C and 800 degrees C.
Transmission elctron microscopic (TEM) investigations on cross-sectio
n-prepared specimens showed that the layers were nanocrystalline with
an average diameter of columnar grains between 50 and 20 nm depending
on bias voltage. The chemical composition of coatings was homogeneous
within the layers and independent of bias. A non-stoichiometric B:Ti r
atio was detectable and a high amount of Ar incorporation occurred. X-
Ray phase analysis showed that the coatings consisted mainly of hexago
nal TiB2 phase with strong (001) fibre texture. Moreover, high compres
sive stresses were measured which could be attributed to Ar incorporat
ion. The microhardness, critical load and failure mode were influenced
by high compressive residual stresses. After annealing at 400 degrees
C the residual stresses were relaxed and the critical load was indepe
ndent of bias voltage. After annealing at 800 degrees C an upwelling o
f the surface was observed connected with crack formations and the occ
urrence of three new phases. (C) 1997 Elsevier Science S.A.