Citation:
J. Rao, R. Cruz, K.J. Lawson and J.R. Nicholls, Carbon and titanium diboride multilayer coatings, Diamond and Related Materials, Volume 13, Issues 11-12, November-December 2004, Pages 2221-2225.
Abstract:
Titanium Diboride, (TiB2) is a metal-based refractory ceramic material that has
been investigated in industrial applications ranging from, cutting tools to wear
parts and for use in the aerospace industry. The unique properties which make
this material so fascinating are, its high hardness, high melting point and its
corrosion resistance. TiB2 is prevented from wider mainstream use because of its
inherent brittle nature. With a view to overcome this in coating form and with
the aim of providing in addition inherent lubricity, in this study 50 layer
TiB2/C multilayer stacks have been fabricated, with varying volume fractions of
ceramic, whereby the interfaces of the layers limit crack propagation in the
TiB2 ceramic. TiB2 has been multilayered with carbon, to make use of the unique
and hybrid nature of the bonding in carbon coatings. DC magnetron sputtering
with substrate bias was the preferred route for the fabrication of these
coatings. AISI tool steel has been used as the substrate material. By varying
the amount of TiB2 ceramic from 50% to 95%, the Hardness of the coating is seen
to increase from 5 GPa to 17GPa. The Hardness is observed to decrease as a
function of increasing carbon content, agreeing with other studies that the
carbon layers are not load-bearing. The graphitic nature of the sp2 bond,
however, acts as a lubricant layer.
