Abstract
Reactive Magnetron Sputtered TiN and TiC films were deposited on AISI H13 tool steel and silicon (111) substrates, under nitrogen and argon
or methane and argon reactive plasma. Depth sensing techniques were used to assess the mechanical properties of the films, namely hardness and
Young modulus using a load of 7.0 mN. TiN and TiC were deposited using a magnetron sputtering technique, the amount of nitrogen in the
sputtering gas being changed from 3 to 38 vol.% and the amount of methane from 2 vol.% to 27 vol.%. The H/E ratio (Hardness/Young Modulus)
of TiN films increases continuously when the amount of nitrogen in the sputtering gas is increased from 3 to 38 vol.%. For TiC films the ratio H/E
reached a maximum for a methane content of 12 vol.% in the sputter gas. The film to substrate adhesion was measured using Rockwell C tests.
The adhesion of the film to the substrate was greater when the H/E ratio of the film and of the substrate were similar.
© 2007 Elsevier B.V. All rights reserved.
Keywords: Magnetron sputtering; H/E ratio; Adhesion and coatings
1. Introduction
The deposition of ceramic films on tool steel by vapor
deposition techniques is now a common practice. These layers
can be produced by different processes, divided basically into
two main groups: chemical vapor deposition (CVD) and
physical vapor deposition (PVD). Each of these processes has
advantages and disadvantages depending mainly on the final
application and on the desired properties of the coating.
Controlling the adhesion of the deposited ceramic layer to
the substrate constitutes one of the main difficulties and an
object of concern of many research groups and of commercial
organizations in the area of surface engineering and surface
science. Some studies, developed during the 80s, showed that
adhesion could be improved through the deposition of a Ti
intermediate layer [1–3]. Other pre-treatments like substrate
hardening and duplex treatments performed before PVD, CVD,
HVOF (high velocity oxygen fuel) and multilayer depositions
have led to a significant improvement of the film-substrate
adhesion due to an increase of the load bearing capacity of the
substrate [4–7]. The first work dealing with TiN coatings
deposited on plasma nitrided tool steel surfaces was published
in the 80s [8] and the plasma nitriding pre-treatments (low and
high pressure) became technologically feasible for industrial
applications [8–16]. When performed in a hybrid reactor (inside
the same chamber), duplex treatments improve the adhesion of
the TiN ceramic film to the substrate [13].
There are three different ways of relating hardness and
Young modulus to the mechanical properties of the film.
Matthews and Leyland proposed the study of the relationship
between the tribological properties of ceramic coatings and the
ratio between the hardness (H) and the Young Modulus (E) of
the film. This ratio, according to the authors, is related to the
elastic strain to failure of the coating [17]. On the other hand, the
H3
/E2 parameter proposed by Johnson [18] was associated to
the coating resistance to plastic deformation [17]. This ratio can
only be used for a configuration similar to a rigid-ball in contact
with an elastic/plastic plate [18], provided that the hardness of
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Surface & Coatings Technology 202 (2007) 1078–1083
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⁎ Corresponding author. Tel.: +55 11 30915656; fax: +55 11 30915243.
E-mail address: antschip@usp.br (A.P. Tschiptschin).
0257-8972/$ - see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.surfcoat.2007.07.073