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JUNE 28 WEDNESDAY MORNING
JS2-WeM-INV.2 TRIBOLOGICAL CHARACTERIZATION OF METAL CAR-
BIDE/AMORPHOUS CARBON NANOCOMPOSITES: FROM MACRO TO THE MICRO-
SCALE. J.C. Sánchez-López*, D. Martínez-Martínez, C. López-Cartes, A. Fernández. Instituto de
Ciencia de Materiales de Sevilla, CSIC-Universidad de Sevilla, Avda. Américo Vespucio 49, 41092-
Sevilla, Spain. *E-mail: jcslopez@icmse.csic.es
The design of multilayered and nanocomposite coatings structures have allowed to achieve superior
hardness, toughness and excellent wear resistance useful for many industrial applications. The optimization
of the tribological performance of such materials represents a challenge as depends not only
on factors intrinsic to the coatings (chemical composition, microstructure, phase composition, texture…)
but, besides, others related to the application conditions (adhesion to the substrate, nature of
the counterfaces, environment, load, etc.). In this work, we review the results obtained for nanocomposite
coatings made of nanocrystalline metal carbides and amorphous carbon (a-C) prepared by
PVD techniques. Their characterization appears complicated mainly due to the lack of long-range
order and the heterogeneity in chemical compositions at the nanometric scale. The nanocrystalline/amorphous
ratio appears to be a key-parameter to control the tribological properties and its
quantification results always not easy. Focusing mainly in the TiC/a-C system prepared by magnetron
sputtering as example, it is showed how the investigation of chemical and structural features at
the micro-scale help to determine the aspects influencing the tribological performance at the macroscale.
By varying the power applied to each target (titanium or graphite), it was possible to prepare a
wide family of film structures covering from a quasi-polycrystalline TiC to a nanocomposite formed
by nanocrystals of TiC. The microstructure of one coating, shown in Fig. 1, reveals a nanometric
grain boundary network around TiC crystals of 5 to 10 nm. A complete characterization has been accomplished
by X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy
(TEM), electron diffraction and electron energy-loss spectroscopy (EELS) and X-ray photoelectron
spectroscopy (XPS), pin-on-disk and nanoindentation measurements. EELS and XPS
techniques are demonstrated to be very appropriate tools for the estimation of the amorphous phase
inside the nanocomposite because they are sensitive to the bonding environment. In the Fig. 2 it is
depicted the modification of the shape and position of the C K-edge for different coatings when the
contents of TiC and a-C are varied. The increment of the TiC contribution is accompanied by a gradual
rise of the friction coefficient due to the lack of sufficient amorphous lubricant phase. Combining
the complementary information given by the different techniques it was possible to obtain a mapping
of the tribological and mechanical properties as a function of the synthesis conditions that helps in
the selection of the best coating for specific applications.
Fig. 2 C K-edge
EELS spectra and
associated friction
values for different
TiC/a-C coatings
Fig. 1: HRTEM image for a TiC/a-C film
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