Wüest M. 51 Wykes M. 82 Yamaguchi M. 17 Ybarra G. 129 Yubero F ...

JUNE 28 WEDNESDAY AFTERNOON
JS2-WeA-P.8 NANO TO MICROMETRIC HFCVD DIAMOND ADHESION STRENGTH
TO Si 3 N 4 . F.A. Almeida, M.S. Amaral, F.J. Oliveira, R.F. Silva. Dept. of Ceramics and Glass Engineering,
CICECO, Univ. of Aveiro, 3810-193 Aveiro, Portugal. A.J.S. Fernandes. Dept. of Physics,
Univ. of Aveiro, 3810-193 Aveiro, Portugal
CVD diamond coated materials possess unique properties (hardness, thermal conductivity, chemical
inertness) that demand their selection as components of tribosystems working under mechanical
and/or chemical severe conditions. Examples of such applications are cutting tools for highly abrasive
materials and mechanical seals for pumping of corrosive liquids. Furthermore, an increasing interesting
field of application is biomedicine, namely cirurgical tools and coatings for articular implants,
where diamond’s biocompatibility is an essential issue. However, the high surface roughness of conventional
microcrystalline CVD diamond is a major problem when considering such purposes, as the
sliding contact of diamond asperities may increase stress and temperature levels, leading to an increasing
wear rate. To overcome this drawback, today’s goal is the development of diamond crystals with
very small grains of nanometric size by adequate CVD parameters, avoiding the typical columnar
growth of microcrystalline diamond structures. When considering tribological and mechanical applications,
adhesion of the film to the substrate determines the success of the component in service. In this
study, distinct diamond coatings on silicon nitride ceramic substrates with different crystallite sizes
were investigated: i) nanocrystalline diamond (~25 nm); ii) submicrometric diamond (~ 40 nm); and
iii) conventional micrometric size (~10 μm). The coatings, with thickness of about 40 μm, were grown
by hot filament CVD technique. The effect of these diamond structures on adhesion strength to the ceramic
substrate will be evaluated by Brale tip indentation and correlated with their Raman signature.
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