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Synthesis and tribological properties of nanostructured WC/a-C coatings deposited by magnetron sputtering

Manuel David Abad ,  Miguel Angel Muñoz ,  Carlos López-Cartes ,  Juan Carlos Sánchez-López 

Instituto de Ciencia de Materiales de Sevilla (ICMSE), Avda. Americo Vespucio, 49, Sevilla 41092, Spain

Abstract

Nanocomposite coatings made of crystalline hard phases in combination with an amorphous soft matrix represent a good solution for achieving a compromise between mechanical and tribological properties. In this work, nanocrystalline tungsten carbide (WC) was combined with amorphous carbon (a-C) in different proportions by magnetron sputtering technique at near room temperature. By controlling the power applied to WC and graphite targets it is possible to obtain nanocomposite coatings with variable hard/lubricant phase composition. The microstructure and chemical composition of the samples were studied by transmission electron microscopy (TEM), electron (ED) and X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electron energy-loss spectroscopy (EELS). The crystalline phases were identified as WC1-x and W2C by XRD dispersed in a disordered carbon matrix. The C1s photoelectron peak was used to estimate the distribution of carbon in WC and a-C phases inside the composite (Cwc/a-C) and this parameter was correlated with the tribological properties measured in a pin-on-disk tester in dry conditions. The friction coefficients decreased from 0.8 to 0.15 when diminishing the Cwc/a-C ratio from »1.7 to 0.7. The endurance of the coatings is increased following the same trend reaching optimum values of 1×10-7 mm3/Nm. In view of the results, relationships among synthesis conditions, microstructure, chemical bonding and compositions and tribological performance of the WC/a-C nanocomposites were established.

 

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Presentation: Poster at E-MRS Fall Meeting 2006, Symposium A, by Juan Carlos Sánchez-López
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-15 13:27
Revised:   2009-06-07 00:44