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Nanocomposite TM-dichalcogenides sputtered self-lubricating coatings alloyed with C

Albano Cavaleiro 1Tomas Polcar Manuel Evaristo 

1. ICEMS - Mechanical Department, Faculty of Science and Technology Coimbra University (ICEMS-FCTUC), Pinhal de Marrocos, Coimbra 3030-201, Portugal

Abstract

Transition metal dichalcogenides (TMD) are compounds with unique and unusual properties based on the extreme degree of anisotropy of the layered structure, which make them suitable as solid lubricants. TMD exists in the MX2 form, where M=Mo,W,Nb and X=S,Se,Te. The deposition of TMD systems leads usually to films with very high porosity with the consequent low values in hardness and adhesion to the substrates. Thus, their tribological behavior was unsuitable whenever high loads were applied or tests were carried out in moisture containing atmospheres.There are a lot of different possibilities to improve the tribological behavior of these coatings. One of the most successful ways is to deposit a composite material associating high strength materials with self-lubricants. Recently, nanocomposite structured coatings were deposited associating a hard DLC phase with WS2 permitting to reach very low friction coefficients in a large range of environments. On the other hand, there are studies showing that diselenides have improved resistance to water in relation to sulfides.It is the aim of this talk to compare the tribological performance of nanocomposite coatings based in two different TMD systems, a sulphide (W-S) and a selenide (Mo-Se). In both cases, the coatings were deposited with increasing contents of carbon (up to 70at.%) by decreasing the number of TMD pellets placed in the C target during the sputtering deposition. Significant improvements of the mechanical properties (hardness, adhesion) in more than one order of magnitude were reached. Pin-on-disc performed in different testing conditions showed that W-S-C system outstand Mo-Se-C coatings at higher temperatures whereas the inverse occurred concerning the global behaviour in environments containing different humidity ratios

 

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Related papers

Presentation: Invited oral at E-MRS Fall Meeting 2006, Symposium A, by Albano Cavaleiro
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-16 16:53
Revised:   2009-06-07 00:44