Quantification of the Thickness of Carbon Transfer Films Using Raman Tribometry

Author: Scharf T.W.   Singer I.L.  

Publisher: Springer Publishing Company

ISSN: 1023-8883

Source: Tribology Letters, Vol.14, Iss.2, 2003-02, pp. : 137-145

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Abstract

A method to quantify transfer film thickness of diamond-like nanocomposite (DLN) coatings during sliding is presented. Previously, we showed that as the transfer film thickened then thinned, Raman carbon spectra evolved from that of the coating, to the transfer film, then back again to the coating. In this paper, the transfer film thickness is quantified using Raman spectra with stylus profilometry and a light-scattering model based on Beer's Law. Non-linear least-square fits of Raman intensity versus thickness data of several transfer films gave an optical mean free path of ∼500 nm. The model was also used to quantify transfer film thickness between 10 and 960 nm from the Raman intensity (at a given frequency) of the combined coating–transfer film spectrum. Finally, the model was applied to in situ spectra during sliding to establish a thickness at which a transfer film wore through causing a rise in friction.