Mariana Fraga - Nano- and microcrystalline diamond deposition on pretreated WC–Co substrates: structural properties and adhesion

Document created by Mariana Fraga on Feb 17, 2016
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    M A FragaA   ContinL   A A RodríguezJ   VieiraR   A CamposE   J Corat and V   J Trava Airoldi.   Nano-   and microcrystalline diamond deposition on pretreated WC–Co   substrates: structural properties and   adhesion. 2016 Mater.   Res. Express 3 025601


    Many developments have been made to improve the quality and   adherence of CVD diamond films onto WC–Co hard metal tools by the   removing the cobalt from the substrate surface through substrate   pretreatments. Here we compare the efficiency of three chemical   pretreatments of WC–Co substrates for this purpose. First, the   work was focused on a detailed study of the composition and   structure of as-polished and pretreated substrate surfaces to   characterize the effects of the substrate preparation.   Considering this objective, a set of WC–9% Co substrates, before   and after pretreatment, was analyzed by FEG-SEM, EDS and x-ray   diffraction (XRD). The second stage of the work was devoted to   the evaluation of the influence of seeding process, using 4 nm   diamond nanoparticles, on the morphology and roughness of the   pretreated substrates. The last and most important stage was to   deposit diamond coatings with different crystallite sizes (nano   and micro) by hot-filament CVD to understand fully the mechanism   of growth and adhesion of CVD diamond films on pretreated WC–Co   substrates. The transition from nano to microcrystalline diamond   was achieved by controlling the CH4/H2 gas   ratio. The nano and microcrystalline samples were grown under   same time at different substrate temperatures 600 °C and 800 °C,   respectively. The different substrate temperatures allowed the   analysis of the cobalt diffusion from the bulk to the substrate   surface during CVD film growth. Furthermore, it was possible to   evaluate how the coating adhesion is affected by the diffusion.   The diamond coatings were characterized by Raman spectroscopy,   XRD, EDS, FEG-SEM, atomic force microscope and 1500 N Rockwell   indentation to evaluate the adhesion.

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