Thermally sprayed coatings as inter layers for DLC-based thin films

• Published in: Journal of thermal spray technology 2009-06, Vol.18 (2), p.231-242
• Main Authors: Bolelli, G, Gualtieri, E, Lusvarghi, L, Mantini, Pighetti F, Pitacco, F, Valeri, S, Volz, H
• Format: Article
• Language: English
• ISSN: 1059-9630
• DOI: 10.1007/s11666-008-9286-x

This article examines the usefulness of a thick thermally sprayed interlayer (plasma-sprayed Ni-50%Cr, plasma-sprayed Al(2)O(3)-13%TiO(2), or high-velocity oxygen-fuel-sprayed WC-17%Co) for enhancing the wear resistance and the corrosion protectiveness of a diamond-like carbon (DLC)-based thin film deposited onto a carbon steel substrate. Scratch tests indicate that the Al(2)O(3)-13%TiO(2) and WC-17%Co interlayers definitely increase the critical spallation load of the thin film, but the Al(2)O(3)-13%TiO(2) interlayer itself undergoes brittle fracture under high-contact loads. Accordingly, during ball-on-disk tests at room temperature, no cracking and spallation occur in the DLC-based film deposited onto the WC-17%Co interlayer, whereas the one onto the Al(2)O(3)-13%TiO(2) interlayer is rapidly removed because the interlayer itself is fractured. At 300 deg C, by contrast, the DLC-based film on the Al(2)O(3)-13%TiO(2) interlayer offers the best tribological performance, possibly thanks to the increased toughness of the ceramic interlayer at this temperature. Electrochemical polarization tests indicate that the thin film/ WC-Co systems possess the lowest corrosion current density.