Highlights

Characterization of Carbide-Derived Carbon (CDC) Films Synthesized on Pure Microcrystalline Tungsten Carbide (WC)

Scientific Achievement

Films of carbide-derived carbon (CDC) were produced on surfaces of pure tungsten carbide substrates by reacting the carbide phase with chlorine or chlorine-hydrogen mixtures at temperatures ranging from 800 C to 1000 C in a sealed tube furnace.  In addition to tribological testing, electron microscopy was used to determine optimal treatment conditions, especially for chlorine-hydrogen mixtures.  It was determined that temperatures of 950 C and higher are required to achieve full conversion of the tungsten carbide surfaces and to obtain films with tribological properties of interest for various applications.  Backscatter imaging allowed to measure film thickness and find its dependence on the length of treatment and gas mixture proportions.  EDS analysis gave important insight into residual chlorine levels resulting from treatment and their correlation with tribological performance.

Significance

Carbide-derived carbon films have previously been produced mostly on silicon carbide films.  This research uses tungsten carbide substrates which is absolutely novel.  The difficulties with the corrosion action of chlorine on tungsten carbide substrates have been overcome and this opens an entirely new avenue for specific applications, especially in precision machinery wherever tungsten carbide tools are used.  Examples include magnesium cutting tools, precision machinery bearings or drill bits.  Several comparison studies were done with similar products synthesized on silicon carbide and the properties were found to be very similar, and the microstructure and tribological performance of tungsten-carbide-based films seems to indicate their superiority for certain applications, especially where high wear resistance is crucial.  Future research is needed to concentrate on the influence of residual chlorine levels on specific applications.  High residual chlorine levels also indicate a micro- or nanoporous structure suitable for gas storage applications (i.e. hydrogen storage).

Performers