A new material called tic coating is being developed that improves the wear and corrosion resistance of graphite. This coating is based on titanium carbide and can be made to have various thicknesses, from a few microns up to 250 Km. These coatings have a high surface hardness that is higher than that of the starting graphite and are capable of polishing to a very smooth surface.
When the tic coating is applied to a tungsten carbide substrate, it has an adhesive strength much higher than the tungsten carbide, and its oxidation resistance is also improved compared to that of the uncoated sample. This is due to the fact that TiC has a more stable structure and chemistry than tungsten carbide.
The oxidation behavior of the tic coating was investigated by performing a boiling concentrated hydrochloric acid test. Unlike graphite, which loses weight during oxidation, TiC oxidizes to titanium dioxide and has a good oxidation resistance.
During the tic coating process, the deposition temperature and gas flow rate have been found to be important factors in changing the characteristics of the resulting tic coating on hot work tool steels. These changes include microhardness, wear resistance and surface roughness that were measured by Knoop hardness testing, pin on disk wear tests and atomic force microscopy.
The equiaxed microstructure adjacent to the coating-substrate interface and columnar grains away from this interface can be seen in the FESEM micrographs shown in figure 4. It is found that the equiaxed microstructure enhances the adhesion of the coating to the graphite substrate.
