Electrospark deposition of coatings using Cr3C2 powder and their characterization
A mixture of titanium granules with chromium carbide powder Cr3C2 was employed to prepare Ti-C-Cr coatings on Ti6Al4V titanium alloy using electrospark treatment in granules. Three mixtures of granules with a chromium carbide content of 2.7; 5.1 and 7.4 vol.% were prepared. According to X-ray analysis, it was found that titanium carbide, αTi, chromium and carbide Cr7C3 were observed in the composition of coatings. Titanium carbide was formed as a result of decarburization of Cr3C2 when interacting with molten titanium under the action of electric discharges. The average thickness of the coatings increased from 18 to 34 μm with an increase in the content of Cr3C2 powder in the mixture of granules. Grains of titanium carbide with a dendritic structure, surrounded by a Ti-Cr binder, were observed in the microstructure of the coatings. According to the EDS data, the concentrations of chromium and carbon decreased when scanning from the surface layers of the coating to the substrate. With an increase in the concentration of Cr3C2 powder in the mixture of granules from 2.7 to 5.1 vol.% hardness of coatings increased from 5.2 to 10.6 GPa. This is 1.7-3.5 times higher than that of the Ti6Al4V alloy. Dry sliding wear tests showed that the Ti-C-Cr coatings had a wear rate ranging from 0.41 to 2.38×10-6 mm3/Nm. Thus, these can improve the wear resistance of the Ti6Al4V alloy from 18 to 107 times. Testing of the samples for resistance to high-temperature gas corrosion at 900°C for 100 hours showed that the technology of electric spark treatment in a mixture of titanium granules with 7.4 vol.% of chromium carbide powder allows increasing the oxidation resistance of the alloy Ti6Al4V three times.