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21XV International Symposium on Self-Propagating High-Temperature Synthesis
FORMATION OF TiC/C LAYER ON Ti ALLOYS BY A SIMULTANEOUS ELECTRO-SPARK AND ARC EVAPORATION TREATMENT WITH GRAPHITE ELECTRODE
A. N. Sheveyko*", K. A. Kuptsov", A. E. Kudryashov", and D. V. Shtansky"
aNational University of Science and Technology MISiS, Moscow, 119049 Russia *e-mail: sheveyko@mail.ru
DOI: 10.24411/9999-0014A-2019-10158
A new technology combining pulsed arc evaporation (PAE) and electric-spark deposition (ESD) in vacuum was developed and used for two-layer wear-resistant Ti-TiC/a-C coating deposition on Ti. Both processes were carried out together in a single vacuum process using the same graphite electrode. In such a process, part of the electrical impulses is realized in the spark discharge due to electrodes contact leading to graphite transfer into the crater of titanium melt, which, in turn, results in carbide formation. Another part of the pulses causes the arc discharge initiation leading to carbon transfer to the substrate surface with the formation of a carbon coating. The structure, elemental and phase composition of the coatings were studied by means of X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, glow discharge optical emission spectroscopy, and Raman spectroscopy. The ESD layer, more than 100 ^m thick, was consisted of a-Ti (~ 50%), TiCx, and a small amount of free carbon. The PAE layer 10-15 |im thick was characterized by a nanocomposite, nearly amorphous structure, in which disordered TiCx crystallites 3-5 nm in size were dispersed in an amorphous carbon matrix with 30% of sp3-hybridized bonds. The ESD layer had a hardness of approximately 15 GPa. The two-layer coating demonstrated a superior tribological performance (CoF < 0.2, wear rate < 5 x 10-7 mm3/Nm), which was attributed to a combination of high toughness and thickness of the ESD layer, which prevented the substrate from plastic deformation, and to low friction coefficient of the top PAE layer due to nearly amorphous structure with large amount of free carbon in graphite state acting as a solid lubricant.
The authors gratefully acknowledge the financial support from the Russian Scientific Foundation (agreement No. 15-19-00203-n).
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