from the conferences organized by TANGER Ltd.
The work reviews phase evolution, mechanical, electrical, thermal and tribological properties of NbMoTaW100-z(CN)z coatings deposited using reactive DC magnetron co-sputtering. The concentrations of the metals were not equimolar, therefore, the resulting material was attributed to the compositionally complex compounds instead of high-entropy stabilized ceramics. The concentrations of anions was the result of the combination of carbon co-sputtering at 300 W and 600 W power levels on carbon target and variable flows of nitrogen. Depending of the carbon and nitrogen additions, the coating compositions transformed from metallic alloy doped by carbon and nitrogen with bcc structure up to carbo-nitrides with variable stoichiometry with fcc structure. The stoichiometry was even exceeded at high carbon and nitrogen additions supply due to the formation of free carbon phase. Nanoindentation measurements of hardness and indentation moduli exhibited additive effects of carbon and nitrogen. The difference between two carbon levels was around 5 GPa. The changes in hardness due to nitrogen were more pronounced due to wider addition range. Superhardness of ~ 50 GPa was obtained in the slightly sub-stoichiometric carbon-rich carbonitride coatings exhibiting fcc structure. Electrical resistance of the coatings decreased when temperature decreased and a transition to superconductive state occurred. Transition temperatures, Tc, increased almost linearly from ~4K in the low stoichiometry coatings to 9 K in the near-stoichiometric carbonitrides. Thermal conductivity of the studied coatings also depended on phase composition and decreased with the increase of nitrogen concentration from 10 W/K.m to 5 W/K.m. The coefficients of dry friction (COF) against alumina were in a narrow range 0.15 - 0.30 and depended on coating stoichiometry and applied load. Friction and wear mechanisms included adhesion combined with the tribochemical reactions leading to the formation of transfer films in the wear track. ACKNOWLEDGMENT: This work was supported by the EU NextGenerationEU through the Recovery and Resilience Plan for Slovakia under project No. 09I03-03-V04-00281 and by the Slovak Research and Development Agency (projects APVV 21-0042 and APVV-24-0038).
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