CC BY
20iSHS 2019
Moscow, Russia
NANOCOMPOSITE Si-Ta-C-N-(Ag) COATINGS FOR WIDE
TEMPERATURE RANGE APPLICATIONS
A. V. Bondarev*", A. N. SheveykoA, M. N. Antonyukfi, T. Polcar", E. A. Levashovfi,
and D. V. ShtanskyA
aCzech Technical University in Prague, Prague, 12135 Czech Republic bNational University of Science and Technology MISIS, Moscow, 119049 Russia
*e-mail: andrei.bondarev@fel.cvut.cz
DOI: 10.24411/9999-0014A-2019-10022
New challenges related to the application of coatings at high temperatures in aggressive media require the development of novel coatings with combination of high hardness and fracture toughness, low coefficient of friction, stable elemental and phase compositions, high oxidation resistance. Among ceramics, the SiC- or Si3N4-based coatings demonstrate high hardness and thermal stability, good tribological properties, but the minor point is that these compounds are brittle and have poor crack resistance. Solution can be found in composition and structure tailoring. Silicon-based ceramics is very flexible in contexts of structure, it can possess crystalline, crystalline + amorphous or fully amorphous structure. Also, it can be easily modified by transition metals addition (Ti, Mo, Ta) and in this way the structure becomes more complex and multiphase. For the tribological applications in wide temperature range Ta-doped coatings are in the focus because of lubricious properties of tantalum oxides which can be formed at elevated temperatures and can be combined with low friction properties of SiOx [1]. Soft component addition with zero solubility in silicon-based phases can significantly increase the crack resistance with compromising decrease in hardness [2], in addition soft metals like silver improve tribological performance of coatings as well [3, 4]. The goal of present study was to fabricate Si-based coatings with different design and to investigate structure-properties relationships with special focus on tribological performance. The Si-(Ta)-C-N-(Ag) coatings were deposited by magnetron of multicomponent targets fabricated using SHS powders [5, 6] and in case of silver co-deposition the metallic Ag target was employed. It was shown, that depending on deposition conditions the coatings consisted of crystalline fcc Ta(Si,C,N), Ta5Si3) or amorphous or nanocomposite structure with nanocrystallites 3 nm in size, embedded in an amorphous matrix. The coatings were characterized by high thermal stability and oxidation resistance at temperatures below 800°C. The coefficient of friction of Si-Ta-C-(N) coatings decreased with temperature from 0.38 (25°C) to 0.28 (600°C) and 0.23 (800°C), while their wear resistance increased. The addition of silver provides a positive effect on mechanical properties of coatings but enchantment of tribological properties was contradictory due to lamination of oxide top layers and Ag that cause adhesion failure. In Ag-free coatings a thin (~ 100 nm) oxide layer and TaSixOy microfibers formed during the tests at elevated temperatures played a key role in enhanced tribological behavior, reducing the coefficient of friction and wear due to rolling/sliding friction. Depending on the elemental composition, hardness and Young's modulus of the coatings were 16-26GPa and 155-268 GPa, respectively.
1. Q. Zeng, T. Chen, Superlow friction and oxidation analysis of hydrogenated amorphous silicon films under high temperature, J. Non-Cryst. Solids, 2018, vol. 493, pp. 73-81.
2. A.V. Bondarev, M. Golizadeh, N.V. Shvyndina, I.V. Shchetinin, D.V. Shtansky, Microstructure, mechanical, and tribological properties of Ag-free and Ag-doped VCN coatings, Surf. Coat. Technol., 2017, vol. 331, pp. 77-84.
XV International Symposium on Self-Propagating High-Temperature Synthesis
3. A.V. Bondarev, P.V. Kiryukhantsev-Korneev, E.A. Levashov, D.V. Shtansky, Tribological behavior and self-healing functionality of TiNbCN-Ag coatings in wide temperature range, Appl. Surf. Sci., 2017, vol. 396, pp. 110-120.
4. A.V Bondarev, D.G. Kvashnin, I. V Shchetinin, D.V. Shtansky, Temperature-dependent structural transformation and friction behavior of nanocomposite VCN-(Ag) coatings, Mater. Des., 2018, vol. 160.
5. A.V. Bondarev, S. Vorotilo, I.V. Shchetinin, E.A. Levashov, D.V. Shtansky, Fabrication of Ta-Si-C targets and their utilization for deposition of low friction wear resistant nanocomposite Si-Ta-C-(N) coatings intended for wide temperature range tribological applications, Surf. Coat. Technol., 2019, vol. 359, pp. 342-353.
6. S. Vorotilo, E.A. Levashov, V.V. Kurbatkina, D.Yu. Kovalev, N.A. Kochetov, Self-propagating high-temperature synthesis of nanocomposite ceramics TaSi2-SiC with hierarchical structure and superior properties, J. Eur. Ceram. Soc., 2018, vol. 38, pp. 433-443.
