CC BY
24■SHS 2019 Moscow, Russia
APPLICATION OF SHS FOR PRODUCTION OF COMPOSITE CERAMIC CATHODES FOR PVD OF HIGH-TEMPERATURE PROTECTIVE
Mo- (Hf/Zr)-Si-B COATINGS
A. Yu. Potanin*", Ph. V. Kiryukhantsev-Korneev", S. I. Rupasov", Yu. S. Pogozhev",
and E. A. Levashov"
aNational University of Science and Technology MISIS, Moscow, Russia
*e-mail: a.potanin@inbox.ru
DOI: 10.24411/9999-0014A-2019-10130
This work is supposed to carry out experimental studies on obtaining high-temperature ceramic materials based on borides and silicides of transition refractory metals of the IV-VI groups of the Periodic Elements Table by self-propagating high-temperature synthesis (SHS) technology [1]. Also, the mechanisms of the phase and structure formation, as well as the stages of reactions during the ceramics synthesis in the Mo-Si-B, Mo-Hf-Si-B, and Mo-Zr-Si-B systems were studied. The high-temperature ceramic experimental samples, including target-cathodes were produced by the hybrid SHS + HP technology. The coatings were deposited by direct current magnetron sputtering. The structure, element and phase composition of coatings were studied by means of scanning and transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive spectroscopy, and glow discharge optical emission spectroscopy. To evaluate their oxidation resistance, the coatings were annealed in air in the temperature range of 500-1600°C during different time slots between 10 min and 5 h. The complex materials researches that establish the relationship between the composition and the structure of ceramic materials, the parameters of sputtering and the properties of coatings were carried out.
The dense composite ceramic cathodes characterized by high hardness and low residual porosity were produced by hot pressing of SHS powders. Phase composition and structure were investigated. The final composition of the reaction products consists of HfB2/ZrB2, MoSi2, and MoB phases. The microstructure of the HP specimen in Mo-Hf-Si-B system is presented in Fig. 1. In the obtained ceramic, MoSi2 (< 10 ^m), MoB (2-10 ^m), and HfB2 (< 1 ^m) grains are present. All phases have comparable size and are randomly distributed in the structure. These compositions are advanced for high-temperature application in oxidizing condition because of formation of strong oxide films SiO2-HfO2-B2O3 along with the complex oxide HfSiO4, which serve as an effective diffusion barrier and reduce the oxidation rate.
Fig. 1. Microstructure of the composite ceramic cathode fabricated by hot pressing of SHS powder in Mo-Hf-Si-B system.
XV International Symposium on Self-Propagating High-Temperature Synthesis
Hard Mo-(Hf,Zr)-Si-B-(N) films were deposited by magnetron sputtering of SHS-targets in Ar + N2 (0, 10, 15, 25, and 100% N2). According to XRD results, the MoSi2 hexagonal phase was the main structural component of all studied samples (Fig. 2). Certain lines were close or overlapped on the lines from the AhO3 substrate, but reflections at angles 20 = 22.2°, 41.7°, and 45.5° evidenced the presence of the h-MoSi2 phase. The MoSiB coating had a pronounced texture in the (100) direction.
It was established that single-layer MoSiB coatings possess a hardness of 27 GPa, elasticity modulus of 390 GPa, and elastic recovery of 48%. They can also resist oxidation up at T = 1200 and 1500°C (Fig. 3), which is caused by the formation of the SiO2-based protective film on their surface. The MoSi2 coatings can have hardness comparable to the hardness of MoSiB coatings, but they are somewhat worse than them in regards to oxidation resistance [2].
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Fig. 2. X-ray diffraction pattern of coating Fig. 3. SEM data for MoSiB coating after
MoSiB.
annealing at T = 1200°C for 1 h.
The reported study was funded by RFBR according to the research project no. 18-08-00269.
1. E.A. Levashov, A.S. Mukasyan, A.S. Rogachev, D.V. Shtansky, Self-propagating high-temperature synthesis of advanced materials and coatings, Int. Mater. Rev., 2017, vol. 62, no. 4, pp. 203-239.
2. Ph.V. Kiryukhantsev-Korneev, A.Yu. Potanin, Structure, mechanical properties, and oxidation resistance of MoSi2, MoSiB, and MoSiB/SiBC coatings, Russ. J. Non-Ferr. Met., 2018, vol. 59, pp. 698-708.
