National University of Science and Technology “MISiS” (Moscow, Russia):

Ph. V. Kiryukhantsev-Korneev, Cand. Eng., Associate Prof., Department of Powder Metallurgy and Functional Coatings; Leading Researcher, Scientific and Educational Center SHS MISiS-ISMAN, e-mail: kiruhancev-korneev@yandex.ru
A. D. Sytchenko, Laboratory Assistant, Scientific and Educational Center SHS MISiS-ISMAN
A. E. Kudryashov, Cand. Eng., Leading Researcher, Scientific and Training Center SHS MISiS-ISMAN
E. A. Levashov, Dr. Eng., Prof., Head of the Department of Powder Metallurgy and Functional Coatings; Director, Scientific and Educational Center SHS MISiS-ISMAN

This paper examines coatings deposited on 40x (analog of 5140) steel substrates by electro-spark alloying with TiCNiCr and TiCNiCr–Eu₂O₃ electrodes. The techniques of X-ray phase analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy and glow-discharge optical emission spectroscopy were applied to analyze the structure, as well as the elemental and phase compositions of the coatings. The mechanical and tribological properties of the coatings were analyzed with the help of nanoindentation and pin-on-disk tests. The coatings were also subjected to electrochemical testing and annealing. The obtained results did not reveal any significant difference between the coatings with Eu₂O₃ in terms of the structure and friction coefficient. However, in terms of heat and corrosion resistance, the coatings with Eu₂O₃ outperform the basic ones. The doped coatings had a more than 20 times lower corrosion current and almost 2 times lower the oxidation number compared with undoped coatings. It is shown that due to the developed coatings the steel parts can be 2.5 times harder, 7 times more wear resistant (with half as high the friction coefficient), more than 20 times more corrosion resistant, and 18 times more heat resistant.

This research was funded by the Ministry of Education and Science of Russia (Assignment No. 11.7172.2017/8.9).
The authors thank A. N. Sheveyko and N. V. Shvyndina for their support with electrochemical testing and structural analysis of the coatings.

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