The Structure Formation and Hardness of High-Entropy Alloy Coatings Obtained by Electrospark Deposition
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THE STRUCTURE FORMATION AND HARDNESS OF HIGH-ENTROPY ALLOY COATINGS OBTAINED BY ELECTROSPARK DEPOSITION O.M. Myslyvchenko,1,4 O.P. Gaponova,2 V.B. Tarelnyk,3 and M. O. Krapivka1 UDC 621.9.048.669.268 This paper examines the use of high-entropy alloys (HEAs) as materials for electrospark deposition (ESD). This method is known to produce high-quality protective coatings with a long service life. Arc-melted AlCrFeCoNiCux (x = 0 and 2 mole) cast alloys were used in the research. The HEA coatings were applied to steel 45 employing an Elitron-52A unit. The phase composition, hardness, and microstructure of the cast alloys and associated coatings were compared. The starting HEAs were found to have an inhomogeneous microstructure peculiar to the cast alloys and crystallize to form simple solid solutions with bcc and fcc phases. The AlCrFeCoNi alloy has higher hardness (6229 MPa) than the AlCrFeCoNiCu2 alloy does (5814 GPa). Studies of the structure and phase state of the samples showed that they consisted of an upper layer (coating), transition zone, and substrate with a ferrite–pearlite structure. The hardness, thickness, and continuity of the coatings increase with higher discharge energies Wd in ESD. At Wd = 0.13 J, the coating is 20 m thick and has 70% continuity; at Wd = 4.6 J, the coating becomes 130 m thick and is 100% continuous. In contrast to the cast alloys, the high-entropy coatings show higher microhardness: 6230 and 7320 MPa for AlCrFeCoNiCu2 and AlCrFeCoNi, respectively, at a discharge energy of 4.6 J. The coating thickness increases when copper is added to the electrode material. Simple solid solutions peculiar to high-entropy alloys form in both the cast alloys and the coatings. Unlike the cast alloys, the coatings are characterized by homogeneous microstructure. Keywords: high-entropy coating, electrospark deposition, solid solution, microhardness, microstructure, X-ray diffraction.
INTRODUCTION The development of new technology in modern evolving civilization continuously required new materials with improved service properties. Pure metals could not impart the required structural strength to parts. The development and use of alloys for the fabrication of parts for extreme applications over wide ranges of temperature– power and dynamic loads improved not only strength but also other properties, such as oxidation and wear resistance, high-temperature creep-resistance, corrosion resistance, etc. The entropy of high-doped alloys increases
1Frantsevich
Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Kyiv, Ukraine. 2Sumy State University, Sumy, Ukraine. 3Sumy National Agrarian University, Sumy, Ukraine. 4To whom correspondence should be addressed; e-mail: [email protected]. Translated from Poroshkova Metallurgiya, Vol. 59, Nos. 3–4 (532), pp. 109–119, 2020. Original article submitted December 16, 2019. 1068-1302/20/0304-0201 2020 Springer Science+Business Media, LLC
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with a greater amount of doping elements. The paper [1] published in 2004 was the first to
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