Cast Protective Coatings of Nano-Structured Polymetallic HEAs by ...
Blucher Material Science Proceedings Novembro de 2014, Número 1, Volume 1 www.proceedings.blucher.com.br/evento/mm-fgm2014
Oral Presentation
Cast Protective Coatings of Nano-Structured Polymetallic HEAs by Means of Centrifugal SHS Process V.N. Sanin*, D.M. Ikornikov, D.E. Andreev, V.I. Yukhvid Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences Chernogolovka, Moscow, 142432 Russia. * [email protected] In recent years, a new alloy design concept that breaks the traditional principles of alloy design has been studied. High entropy alloys (HEAs) have attracted considerable attention around the World. HEAs contain five or more principal elements in equal or near-equal atomic ratios, in which all the atomic concentrations are between 5% and 35%, and none of them should be over 50%. Different from the traditional alloys that form complex phases, HEAs may form simple solidsolution structures like the face-centered cubic (FCC) and body-centered cubic (BCC) ones. HEAs demonstrate superior potential for engineering applications due to their high strength, hardness, wear resistance, high-temperature softening resistance and oxidation resistance. Nevertheless preparation of the multicomponent materials is not easy science and technological task. The high homogeneity(fine distribution of all elements into volume of alloy) should be provided. Besides the alloy consist of high chemical active component (Ti, Al, Zr, Hf etc.) requires expensive mold materials and complicated techniques. This study aimed at developing a new cost-effective process for fabricating cast NiCrCoFeMnAlX, NiCrCoFeAlCu high-entropy alloys and deposition of such coatings through thermite-type SHS reactions in centrifugal machines through the following aluminothermic reaction: (MeO)1 + (MeO)2 + (MeO)3 + (MeO)i + Al+ (FA) HEA + Al2O3 + Q, where (MeO) – NiO, Cr2O3, Fe2O3, Co3O4, etc.; Al-metal reducer, FA is an additive facilitating phase segregation, and Q the reaction heat. The flowsheet of the process is given in Fig. 1. Because the attained temperatures (up to 3000С) are well above the m.p. of reaction products, the melt represents a mixture of mutually insoluble metallic (MMC) and oxide (Al2O3) phases. Due to strongly different specific weights, these phases undergo gravity-assisted phase segregation and subsequent interaction between high temperature alloys and substrate. As a result, a cast protective coating is formed. Combustion was performed at centrifugal acceleration a = 10–200g. In this way we (a) (b) (c) (d) expected to (a) improve the yield of target Fig. 1. Schematic of the process for fabrication of cast HEAs: (a) product, (b) remove gaseous byproducts, (c) charge preparation, (b) combustion, (c) phase separation, (d) pattern diminish the grain size in the product, and (d) formation: 1, igniting coil; 2, refractory mold; 3, green composition; 4, make product composition more uniform. combustion front; 5, HAE globules in the melt; 6, oxide melt; and 7, The optimal experimental parameters for cast HEA. production of the cast protective coating were verified experimentally. The phase composition and microstructure of protective coatings was investigated. The gradient concentration of components over height of coatings was revealed. This work can be regarded as the first positive experience of SHS surfacing by cast HEAs. Keywords: Cast protective coatings, centrifugal SHS Process, HEA, polymetallic alloys The work was supported by the Russian Foundation for Basic Research (project no. 14-08-00694)
Presenting and corresponding author: Vladimir Sanin, ISMAN, E-mail: [email protected] Chernogolovka, Moscow Region, 142432, Russia
Oral Presentation
Cast Protective Coatings of Nano-Structured Polymetallic HEAs by Means of Centrifugal SHS Process V.N. Sanin*, D.M. Ikornikov, D.E. Andreev, V.I. Yukhvid Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences Chernogolovka, Moscow, 142432 Russia. * [email protected] In recent years, a new alloy design concept that breaks the traditional principles of alloy design has been studied. High entropy alloys (HEAs) have attracted considerable attention around the World. HEAs contain five or more principal elements in equal or near-equal atomic ratios, in which all the atomic concentrations are between 5% and 35%, and none of them should be over 50%. Different from the traditional alloys that form complex phases, HEAs may form simple solidsolution structures like the face-centered cubic (FCC) and body-centered cubic (BCC) ones. HEAs demonstrate superior potential for engineering applications due to their high strength, hardness, wear resistance, high-temperature softening resistance and oxidation resistance. Nevertheless preparation of the multicomponent materials is not easy science and technological task. The high homogeneity(fine distribution of all elements into volume of alloy) should be provided. Besides the alloy consist of high chemical active component (Ti, Al, Zr, Hf etc.) requires expensive mold materials and complicated techniques. This study aimed at developing a new cost-effective process for fabricating cast NiCrCoFeMnAlX, NiCrCoFeAlCu high-entropy alloys and deposition of such coatings through thermite-type SHS reactions in centrifugal machines through the following aluminothermic reaction: (MeO)1 + (MeO)2 + (MeO)3 + (MeO)i + Al+ (FA) HEA + Al2O3 + Q, where (MeO) – NiO, Cr2O3, Fe2O3, Co3O4, etc.; Al-metal reducer, FA is an additive facilitating phase segregation, and Q the reaction heat. The flowsheet of the process is given in Fig. 1. Because the attained temperatures (up to 3000С) are well above the m.p. of reaction products, the melt represents a mixture of mutually insoluble metallic (MMC) and oxide (Al2O3) phases. Due to strongly different specific weights, these phases undergo gravity-assisted phase segregation and subsequent interaction between high temperature alloys and substrate. As a result, a cast protective coating is formed. Combustion was performed at centrifugal acceleration a = 10–200g. In this way we (a) (b) (c) (d) expected to (a) improve the yield of target Fig. 1. Schematic of the process for fabrication of cast HEAs: (a) product, (b) remove gaseous byproducts, (c) charge preparation, (b) combustion, (c) phase separation, (d) pattern diminish the grain size in the product, and (d) formation: 1, igniting coil; 2, refractory mold; 3, green composition; 4, make product composition more uniform. combustion front; 5, HAE globules in the melt; 6, oxide melt; and 7, The optimal experimental parameters for cast HEA. production of the cast protective coating were verified experimentally. The phase composition and microstructure of protective coatings was investigated. The gradient concentration of components over height of coatings was revealed. This work can be regarded as the first positive experience of SHS surfacing by cast HEAs. Keywords: Cast protective coatings, centrifugal SHS Process, HEA, polymetallic alloys The work was supported by the Russian Foundation for Basic Research (project no. 14-08-00694)
Presenting and corresponding author: Vladimir Sanin, ISMAN, E-mail: [email protected] Chernogolovka, Moscow Region, 142432, Russia
