Influence of Granulation and Ni-Containing Binder Composition on the Self-Propagating High-Temperature Synthesis of Carb
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uence of Granulation and Ni-Containing Binder Composition on the Self-Propagating High-Temperature Synthesis of Carbides in the Ti–Cr–C System B. S. Seplyarskiia, *, R. A. Kochetkova, N. I. Abzalova, I. D. Kovaleva, and T. G. Lisinaa aMerzhanov
Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia *e-mail: [email protected] Received December 6, 2019; revised March 10, 2020; accepted March 25, 2020
Abstract—We have studied the combustion process and the phase composition of its products using granulated 70 wt % (Ti + C) + 30 wt % (3Cr + 2C) and 80 wt % (Ti + C) + 20 wt % (3Cr + 2C) mixtures with nickel-containing binders. The results demonstrate that the addition of a nickel binder reduces the chromium content of the (Ti,Cr)C double carbide, because nickel reacts with chromium to form Nichrome. In the case of combustion of the granulated 80 wt % (Ti + C) + 20 wt % (3Cr + 2C) mixture with the addition of Kh20N80 Nichrome, a Nichrome-binder-containing (Ti,Cr)C double carbide essentially free of impurity phases according to X-ray diffraction data has been prepared in a single step. A two-step mechanism of final product formation has been proposed. According to scanning electron microscopy data, the grain size of the combustion products is 2–5 μm, which is an order of magnitude smaller than the initial titanium and chromium particle size. In contrast to powder mixture combustion products, which are difficult to disintegrate, the agglomerate obtained via the combustion of a granulated mixture broke into separate granules, which could be ground to a desired particle size under laboratory conditions. Keywords: self-propagating high-temperature synthesis, cermets, (Ti,Cr)C, Nichrome, granulation DOI: 10.1134/S0020168520080142
INTRODUCTION Titanium carbide (TiC) based cermets have a high melting point, hardness, corrosion resistance, and ablation resistance. Having the same advantages as titanium carbide, the titanium chromium double carbide (Ti,Cr)C offers a higher oxidation resistance owing to the formation of a protective chromium oxide (Cr2O3) layer [1]. To reduce brittleness and improve adhesion of protective coatings produced by flame spraying, a metallic binder (Ni, Mo, NiCr, Cu, and others) is added to powders based on titanium chromium double carbides [2, 3]. Among known methods for the fabrication of composites based on double carbides [4], self-propagating high-temperature synthesis (SHS) is distinctive in that it offers low energy consumption and fast process rate in combination with high purity and homogeneity of synthesis products obtained in a single processing cycle. These features of SHS are due to the melting of individual components of the starting mixture during the synthesis process, which leads to self-dispersion of the reactants, improving the homogeneity of the synthesis products [5]. Zhang et al. [6, 7] studied the influence of Cr content and Ti/C ratio on the SHS of
a titanium chromium double carbide, using pressed pellet
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