Nitride-Bonded Silicon-Carbide Composites Based on Artificial Ceramic Binders
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Vol. 61, No. 1, May, 2020
NITRIDE-BONDED SILICON-CARBIDE COMPOSITES BASED ON ARTIFICIAL CERAMIC BINDERS N. K. Kirillova,1 N. V. Shakurova,1 V. A. Doroganov,1,2 and I. Yu. Moreva1 Translated from Novye Ogneupory, No. 2, pp. 26 – 29, February, 2020.
Original article submitted October 14, 2019. Compositions for producing silicon-carbide materials with a nitride binder in which the initial binders were artificial ceramic binders based on silicon and silicon carbide were studied. The influence of the firing regime and binder composition on the main physicomechanical characteristics and microstructure of samples after nitriding firing was studied. Keywords: silicon-carbide composites, artificial ceramic binders (ACBs), nitride binder.
pression at 0.1 MPa. This forming method is widely used to produce SiC items for various purposes and typically requires less material and energy. The optimal filler grain composition was selected according to the particle packing coefficient [11] for vibrational compression at 0.1 MPa. It was found that a composition containing 20% of the fraction 2.5 mm had the maximal packing coefficient of 0.59. Previous research [9, 12] found that the optimal ACB concentration was 55% if a suspension based on SiC was used as the binder for SiC composites. Samples fired at 1300°C in an oxidizing medium were characterized with the best physicomechanical parameters. Compositions of SiC composites with an analogous binder content and 45% polydisperse filler of the optimal composition were studied. Experimental samples were formed by vibrational compression, dried at 100 – 110°C, and fired in N2 at 1000 – 1400°C with holding at the maximum temperature for 2 h. The main physicomechanical characteristics of the fired samples were determined (Fig. 1). The open porosity (Pop) decreased to 26.5 – 26.8%; apparent density (rapp), by 1.5 – 2.0%, if the nitriding firing temperature was increased to 1400°C. However, the compression strength (scom) increased to its maximum value of 24 – 25 MPa. Such low physicomechanical parameters, especially the strength even at the maximum firing temperature, were indicative of insignificant formation of nitrides (1.5 – 2.0%) in the SiC binder. This agreed with previous investigations [10], which found that a combined ACB based on SiC and Si was highly effective and increased the
Silicon-carbide (SiC) composites are used in various technology areas, including ferrous and nonferrous metallurgy, the chemical and ceramic industries, etc. They are especially useful in nonferrous metallurgy for production of Zn, Al, and other metals. SiC refractories are heterogeneous composites in which separate SiC grains are cemented by binders with compositions and physicochemical properties that differ from those of the main phase. SiC materials based on nitride and oxynitride binders with high oxidation resistance at high temperatures are especially interesting [1 – 3]. SiC refractories are prepared from formulations consisting of polydisperse SiC filler, finely disperse Si powder (sometimes f
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