Abstract
We have studied alloys in the W - C system with compositions 24 to 48 at.% C, melted in an arc furnace, homogenized and quenched from temperatures of 1450°C to 2650°C or cooled stepwise from a subsolidus temperature down to 850°C, and annealed for a prolonged period at this temperature or at temperatures close to it. We studied the specimens by x-ray single-crystal and powder diffraction, metallography, and differential thermal analysis. We have shown that the carbide W2C exists in two modifications: an hexagonal phase with structure of type L′3 crystallizes from the melt, which at T ≈ 1850°C transforms to an ordered hexagonal phase of the ε-Fe2N type. The latter, for a carbon content of about 32 at.% and T ≈ 1250°C, also decomposes according to a eutectoid reaction to 〈W〉 and WC. This decomposition is accompanied by formation of a metastable phase of the ξ-Fe2N type as an intermediate. Taking the results obtained and literature data into consideration, we have corrected the phase diagram for the W - C system.
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Translated from Poroshkovaya Metallurgiya, Nos. 11–12(440), pp. 101–116, November–December, 2004.
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Kublii, V.Z., Velikanova, T.Y. Ordering in the carbide W2C and phase equilibria in the tungsten — carbon system in the region of its existence. Powder Metall Met Ceram 43, 630–644 (2004). https://doi.org/10.1007/s11106-005-0032-3
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DOI: https://doi.org/10.1007/s11106-005-0032-3