Composition of Al 2 O 3 -W-WC composite prepared by WO 3 -Al reaction under coke

Abstract

Pellets pressed from WO₃, Al, and fused Al₂O₃ powder mixes according to the stoichiometry 3Al + WO₃ + xAl₂O₃ = (x + 1)Al₂O₃ + W (x = 0·1-0·5) were heated at 1473, 1623, and 1773 K for 3 h under coke granules. The composition and microstructure of samples were examined by X-ray diffraction analysis, scanning electron microscopy, and energy dispersive X-ray analysis. The products of the Al-WO₃ reaction were found to consist of tungsten, corundum, and tungsten carbides. For x ≤ 0·3, temperature had little effect on the X-ray intensity ratios (I_WC(101) + I_W2C(101)) / I_W(101) and I_WC(101) / I_W2C(101), whereas at x = 0·5 the influence of temperature was significant. Tungsten was converted to tungsten carbides in the samples heated at 1773 K. High temperature improved diffusion in the tungsten carbide layer and promoted the transformations from W to WC and from W₂C to WC. Sintering of the corundum and tungsten resulted in cracks that provided rapid diffusion pathways for CO to penetrate and react with W.

Keywords

ALUMINA TUNGSTEN COMPOSITE SYNTHESIS MICROSTRUCTURE

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