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THE CARBURIZATION OF TUNGSTEN AND CONVERSION INTO ANISOTROPIC ZIRCONIUM CARBIDE/TUNGSTEN CERMETS
Anisotropic ceramic/metal composites can be attractive due to their tailorable and directional thermal and mechanical properties. As one of the ceramic/metal composites, ZrC/W composites fabricated by the reactive infiltration method, known as the Displacive Compensation of Porosity (DCP) method, have been found to exhibit impressive thermal and mechanical properties. Here, we proposed a novel method for fabricating anisotropic ZrC/W composites via the DCP method from wound tungsten wire preforms. Tungsten wire is wound and sintered to form a rigid preform. The preform is carburized with CO gas to form WC and then converted to ZrC/W with Zr2Cu liquid via the DCP method. The kinetic mechanism of the formation of WC for the reaction between W and CO gas at 1000 ℃ was investigated by carburizing W plates with CO gas for 12 h, 24 h, 36 h, 48 h, and 96 h. Thickening rates of the WC films have been found to follow the parabolic rate law, which indicated that the formation of WC film with CO gas was limited by the lattice diffusion of reactant species through the WC film. An inert marker experiment reveals that the formation of WC with the reaction between W and CO gas was controlled by the inward diffusion of C through the WC film. The feasibility of fabricating anisotropic ZrC/W composites via the DCP method from the wound tungsten wire preform was validated. A rigid tungsten wire preform was prepared by hand-winding and sintering at 1800 ℃. The preform was carburized with CO gas at 1000 ℃ for 96 h. XRD analyses confirmed the formation of WC coated W. An anisotropic ZrC/W composite was successfully fabricated by infiltrating the carburized preform with Zr2Cu liquid. XRD and EDX analyses confirmed the conversion of WC to ZrC/W.