Formation of ZrC during liquid-reactive sintering of the high energy ball-milled powder mixture of tungsten, Zr
Cu and multi-walled carbon nanotubes (MWCNTs) was investigated. The composite powder was compacted and sintered at 1400°C up to 12 h. During sintering, carbon atoms from the well-dispersed MWCNTs diffuse to the tungsten matrix to form WC, and Zr
Cu liquid phase flows into fine capillaries between the tungsten particles. Carbon atoms from WC in the tungsten matrix diffuse into Zr
Cu liquid phase and form ZrC because Gibbs free energy of ZrC formation is lower than that of WC formation. Formation of WC and ZrC was observed by the SEM microstructures of the sintered composites. The formation of carbides in the sintered composite was confirmed by FT-IR spectra and XRD analysis. The density of the sintered composite increases from 80% to 91% theoretical density, after 6 h of sintering. The hardness of the sintered composite (720 Hv) increased up to ~230% more than monolithic tungsten (310 Hv), due to the formation of ZrC and the densification of the sintered composite.
Keywords: liquid-reactive sintering, tungsten matrix composite, high energy ball milling, hardness, diffusion