Experimental investigation on fabrication, characterization and properties of spark plasma sintered alumina-based tungsten carbide composites reinforced by carbon nanotubes

Abstract

In this study, the alumina-based tungsten carbide (WC-Al2O3) composites reinforced by different weight percentages of carbon nanotubes were successfully prepared by the advanced spark plasma sintering technique. This study has the novelty that such composites with the given compositions were never sintered before using spark plasma sintering. The WC-Al2O3-CNTs composites were fabricated to design advanced tool materials with an optimum set of mechanical and thermal properties for high-temperature cutting applications. The experimental results revealed considerable growth in micro-hardness and fracture toughness in WC-Al2O3-CNTs composites as compared to WC-Al2O3 composites. The ideal set of mechanical properties was acquired by WC-Al2O3-CNTs-0.5 composite which also exhibited a minimum value of grain size. At higher concentrations of carbon nanotubes, the mechanical properties of composites tend to degrade due to the agglomeration of carbon nanotubes. The study presented better results in sintered composites than the composites fabricated through other sintering techniques. The improved strengthening and toughening results of WC-Al2O3-CNTs composites along with the fine microstructures were mainly acquired by inhibiting grain growth during sintering, improved dispersion of the constituents in the composites (electron probe microscopy analysis/wavelength dispersive spectroscopy mapping) and consolidation at shorter sintering periods in spark plasma sintering. A thermal study was also conducted to discuss the thermal stability of sintered composites at ambient as well as at higher temperatures to estimate the behavior of thermal conductivity and thermal diffusivity of composites at different temperatures.