High hardness-high toughness WC-20Co nanocomposites: Effect of VC variation and sintering temperature

摘要

WC-Co nanocomposites with variable VC content are synthesized by liquid phase sintering at two different temperatures. The as synthesized samples are characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and optical microscope. The mechanical properties are obtained by Vickers indentation method. The high content of VC, lead to high porosity when sintering temperature is increased from 1350 to 1400 ℃ The relative density of all the samples is more than 95%. Microstructure reveals that agglomeration of W-Co-C and V-W-C increases at 1400 ℃, which generates layered interfaces in radial direction and hence the material inhomogeneity. XRD pattern shows that the formation of η phase increases at 1400 ℃, which is responsible to decrease the fracture toughness of the present samples. The average particle size of 102 nm, highest hardness of 1870.6 kgf/mm~2 with fracture toughness of 14.4 MN/mm~(3/2) is observed in sample having 7.5 wt% VC, sintered at 1350 ℃ for one minute. This combination shows the highest hardness and reasonably high toughness as compared to conventionally sintered materials reported so far.