Abstract :
Nanocrystalline WC–Co cemented carbides containing different proportions of cobalt, i.e. 5, 10 and 15 wt.%, were prepared by chemical route. Another series of these composites containing 10 wt.% of cobalt with 5 wt.% Fe or Mn or Zn or Ni were also prepared by the same method. Polyacrylonitrile and tungestic acid were used as a source of carbon and tungsten, respectively. Phase composition, crystallite sizes and microstructure evaluation were investigated by X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). The results revealed that the present chemical method is effective route to synthesize nanocrystalline WC–Co composites. By doping Co and/or Fe or Mn or Zn or Ni in WC–Co nanocomposite, nanocrystalline cemented carbide with inhibited grain growth were obtained. XRD showed peaks characterizing WC and Co in case of WC–15 wt.% Co, but showed addition peaks characterizing some oxides of tungsten and cobalt with W metal in case of WC–10 wt.% Co and/or 5 wt.% Fe of Mn or Zn or Ni. The crystallite size of the prepared WC–15 wt.% Co and heat-treated at 1000 °C was in the range of 1.1–7.4 nm, while it was 12–50 nm for WC–Co containing Fe or Mn or Zn or Ni as detected from XRD. On the other hand, the particle size was in the range of 200–400 and 300–500 nm, respectively, as detected from TEM and SEM.
