Effect of Cu, Ni on the property and microstructure of ultrafine WC-10Co alloys by sinter–hipping

Sub-micron size (0.4–0.6 μm) Co–Cu/Ni composite powders were synthesized by a co-precipitation method. The effects of minor Cu and Ni additions on the microstructure and the mechanical properties of ultrafine WC-10Co alloys were investigated using scanning electron microscope, X-ray diffraction and mechanical properties tests. The results show that Co–Cu binder phase refines the WC grains and increases the hardness of the base alloys. But the addition of Ni can't refine the WC grains and increase the hardness. The addition of minor Cu or Ni can improve transverse rupture strength of alloys through the solid solution strengthening. However, adding excess Cu can lead to the decrease in transverse rupture strength. With the partial substitution of Co by Cu and Ni, the hardness and transverse rupture strength of the alloys have a little change.

Research highlights
► The authors first reported the substitution of Co with Cu in the ultrafine grain hardmetals through the co-precipitation process.
► The research results show that the grain growth of WC particles of the based alloys was inhibited with the addition of Cu.
► Addition of Cu or Ni can improve transverse strength of alloys through the solid solution strengthening of Cu or Ni.
► The substitution of Co with Ni in fine-grained tungsten carbide cermets is assumed to be unsuitable due to WC grain growth.
► However, partial substitution of Co by Cu and Ni may be a very good method to solve the limitations of substitution of Co with Ni in fine-grained hardmetals.