Synthesis of WC hard materials using coated powders

摘要

Nickel and cobalt were used as binder materials for tungsten carbide powders (WC) hard materials. Ni and Co binder were added individually to the WC powder by two different methods namely, mechanical mixing and chemical electroless coating. In this study WC powders of grain sizes 0.3-1.0 μm were elec-troless coated with either nickel or cobalt. The loading of either Ni or Co coating was 13 wt.%. The elec-troless-coating method conditions of both Ni and Co on WC powders are described. The coated powders were cold compacted and sintered in vacuum at different sintering temperatures. For comparison, identical materials compositions were prepared by mixing the powders constituents mechanically, compacted and sintered under the same conditions.The prepared powders and sintered materials were investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM). The results revealed that coated WC materials have smaller values of porosity and more homogeneous microstructure while other properties, such as transverse rupture strength, and hardness exhibit greater values than those produced using mixing elemental powders. It is possible to outline the benefits of coated powder approach in the following: high homogeneity and better distribution of binder materials within WC hard materials, higher density and good interfacial bonding, capability of using fine powders, and possibility of using small alloying and/or reinforcement additions in a more uniform manner.