Preparation And Properties Of Pure Tungsten Carbide

In this paper, highly dense and fine grain WC ceramics have been successfully prepared by hot pressing (HP) and hot isostatic pressing (HIP) using sub-micron WC powders (doped with0.33wt%VC and0.54wt%Cr3C2).Firstly, consolidated WC powders using HP at different temperatures to preliminaryly explore the HP sintering process of preparing the densely WC ceramics, and then treated the densely WC ceramics by HIP to prepare the high densely WC ceramics, and the mechanical properties of the sintered WC ceramics have carried on the comprehensive analysis and test. In addition, the inhibition mechanism of grain growth inhibitor was studied by TEM and EDX. Finally, we successfully prepared the fully dense WC ceramics by optimizing the HP sintering process.The microstructure and mechanical performances of WC ceramics sintered by HP were analyzed; the results show that the dense sub-micron WC ceramics could be obtained under the HP sintering process of1900～2000℃,28MPa and30min and the fully dense WC ceramics could be obtained by HP at2000℃,35MPa and30min. For the dense WC ceramics could be further improve the density by HIP under the condition of the WC grains were not obviously grew up to prepare the highly dense WC ceramics, which hardness was significantly improved, up to26GPa.The fatigue performance of the highly dense WC ceramics was tested; the results show that fatigue fracture of WC ceramics has the characteristics of the typical morphology of fatigue, fatigue fracture can be divided into three areas namely fatigue source area, the fatigue crack spreading area and transient breaking area. The macro fracture of high stress and high cycle fatgue compared with the low stress and low cycle fatigue, its fatigue source area and the fatigue crack propagation region was obvious and the proportion was larger, while the proportion of transient breaking region was relatively small.The erosion wear performance of the fully dense WC ceramics was tested; the researches show that the erosion wear rate of the WCceramics was related to erosion angles. In45°the erosion rate was the maximum, the erosion mechanism was that under the effect of normal stress, bending stress and shear stress, the micro cracks formed, then the micro cracks extended to form crack cracks, and the crack cracks expanded to deepen under the impact of particles; in70°the erosion rate was the minimum, the erosion wear mechanism was that under the normal stress, the contact fatigue produced; meanwhile the shear stress caused shear failure on the WC surface, the surface micro cracks once formed, the material will be timely erosion off, so it was not easy to form big crack.The distribution of grain growth inhibors was studied byTEM and EDX; the results show that the migration of grain boundaries was hindered by the segregation of the inhibitors at the grain triple junctions and the faced grain boundaries, thereby limiting the WC grain growth and inhibiting the WC abnormal grain growth.