ABSTRACT Ultrafine tungsten carbide powder is one of the main raw materials for ultrafine grained cemented carbide.The types of micro defects in three grades of ultrafine tungsten carbide powder with different particle sizes and their distribution in the grains were studied via XRD, SEM, TEM, in addition the formation reasons of the micro defects were discussed. The results show that, the ultrafine tungsten carbide powder includes many multigrains. The dislocation density of ultrafine tungsten carbide powder is higher than that of the general metals or alloys in normal state, the types of micro defects are dislocation, stacking fault and twin crystal and so on. The analysis show that during the process of tungsten phase transforming into tungsten carbide phase, the density of tungsten atom decreases from 6.309 446 per cubic nanometer to 3.211 922, the volume of tungsten expands of 31%. A considerable number of micro defects exist mainly due to the release of the stress.
KEY WORDS WC; ultrafine powder; micro defects; dislocation; cemented carbide
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