Formation of stacking faults in tungsten carbide during sintering

Abstract

Ultra-high density of parallel planar defects is discovered within WC grains in V-doped cemented carbide. High resolution transmission electron microscopy (HRTEM) shows that such defects are stacking faults on the {101‾0} prismatic planes. The presence of multiple stacking faults within WC grain gives rise to a series of anomalous diffraction patterns, including the streaking of diffraction spots and forbidden fractional diffraction spots. Interestingly, quantitative analysis indicates that the density of stacking faults within the V-doped sample is one order of magnitude higher than that of the Ti-doped counterpart. Because the two doped samples are processed under the same condition, we conclude that the planar defects of WC grains in V-doped samples are largely produced during the sintering of cemented carbide. Aberration-corrected TEM images suggest that the formation of stacking faults can be ascribed to the merging of independently developed WC micro-pillars. The formation of such pillars can be further explained by the segregation of V-rich precipitates at the corners between basal and prismatic planes. The current finding not only unravels a new formation mechanism of stacking faults within WC grains, but also provides a new route to design superhard cemented carbides with interlaced stacking faults by simply doping solute atoms and controlling the sintering process, other than the traditional deformation method.