On the formation of very large WC crystals during sintering of ultrafine WC–Co alloys

摘要: Abstract During liquid phase sintering of very fine-grained WC powders (average particle size in the range 100–200 nm) large crystals form with sizes > 20 μm . Such grains typically exhibit shape plates. On tracing back formation these during it was observed that already on heating to 1150 °C small platelets were present still porous body. At 1250 °C, i.e. before eutectic formed, they had grown a plate length up 7 aspect ratios higher than 1:10. This early rapid crystal growth preferentially outer areas body where sample is closer contact atmosphere. SEM imaging and TEM studies reveal presence twin boundaries plate-like crystals, rendering possibility defect-assisted WC. Intermediate η-carbides (M12C, M6C) their subsequent transformation might be an explanation for this occurrence extraordinarily grains.