Powder Preparation and Comparison of the Sintering Methods in Compaction of the WC-12Co Powder

摘要

Homogeneous powder mixtures of fine WC (av. particle size 0.2 urn) and 12 wt% Co (av. part, size 4.83 urn) were prepared in 30 minutes in air by using the Spex 8000 high energy vibratory ball mill. Conventional sintering (CS) at 1623 K (60 min) and HIPing at 1373 K (120 min) resulted in 98 % T.D., spark plasma sintering at 1523 K (3 min) in about 94 % T.D. This lower density was connected to the smallest WC grain size and higher hardness (1983 HV1) than in CS (1687 HV1) or HIPing (1813 HV1) samples. The poor density of the SPS sample may be related to the oxides of the powder that prohibited the good wetting of WC by cobalt. In CS this problem was avoided with mildly reducing atmosphere.