Microstructure, grain size distribution and grain shape in WC-Co alloys sintered at different carbon activities

作者：Borgh Ida^*; Hedstrom Peter; Persson Tomas; Norgren Susanne; Borgenstam Annika; Agren John; Odqvist Joakim

来源：International Journal of Refractory Metals and Hard Materials, 2014, 43: 205-211.

DOI：10.1016/j.ijrmhm.2013.12.007

• Cemented carbide
• Carbon activity
• Coarsening
• WC shape
• Electron backscatter diffraction (EBSD)

The properties of cemented carbides strongly depend on the WC grain size and it is thus crucial to control coarsening of WC during processing. The aim of this work was to study the effect of sintering at different carbon activities on the final microstructure, as well as the coarsening behavior of the WC grains, including the size distribution and the shape of WC grains. These aspects were investigated for five WC-Co alloys sintered at 1410 degrees C for 1 h at different carbon activities in the liquid, in the range from the graphite equilibrium (carbon activity of 1) to the eta (M6C) phase equilibrium (carbon activity of 0.33). The grain size distribution was experimentally evaluated for the different alloys using EBSD (electron backscatter diffraction). In addition, the shape of the WC grains was evaluated for the different alloys. It was found that the average WC grain size increased and the grain size distribution became slightly wider with increasing carbon activity. Comparing the two three-phase (WC-Co-eta and WC-Co-graphite) alloys a shape change of the WC grains was observed with larger grains having more planar surfaces and more triangular shape for the WC-Co-graphite alloy. It was indicated that in alloys with a relatively low volume fraction of the binder phase the WC grain shape is significantly affected by impingements. Moreover, after 1 h of sintering the WC grains are at a non-equilibrium state with regards to grain morphology.

• 出版日期2014-3