Suppression of Abnormal Grain Growth in WC–Co via Two‐Step Liquid Phase Sintering

Microstructure refinement via two‐step sintering and its mechanism have been investigated in 92WC–8Co (wt%) alloys. Samples were prepared using conventional and two‐step sintering techniques. For conventional sintering, the powder compacts were sintered at 1400°C for various times. For two‐step sintering, the powder compacts were heated up to 1500°C, immediately cooled down to 1400°C, and held for various times at 1400°C. In the conventional sintering, >99% relative density (RD) was obtained after 2 h; however, abnormal grain growth (AGG) occurred. In the two‐step sintering, >99% RD was obtained without AGG for up to 2 h sintering times at 1400°C, showing a uniform microstructure with fine grains of ∼0.6 μm in average size. Computer calculation suggested a reduction of the maximum driving force for grain growth right after the first‐step sintering at 1500°C. Retardation of AGG in two‐step sintering is thus attributed to the change in average grain size and size distribution after the first step of sintering.