The effect of vacuum annealing on the oxidation behavior of milled WC-15%Co powder mixture has been studied. A cobalt component in the milled powder mixture was oxidized preferentially above 175 in air. The specimens showed a steady increase in weight at 175 but did constant weight followed by rapid increase in specimen weight at the beginning above 20. Oxidation of the milled powder mixture was significantly suppressed by vacuum annealing at 30 for 10 h. Suppression of oxidation by vacuum annealing and different oxidation behaviors of the milled powder mixture between 175 and 20, were attributed to removal of strain energy stored in the cobalt powder during vacuum annealing or oxidation treatment above 20. The role of stored strain energy on oxidation of milled WC-15%Co powder mixture was proved by X-ray diffraction method and differential thermal analysis.

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