粗粒WC-Co合金の性質に及ぼすVC添加の影響 Some Properties of Coarse-grained WC-Co Alloy Affected by VC Addition

Microstructures and mechanical properties of the coarse-grained low-carbon WC-lomass%Co alloy having carbide grain size of 1.5-2.0 μm were mainly studied in relation to the amount of additional VC up to 5mass% in binder. It was found that the carbide grain size became uniform with increasing the amount of VC, because of suppression of the anomalous grain growth of WC. It was also found that transverse-rupture strength of the alloy was improved with increasing the amount of VC up to about 2-3mass%; however, it sharply decreased with additional amount of VC over about 3mass%. The phenomenon of this strength decrease, being never observed in micro-grained alloy, was attributed to the fact that (W, V)C phases crystallized so largly in the size in coarse-grained alloy, in contrast to micro-grained alloy, that it easily acted as a fracture source.