Morphology of In Situ VC Ceramics in High Speed Steel with High Vanadium Content

The morphology and distribution of in-situ VC ceramics in cast high speed steel with about 5-10wt.% vanadium and 1.7-3.2wt.% carbon were studied. The results show that the elementary morphology of in-situ VC ceramics has six kinds: spherical, lumpy, flower shaped, strip, short rod shaped, and vermicular. The in-situ VC in high-speed steel has three kinds of distributions: grain boundary, chrysanthemum-like and homogeneous distributions, depending on the chemical composition of high-speed steel. The in-situ VC ceramics grows up along grain boundaries if the high-speed steel is hypoeutectic, leading to grain boundary distribution of VC ceramics. On the contrary, it distributes homogeneously when the high-speed steel is hypereutectic. Whereas, the in-situ VC ceramics takes on chrysanthemum distribution if the high speed steel is just eutectic. Modification can improve the morphology of primary VC ceramics, but has not obvious effect on the morphology of eutectic VC.