Abstract
The solidification sequences and the amounts of primary and eutectic carbides were investigated on hyper-eutectic high Cr-Nb-V cast irons containing 3.5 mass %, 4.7 mass % C, 15mass % Cr, 0∼10 mass % Nb and 0∼10 mass % V. Solidification proceeded in the order of primary MC, eutectic γ + MC, and eutectic γ + M7C3 in the lower C cast irons, while primary MC was followed by a peritectic reaction L + MC→M7C3 and a eutectic reaction L→γ + M7C3 in the high C irons. The peritectic M7C3 crystallized into a hexagonal columnar structure just like a primary M7C3. The total amount of carbides increased more or less linearly with the increase in the C content of iron. On the other hand, the amount of MC was increased with the increase in Nb and V contents and barely influenced by the C content. In the iron containing similar levels of Nb and V, Nb rich MC crystallized first and were surrounded by V rich MC which crystallized next.
