Niobium alloying effect in high carbon equivalent grey cast iron

The effect of niobium on the formation of NbC phase and solidification structure in high carbon equivalent grey cast iron was investigated. The experimental results indicated that an increase in the niobium content is favorable to refining the graphite and eutectic cell;and the pearlite lameliar spacing is reduced. Based on the thermodynamic calculation the formation of NbC is prior to the eutectic reaction. The reduction in the pearlite lamellar spacing is mainly attributed to the decrease of eutectic temperature with the addition of niobium. Additionally,properties including hardness and wear resistance were improved after the addition of niobium.