Effects of Niobium Content on MC Carbide Segregation in Multi-component White Cast Iron by Centrifugal Casting

Abstract

  Multi-component white cast iron containing Cr, Mo, W, V has excellent abrasive wear resistance due to the MC carbide with high hardness. In the centrifugal casting, since the MC carbide formed by V has a lower specific gravity than that of molten metal, there is a tendency to segregate itself toward the inside because of the centrifugal force. As a measure to solve this problem, it has been proposed to add Nb which forms the same type of MC carbide with a high specific gravity and to suppress the segregation by making the composite M (V, Nb) C carbide crystallize. In this research, the effect of Nb content on the degree of segregation was investigated. In the hyper-eutectic region, Nb with a higher specific gravity was enriched outward by the centrifugal force. In the hypo-eutectic region, a simultaneous enrichment of Nb and V was observed near the inner surface. Although the effective range of Nb content must be limited, the possibility to reduce the segregation by Nb-addition was confirmed.