(DEVELOPMENT OF CARBIDIC AUSTEMPERED DUCTILE IRON (CADI

Abstract

CADI is ductile iron containing carbides that is subsequently austempered to produce an ausferritic matrix with an engineered amount of carbides. The properties of this material are improved by alloying and also by varying the austempering heat treatment process parameters, and by dynamic and static condition. The presence of carbides is expected to promote an increase in the abrasion wear resistance, but on the other hand toughness is expected to decrease. Therefore, to maximize the performance of the CADI alloys to be used in a number of wear applications such as grinding balls, a good balance between abrasion resistance and toughness. To score this goal, four ways were achieved. The first one involved dynamic solidification, i.e. the introduction of mechanical vibration during solidification. The second involved alloying with Nb (1 %). The third was involved the combined action of Nb-alloying and dynamic solidification. Finally, heat treatment was carried out which included a two austempering temperature, in order to study the role of retained austenite during abrasion.