THE EFFECT OF CHROMIUM ADDITIONS ON MICROSTRUCTURE AND SOME MECHANICAL PROPERTIES OF NODULAR CAST IRON

Abstract

The effect of chromium additions on the microstructure and some mechanical properties of Bamford nodular cast iron have been investigated. The nodular cast iron samples containing from 0.5 to 2.5%wt of chromium were produced at BAMFORD International, Jos. The mechanical properties studied include: tensile strength, hardness and percentage elongation. The results indicate that the tensile strength and hardness of the samples increased with percentage chromium additions from 449 N/mm² at 0% wt chromium to 543 N/mm² at 2.5%wt chromium and from 195BHN at 0%wt chromium to 232BHN at 2.5%wt chromium. However, the percentage elongation of the nodular cast iron samples decreased with increasing percentage chromium additions from 8% at 0%wt chromium to 1% at 2.5%wt chromium additions. This indicates the reduction in ductility of the nodular cast iron with chromium additions. The microstructure revealed an increase in degree of pearlite phase together with some precipitates of chromium carbide phase as the chromium level increased.