Microstructure Evolution and Hardness Properties of Nodular Cast Iron for Varying Tempering Time

Abstract

Nodular cast iron is usually used for components that require good mechanical properties such as strength, toughness, and ductility. Heat treatment is applied to the components made from the nodular cast iron to improve their mechanical properties. This study aimed to investigate the influence of tempering time on the microstructure, hardness, and wear rate of nodular cast iron. The heat treatment was performed by austenitizing to 850 °C with a holding time of 1 hour and quenched in the oil medium. After quenching, it was tempered at a temperature of 450 °C by varying the tempering time to 15, 30, 45, and 60 min. The investigation consists of microstructure observation, hardness, and wear rate measurements. The results show that the highest hardness was 55.3 HRC at a tempering time of 15 min, and the lowest hardness was 54 HRC at a tempering time of 60 min. The lowest wear rate was 0.00476 g/min at a tempering time of 15 min, and the highest wear rate was 0.00574 g/min at a tempering time of 60 min. It can be concluded that the longer the holding time of tempering, the lower the hardness and the higher the wear rate.