Effect of Sintering Temperature, Heat Treatment and Tempering on Hardness of Sintered Hardened Grade Steels (SH737-2Cu-0.9C)

Abstract

The present study examines the change in hardness of sintered hardened steel (SH737-2Cu-0.9C) sintered at different temperatures, heat treated by various methods and then tempered at different temperatures. The samples were transient liquid phase sintered at 1120 °C, 1180 °C and 1250 °C respectively. The sintered samples were characterized then for density and densification parameter. The samples were austenitized at 900 °C and cooled by four different methods viz. furnace cooling (annealing), air cooling (normalizing), oil quenching, and brine quenching. The samples were then tested for their hardness using Vickers's hardness at 10 kgf load. The trend of hardness observed was found minimum for air cooled and maximum for brine quenched. In case of sample sintered at 1250 °C, relatively higher hardness was observed. The oil and brine quenched samples were then tempered at 200 °C, 400 °C, 600 °C and 700 °C. The hardness pattern observed typically showed secondary hardness taking place (due to presence of Mn and Mo) and reaching the maximum around 600 °C.