Investigation of the effect of different cooling medium on the physical and tribological properties of heat treated EN 31 and EN 8 steel

EN 8 and EN 31 steel find its major application in the field of automobile and wear resistance machine constituents. Based on wide range of applications of EN 8 and EN 31 grade steel, in the present work an experimental based investigation regarding effect of different cooling medium on the mechanical and tribological properties of heat treated EN 8 and EN 31 steel is carried out at constant temperature using quartz tube furnace. The microstructural images captured from optical microscope revealed refinement of grain structure of EN 8 steel with change in cooling medium from furnace cooling to oil quenching. However, negligible microstructural changes of EN 31 steel has been observed with change in cooling medium. The hardness of EN 8 and EN 31 found to be increased by changing the cooling medium from furnace cooling to water quenching and the maximum hardness in the both the cases were observed as 241.18 BHN and 254.60 BNH respectively. The tensile strength of EN 8 and EN 31 steel evaluated through universal testing machine (UTM) found to be decreased with change in cooling medium from furnace cooling to water quenching. The maximum tensile strength of water quenched EN 8 and EN 31 was observed as 631 N/mm2 and 675 N/mm2 respectively.