Effect of hardening and tempering on microstructure and mechanical properties of steel grade AISI 5160

Abstract

In this research, an as-sheet steel grade AISI 5160 was studied. The heat treatment consists of hardening at 850 – 1,050 °C for 30 – 120 minutes followed by quenched in water at 50 °C. Tempering was performed at 250 – 550 °C for 30 – 120 minutes followed by quenched in water. Microstructures were measured by optical microscopy (OM) and scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). For each
condition hardness and tensile testing were measured. It was found that the microstructure in the as-sheet condition consisted of ferrite and pearlite. The resultant microstructures after hardening process are observed as lath and plate like of martensite with small amount of retained austainite. After the tempering process, the bushy type of tempered martensite and bainite was occurred. The hardness in the as-sheet condition was 40 HRC. The
hardening increased the hardness compared to the as-sheet condition. Peak hardness was obtained 62 HRC after hardening at 850 °C for 30 minutes. However, after tempering, the hardness was slightly decreased while gradually increased ultimate tensile strength and %elongation due to the process reduced brittleness by plastic deformation
and ductile fracture.