Effect of tempering temperature on mechanical properties and microstructure of AISI 4140 and AISI 4340 tempered steels

Abstract

Abstract The AISI 4140 and AISI 4340 tempered steels are widely used in industry. This study investigated the effects of the tempering temperature on the mechanical properties of these steels. The steels were kept at 850 °C for 30 min, left in an oil environment, and then subjected to hardening. The samples were then tempered for 1 h at four different temperatures (300, 450, 550, and 650 °C). Hardness measurements were performed to determine the mechanical properties of the materials. In addition, the samples were subjected to tensile, notch impact, and wear tests. The samples were also examined microstructurally. The results revealed that the hardness, impact energy, and wear rates of samples of both steels decreased when tempering was applied after quenching. As the tempering temperature was increased, these values tended to decrease. However, the impact value increased in parallel with the tempering heat treatment and tempering temperature.