<b>Effect of Deep Cryogenic Treatment on the Tensile Behavior of AISI 8620 Gear Steel</b> Life expectancy of mechanical systems is always dependent on the most critical component of the system. Gears represent the most highly stressed parts of a heavy vehicle these are typically made of AISI 8620 steel. This paper investigates the influence of cryogenic treatment on the tensile properties of hardened tempered AISI 8620 steel. In the current research study, specimens of gear steel AISI 8620 were hardened at 1193K, tempered at 473K and then cryogenically treated at 88K followed by soft tempering in the oven at 373K for 1hr to relieve cooling stresses. A comparative study on the effects of deep cryogenic treatment DCT on hardened tempered specimens and conventional heat treated specimens was made by means of tension testing. This test was conducted as per ASTM standard E 8M. The present results confirms that the tensile behavior is marginally reduced after cryogenic treatment for AISI 8620 steel when compared with conventional hardened tempered steel. Stereographic image analysis of the fracture surface indicates the presence of dimples and flat regions are more common in DCT – processed material. Deep cryogenic treatment, Stereographic image analysis, Tensile strength, AISI 8620 31-35 Issue-2 Volume-2 Prasenjit Ghosh