Effect of Cryogenic Treatment on Mechanical Properties of AISI 4340 and AISI 4140 Steel

Abdul Rauf Jamali; Waseem Khan; Ali Dad Chandio; Zubai Anwer; Muhammad Hayat Jokhio

doi:10.22581/muet1982.1903.18

Abdul Rauf Jamali Department of Metallurgical Engineering, NED University of Engineering and Technology, Karachi, Pakistan.
Waseem Khan Department of Metallurgical Engineering, NED University of Engineering and Technology, Karachi, Pakistan.
Ali Dad Chandio Department of Metallurgical Engineering, NED University of Engineering and Technology, Karachi, Pakistan.
Zubai Anwer Department of Metallurgical Engineering, NED University of Engineering and Technology, Karachi, Pakistan.
Muhammad Hayat Jokhio Department of Metallurgy and Material Engineering, Dawood University of Engineering and Technology, Karachi, Pakistan

DOI: https://doi.org/10.22581/muet1982.1903.18

Abstract

From last epoch till to date, AISI 4340 and AISI 4140 have been widely used in different engineering applications. These applications include bolt, screws, gears, drive shafts, crane shaft and piston rods for engines due to its upright mechanical properties, cost-effective and easily available in market. In present work, deep cryogenic treatment effect on the mechanical properties of AISI 4340 and AISI 4140 have been studied. Present work was carried out at laboratory scale and can be extended for mass production. Our work is simple, straight forward safe and economical. In our work, samples were heat treated in simple muffle furnace and followed by cryogenic treatment in liquid nitrogen. Before cryogenic treatment, all samples were normalized at 860Â°C to obtain homogenized microstructure. Samples were also compared conventionally heat treatment with quenched in oil quenchant. Experimental results showed that after cryogenic treatment with tempering treatment, one could easily increase the tensile strength, impact toughness and hardness. Advanced optical microscopy (IMM 901) and SEM (Scanning Electron Microscopy), FIT Quanta 200 methods have also been deployed to reveal and interpret the internal structure of samples. It was found from microstructure that cryogenic treated sample increases the impact strength, hardness and tensile strength as compared conventional heat treated quenching approaches.