Analysis of tempering temperature and vegetable oil quenchant viscosity effect on mechanical properties of 42CrMo4 steel

Environment is the main concern nowadays to protect the soil. Heat treatment processes used to enhance the properties of steel should not affect the environment badly. In this study, eco-friendly oil-quench specimens of 42CrMo4 steel are subjected to different tempering temperatures for about 4 hours and tested. Hardness, room temperature impact toughness, and microstructure of specimens were determined. Results showed that as the tempering temperature increased, there was an increase in impact toughness with slight decrease in the hardness. Blend oil-quench specimen, tempered at 450°C and 500°C, shows reasonably good hardness (40 and 39 Rc, respectively) and impact toughness (35 and 40 J, respectively). Response surface approach for combined optimization has given the optimized value for tempering temperature and oil viscosity as 453°C and 34.7 centistokes, respectively. Confirmation test results have shown that the regression equation developed is the best fit with percentage error less than 3%.