Fatigue failure of SUP-9 spring steel

Abstract The SUP-9 is a widely used steel for the construction of springs due to its resistance to permanent deformation and quick vibration relief. Spring steels are subjected to heat treatment to improve their fatigue life. In this paper, the heat treatment procedure to improve the endurance limit of the SUP-9 is reported. The process of heat treatment was carried out to investigate its effect on Brinell and Rockwell hardness metrics. The endurance limits of steel before and after heat treatment were also measured. The heat treatment procedure reported in this paper resulted in an increased harness and endurance limit due to a change in the microstructure of the specimen. The test results showed that Brinell hardness and endurance limit increased by 50% and 20% respectively after heat treatment.