The Effect of Heating Time in Induction Hardening Process on the Hardness Profile of a Ball Stud: A Case Study

The induction hardening method is widely used for the surface hardening of industrial products to improve the resistance of the material to various failure modes such as fatigue, wear, etc. Hence, surface hardening of parts that undergo repetitive forces and that work in close contact with other moving components plays a significant role in their service life. In this study, an automotive ball stud part, which is a highly prone part to fatigue and wear failures, has been induction hardened for varying amounts of heating time (2s, 3s, 4s and 5s) under constant power (135 A) and frequency (50 Hz). The hardness, the hardness depth and the microstructure of the parts have been investigated utilizing hardness tests and optical microscopy. Additionally, the effect of different cooling durations (3s, 5s, and 7s) and the resistance of the parts to the bending force has also been examined. The results show that the increase in heating time has an increasing impact on the hardness of parts and the hardness depth. The bending forces have also been shown to be increasing by increasing the heating time. The highest hardness level, hardness depth and bending resistance have been found when induction heating the specimens for 5s. Increasing the cooling time has not led to a considerable variation in the hardness profile of the specimens.