Fatigue Behavior of Heat Treated 30MSV 6 Vanadium Micro alloyed Steel

‌‌‌Fatigue behavior of a vanadium microalloy steel has been studied in this research. Here, microstructure constituents were considered which essentially are dependent on the heat treatment conditions. The results of high cycle fatigue tests revealed that heat treatment procedure and cooling rates have significant effects on fatigue properties. Optimal heat treatment cycle of the microalloyed steel was determined to be austenitizing at 950 °С for 1 h and air cooling to room temperature followed by aging at 600 °С for 1.5 h. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were utilized to characterize the microstructure of heat treated specimens so as to understand the effect of microstructure on fatigue behavior. The optimal heat treatment cycle resulted in significant improvement of fatigue strength due to the development of uniform distribution of fine precipitates in a refined microstructure. Further study based on the Basquin's equation showed that at a constant stress, maximum fatigue life belongs to the specimen, heat treated at the optimal condition. Furthermore, minimum fatigue life is related to the specimen cooled at the rate of 6.4 °С/s. In addition, at the constant value of fatigue life, the maximum and the minimum fatigue strengths are related to the optimally heat treated specimen and the specimen cooled at the rate of 6.4 °С /s, respectively.