The effect of shot peening on fatigue and corrosion behavior of 316L stainless steel in Ringer's solution

Stainless steel 316L is one of the most common biomaterials utilized for producing orthopedic implants. But it has low resistance to fatigue and wear. Therefore surface treatments such as shot peening are used to modify the surface properties. In the present research, the influence of shot peening treatment on hardness, fatigue and corrosion behavior of 316L stainless steel in Ringer's solution was investigated. For this purpose, the steel specimens were shot peened for 5, 10, 15, 20 and 25 min. Hardness, fatigue and electrochemical tests were performed on each specimen before and after shot peening treatment. The open circuit potential (OCP) of the specimens, after 2 h of equilibrium time, was measured in Ringer's solution for 300 s. The cyclic potentiodynamic polarization tests were performed with 5 mV/s scan rate. According to the results, the shot peening treatment increases the surface hardness and fatigue resistance. In addition, this treatment decreases the break-down potential of the passive layer and increases the corrosion current density in shot peened specimens up to 10 min, which shows a reduction in resistance to pitting corrosion. However, the break-down potential of the passive layer begins to increase and the corrosion current density decreases at upper times. This trend continues such that even the conditions of resistance to pitting corrosion improve in comparison with un-shot peened specimens at longer times of shot peening. The morphology of the fractured surfaces of samples was investigated by scanning electron microscopy (SEM).