Fatigue Life Extension of 2205 Duplex Stainless Steel by Laser Shock Processing: Simulation and Experimentation

Abstract

Laser Shock Processing (LSP) is a technique for improving fatigue strength in metal alloys by introducing a compressive residual stresses field. The effect of LSP in extending fatigue life of notched specimens made by 2205 duplex stainless steel (DSS) is analyzed in this research. The setup implemented to perform the surface treatment consists of a Nd:YAG pulsed laser system with a fundamental wavelength of 1064 nm and pulse density of 2500 pulses/cm2 with frequency of 10 Hz, releasing an energy of 850 mJ/pulse. Fatigue tests were performed on a MTS 810 servo-hydraulic system at room temperature, the load ratio used was R = 0.1 with a frequency of 20 Hz. The residual stress field produced by the LSP process was estimated by a finite element simulation of the process using Abaqus. A fatigue analysis simulation of the notched specimens was conducted using the commercial code FE-Safe using different multiaxial fatigue criteria to predict fatigue lives of samples with and without LSP. A good comparison of the predicted and experimental fatigue lives was observed. The beneficial effect of LSP in extending fatigue life of notched components made by DSS is demonstrated. A significant fatigue life extension is obtained by delaying fatigue crack initiation in specimens with LSP treatment. In addition, an analysis of the fracture surface by SEM microscopy shows that the crack initiation in specimens with LSP treatment is moved from the surface to the center of the specimen, where the LSP treatment effect had not influence.