Effect of shot peening on the residual stress and microstructure of duplex stainless steel

The effect of shot peening (SP) treatment on duplex stainless steel S32205 is studied in order to improve the material surface properties. Residual stress distributions in both ferrite and austenite are investigated by X-ray diffraction, and microstructure is explored using Rietveld method. The results reveal that different distributions of compressive residual stress between ferrite and austenite under the same SP condition are resulted from the diverse hardness for different phases in duplex stainless steel. After SP, domain sizes in both ferrite and austenite are refined, and microstrain, dislocation densities and compound fault probabilities are observed to increase sharply in the near surface layer. It is found that distribution trends of residual stresses along the variation of depths are similar to those of lattice parameters for both phases. It can be obtained that in the near-top surface layers, the SP influence on residual stresses and microstructure of austenite is stronger than those of ferrite under the same SP condition. These results reveal that SP treatment with proper processing is efficient for the improvement of the surface properties of duplex stainless S32205.