Surface layer investigation of duplex stainless steel S32205 after stress peening utilizing X-ray diffraction

Residual stresses and micro-hardness of duplex stainless steel S32205 after stress peening are measured and domain sizes and microstrain are calculated. The results show that stress peening can significantly improve the compressive residual stresses and micro-hardness in both austenite and ferrite, and the former is affected by both the prestress and the measurement directions. Microstructure investigation reveals that material deformation is enhanced after stress peening, and smaller domain sizes and higher microstrain are introduced. The compressive residual stress enhancement by stress peening in ferrite is more than that in austenite under the same stress peening, which is due to the more elastic deformation recover in ferrite. Therefore, the difference of residual stresses between ferrite and austenite can be narrowed down by conducting appropriate stress peening. Based on these investigations, it is concluded that stress peening is superior to conventional shot peening treatment to improve the surface properties of duplex stainless steel.

► The stress shot peening is superior to the conventional shot peening.
► Residual stresses along the loaded direction are bigger than transverse direction.
► Higher prestress leads to smaller domain size, high density of dislocation.
► Compared to ferrite, austenite has much higher hardness and work hardening.
► Ferrite has higher recover of elastic deformation than austenite after unloading.