Xueyan Wu

Microstructure thermostability of shot peened duplex stainless steel surface layer

Abstract Shot peening treatment was employed to introduce deformation into the surface layer of duplex stainless steel S32205, and the microstructure thermostability during isothermal annealing was investigated using X-ray diffraction line profile analysis. Microstructure variation in shot peened layer is observed with the extension of annealing time. The domain growth activation energy and microstrain relaxation energy in both ferrite and austenite were calculated by computer regression analysis. Compared to ferrite, the shot peened austenite exhibits a higher dislocation density, a larger driving force for recrystallisation and relaxation; however, it has higher activation energy of domain growth and higher microstrain relaxation energy. The results show that the microstructure thermostability of austenite is higher than that of ferrite.

Surface Layer Investigation of a Shot-Peened Duplex Stainless Steel Utilizing X-ray Diffraction

Distributions of residual stresses and microstructure in the surface layers of shot-peened duplex stainless steel (DSS) S32205 were investigated. The results reveal that both compressive residual stresses (CRS) and microhardness increase with the enhancement of shot-peening (SP) intensity in the surface deformation layers. The maximum value of CRS of ferrite lies in the surface layer but that of austenite locates below the surface layer after SP. SP influence on the microstructure of DSS was studied using x-ray diffraction profiles, and the domain size and microstrain were calculated via Voigt method. After SP, the domain sizes are refined, and microstrain becomes severe at surface layers in both phases. On comparing the calculated results, it is found that the more evident domain size subdivision and the more serious microstrain increase in austenite than those in ferrite are due to the higher work hardening of austenite.

The Effect of Multiple Shot Peening on the Corrosion Behavior of Duplex Stainless Steel

Various types of shot peening treatments were applied to duplex stainless steel. The effects of shot peening intensity and working procedures on the microstructure were investigated. The domain size and microstrain evolution in the surface layer were characterized utilizing the Rietveld method. As the shot peening intensity increased, the surface roughness increased in the surface layer; however, it decreased after multiple (dual and triple) shot peening. The mole fraction of strain-induced martensite as a function of the intensity of shot peening was evaluated by XRD measurements. Both potentiodynamic polarization curves and salt spray tests of shot-peened samples in NaCl solution were investigated. The results indicate that traditional shot peening has negative effects on corrosion resistance with increasing shot peening intensity; however, the corrosion rate can be reduced by means of multiple shot peening.