Effects of Shot Peening on Corrosion and Stress Corrosion Cracking Behaviors of Sensitized Alloy 600 in Thiosulfate Solution

Abstract

Abstract Effects of shot peening on the corrosion and stress corrosion cracking (SCC) behaviors of sensitized alloy 600 (UNS N06600) were studied. Electrochemical potentiokinetic reactivation (EPR) tests in 0.01 M sulfuric acid (H2SO4) + 0.001 M potassium thiocyanate (KSCN) solution and immersion tests in boiling 25% nitric acid (HNO3) solution were used to evaluate the effect of heat treatment on the degree of sensitization of alloy 600. Potentiodynamic polarization tests in 0.01 M sodium thiosulfate (Na2S2O3) solution at 95°C revealed shot peening increased the anodic current density (CD) of the alloy. However, SCC tests using U-bend specimens indicated shot peening substantially increased the crack initiation time in the same environment. The delayed crack initiation of SCC for shot-peened alloy 600, which is potential dependent, was attributed to the presence of compressive residual stresses and the severely deformed surface microstructure.