| Effects of shot peening(SP) on the intergranular and pitting corrosion behavior of AISI 316 type stainless steels(SS) have been studied by using the electrochemical techniques. Samples were solutionized for an hour at 1050℃ and sensitized for five hours at 650℃ in Ar gas atmosphere. Subsequently shot-peening treatments were carried out on the heat-treated surface of AISI 316SS for 1, 2, 4, and 10 minutes using the steel balls of Φ 0.5 ㎜. The structure and corrosion morphology of samples were investigated using TEM, SEM and XRD. The Cr-carbide(Cr_(23)C_6) peaks were not observed from X-ray diffraction pattern studies as SP treatment time increased. Electrochemical measurements showed that, in the case of solution treated samples, the corrosion and pitting potential decreased for SP treated SS, whereas reactivation, passivation and active current density increased as the SP time increased. For the samples with sensitization treatment pitting potential increased as the SP time increased from 1 min to 4 min, but reactivation current density decreased with SP time due to the SP induced removal of Cr-carbide(Cr_(23)C_6) from the grain boundaries. The corrosion morphology of shot-peened SS after sensitization showed the appearance of reduced intergranular corrosion, due to the removal of chromium carbide(Cr_(23)C_6) as SP time increased. |
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