Thermal Aging Effects on Mechanical and Intergranular Corrosion Resistance of Super-Austenitic Stainless Steel exposed at 600˚C

Super-austenitic stainless steels (SASS) are alloys with better performance in industrial applications in comparison with standard degrees of austenitic stainless steels (ASS), mainly because of elevated Ni and Mo contents and residual control of certain elements because the improvement of refine techniques. These facts, promotes an improvement of mechanical properties and minimize detrimental effects of intergranular corrosion. Besides, some industrial applications involve high temperatures services, because these alloys families have an excellent creep and oxidation resistances performances. In this work, the objective is evaluate the microstructural and mechanical properties in high Mo SASS exposed at 600˚C in specimens aged until 2000 hours. Thus, hardness and toughness values and Double Loop Electrochemical Potentiodynamic Reactivation (DL-EPR) measurements were analyzed in several thermal aging in comparison to solution treatment condition. Complementary, analysis by Light Optical (LOM), of specimens tested by DL-EPR, and Scanning Electron Microscopies (SEM) in fractured surface from Charpy specimens were also analysed by SEM by backscattered electron mode (BSE). The results show that the aging provokes intergranular embrittlement by inhomogeneous distribution in grain boundaries of Mo rich phase precipitation.

Keywords:
Super Austenitic Stainless Steels; Thermal Aging; Mechanical Properties; Corrosion Resistance; Double Loop Electrochemical Potentiodynamic Reactivation