Effects of thermal history on sensitization behavior and Charpy impact property of type 316L and 316 stainless steels for applications in a fired heater

Abstract

Type 316L stainless steel (SS) reveals its superior corrosion resistance against uniform and localized corrosion. But, it might be prone to intergranular corrosion (IGC) and intergranular stress corrosion cracking (IGSCC) due to detrimental Cr-rich carbides formed along the grain boundaries. The present investigation was aimed to study the sensitization behavior and Charpy impact property of type 316L SS experienced isothermally aging at 650, 750 and 850 °C for 2 h to compare with type 316 SS exposed to the actual service at temperature between 800 and 900 °C for nearly 20 years. The results indicated that the degree of sensitization (DOS) values of below 0.5 % were obtained for type 316L SS, whereas type 316 SS revealed its DOS value of around 48 %. The presence of σ-phase transformed from δ-ferrite was a predominant factor to lower the Charpy impact energy of type 316L SS. The grain boundary Cr-rich carbide network played a key role in decreasing the Charpy impact energy of type 316 SS with indicating an intergranular fracture mode.