Effects of composition and microstructure on oxidation and stress corrosion cracking susceptibility of stainless steel claddings in hydrogenated PWR primary water

•Oxidation and SCC behaviour of 309 L/308 L SS welds were studied in PWR primary water.•There was no indication of SCC for low alloy steel (LAS) after SSRT tests.•The oxidation resistance of 309 L SS was lower than that of 308 L SS.•309 L SS was more susceptible to SCC than 308 L SS in PWR primary water. Oxidation resistance and stress corrosion cracking (SCC) susceptibility of A508Ⅲ-309 L/308 L stainless steel (SS) claddings were investigated in simulated pressurized water reactor (PWR) primary water following a microstructure characterization. Preferential oxidation of slip bands was observed in 309 L SS. The oxidation resistance of 309 L SS was found to be lower than that of 308 L SS due to the higher Cr- and ferrite-content in 308 L SS than in 309 L SS after cladding. There was no indication of SCC for low alloy steel (LAS) after slow strain rate tensile (SSRT) tests. The presence of type-I and type-II boundaries, composition dilution and less δ-ferrite content synergistically contributed to increasing the SCC susceptibility of 309 L SS cladding. The effect of chemical composition and microstructure on SCC performance of the SS claddings was discussed.