Short-term oxidation behavior of domestic forged and solution annealed 316LN stainless steel in high temperature pressurized water

Effect of forging on the average grain size, residue strain and grain orientation distribution of nuclear grade 316LN stainless steel (316LNss) was studied by means of electron back scattering diffraction (EBSD). The morphology and chemical composition of the oxide films formed on the as-received 316LNss as well as the forged and solution annealed 316LNss after immersion in borated and lithiated high temperature pressurized water at 300℃ for 190 h were also investigated. The results show that the average grain size was reduced and the residual strain was eliminated by forging and followed solution annealing. There were no obvious textures in the forged and solution annealed 316LNss. A two-layered oxide film grew on 316LNss after immersion in high temperature pressurized water. The outer layer composes of hydroxides and Fe-enriched spinal oxides and the inner layer composes of Cr-enriched spinal oxides. The forged and solution annealed 316LNss exhibited a lower oxidation rate rather than the as received ones due to the formation of a thinner and more Cr-enriched oxide film. The oxidation mechanism was also discussed.