GRAIN-BOUNDARY COMPOSITION AND IRRADIATION-ASSISTED STRESS-CORROSION CRACKING RESISTANCE IN TYPE-348 STAINLESS-STEEL

Scanning transmission electron microscopy (STEM) analyses, in-reactor swelling mandrel tests, and laboratory constant extension rate tensile (CERT) tests were conducted on nine custom type 348 (UNS 534800) stai nless steel (SS) alloys in an attempt to correlate grain boundary comp osition with irradiation-assisted stress corrosion cracking (IASCC) re sistance. Phosphorus (P) enrichment showed the best correlation with i n-reactor test results, and chromium (Cr) depletion showed the best co rrelation with laboratory results. Silicon (Si) and P enrichment were found to depend quantitatively on the bulk concentrations of these ele ments. The amount of Cr depletion seemed dependent at least partially on the amounts of Si and/or P enrichment. Si and P enrichment and Cr d epletion were suppressed by higher carbon (C) contents, such as that p resent in commercial-purity type 348 SS.