Dissimilar-metal interactions between niobium or Nb—1％ Zr and type 316 or 318 stainless steel in sodium or NaK were investigated in static capsules at temperatures from 816 to 982℃. The principal interaction was the transfer of carbon and nitrogen from the stainless steel to the niobium or niobium alloy. Complex carbide-nitride layers formed on the surface of the niobium, and nitrogen but not carbon diffused appreciably into the niobium. The subsurface nitrogen pickup greatly increased tensile strength and decreased ductility. The amount of carbon and nitrogen transfer depended on temperature, exposure time, and ratio of surface areas of the dissimilar metals. The transfer was independent of stress and occurred to the same extent with types 316 and 318 stainless steels.
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