Properties of a New Lean Duplex Alloy

A new, lean duplex stainless steel with low nickel content has been developed. This alloy, identified as ATI 2102™, has mechanical and corrosion properties superior to Type 304L stainless steel, and was developed to be used as a high-strength substitute for Type 304L stainless steel. In some environments it shows corrosion resistance as good as Type 316L stainless steel. In the absence of a UNS designation assignment, the alloy is identified as S821XX alloy in this paper. A UNS number for this alloy has been requested. The composition of S821XX alloy (nominally 21%Cr, 1.5% Ni, 2.8% Mn, and 0.2% N, balance Fe) provides this alloy with outstanding resistance to a broad range of corrosive environments.

S821XX alloy was tested, in both as-welded and mill-annealed conditions, to determine its resistance to corrosion in many environments. Its resistance to intergranular attack was measured using ASTM A262 Practices B, C and E. The corrosion resistance of this alloy was also determined in various boiling acid solutions, and compared to that for Type 304L, 316L, and similar stainless steels. The critical pitting temperature (CPT) and critical crevice corrosion temperature (CCCT) of the new alloy were determined using ASTM G150 and ASTM G48 Practice B and the results are compared to those for Types 304L and 316L stainless steel. Stress corrosion cracking (SCC) behavior was also investigated in several different chloride environments, and compared to other alloys. The relevance of the above corrosion data will be related to the probable performance of the new duplex stainless steel in corrosive environments present in downhole environments as well as in the chemical process industries.