Abstract
UNS S20910 (XM-19) is an austenitic stainless steel with excellent corrosion resistance and high strength due to its high nitrogen content. In solution annealed condition, it exhibits better corrosion resistance than UNS S31603 and UNS S31703 while having approximately twice their yield strength at room temperature (> 345 MPa (50 ksi)). The tensile strength of UNS S20910 can be further increased by cold-working, which makes the material more versatile. This paper discusses the influence of strain hardening on the mechanical and corrosion properties of UNS S20910. The corrosion behavior was studied in terms of intergranular corrosion resistance, pitting corrosion and stress corrosion cracking susceptibility in chloride-containing solutions at different temperatures. UNS S20910 in strain hardened condition presents a fully austenitic microstructure with niobium-rich primary precipitates and Z-phase, a complex nitride. In addition, the material shows a yield strength and ultimate tensile strength higher than 890 MPa (129 ksi) and 1035 MPa (150 ksi), respectively, as well as an elongation above 20 %, and impact energy higher than 100 J (74 ft-lbs). Strain hardened material did not exhibit any sensitization; therefore, it retained its excellent pitting corrosion resistance in chloride-containing solutions, which decreases with increasing temperature, though. The material has also shown good resistance to stress corrosion cracking in brines at elevated temperature. It was confirmed that the strain-hardening process increases tensile strength without significantly affecting the corrosion properties of this stainless steel. Therefore, strain hardened UNS S20910 can be used in applications involving very aggressive environments where also high strength, good ductility and non-magnetic properties are required.
