High interstitial austenitic stainless steels (HIS) contain approximately 18% chromium, 18% manganese and a combined carbon plus nitrogen content between 0.8 and 1.1%. They are non-magnetic and show outstanding mechanical properties and good corrosion resistance. This paper presents test results of two newly developed non-magnetic high interstitial austenitic stainless steels with PREN of 28 and 36. Two variants were produced:

  • a Fe18Cr18Mn0.85CN-HIS with 0.85% (C+N) ⇨ CN0.85

  • A Fe18Cr18Mn1.1CN2.2Mo-HIS with 1.1% (C+N) and 2.2% Mo ⇨ CN1.1Mo

Mechanical and corrosion properties were investigated in solution annealed condition. After solution annealing, both alloys possess fully austenitic microstructure without detrimental phases. They exhibit similar yield strength (> 600 MPa), elongation (> 60 %) and impact energy (> 350 J), while ultimate tensile strength is higher for FeCrMn1.1CN2.2Mo-HIS (> 980 MPa) than for FeCrMn0.85CN-HIS (> 930 MPa). FeCrMn1.1CN2.2Mo-HIS shows better pitting corrosion resistance and higher critical pitting temperature than FeCrMn0.85CN-HIS as well as higher pitting potential in 3.56 % NaCl at RT. The Morich variant did not display cracking or pitting after stress corrosion cracking test. The new nonmagnetic high interstitial austenitic stainless steels are promising grades for application in oil and gas industry due to their outstanding combination of high strength, good ductility and excellent corrosion properties.

Subject
Pits, Materials, Microstructure, Solution annealing, Sodium chloride, Solid solutions, Nitrogen, Steel, Pitting, Corrosion resistance, Stainless steel, Pitting resistance equivalent number, Stress corrosion cracking
Keywords:
Non-magnetic high-interstitial austenitic stainless steel, mechanical properties, corrosion properties
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2021
Association for Materials Protection and Performance (AMPP)
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