6Mo Stainless Steel

6Mo Stainless Steel is Super Austenitic Stainless Steel - constituents increased relative to 316 as follows:

  • Chrome (Cr)
  • Nickel  (Ni)
  • Molybdenum (Mo) 6%

These materials are also known as Avesta 254 SMO,UNS S31254,UNS N08926, UNS N08367, UNS J93254

Common Material Specifications

Ni Cr20 Ni18.5 Mo6.5 (UNS J93524)

  • Cast Avesta 254 SMO
  • CK-3MCuN

OTHERS

  • UNS S31254, Avesta, wrought
  • UNS N08926, UNS N08367
  • AL-6X, AL-6XN (UNS N08366/7) Allegheny Ludlum; tubing plate strip and bar
  • AL-6X, AL-6XN (UNS N08366/7) Allegheny Ludlum; tubing plate strip and bar

Typical Properties

  • Tensile 550 min, 650 typ. N/mm2
  • Yield 250 min, 290 typ. N/mm2
  • Elongation 35-50%
  • Hardness 55 HB typ
  • Density 8.0 g/cm3
  • Difficult to cast well, welding possible but difficult
  • P/T rating , various, but typically B16.34 Group 2.8= 20 bar class 150 (J93254)

Corrosion Properties

  • Good for sea water service
  • Especially good for:
    • Pitting corrosion
    • General corrosion
    • Erosion /corrosion
    • Stress corrosion cracking
  • Poor fouling resistance

 Additional Uses & Comments

  • Chlorides
  • Pulp and paper bleach plants
  • Flue gas desulphurisation
  • Welding (Inconel 625 filler material often used) can be a problem.
  • NACE HRB100 max, no sulphur

Cautions- All exotic stainless steels

  • Ease of manufacture: control of casting and welding important (ref SHELL ES247)
  • Poor galling performance; hardfacing can cause problems difficulty.
  • Cost: is it appropriate?