DUPLEX STAINLESS STEEL - Ferritic/Martensitic & Austenitic/Ferritic

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These stainless steels provide a balance of properties resulting from their duplex structures. The mixed ferritic-martensitic structure of the 409LNi provides better strength and hardness compared to the straight ferritic materials, and better sinterability and ductility compared to the martensitic alloys. The mixed austenitic-ferritic alloys provide higher strength compared to the straight powdered austenitic alloys while maintaining good corrosion resistance.

The following tables contain a list of the materials available. For more complete coverage of properties, reference MPIF Standard 35, and download the technical information bulletins of interest.

TYPE GRADES DESCRIPTION
409LNi SSI-409LNi-HTS Small nickel addition (1.25%) increases tensile and yields strength by promoting a mixed ferrite-martensite structure. Used for automotive exhaust flanges.
Ultimet 304 SSI-304LSi-HTS Type 304L with high silicon content (2.5-3.5%) results in a mixed austenitic-ferritic structure, which leads to improved densification during high temperature sintering and improved corrosion and mechanical properties.
Ultimet 16 SSI-316LSi-HTS Type 316L with high silicon addition (1.5-2.5%) sinters to over 95% of theoretical density. The material compares favorably with cast CF-3M and wrought 316 stainless steel. The high density and non-interconnected porosity is suitable for applications in the food processing equipment industry and pump rotors for corrosive environments.

Duplex Stainless Steel – As-sintered

Chemistry Typical Properties
GRADE Fe C N Cr Ni Mo Nb (Cb) Density g/cm 3 Tensile Strength ksi (MPa) Yield Strength ksi (MPa) Elongation % Unnotched Impact Energy ft-lb (J) Apparent Hardness HRB
SSI-409LNi -HTS Bal <0.03 <0.03 10.5-13.5 1.1-1.4 - 0.3-0.8 7.3 77 (530) 67 (460) 5 70 (95) 85
SSI-304LSi-HTS Bal1 <0.03 <0.03 18-20 8-12 - - 7.6 90 (620) 45 (310) 40 - 80
SSI-316LSi-HTS Bal1 <0.08 <0.03 17.5-19.5 11.5-13.5 2-3 - 7.6 81 (560) 37 (255) 35 - 73

Density ranges for the materials listed are typically for single-pressed parts. Higher densities can be achieved with double-pressing. “HTS” indicates the material has been “high temperature sintered”, i.e. sintered at a minimum temperature of 2200 F (1200 C).