Ferralium® 255 (Super Duplex 50)

Ferralium® 255 - Super Duplex 50 (SD50) - UNS S32550 - W. Nr. 1.4507 - Alloy 255 - F61 - NiCrMoW Alloy

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Table of Contents
Datasheet Chemistry
Inventory Applications
General Data Mechanical Properties
Specifications Machining, Welding, & Processing


View or download Langley Alloys' Ferralium® 255 datasheet here


Min. Max.
Fe Balance
Cr 24.5 26.5
Ni 5.50 6.50
Mo 3.10 3.80
Cu 1.50 2.00
C 0.025
Mn 0.80 1.20
N 0.20 0.25
Si 0.70
P 0.025
S 0.005
*Composition information provided by Langley Alloys' datasheet on Ferralium® 255, available here.

Typical Inventory

Round Bar, Sheet, Plate, Tubing, Fittings, Fastener


  • Waste Processing
  • Fertilizer Production
  • Seawater & Marine Environments
  • Sour Services
  • Chemical Processing
  • Pulp & Paper
  • Flue Gas Desulfurization
  • Pumps & Valves

General Data

Alloy 255 is a highly alloyed super duplex, austenitic and ferritic, that provides high strength and corrosion resistance superior to Type 316 stainless. This alloy offers a wide variety of applications due to its excellent corrosion resistance. Alloy 255 has been tested for maximum continuous operations at 500°F per ASME Boiler & Pressure Vessel Code.

  • Superior sulfuric acid resistance
  • High strength
  • Sour services

Mechanical Properties

The typical properties listed can usually be provided in rounds, sheet, strip, plate, & custom forgings. We have the equipment to produce small quantities in special sizes to meet our customers’ specific needs.

Typical Strength & Elongation at Room Temperature
Form Ultimate Tensile Ksi (MPa) Yield Strength Ksi (MPa) Elongation %
Bar 4"Ø or Under 114.5 (789) 85 (586) 25
Bar Over 4"Ø Up to 12"Ø 114.5 (789) 85 (586) 25
Bar 12"Ø or Over 110 (758) 83 (573) 25
*Information provided by Langley Alloys' datasheet on Ferralium® 255, available here.

Common Specifications

Note that the specifications listed are common for this alloy but are for reference only and may be specific to a certain form. The specifications listed are not comprehensive nor indicative of any edition, revision, or similar such as an amendment. Please, reach out to our sales department to request the Material Test Report (MTR) or to confirm your required specifications.

Form Standard
Identification UNS S32550, W. Nr. 1.4507
Bar ASTM A276, ASTM A479, ASME SA276, ASME SA479
Sheet, Plate, or Strip ASTM A240, ASME SA240
Pipe ASTM A790, ASME SA790
Tube ASTM A789, ASME SA789
Fitting ASTM A815, ASME SA815
Forging ASTM A182 F61, ASME SA182 F61
Weld Wire UNS W39553/ AWS A5.4 E2553-XX / ASME IX Group P10H


Nickel and cobalt based alloys can be difficult to machinine. However, it should be emphasized that these alloys can be machined using conventional production methods at satisfactory rates. These alloys harden rapidly, generate high heat during cutting, weld to the cutting tool surface and offer high resistance to metal removal because of their high shear strengths. The following are key points which should be considered during machining operations:

  • CAPACITY - Machine should be rigid and overpowered as much as possible.
  • RIGIDITY - Work piece and tool should be held rigid. Minimize tool overhang.
  • TOOL SHARPNESS - Make sure tools are sharp at all times. Change to sharpened tools at regular intervals rather than out of necessity. A 0.015 inch wear land is considered a dull tool.
  • TOOLS - Use positive rake angle tools for most machining operations. Negative rake angle tools can be considered for intermittent cuts and heavy stock removal. Carbide-tipped tools are suggested for most applications. High speed tools can be used, with lower production rates, and are often recommended for intermittent cuts.
  • POSITIVE CUTS - Use heavy, constant, feeds to maintain positive cutting action. If feed slows and the tool dwells in the cut, work hardening occurs, tool life deteriorates and close tolerances are impossible.
  • LUBRICATION - lubricants are desirable. Soluble oils are recommended especially when using carbide tooling.

Langley Alloys' datasheet on Ferralium® 255

Ferralium® is a registered trademark of Langley Alloys Ltd.

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