Incoloy 825 – Properties, applications, fabrication, machinability and weldability of Incoloy 825

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The Incoloy 825 is very resistant to corrosion. It has a high nickel content, sufficient to resist chloride ion stress corrosion cracking, and a very stable austenite structure. The molybdenum and copper contents allow the alloy to resist reducing agents and acids. Chromium confers resistance to oxidizing conditions, such as nitric acid solutions, nitrates and oxidizing salts. The alloy is titanium stabilized to resist pitting and intergranular attack after fabrication, particularly welding, which includes heating to the critical sensitization temperature range (650 ° C – 760 ° C).

Alloy 825 offers exceptional resistance to corrosion by sulfuric and phosphoric acids and is often the most cost effective alloy for sulfuric acid service.

Austral Wright Metals can supply this alloy in the form of plate, sheet, strip, bar, rod, wire, tube, pipe, fittings, fasteners.

Pressure vessels

The Incoloy 825 is approved for operating temperatures of pressure vessels up to 525 ° C (AS1210, AS4041), 538 ° C (ASME Boiler & Pressure Vessel Code, Sections I, III, VIII, IX, Cases 1936, N-188). Brittle phases can form in Alloy 825 at temperatures above ~ 540 ° C, so it is not normally used at these temperatures, where creep failure properties would be design factors.

Applications of Incoloy 825

Typical applications of the Incoloy 825 alloy include:

  • Sulfuric acid pipes and tanks
  • Phosphoric acid evaporators
  • Pickling tank heaters, pickling tanks and equipment
  • Chemical processing equipment
  • Transmission shafts
  • Tank trucks
  • Heaters
  • Electrostatic precipitation electrodes
  • Hot containers for food, water and seawater,
  • Ammonium sulfate containers
  • Expansion bellows
  • Marine exhaust systems
  • Power plant ash hoppers

Chemical composition of Incoloy Alloy 825

Table 1. Chemical Composition of Incoloy 825 Alloy (ASTM B163 – Heat Exchanger Tube)

Nickel

38.0 – 46.0

Carbon

0.05 maximum

Chromium

19.5 – 23.5

Manganese

1.0 maximum

Molybdenum

2.5 – 3.5

Sulfur

0.03 maximum

The copper

1.5 – 3.0

Silicon

0.5 maximum

Titanium

0.6 – 1.2

Aluminum

0.2 maximum

The iron

22.0 minutes (~ 33%)

Tensile properties of Incoloy 825 alloy

Table 2. Typical tensile properties at room temperature (not for design. See corresponding material or product specifications for design values)

Tube

annealed

440

770

35

Tube

Cold drawn

880

1000

15

Bar

annealed

325

690

45

Plaque

annealed

340

660

45

Sheet

annealed

420

760

39

Figure 1. High temperature tensile properties of the annealed Incoloy 825 bar.

Corrosion resistance

The exceptional property of Incoloy 825 is its corrosion resistance. Under reducing and oxidizing conditions, Incoloy 825 is resistant to general corrosion, pitting and crevice corrosion, intergranular corrosion and stress corrosion cracking. It is particularly useful in sulfuric and phosphoric acids, flue gases containing sulfur, acid gases and oil wells and seawater.

Figure 2. Laboratory pure sulfuric acid isocorrosion table.

Manufacturing

The Incoloy 825 can be easily worked hot or cold. Hot work should be between 870 and 1180 ° C, to finish between 870 and 980 ° C. For maximum corrosion resistance, hot worked parts should be stabilized and annealed before use. The alloy is easier to cold form than stainless steels.

Machinability

The Incoloy 825 is classified as a “C” alloy and is relatively easy to machine.

Welding

The alloy is easily weldable by normal processes (GMAW (MIG), GTAW (TIG), SMAW (manual), SAW). The joint must be clean to avoid contamination of the weld pool.

Welding consumables

Table 5. A guide to welding consumables for use with the Incoloy Alloy 825 under various conditions.

Welding electrode

Inconel WE 112

Inconel WE 112

Inconel WE 112

Filler metal

Inconel FM 625

Inconel FM 625

Inconel FM 625

Cored wire

Inco Coated 625DH

Inco Coated 625DH

Inco Coated 625DH

Heat treatment

Incoloy 825 is annealed stabilized at 940 ° C. The softest structure is obtained at 980 ° C. Sections heavier than sheet metal, tape and wire should be soaked to prevent sensitization.

Please consult Austral Wright Metals for specific advice on your application.

ASTM Product specification

Table 6. ASM specifications for Incoloy Alloy 825.

B163

Seamless nickel and nickel alloy condenser tubes and heat exchangers

B423

Nickel-iron-chromium-molybdenum-copper alloy (UNS N08825 and N08221) * Seamless tubes and pipes

B424

Ni-Fe-Cr-Mo-Cu alloy (UNS N08825 and UNS N08221) * Plate, sheet and strip

B425

Ni-Fe-Cr-Mo-Cu alloy (UNS N08825)

B704

Welded tubes in alloy UNS N06625 and UNS N08825

B705

Nickel Alloy Welded Pipe (UNS N06625 and N08825)

B751

General requirements for welded nickel and nickel alloy pipes

Equivalent quality designations

Table 7. Other international grades equivalent to Incoloy Alloy 825.

United States

UNS

N08825

France

AFNOR

NC 21 FeDU

FR

BS

NA 16

Germany

VACARME

NiCr21Mo

Germany

Werkstoff

No. 2.4858


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