VDM® Alloy 825

Alternative and trade names
Nicrofer 4221, Incoloy 825, VDM® Alloy 825
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Description

2.4858 (NiCr21Mo) is a titanium-stabilized fully austenitic nickel-iron-chromium alloy with additions of copper and molybdenum that shows the following features and properties:


  • High resistance to chloride-induced stress corrosion
  • Good resistance to chloride-induced pitting and crevice corrosion
  • Good resistance to oxidizing and non-oxidizing hot acids
  • Good toughness, even under continuous operation, at both room and elevated temperatures, up to approximately 550°C
  • Approval for pressure vessels with wall temperatures up to 450 °C (842°F) acc. to VdTÜV and 538 °C (1,000°F) for Section VIII Division 1 vessels acc. to ASME.
  • Equivalent Materials

    This material data has been provided by VDM Metals.

    "Typical" values were obtained via a literature search. "Predicted" values were imputed via artificial intelligence technology. While we have placed significant efforts in ensuring data accuracy, "typical" and "predicted" data should be considered indicative and verified by appropriate material testing. Please do contact us if additional information on the the predicted data method is required.
    All metrics apply to room temperature unless otherwise stated. SI units used unless otherwise stated.
    Equivalent standards are similar to one or more standards provided by the supplier. Some equivalent standards may be stricter whereas others may be outside the bounds of the original standard.

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    Properties

    General

    PropertyTemperatureValue

    Density

    23.0 °C

    8.14 g/cm³

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    Mechanical

    PropertyTemperatureValue

    Elastic modulus

    20.0 °C

    195 GPa

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    100.0 °C

    190 GPa

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    200.0 °C

    185 GPa

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    300.0 °C

    179 GPa

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    400.0 °C

    174 GPa

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    500.0 °C

    168 GPa

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    600.0 °C

    161 GPa

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    700.0 °C

    154 GPa

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    800.0 °C

    142 GPa

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    900.0 °C

    130 GPa

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    1000.0 °C

    119 GPa

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    Elongation

    23.0 °C

    30 %

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    Impact strength, Charpy notched

    23.0 °C

    1500 kJ/m²

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    Tensile strength

    20.0 °C

    585 MPa

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    100.0 °C

    530 MPa

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    150.0 °C

    525 MPa

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    200.0 °C

    515 MPa

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    250.0 °C

    510 MPa

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    300.0 °C

    500 MPa

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    350.0 °C

    495 MPa

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    400.0 °C

    490 MPa

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    450.0 °C

    485 MPa

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    Yield strength Rp0.2

    20.0 °C

    240 MPa

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    100.0 °C

    205 MPa

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    150.0 °C

    190 MPa

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    200.0 °C

    180 MPa

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    250.0 °C

    175 MPa

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    300.0 °C

    170 MPa

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    350.0 °C

    165 MPa

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    400.0 °C

    160 MPa

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    450.0 °C

    155 MPa

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    impactTransVNotch

    23.0 °C

    1000 kJ/m²

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    Thermal

    PropertyTemperatureValue

    Coefficient of thermal expansion

    100.0 °C

    1.41E-5 1/K

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    200.0 °C

    1.49E-5 1/K

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    300.0 °C

    1.52E-5 1/K

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    400.0 °C

    1.56E-5 1/K

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    500.0 °C

    1.58E-5 1/K

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    600.0 °C

    1.6E-5 1/K

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    700.0 °C

    1.67E-5 1/K

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    800.0 °C

    1.72E-5 1/K

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    900.0 °C

    1.76E-5 1/K

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    1000.0 °C

    1.79E-5 1/K

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    Melting point

    1370 - 1400 °C

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    Specific heat capacity

    20.0 °C

    440 J/(kg·K)

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    100.0 °C

    462 J/(kg·K)

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    200.0 °C

    488 J/(kg·K)

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    300.0 °C

    514 J/(kg·K)

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    400.0 °C

    540 J/(kg·K)

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    500.0 °C

    565 J/(kg·K)

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    600.0 °C

    590 J/(kg·K)

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    700.0 °C

    615 J/(kg·K)

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    800.0 °C

    655 J/(kg·K)

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    900.0 °C

    680 J/(kg·K)

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    1000.0 °C

    710 J/(kg·K)

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    Thermal conductivity

    20.0 °C

    10.8 W/(m·K)

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    100.0 °C

    12.4 W/(m·K)

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    200.0 °C

    14.1 W/(m·K)

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    300.0 °C

    15.6 W/(m·K)

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    400.0 °C

    16.9 W/(m·K)

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    500.0 °C

    18.3 W/(m·K)

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    600.0 °C

    19.6 W/(m·K)

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    700.0 °C

    21 W/(m·K)

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    800.0 °C

    23.2 W/(m·K)

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    900.0 °C

    25.7 W/(m·K)

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    1000.0 °C

    28.1 W/(m·K)

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    Electrical

    PropertyTemperatureValue

    Electrical resistivity

    20.0 °C

    1.12E-6 Ω·m

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    100.0 °C

    1.14E-6 Ω·m

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    200.0 °C

    1.18E-6 Ω·m

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    300.0 °C

    1.2E-6 Ω·m

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    400.0 °C

    1.24E-6 Ω·m

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    500.0 °C

    1.26E-6 Ω·m

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    600.0 °C

    1.26E-6 Ω·m

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    700.0 °C

    1.27E-6 Ω·m

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    800.0 °C

    1.28E-6 Ω·m

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    900.0 °C

    1.29E-6 Ω·m

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    1000.0 °C

    1.3E-6 Ω·m

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    Magnetic

    PropertyTemperatureValueComment

    Relative magnetic permeability

    23.0 °C

    1.01 [-]

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    max.

    Chemical properties

    PropertyValueComment

    Aluminium

    0.2 %

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    max.

    Carbon

    0.025 %

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    Chromium

    19.5 - 23.5 %

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    Cobalt

    1 %

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    max.

    Copper

    1.5 - 3 %

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    Iron

    20 - 38 %

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    Manganese

    1 %

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    Molybdenum

    2.5 - 3.5 %

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    Nickel

    38 - 46 %

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    Phosphorus

    0.02 %

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    max.

    Silicon

    0.5 %

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    max.

    Sulfur

    0.015 %

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    Titanium

    0.6 - 1.2 %

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    Technological properties

    Property
    Application areas

    VDM® Alloy 825 is used in the oil and gas industry and in a wide variety of chemical processes. Typical application fields include: Pipes, tubes and fittings in the oil and gas extraction, e. g. in heat exchangers, evaporators, washers, immersion pipes in sea water cooled heat exchangers, offshore piping, components in sulfuric acid pickling plants like heating coils, vessels, boilers, baskets and chains, heat exchangers, evaporators, washers, immersion pipes in phosphoric acid production, food industry, approval for pressure vessels with wall temperatures up to 450 °C acc. to VdTÜV and 538 °C or Section VIII Division 1 vessels acc. to ASME.

    Cold Forming

    Cold working should be carried out on annealed material. VDM® Alloy 825 has a higher work hardening rate than austenitic stainless steels. This must be taken into account during design and selection of forming tools and equipment and during the planning of the forming processes. Intermediate annealing may be necessary at high degrees of cold working deformation. After cold working with more than 15 % of deformation the material should be soft annealed.

    Corrosion properties

    VDM ® Alloy 825 is a versatile engineering alloy with resistance to corrosion in acids and alkalis under both oxidizing and reducing conditions. The high nickel content gives the alloy virtual immunity to stress corrosion cracking. The corrosion resistance in various media like sulfuric, phosphoric, nitric and organic acids is good, as well as the corrosion resistance in alkalis or ammoniac, sea water and caustic chloride. The versatility of VDM® Alloy 825 is illustrated by its use in nuclear fuel element dissolvers where a variety of corrosive media, e. g. sulfuric and nitric acids and sodium hydroxide, are handled in the same equipment.

    General machinability

    VDM® Alloy 825 should be machined in the annealed temper. As the alloy is prone to work-hardening, low cutting speeds and appropriate feed rates should be used and the tool should be engaged at all times. Sufficient chip depths are important to get below the work-hardened surface layer. The optimum dissipation of heat through the use of large amounts of appropriate, preferably water containing cooling lubricants is crucial for a stable machining process.

    Heat Treatment

    Soft or stabilizing annealing should be carried out at temperatures between 920 and 980°C (1,690 to 1,800°F), preferably at 940±10°C (1,725±15°F). Water quenching should be carried out rapidly to achieve optimum corrosion characteristics. Workpieces of less than 3 mm (0.12 in) thickness can be cooled down using air nozzles. The workpiece has to be put into the pre-heated furnace. The furnace should be heated up to the maximum annealing temperature. The retention time during annealing depends on the workpiece thickness.

    Hot forming

    VDM® Alloy 825 may be hot-worked in the temperature range 1,150 to 900 °C (2,100 to 1,650 °F) with subsequent rapid cooling down in water or by using air. The workpieces should be placed in the furnace heated to hot working temperature in order to heat up. Once the temperature has equalised, a retention time of 60 minutes for each 100mm (4 in) of workpiece thickness is recommended. After this, the workpieces should be removed immediately and formed during the stated temperature window. If the material temperature falls below the minimum hot working temperature, the workpiece must be reheated. Heat treatment after hot working is recommended in order to achieve optimum properties and corrosion resistance.

    Other

    VDM® Alloy 825 has a face-centered-cubic crystal structure.

    Welding

    VDM® Alloy 825 can be joined to itself and to many other metals by conventional welding processes. These include GTAW (TIG), plasma arc, GMAW (MIG/MAG) and SMAW (MMA). Pulsed arc welding is the preferred technique. For the MAG process the use of a multi-component shielding gas (Ar + He + H2 + CO2) is recommended. For welding, VDM® Alloy 825 should be in the annealed temper and be free from scale, grease and markings. When welding roots, sufficient protection of the root needs to be ensured with pure argon (Ar 4.6) so that the welding seam is free of oxides after welding. Root backing is also recommended for the first intermediate pass following the initial root pass and in some cases even for the second pass, depending on the weld set-up. Any discoloration/heat tint should be removed preferably by brushing with a stainless steel wire brush while the weld metal is still hot.