VDM® Alloy 625

Alternative and trade names
Nicrofer 6020 hMo, Inconel 625


VDM® Alloy 625 is a nickel-chromium-molybdenum-niobium alloy with excellent resistance to a variety of corrosive media. In the soft-annealed condition (grade 1), the alloy is used for wet corrosion applications and is approved by TÜV for pressure vessels in a temperature range from -196 to 450 °C.

VDM® Alloy 625 is also approved by ASME in both the grade 1 and grade 2 conditions for sections I, III, VIII and XII at temperatures defined in ASME Section IID (temperature limits vary by construction code).

For high temperature applications above 600 °C, the solution annealed variant (grade 2) is generally used. The strength of VDM® Alloy 625 can be enhanced by heat treatment.

Related Standards



Density ρ

8.47 g/cm³ at 20 °C


Creep strength Rm,creep

440 MPa at 600 °C

Rm/10⁴ h measured in the solution annealed condition (grade2)

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Elastic modulus E

209 GPa at 20 °C

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Elongation A

35 % at 20 °C

Impact strength, Charpy notched Ivnot

1250 kJ/m² at 20 °C

Tensile strength Rm

730 MPa at 20 °C

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Yield strength Rp0.2 Rp0.2

330 MPa at 20 °C

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Coefficient of thermal expansion α

1.251E-5 1/K at 100 °C

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Melting point Tm

1290 - 1350 °C

Specific heat capacity cp

496 J/(kg·K) at 100 °C

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Thermal conductivity λ

12.4 W/(m·K) at 100 °C

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Electrical resistivity ρel

1.25E-6 Ω·m at 20 °C

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Relative magnetic permeability μrel

1 [-] at 20 °C

Chemical properties


Weight %



58 - 71 %


21 - 23 %


8 - 10 %


5 %



3.2 - 3.8 %

Nb + Ta


Technological properties

Application areas

Equipment for the production of super phosphoric acid, plants for the treatment of radioactive waste, production pipe systems and linings of risers in oil production, offshore industry and seawater exposed equipment, sea water piping in shipbuilding, stress corrosion cracking resistant compensators, furnace linings. For high temperature applications up to 1000°C, the solution treated variant (grade 2) according to ASME Code for Pressure Vessels is used. Typical applications include: Recuperators and compensators for hot exhaust gases VDM® 625 is used as a matching filler metal for corrosion-resistant coatings of less resistant steels (overlay welding). Typical applications include: Components in the oil and gas extraction, superheater tubes in waste incineration plants.

Corrosion properties

Optimum corrosion resistance can only be obtained if the material is in the correct metallurgical condition and possesses a clean structure. Under these circumstances In the soft annealed condition VDM® Alloy 625 (grade 1) has excellent corrosion resistance to a variety of corrosive media: Excellent resistance to pitting and crevice corrosion in chloride-containing media; Virtual immunity to chloride-induced stress corrosion cracking; High resistance to corrosion attack by mineral acids such as nitric, phosphoric, sulfuric, and hydrochloric acid; as well as by concentrated alkalis and organic acids, both under oxidizing and reducing conditions; Very good resistance in seawater and brackish water, even at elevated temperatures; High resistance to intergranular corrosion after welding and heat treatment; High resistance to erosion corrosion. In the solution annealed variant VDM® Alloy 625 (grade 2) is highly resistant to many corrosive gas atmospheres: Good resistance to carburizing and scaling under static and cyclic conditions; Resistance to nitriding; Good resistance to gases containing halogens, and hydrogen chloride.

General machinability

VDM® Alloy 625 should be machined in the annealed condition. 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.


VDM® Alloy 625 has a face-centered cubic lattice.

This material data has been provided by VDM Metals.

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.