Inconel 625 Properties and Chemical Composition – UNS N06625 / Alloy 625
SEO Title: Inconel 625 Properties & Chemical Composition – UNS N06625
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Secondary Keywords: Inconel 625 chemical composition, UNS N06625 properties, Alloy 625 material properties, Inconel 625 mechanical properties, EN 2.4856 alloy, NiCr22Mo9Nb, Inconel 625 corrosion resistance, Inconel 625 specifications
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Meta Description: Explore Inconel 625 properties, chemical composition, mechanical strength and corrosion resistance. Learn about Alloy 625, UNS N06625 and EN 2.4856.
Table of Contents
- What Is Inconel 625?
- Inconel 625 Equivalent Grades and Designations
- Inconel 625 Chemical Composition
- Inconel 625 Mechanical Properties
- Physical Properties of Alloy 625
- Corrosion Resistance of UNS N06625
- High-Temperature Performance and Fabrication
- Industrial Applications of Inconel 625
- Frequently Asked Questions
- Enquire About Inconel 625 from Manan Steel & Metals
1. What Is Inconel 625?
Inconel 625 is a nickel-based alloy containing chromium, molybdenum and niobium. It is commonly identified as Alloy 625, UNS N06625 and W.Nr. 2.4856, with the European designation NiCr22Mo9Nb.
The alloy is known for its combination of mechanical strength, corrosion resistance, fabricability and performance in selected high-temperature environments. Unlike precipitation-hardened nickel alloys, Inconel 625 derives much of its strength from solid-solution strengthening, particularly the effects of molybdenum and niobium in its nickel-chromium matrix.
These characteristics make the material relevant to chemical processing, marine engineering, offshore equipment, aerospace systems and other demanding industrial applications.
For engineers and procurement teams, understanding Inconel 625 properties is important when deciding whether the grade is appropriate for a specific component, operating environment and material specification.
2. Inconel 625 Equivalent Grades and Designations
Inconel 625 can appear under different designations in technical documents, manufacturer datasheets and industrial purchase orders.
| Designation | Identification |
|---|---|
| Inconel 625 | Common commercial name |
| Alloy 625 | Alternative common name |
| UNS N06625 | Unified Numbering System designation |
| W.Nr. 2.4856 | European material number |
| NiCr22Mo9Nb | European designation |
| ASTM B446 | Relevant specification for applicable rod and bar products |
| ASTM B444 | Relevant specification to check for applicable seamless pipe and tube products |
Important: These names identify the alloy family, while product standards define the requirements for particular forms. Always confirm the exact product standard, condition, dimensions and certification requirements before purchasing.
Reference: Special Metals – INCONEL Alloy 625 Technical Bulletin.
3. Inconel 625 Chemical Composition
The chemical composition of Inconel 625 is central to its strength and corrosion performance.
The following values are the limiting composition published in the Special Metals technical bulletin. Confirm the applicable product standard and actual heat analysis before accepting a material batch.
| Element | Composition, weight % |
|---|---|
| Nickel (Ni) | 58.0% minimum |
| Chromium (Cr) | 20.0–23.0% |
| Molybdenum (Mo) | 8.0–10.0% |
| Niobium plus tantalum (Nb + Ta) | 3.15–4.15% |
| Iron (Fe) | 5.0% maximum |
| Carbon (C) | 0.10% maximum |
| Manganese (Mn) | 0.50% maximum |
| Silicon (Si) | 0.50% maximum |
| Phosphorus (P) | 0.015% maximum |
| Sulphur (S) | 0.015% maximum |
| Aluminium (Al) | 0.40% maximum |
| Titanium (Ti) | 0.40% maximum |
| Cobalt (Co) | 1.0% maximum, where determined |
Source: Special Metals Alloy 625 Technical Bulletin.
Why do these elements matter?
- Nickel: Forms the main alloy matrix and contributes to corrosion resistance in a range of environments.
- Chromium: Supports oxidation resistance and corrosion performance.
- Molybdenum: Improves resistance to localized corrosion, including pitting and crevice corrosion in suitable environments.
- Niobium: Contributes to strengthening and helps stabilize the alloy against certain sensitization-related effects during welding.
- Low carbon content: Helps manage carbide-related effects within the limits of the relevant manufacturing and service conditions.
The balance of these elements is one reason Alloy 625 is used in specialised industrial equipment.
4. Inconel 625 Mechanical Properties
Inconel 625 provides useful tensile strength, ductility and toughness. However, its mechanical properties depend on product form, manufacturing process, dimensions and delivery condition.
The following values are nominal room-temperature values published by Special Metals for representative product forms and conditions. They are not universal acceptance limits for every supplied product.
| Product form and condition | Tensile strength | 0.2% yield strength | Elongation |
|---|---|---|---|
| Rod, bar and plate — annealed | 827–1,034 MPa | 414–655 MPa | 30–60% |
| Rod, bar and plate — solution-treated | 724–896 MPa | 290–414 MPa | 40–65% |
| Sheet and strip — annealed | 827–1,034 MPa | 414–621 MPa | 30–55% |
| Cold-drawn tube and pipe — annealed | 827–965 MPa | 414–517 MPa | 30–55% |
| Cold-drawn tube and pipe — solution-treated | 689–827 MPa | 276–414 MPa | 40–60% |
Source: Special Metals, INCONEL Alloy 625 Technical Bulletin. The published values are composites for specified product sizes and are not suitable as a replacement for governing specification requirements.
What do these properties mean for buyers?
Tensile strength indicates resistance to pulling forces before failure. Yield strength indicates the stress at which permanent deformation begins under the defined test method. Elongation provides an indication of ductility.
These properties should be evaluated against the component’s design loads, operating temperature, applicable code and material standard. Do not use a typical datasheet value as a substitute for the certified mechanical test results required by a purchase order.
5. Physical Properties of Alloy 625
Physical properties can be important when designing equipment, calculating component weight or evaluating thermal performance.
| Property | Reference value |
|---|---|
| Density | Approximately 8.44 g/cm³ |
| Melting range | Approximately 1,290–1,350°C |
| Specific heat at approximately 21°C | Approximately 410 J/kg·°C |
| Modulus of elasticity in tension at approximately 21°C | Approximately 205–208 GPa, depending on condition |
These are reference values from the manufacturer’s technical bulletin. Actual design calculations should use the appropriate property data for the supplied condition and intended operating temperature.
6. Corrosion Resistance of UNS N06625
Corrosion resistance is one of the main reasons engineers consider Inconel 625 for demanding service environments.
Pitting and crevice corrosion
The alloy’s molybdenum and chromium content contributes to resistance against localized corrosion in suitable environments. This is relevant to selected marine, offshore and chemical-processing applications.
Chloride-containing environments
Inconel 625 has resistance to chloride-ion stress-corrosion cracking in many conditions and is used in selected seawater applications. Suitability still depends on temperature, fluid chemistry, stress, deposits and component design.
Chemical processing environments
The combination of nickel, chromium and molybdenum helps the alloy withstand a range of corrosive media. However, the performance of any alloy varies according to the specific chemical, concentration, temperature and exposure conditions.
Oxidation resistance
Inconel 625 also offers resistance to oxidation and scaling at elevated temperatures, making it useful for selected high-temperature components.
Material selection note: Inconel 625 is not immune to every form of corrosion. Verify compatibility using the actual operating conditions and appropriate engineering data before specifying the grade.
7. High-Temperature Performance and Fabrication
Inconel 625 is used in applications that require a combination of mechanical performance and resistance to high-temperature oxidation.
The Special Metals technical bulletin discusses service applications ranging from cryogenic conditions to elevated temperatures approaching 982°C in selected environments. This is not a universal allowable design temperature for every component.
Actual service limits depend on factors such as:
- Applied load and design stress
- Exposure duration
- Oxidizing or corrosive atmosphere
- Product form and material condition
- Applicable engineering code
- Fabrication, welding and inspection requirements
The alloy can be joined using conventional welding processes with suitable procedures and compatible filler materials. Welding qualification, joint design, heat input and post-weld requirements should be determined for the specific application.
8. Industrial Applications of Inconel 625
The combination of strength and corrosion resistance makes Inconel 625 relevant to several sectors.
Chemical processing
Selected reaction vessels, transfer piping, valves, heat exchangers and other process equipment may use the alloy where its corrosion performance is suitable.
Marine and offshore engineering
Applications may include selected seawater-exposed components, connectors, bellows and specialised offshore equipment.
Aerospace systems
The alloy is used in selected exhaust systems, ducting, heat exchangers and other components where strength, fatigue performance and high-temperature resistance are required.
Oil and gas
Certain equipment and components may specify Alloy 625 for demanding service conditions. The required grade condition and applicable project standards must be confirmed.
Specialised industrial equipment
The alloy may be selected for components where resistance to corrosion, thermal effects and mechanical loads must be considered together.
Not every application requires Inconel 625. The grade should be chosen according to the actual engineering need rather than the alloy’s reputation alone.
9. Frequently Asked Questions
What are the main properties of Inconel 625?
Inconel 625 is known for its strength, corrosion resistance, oxidation resistance, ductility and fabricability. Exact properties depend on product form and material condition.
What is the chemical composition of Inconel 625?
The principal elements are nickel, chromium, molybdenum and niobium plus tantalum. The manufacturer’s limiting composition includes at least 58% nickel, 20–23% chromium, 8–10% molybdenum and 3.15–4.15% niobium plus tantalum.
What is the UNS number for Alloy 625?
The UNS designation is N06625.
What is the European material number for Inconel 625?
The commonly associated material number is 2.4856, with the designation NiCr22Mo9Nb.
Is Inconel 625 suitable for seawater?
It is used in selected seawater applications because of its corrosion resistance. Suitability depends on the actual environment, component design and operating conditions.
Does Inconel 625 need precipitation hardening?
Inconel 625 derives much of its strength from solid-solution strengthening. Precipitation-hardening treatment is not required for its basic strengthening mechanism, although the specified delivery condition and any processing requirements must be checked.
Which standard applies to Inconel 625 round bars?
ASTM B446 is a relevant standard for applicable rod and bar products. Always confirm the exact grade, product dimensions, required condition and current specification.
Where can I enquire about Inconel 625 in India?
Contact Manan Steel & Metals with your required product form, dimensions, quantity and applicable standard to discuss your industrial enquiry.
10. Enquire About Inconel 625 from Manan Steel & Metals
Looking for Inconel 625 / Alloy 625 / UNS N06625 / EN 2.4856 for an industrial or engineering requirement?
Manan Steel & Metals welcomes enquiries from manufacturers, engineers, fabricators and industrial procurement teams. Share the product form, dimensions, quantity, material standard and documentation requirements to discuss availability and quotation requirements.
Contact Manan Steel & Metals
- Website: https://www.manansteel.com/
- Phone: +91 7977369869
- Email: manansteel@gmail.com
- Address: Shop No. 2, Hira Building, 97 Khetwadi Main Road, Girgaon, Mumbai – 400004, Maharashtra, India.
Send your material specification and quantity for an enquiry.
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