Inconel 625 equivalent grades are UNS N06625 in the United States, W.Nr. 2.4856 in Europe, GH3625 in China’s superalloy framework, NCF625 in Japan, and NA21 in the United Kingdom. Every one of those designations names the same nickel-chromium-molybdenum-niobium alloy. What changes is the standard document each one sits inside, and that is where purchase orders go wrong.
Here is how narrow the margin is.
In February 2025, a procurement engineer at a specialty chemicals plant in Antwerp released a purchase order for 4 tonnes of “Alloy 625, W.Nr. 2.4858.” The digit came from a supplier datasheet that had been circulating internally for two years. Material arrived six weeks later with a valid mill certificate, correct dimensions, and full compliance to the standard named. It was Incoloy 825.
A legitimate alloy, correctly certified, and the wrong metal for a chloride-bearing line that had specified 625 for its pitting resistance. The error surfaced at positive material identification, three days into a planned shutdown window.
The digit was the failure, not the alloy.
If you are holding a designation and need to know what it names, this page resolves it. It maps every system that designates 625, shows which ASTM standard governs each product form, and then walks through six look-alike traps that catch experienced buyers. For the full specification behind the designation, the Inconel 625 pipe guide covers composition, conditions and properties in depth.
Key Takeaways
- Thirteen designation systems name Inconel 625 across UNS, European, British, French, Japanese, Russian, Chinese, ISO and aerospace frameworks. All resolve to one metal. China names it twice, under two different standards.
- 2.4856 is 625. 2.4858 is Incoloy 825. One digit separates two different alloys, and the transposition is published on live supplier pages.
- The alloy designation does not tell you the standard. Seamless pipe runs to ASTM B444, welded pipe to B705, welded tube to B704, plate to B443, bar to B446, forgings to B564 and fittings to B366.
- EN 10216-5 does not cover 625. It is scoped to stainless steels only, despite appearing beside 625 on countless supplier listings.
- An equivalent grade is the same metal under another name. A substitute, such as 254 SMO, AL-6XN or Incoloy 825, is a different metal that may or may not do the job.
Have a designation you cannot resolve? Send us the line exactly as it appears on your purchase order and our technical team will confirm which alloy and which condition it names, within 24 hours. Send it here.
Inconel 625 Equivalent Grades: The Complete Map
An Inconel 625 equivalent grade is any national or international designation that specifies the same nickel-chromium-molybdenum-niobium composition as UNS N06625. The designations differ by standards body, not by metallurgy. Every row below names the same alloy. What differs is the document each designation sits inside.
| System | Designation | Notes |
|---|---|---|
| Commercial, US | Inconel 625 | Special Metals trade name, not a specification |
| Commercial, generic | Alloy 625 | What other mills and most purchase orders use |
| UNS, US | N06625 | The number that actually resolves ambiguity |
| W.Nr., Germany | 2.4856 | Werkstoff number |
| EN symbol | NiCr22Mo9Nb | Composition-based designation |
| BS, UK | NA21 | Within BS 3074 for seamless pipe and tube |
| AFNOR, France | NC22DNb | Also appears as NC22FeDNb |
| JIS, Japan | NCF625 | |
| GOST, Russia | KhN75MBTYu | Confirm on the purchase order |
| GB, China, superalloy | GH3625 | Formerly GH625, within GB/T 14992 |
| GB, China, corrosion | NS336 / NS3306 | A different GB framework, same base chemistry |
| ISO | NW6625 | |
| Aerospace, SAE | AMS 5666, AMS 5599, AMS 5581 | Bar and forgings, sheet, seamless tube |
Read the last three rows carefully. The Chinese entries are the ones that cost money, because GH3625 and NS336 are not interchangeable documents even though the alloy beneath them is the same. The superalloy framework writes for high-temperature and aerospace duty; the corrosion-resisting framework writes for chemical process service. Trace-element control, test schedules and documentation differ.
A mill certificate citing GH3625 and a European order citing ASTM B444 have not necessarily agreed on the same purchase. That reconciliation has to happen before the material ships, not after it lands.
Is Inconel 625 the Same as 2.4856, N06625 and Alloy 625?
Yes. Alloy 625, Inconel 625, UNS N06625, W.Nr. 2.4856 and EN NiCr22Mo9Nb all designate one alloy. The distinction that matters commercially is which of those names is legally enforceable.
Inconel is a trademark, held by Special Metals Corporation. It describes a family of nickel-chromium alloys from one producer. A purchase order that says only “Inconel 625” relies on a brand name to specify a material, which is weaker than it looks. Other mills make the same alloy and cannot call it Inconel.
Alloy 625 is the generic name, and it is what most non-Special-Metals producers and most international purchase documents use. It is not tied to a producer.
UNS N06625 is the identifier that resolves ambiguity. UNS stands for Unified Numbering System, administered jointly by ASTM International and SAE International. An N06625 callout is unambiguous in a way a trade name is not. Where European standards govern, pair it with W.Nr. 2.4856.
The practical rule is simple. Write all three on the order: alloy name, UNS number, and European number where relevant. That single line closes the gap between what you meant and what a mill in another country read.
The Standard Changes With the Product Form
Designations name the alloy. Standards name the product. Confusing the two is the more expensive error, because an equivalent grade tells you nothing about which document governs the pipe you are buying.
| Product form | ASTM standard | General requirements | Aerospace (SAE) |
|---|---|---|---|
| Seamless pipe and tube | B444 | B829 | AMS 5581 |
| Welded pipe | B705 | B775, B751 | Not applicable |
| Welded tube | B704 | B751 | Not applicable |
| Plate, sheet and strip | B443 | B906 | AMS 5599 |
| Bar and rod | B446 | B906 | AMS 5666 |
| Forgings | B564 | B906 | AMS 5666 |
| Wrought fittings | B366 | B829 | Not applicable |
Two facts in that table are routinely got wrong.
B705 and B704 are pipe and tube, not old and new. Both are current documents. A supplier quoting “B704 welded pipe” has mis-cited the standard, because B704 covers welded tube and B705 covers welded pipe.
B444 pairs with B829, and B704 or B705 pair with B751. The general-requirements document is part of your purchase specification whether or not it appears on the order. Buyers who write only “ASTM B444” leave testing, tolerances and marking to the mill’s default. That is a legitimate mill choice, not necessarily yours.
What to Write on the Purchase Order
Six lines close every ambiguity this article describes.
- Grade and condition. “Alloy 625, Grade 1 annealed” or “Grade 2 solution annealed.” Never “625” alone, because the condition decides your yield strength.
- UNS number. N06625, plus W.Nr. 2.4856 where European standards apply.
- Product-form standard with edition. “ASTM B444-23,” not “ASTM B444.”
- General-requirements standard. B829 for seamless, B751 for welded.
- Documentation level. EN 10204 3.1 as a minimum, 3.2 where a notified body is required.
- Verification. Positive material identification on receipt, because 625 and Inconel 600 are visually identical on the rack.
Grade 1 and Grade 2 deserve one clarification here. They are conditions of the same grade, not equivalent grades. Grade 1 is annealed at a minimum of 871 °C and delivers 414 MPa minimum yield; Grade 2 is solution annealed at 1083 to 1093 °C and delivers 276 MPa, yet it is the correct choice above roughly 593 °C. The full reasoning sits in the Grade 1 versus Grade 2 comparison, and it is worth reading before you write line one.
The Six Look-Alike Traps
Every trap below is a documented confusion, not a hypothetical.
2.4856 vs 2.4858
2.4856 is Inconel 625. 2.4858 is Incoloy 825, a nickel-iron-chromium alloy with roughly 22% iron, titanium stabilization and 1.5 to 3.0% copper. The numbers differ by one digit; the alloys differ in nickel content by more than thirty percentage points.
During this research, a live supplier page described 625 as “UNS N06625 / DIN 2.4858,” which is exactly how the Antwerp error enters circulation. If you need the other side of that comparison, the Incoloy 825 pipe guide covers it properly.
GH3625 vs NS336
China designates this alloy in two frameworks. GH3625 sits in GB/T 14992, the wrought superalloy standard, and is written for high-temperature and aerospace service; NS336 and NS3306 sit in the corrosion-resisting alloy framework and are written for chemical process duty. The base chemistry is the same.
The surrounding requirements are not identical, and this research did not verify a clause-by-clause comparison. Treat them as one alloy under two documents, and confirm which document governs before you accept a certificate.
Grade 1 vs Grade 2 Is a Condition, Not a Grade
An “equivalent grade” answer resolves the alloy. It says nothing about the condition, and a mill will ship Grade 1 by default unless the order states otherwise. This is the single most common specification failure in the 625 family.
EN 10216-5 Does Not Cover 625
EN 10216-5 is scoped to seamless tubes of austenitic and austenitic-ferritic stainless steels for pressure purposes. Alloy 625 is a nickel-based superalloy and is not among its listed grades. Chinese supplier pages list EN 10216-5 beside 625 constantly, because it is a familiar pressure-piping standard; it does not apply. The European route for 625 tube runs through DIN 17751 or ISO 6207, with VdTÜV 499 frequently cited as an approval reference.
N06625 vs N06626
N06626 is Inconel 625LCF, a low-cycle-fatigue variant developed for bellows and expansion joints. It is a related alloy with different heat treatment logic, not an equivalent. Anyone cross-referencing “625” and landing on N06626 has found the wrong grade.
Equivalent Is Not a Substitute
254 SMO (UNS S31254), AL-6XN (N08367), super duplex 2507 (S32750) and Incoloy 825 (N08825) are all proposed as 625 alternatives. None is an equivalent. The 6% molybdenum stainless grades carry 18 to 25% nickel against roughly 58 to 61% in 625, and nickel content governs resistance to chloride stress corrosion cracking rather than pitting.
Comparing the grades on PREN alone, as many vendor pages do, measures the wrong property. The section below covers when substitution is legitimate.
Before you accept a cross-reference, have the certificate checked against the standard it cites. That check takes our team under a day and has caught more substitution errors than any other step in the process. Request a certificate review.
Chinese, Japanese and European Designations in Practice
GH3625 appears most often on Chinese mill certificates for bar, plate and tube destined for high-temperature service. NS336 appears on certificates for chemical plant piping. NCF625 appears on Japanese material. NC22DNb and NA21 appear on French and British documents respectively, and both are increasingly rare outside legacy project specifications.
The complication is dual certification. A Chinese mill will often issue a certificate citing both GH3625 and ASTM B444 on the same page, because the chemistry satisfies both. That is legitimate practice and it is not, by itself, a problem.
The problem is what the certificate does not say.
Rajesh Nair, a QA inspector with an EPC contractor in Singapore, rejected a dual-certified 625 heat in September 2025 for exactly this reason. The certificate listed both standards and both sets of mechanical results, but never stated which standard governed. His client’s specification required ASTM B444 Grade 1; the GH3625 column showed a different test schedule.
The mill had done nothing wrong and the material was almost certainly correct. The documentation could not prove it, so the heat sat in quarantine for eleven days while the mill reissued the certificate.
Dual certification is a documentation instruction, not a mill default. Ask for the governing standard to be named explicitly, and the reissue never happens.
Substitutes That Are Not Equivalents
The substitution question is legitimate. 625 is expensive, and buyers are right to ask whether something cheaper will do.
The answer depends on which property is governing. Where the risk is chloride stress corrosion cracking, nickel content decides, and the 6% molybdenum stainless grades do not have enough. Where the risk is pitting in a moderate-chloride stream below about 40 °C, 254 SMO and AL-6XN can be genuinely adequate at a fraction of the cost. Where the medium is dilute sulfuric acid, Incoloy 825 often outperforms 625 outright.
The Nickel Institute publishes the family data behind those nickel thresholds, and it is the reference we cite when a substitution question reaches the technical stage.
Substitution is a legitimate engineering decision. It is not a designation exercise. It requires the medium, the temperature, the chloride level and the pressure to be reviewed by someone who will sign for the outcome. A purchasing department that substitutes on price alone is making an engineering decision it is not equipped to make.
If you are weighing a substitution, the 625 versus 718 comparison shows how a related decision is structured, and the complete nickel alloy pipe guide places 625 among the grades it is most often confused with.
Frequently Asked Questions
What is Inconel 625 equivalent to?
Inconel 625 is equivalent to UNS N06625 in the United States, W.Nr. 2.4856 and EN NiCr22Mo9Nb in Europe, NA21 in the United Kingdom, NC22DNb in France, NCF625 in Japan, KhN75MBTYu in Russia, and GH3625 or NS336 in China. All designate the same nickel-chromium-molybdenum-niobium alloy.
Is Inconel 625 the same as 2.4856?
Yes. W.Nr. 2.4856 is the German Werkstoff number for Inconel 625, and EN NiCr22Mo9Nb is the matching European symbol. The near-miss is 2.4858, which is Incoloy 825 and a completely different alloy.
Is Inconel 625 stainless steel?
No. Inconel 625 is a nickel-based superalloy with roughly 58 to 61% nickel and about 20 to 23% chromium. Stainless steel is iron-based with chromium as the principal alloying addition. The two are separate material families with separate standards.
Is GH3625 the same as Inconel 625?
GH3625 is the Chinese designation for the same base alloy, within the GB/T 14992 superalloy framework. The chemistry is essentially the same. The surrounding test and documentation requirements are not identical to ASTM B444, so a GH3625 certificate and a B444 order are not automatically the same purchase.
What is the Chinese equivalent of Inconel 625?
China uses two: GH3625 in the wrought superalloy framework, and NS336 or NS3306 in the corrosion-resisting alloy framework. Which one appears on your certificate depends on the intended service.
Can I use Incoloy 825 instead of Inconel 625?
Not as an equivalent. Incoloy 825 is UNS N08825, a nickel-iron-chromium alloy with copper and titanium additions. It outperforms 625 in dilute sulfuric and phosphoric acid, and falls well short in chlorides and at high temperature. Substitution requires an engineering review, not a cross-reference.
What ASTM standard covers Inconel 625 pipe?
Seamless pipe and tube run to ASTM B444 with B829 as the general-requirements document. Welded pipe runs to ASTM B705, and welded tube to ASTM B704, both with B751. The nickel alloy pipe standards index maps the full standard set across grades.
What is the difference between Inconel 625 and 625LCF?
625LCF is designated UNS N06626. It is a low-cycle-fatigue variant developed for bellows and expansion joints, with different heat treatment logic from standard 625. It is a related alloy, not an equivalent grade.
Conclusion: Resolve the Designation Before You Release the PO
Inconel 625 equivalent grades all name one alloy, and the differences between them are documentary rather than metallurgical. Five points carry most of the risk.
The designation set is UNS N06625, W.Nr. 2.4856, GH3625, NCF625 and NA21, and none of them tells you the product-form standard. B705 is welded pipe, B704 is welded tube, and B444 always travels with B829. 2.4858 is Incoloy 825, one digit away and a different metal.
EN 10216-5 does not cover 625 at all. An equivalent grade resolves the alloy without resolving the condition, which is why Grade 1 and Grade 2 have to be written explicitly.
None of this is difficult once it is on one page. All of it is expensive when it is not.
Send us your line list with the designations exactly as written and we will confirm the alloy, the condition and the governing standard before the order leaves your desk. Our technical team responds within 24 hours. Start the check here.
