Inconel 625: properties, composition, uses and standards
Inconel 625 is a nickel–chromium–molybdenum alloy with niobium, chosen for seawater, high strength and high temperature in one alloy. UNS N06625, W.Nr 2.4856, PREN ≈ 51, density 8.44 g/cm³.
What is Inconel 625?
Inconel 625 is a nickel–chromium–molybdenum alloy with niobium. Engineers choose it for seawater, high strength and high temperature in one alloy. It is also known as Alloy 625, UNS N06625, W.Nr 2.4856, Nicrofer 6020.
- UNS
- N06625
- W.Nr
- 2.4856
- EN
- NiCr22Mo9Nb
- BS
- NA 21
- JIS
- NCF 625
- Trade names
- Inconel 625 · Nicrofer 6020
- Density
- 8.44 g/cm³
- Melting range
- 1290 – 1350 °C
- Magnetic
- Non-magnetic
- PREN (approx.)
- ≈ 51
Chemical composition and what each element does
Under technical review for TDS.
| Element | Current requirement |
|---|---|
| Nickel | As specified |
| Chromium | As specified |
| Molybdenum | As specified |
| Niobium + Tantalum | As specified |
| Iron | As specified |
| Carbon | As specified |
| Manganese | As specified |
| Silicon | As specified |
| Titanium | As specified |
| Aluminium | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification to be verified: ASTM B443 for UNS N06625.
About 9% molybdenum gives PREN above 50 — seawater pitting is rarely a concern.
Niobium strengthens the matrix without heat treatment.
High nickel makes it virtually immune to chloride stress-corrosion cracking.
Keeps useful strength and oxidation resistance at high temperature.
Inconel 625 at a glance
See the Inconel 625 product page for every form we supply and its standard.
Mechanical properties
Under technical review for TDS.
| Property | Current requirement |
|---|---|
| Tensile strength | As specified |
| Yield strength 0.2% | As specified |
| Elongation | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification and condition to be verified: ASTM B443 for UNS N06625 — Grade 1 annealed plate.
Where Inconel 625 is used
- Offshore & subsea. Risers, flowlines and clad pipe. Industry →
- Aerospace. Ducting, exhaust and bellows. Industry →
- Chemical. Mixed-acid and chloride service. Industry →
- Flue-gas desulphurisation. Scrubber and stack linings. Industry →
- Marine. Propeller blades and seawater parts. Industry →
Welding 625
The matching filler is ERNiCrMo-3 (AWS A5.14). ENiCrMo-3 electrode.
Keep heat input moderate and interpass temperature low, clean joints thoroughly, and pickle or passivate after welding where the service is corrosive.
Inconel 625 compared with similar grades
| Grade | PREN | Choose it for |
|---|---|---|
| Inconel 625 | ≈ 51 | Seawater, high strength and high temperature in one alloy |
| Inconel 825 | ≈ 31 | Sulphuric and phosphoric acid service, chloride stress-corrosion cracking and sour gas |
| Super Duplex 2507 | ≈ 42 | Seawater and high-chloride service where strength also matters |
| Hastelloy C276 | ≈ 68 | The most aggressive mixed acids, wet chlorine and hypochlorite |
Inconel 625 standards by product
| Product | Standard |
|---|---|
| Inconel 625 sheet | ASTM B443 |
| Inconel 625 plate | ASTM B443 |
| Inconel 625 coil | ASTM B443 |
| Inconel 625 pipe & tube | ASTM B444 · ASTM B705 |
| Inconel 625 fittings | ASTM B366 WPNCMC · ASTM B564 |
| Inconel 625 flanges | ASTM B564 |
| Inconel 625 fasteners | ASTM F468 (N06625) where specified for applicable bolts, hex cap screws, socket-head cap screws and studs (0.250–1.500 in.), and ASTM F467 for applicable nuts (0.250–1.500 in.); for other types, material may be supplied to ASTM B446 bar where applicable, subject to the purchase specification |
Buying Inconel 625: what to specify
- The product standard and the UNS or designation — for example ASTM B443 UNS N06625.
- Size, thickness or schedule, and quantity in pieces and kg or metres.
- Heat-treatment condition where the standard offers a choice.
- Certificate: EN 10204 3.1 or 3.2 available on request / as specified in the PO; ask for 3.2 if a third party must witness.
- NACE MR0175 / ISO 15156 compliance if the service contains H₂S.