Inconel® 725 (UNS N07725)
Age-hardened 625: the corrosion resistance of Inconel 625 with 150 ksi strength, NACE listed for sour service — the subsea and downhole fastener alloy.
What Inconel 725 is.
Inconel 725 is a nickel-chromium-molybdenum alloy, essentially 625 with titanium and niobium adjusted so that it can be age hardened. It combines the pitting, crevice and sour-gas resistance of 625 with strength approaching 718, and is listed in NACE MR0175 / ISO 15156 for the most severe sour-service environments at up to 43 HRC. It is the alloy of choice for subsea wellhead, hanger and riser fasteners.
We machine 725 studs, bolts, nuts and components from certified B637 bar, aged to the specification, with hardness controlled to the NACE limit and PMI on every lot.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.03 |
| Manganese | Mn | — | 0.35 |
| Silicon | Si | — | 0.20 |
| Phosphorus | P | — | 0.015 |
| Sulfur | S | — | 0.010 |
| Chromium | Cr | 19.00 | 22.50 |
| Molybdenum | Mo | 7.00 | 9.50 |
| Niobium + tantalum | Nb+Ta | 2.75 | 4.00 |
| Titanium | Ti | 1.00 | 1.70 |
| Aluminium | Al | — | 0.35 |
| Nickel | Ni | 55.0 | 59.0 |
| Iron | Fe | balance | — |
Values per ASTM B637-16 Tables 1 and 3 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Mechanical properties.
| Condition and nominal diameter (in.) | Tensile strength, min (ksi) | Yield strength 0.2% offset, min (ksi) | Elongation, min (%) | Reduction of area, min (%) | Hardness |
|---|---|---|---|---|---|
| Solution treated and aged — all | 150 | 120 | 20 | 35 | 43 HRC max |
Values per ASTM B637-16 Tables 1 and 3 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Specifications that apply.
How Inconel 725 ships from Houston.
- Studs and stud bolts
- Hex and heavy hex bolts
- Nuts and washers
- Socket head cap screws
- Machined components from certified bar
Inconel 725 fasteners we make.
Every item is manufactured to your drawing or standard in Inconel 725, imperial or metric, with an EN 10204 3.1 certificate.
What is Inconel 725?
725 answers the question of how to get high strength from 625. Its chromium and molybdenum are the same, so it resists chlorides, hydrogen sulfide and acids the way 625 does, but a controlled titanium and niobium content lets it age harden to 150 ksi. NACE lists it for the most severe sour environments at up to 43 HRC, which makes it one of very few materials that combine strength, corrosion resistance and sour-service acceptance in one bolt.
725, 718 or 925?
- 725: the most corrosion resistant and the widest sour-service approval; the premium choice for subsea and severe wells.
- 718: stronger and less costly, but its sour-service limits are tighter and it pits more readily in chlorides.
- 925: an iron-nickel alloy at lower cost, good for moderate sour service and hangers, weaker than both.
Testing, certification and marking
- Tensile and hardness tested per heat-treat lot
- Grade or alloy symbol and manufacturer's identification on every piece
- EN 10204 3.1 material test report with heat number and chemistry; 3.2 witness available
- PMI verification standard on nickel alloys
Inconel 625 (UNS N06625)
The corrosion all-rounder — 120 ksi in the annealed condition, resistant to seawater, sour gas, acids and oxidation to 1800 °F, and the F468 nickel fastener grade Ni 625.
ASTM B637 bar · AMS 5662 / 5663 · API 6A CRAInconel 718 (UNS N07718)
The premier high-strength nickel superalloy — 185 ksi tensile and 150 ksi yield from cryogenic temperatures to 1200 °F, with corrosion and sour-gas resistance to match.
ASTM B637Incoloy® 925 (UNS N09925)
Age-hardened 825: an iron-nickel alloy with 140 ksi strength, sour-gas and chloride resistance and NACE approval — the economical downhole and wellhead fastener alloy.