Incoloy® 825 (UNS N08825)
The acid and sour-gas alloy: nickel-iron-chromium with molybdenum and copper for sulfuric and phosphoric acid, chlorides and hydrogen sulfide — for chemical plant, pollution control and oilfield fasteners.
What Incoloy 825 is.
Incoloy 825 is a titanium-stabilized nickel-iron-chromium alloy with about 3 percent molybdenum and 2 percent copper. The nickel content resists chloride stress-corrosion cracking, copper and molybdenum resist reducing acids such as sulfuric and phosphoric, chromium resists oxidizing ones, and titanium, with the right heat treatment, stabilizes it against sensitization to intergranular corrosion. It is not age hardenable, so strength is moderate, but it is one of the most versatile corrosion-resistant alloys for acid, sour and seawater service.
We machine 825 studs, bolts, nuts and components from certified bar in the solution-annealed condition, with PMI on every lot. For a stronger alloy with the same resistance, see Incoloy 925.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.05 |
| Manganese | Mn | — | 1.0 |
| Silicon | Si | — | 0.5 |
| Sulfur | S | — | 0.03 |
| Chromium | Cr | 19.5 | 23.5 |
| Molybdenum | Mo | 2.5 | 3.5 |
| Titanium | Ti | 0.6 | 1.2 |
| Aluminium | Al | — | 0.2 |
| Copper | Cu | 1.5 | 3.0 |
| Nickel | Ni | 38.0 | 46.0 |
| Iron | Fe | 22.0 | — |
Limiting chemical composition for UNS N08825 per ASTM B425, matching the producer’s datasheet (Special Metals, INCOLOY alloy 825, publication SMC-030, Table 1).
Mechanical properties.
| Condition | Tensile strength (ksi) | Yield strength 0.2% offset (ksi) | Elongation (%) | Reduction of area (%) | Hardness |
|---|---|---|---|---|---|
| Annealed rod and bar — ASTM B425 minimum | 85 | 35 | 30 | — | — |
| Annealed bar — typical (Special Metals) | 100 | 47 | 45 | — | — |
ASTM B425 minimums for annealed rod and bar; the elongation requirement does not apply under 3/32 in. Typical values are from the producer’s datasheet (Special Metals SMC-030, Table 5). The alloy can be strengthened substantially by cold work.
Specifications that apply.
How Incoloy 825 ships from Houston.
- Studs and stud bolts
- Hex and heavy hex bolts
- Nuts and washers
- Socket head cap screws
- Machined components from certified bar
Incoloy 825 fasteners we make.
Every item is manufactured to your drawing or standard in Incoloy 825, imperial or metric, with an EN 10204 3.1 certificate.
What is Incoloy 825?
825 is a general-purpose corrosion-resistant alloy that sits between the stainless steels and the nickel-base Hastelloys. Its balanced chemistry handles both reducing acids, thanks to copper and molybdenum, and oxidizing conditions, thanks to chromium, and its roughly 40 percent nickel gives it strong resistance to the chloride stress-corrosion cracking that fails 316. It welds well by all conventional processes and is listed in NACE MR0175 for sour service. Its one limitation for fasteners is strength, which is why 925 exists.
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
Incoloy® 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.
ASTM B408 barIncoloy 800 / 800H / 800HT (UNS N08800 / N08810 / N08811)
The economical high-temperature alloy — 32 % nickel, 21 % chromium — for furnace, reformer and heat-exchanger hardware from 1000 to 1800 °F.
ASTM B446 bar · ASTM F468 / F467 fastenersInconel 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.