NI · superalloy
Nickel-Iron Alloy Incoloy 825 (UNS N08825)
A nickel-iron-chromium alloy with molybdenum and copper: easier to machine than the nickel-rich superalloys and still resistant to a wide range of corrosive media.
Quoting this material
- Typical lead time
- 20–35 working days
- Condition
- Annealed
- Achievable finish
- Ra 1.6 µm typical · Ra 0.8 µm best
Machined in-house to your drawing: see the precision CNC machining service and the machine and inspection capability it runs on.
Machinability
Our own 1–10 shop ranking, not a published index: 10 is free-cutting brass C360, 1 is Inconel 718. It ranks how a material behaves on the floor - cycle time, chip control and tool life together. Where a published index exists it is quoted in the note.
A nickel-iron-chromium alloy with molybdenum and copper: easier to machine than the nickel-rich superalloys and still resistant to a wide range of corrosive media.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Tensile strength | 620 | MPa |
| Yield strength (0.2%) | 240 | MPa |
| Elongation | 30 | % |
| Hardness | ~200 | HB |
| Service temperature | To 540 | °C |
| Thermal conductivity | 11.1 | W/m·K |
Hardness, tensile and thermal figures are typical published values for the condition stated. Actual mill certificates govern; send the specification with the drawing and we confirm against the certificate before the material is cut.
Condition
Annealed
Heat treatment
Solid-solution strengthened; no ageing treatment. It is a workhorse corrosion alloy rather than a high-temperature structural one.
Achievable surface finish
Ra 1.6 µm
Ra 0.8 µm
Takes a clean finish; the surface matters in corrosive service, so a torn finish is a corrosion site rather than a cosmetic flaw.
Tooling and cutting parameters
Cutting speed
- 30–60 m/min (carbide)
Feed
- 0.08–0.20 mm/rev turning · 0.05–0.12 mm/tooth milling
Tooling
- Fine-grain carbide, sharp positive rake, good clearance
Coolant
- High-pressure flood
Starting points for carbide on a rigid setup, not a guarantee. The right numbers depend on the machine, the toolholder and the fixturing - ask and we will say what we would actually run.
Typical applications
- Sulphuric and phosphoric acid equipment
- Chemical process piping and fittings
- Nuclear fuel reprocessing hardware
- Oil and gas sour service
- Pickling and acid handling equipment
DFM notes for this grade
- It is chosen for acid service: sulphuric and phosphoric acid at moderate temperature, where stainless fails and pure nickel is too expensive
- The nickel-iron base makes it cheaper than a nickel-rich alloy while keeping most of the corrosion envelope - the cost-driven corrosion answer
- It work-hardens, but less aggressively than C-276: the same rules apply with a little more forgiveness
Questions buyers ask
- Incoloy 825 or Hastelloy C-276 for acid service?
- Start with the chemistry and the temperature. 825 handles sulphuric and phosphoric acid well at moderate temperature and costs less; C-276 covers the wider range including chlorides and oxidising conditions. Where 825 survives, specifying C-276 is money spent for nothing.
- Does 825 need a post-weld heat treatment?
- Generally not for corrosion service - it is a stabilised alloy and keeps its resistance as welded. Where the service is at the top of its temperature range, the specification may still call for an anneal.
Grades we would quote instead
Inconel 600
2/10The mildest of the common nickel alloys to machine - still awkward, but it work-hardens less aggressively than 625 and far less than 718.
Monel 400
3/10The most forgiving of the nickel alloys: it machines closer to a tough stainless than to a superalloy, although it work-hardens and galls like its relatives.
Hastelloy C-276
1/10One of the hardest materials in this catalogue: very tough, work-hardening, and abrasive.