NI · superalloy
Nickel Superalloy Inconel 625 (UNS N06625)
Harder to machine than the 600-series grades and easier than 718. It work-hardens aggressively and galls badly, but it does not need an ageing treatment to reach its strength.
Quoting this material
- Typical lead time
- 18–30 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.
Harder to machine than the 600-series grades and easier than 718. It work-hardens aggressively and galls badly, but it does not need an ageing treatment to reach its strength.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Tensile strength | 930 | MPa |
| Yield strength (0.2%) | 517 | MPa |
| Elongation | 42 | % |
| Hardness (annealed) | ~200 | HB |
| Service temperature | To 980 | °C |
| Thermal conductivity | 9.8 | 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
Strengthened by solid solution rather than precipitation, so there is no ageing step and nothing the shop can do to change the strength. Annealing after welding relieves stress and restores corrosion resistance.
Achievable surface finish
Ra 1.6 µm
Ra 0.8 µm
Galling is the surface problem - the material tends to tear rather than shear, so a sharp edge and a positive rake are the difference between a clean finish and a torn one.
Tooling and cutting parameters
Cutting speed
- 25–50 m/min (carbide)
Feed
- 0.06–0.18 mm/rev turning · 0.05–0.12 mm/tooth milling
Tooling
- Fine-grain carbide, sharp positive geometry, tough substrate
Coolant
- High-pressure flood; do not cut it dry
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
- Seawater and marine exhaust systems
- Chemical process equipment
- Aerospace ducting and engine parts
- Nuclear and offshore hardware
- Pollution control and scrubber components
DFM notes for this grade
- Excellent weldability for a superalloy - it is often chosen because the assembly is welded, unlike 718 which is harder to join
- Galling against itself or a stainless is a real risk: specify a lubricant and a dissimilar material where a joint slides
- It is not as strong as 718 and cannot be aged to be, so if the load needs 1,200 MPa the answer is a different alloy, not a heat treatment
Questions buyers ask
- Why choose 625 rather than 718?
- Weldability and corrosion resistance. 625 welds far more easily, resists a wider range of corrosive media, and needs no ageing treatment - if the part is a welded fabrication in a severe environment rather than a high-stress rotating component, 625 is usually the right answer.
- Can 625 be machined dry with ceramic tooling?
- Roughing with ceramic is possible and fast, but the finishing passes are still carbide with coolant. Ceramic inserts are brittle and unforgiving in an interrupted cut, so they get used for the stable roughing on a rigid machine.
Grades we would quote instead
Inconel 718
1/10The bottom of our scale and the reason the scale exists.
Hastelloy C-276
1/10One of the hardest materials in this catalogue: very tough, work-hardening, and abrasive.
Incoloy 825
2/10A 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.