Inconel 625 is a nickel-chromium-molybdenum alloy strengthened by niobium. It stays strong from very low temperatures up to about 980 °C and resists seawater, acids and oxidation. It is used for chemical plant parts, heat exchangers, marine fittings, exhaust and turbine parts. It is very expensive and slow to machine.
Quick facts
- Type
- Nickel-based superalloy
- Nickel
- About 58% min
- Chromium / molybdenum
- About 20–23% / 8–10%
- Service temperature
- Up to about 980 °C
- Tensile strength
- About 830–1,000 MPa
- Machinability
- Poor; work-hardens fast
Typical chemical composition
| Element | % |
|---|---|
| Nickel (Ni) | 58 min |
| Chromium (Cr) | About 20–23 |
| Molybdenum (Mo) | About 8–10 |
| Niobium + tantalum | About 3.2–4.2 |
| Iron (Fe) | 5 max |
Values are typical. The exact limits depend on the standard and supplier; ask for the mill test certificate when it matters.
Machining and welding
- Rigid machines, sharp carbide or ceramic tools, low speeds
- Keep the tool cutting: rubbing work-hardens the surface
- High-pressure coolant
- Welds well by TIG with Inconel 625 filler (also used to clad other metals)
Typical uses
- Chemical and petrochemical plant parts
- Seawater and offshore fittings
- Heat exchanger and exhaust parts
- Weld overlay on valves and pipes
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Questions
- Why is Inconel so hard to machine?
- It keeps its strength at the high temperatures of cutting and work-hardens quickly, so tools wear fast.
- Inconel 625 or SS316L?
- 625 resists far stronger acids, seawater and high temperatures, but costs many times more. Use it only where 316L fails.
- Is Inconel magnetic?
- Inconel 625 is essentially non-magnetic.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 23 October 2026.