Inconel 625 Tube Sheet
A solid-solution-strengthened nickel alloy that holds its strength and oxidation resistance up to roughly 980°C — the grade reached for once stainless and duplex have both run out of temperature margin, without moving all the way to a specialist alloy like Hastelloy.
Chemical Composition
| Element | Min % | Max % |
|---|---|---|
| Nickel (Ni) | 58.0 | — |
| Chromium (Cr) | 20.0 | 23.0 |
| Molybdenum (Mo) | 8.0 | 10.0 |
| Niobium + Tantalum (Nb+Ta) | 3.15 | 4.15 |
| Iron (Fe) | — | 5.0 |
Mechanical Properties
| Property | Typical Value |
|---|---|
| Tensile Strength | 827 MPa min (annealed) |
| Yield Strength (0.2% offset) | 414 MPa min (annealed) |
| Elongation | 30% min |
| Max. Practical Service Temp. | ~980°C (oxidation-limited) |
Equivalent Grades
| Standard | Designation |
|---|---|
| ASTM / UNS | N06625 |
| EN / DIN | 2.4856 |
| JIS | NCF625 |
| Trade Name | Inconel® 625 (Special Metals) |
Temperature Capability in Context
*316L's high number reflects oxidation resistance alone; its practical strength-limited service temperature for pressure parts is considerably lower. Always confirm allowable stress at temperature against the governing code, not oxidation limits alone.
Available Product Forms
Inconel 625 is most commonly ordered as U-Tube Tube Sheets for high-temperature boiler and refinery service, and as Forged Tube Sheets for large, high-pressure applications.
Applications
Refinery high-temperature process streams, sour gas service resistant to sulfide stress cracking, and power generation components exposed to cyclic high-temperature operation where stainless would show creep or oxidation degradation.
Advantages & Limitations
Advantages
- Excellent strength retention at high temperature
- Good resistance to sour (H₂S-bearing) service
- No age-hardening heat treatment required
Limitations
- Significant cost premium over stainless and duplex
- Slower machining, higher tool wear than stainless
- Overkill for services that don't need the temperature margin
FAQ
Usually yes — if the service temperature is within stainless or duplex's practical range, 625 adds significant cost without a corresponding benefit. It earns its cost premium specifically in high-temperature, sour, or highly oxidizing services where those grades fall short.
Both resist sulfide stress cracking, but 625 generally offers a higher strength and broader temperature range at a higher cost, while 825 is often selected as a more cost-effective option when its lower temperature capability is still sufficient for the service.
Longer than stainless or duplex due to lower stock availability and more demanding machining — send your specification and quantity for a confirmed lead time rather than assuming standard turnaround.