When specifying materials for high-temperature, corrosive, or thermal cycling environments, understanding the thermal expansion coefficient of Inconel 625 alloy is crucial. For purchasing managers, engineers, and engineering contractors, thermal expansion directly impacts dimensional stability, sealing performance, fatigue life, and long-term reliability.
This article will explain the thermal expansion characteristics of Inconel 625 and compare it to other alloys, while also demonstrating how purchasers can mitigate risks and reduce life cycle costs through proper material selection.
What is Inconel 625?
Inconel 625 (UNS N06625 / EN 2.4856) is a nickel-chromium-molybdenum high-temperature alloy that derives its strength primarily from solid-solution strengthening rather than precipitation hardening. Key characteristics related to thermal expansion include: a high nickel content (approximately 60%), and excellent strength over a temperature range from cryogenic temperatures to approximately 980°C. These properties make Inconel 625 widely used in aerospace, oil and gas, chemical, marine, and power generation industries.
Why is the thermal expansion coefficient of Inconel 625 important to buyers?
The coefficient of thermal expansion (CTE) defines the extent to which a material expands when its temperature increases.
Mismatched thermal expansion coefficients can lead to: thermal fatigue cracking, gasket and flange leaks, deformation of plates, pipes, or profiles, and premature failure of welded assemblies.
For buyers, understanding the thermal expansion coefficient helps ensure: compatibility with mating materials, dimensional stability during thermal cycling, and compliance with design specifications and tolerance requirements.
Inconel 625 Thermal Expansion Coefficient
Linear Thermal Expansion of Inconel 625
| Temperature Range | Mean CTE (µm/m·°C) | Mean CTE (×10⁻⁶ /°C) |
|---|---|---|
| 20–100°C | 12.8 | 12.8 |
| 20–200°C | 13.0 | 13.0 |
| 20–300°C | 13.3 | 13.3 |
| 20–400°C | 13.6 | 13.6 |
| 20–600°C | 14.0 | 14.0 |
| 20–800°C | 14.6 | 14.6 |
Inconel 625 Compares to Other Alloys (CTE)
| Material | Thermal Expansion (×10⁻⁶ /°C, 20–400°C) |
|---|---|
| Carbon Steel | ~12.0 |
| Stainless Steel 316 | ~16.0 |
| Inconel 600 | ~13.3 |
| Inconel 625 | 13.6 |
| Inconel 718 | ~13.0 |
| Hastelloy C276 | ~11.2 |
What is the coefficient of thermal expansion of Inconel 625?
The coefficient of thermal expansion (CTE) for Inconel 625 is around 12.8 to 13.1 µm/(m·°C) (or \(12.8\times 10^{-6}\,\text{m/m/\degree C}\)) for the range of 20°C to 100°C, increasing slightly with temperature, equivalent to about 7.1 µin/(in·°F), making it comparable to stainless steels but generally lower than many other high-temperature alloys.
Does Inconel 625 have better thermal expansion properties than 316 stainless steel?
Inconel 625 doesn't necessarily have "better" thermal expansion than 316 SS; they just behave differently, with Inconel 625 generally having a slightly lower or comparable expansion rate at lower temps but maintaining its properties at much higher temperatures, while 316 SS expands more readily and loses strength as heat increases, making Inconel superior for extreme thermal cycling where dimensional stability at high heat is key.
Does Inconel 625 expand more than Inconel 718?
Yes, Inconel 625 generally expands slightly more (has a higher Coefficient of Thermal Expansion, CTE) than Inconel 718, especially at lower temperatures; for instance, 625's CTE is around 12.8 µm/m-°C (20-100°C), while 718 is closer to 12.5 µm/m-°C in a similar range, though both are very similar nickel superalloys, with Inconel 718 prized for its much higher strength and Inconel 625 for superior corrosion resistance.
Inconel 625 suppliers
At GNEE, Inconel 625 is available in various forms to meet diverse industrial needs:
Plates and Sheets (cold rolled and hot rolled)
Bars and Rods (round, square, hexagonal)
Tubes (seamless and welded)
Wires and Strips (for springs, fasteners, electrical applications)
Forgings and Custom Parts (according to drawings or specifications)
Testing and Documentation: Mill Test Certificates, EN 10204 3.1, Chemical Reports, Mechanical Reports, Destructive Testing Reports, Non-Destructive Testing Reports, PMI Test Reports, Visual Inspection Reports, Third-Party Inspection Reports, NABL Certified Laboratory Reports.
Packaging: Wooden crates, bubble wrap, steel strapping, or packaged according to customer requirements.
