Extreme Corrosion Resistance • High Temperature Strength • Outstanding Fabricability
Inconel 625 is a nickel-chromium-molybdenum alloy renowned for exceptional resistance to extreme environments. Combining outstanding corrosion resistance with high strength from cryogenic temperatures to 982°C (1800°F), it excels in the most demanding aerospace, chemical processing, marine, and oil & gas applications where conventional materials fail.
Inconel 625 is a solid-solution strengthened nickel-chromium alloy with additions of molybdenum and niobium. Its austenitic structure provides exceptional resistance to oxidation, corrosion, and pitting across an extraordinarily wide temperature range. The alloy maintains its strength and ductility from cryogenic temperatures through 982°C (1800°F), making it ideal for extreme service conditions.
The combination of nickel, chromium, and molybdenum gives Inconel 625 exceptional versatility. It resists a wide range of corrosive media including seawater, acidic solutions, and alkaline environments. The material's resistance to high-temperature oxidation and carbonization makes it indispensable in gas turbine, nuclear, and chemical processing applications.
| Element | Weight % | Purpose |
|---|---|---|
| Nickel (Ni) | ≥ 58.0 (min) | Base metal, provides corrosion and oxidation resistance |
| Chromium (Cr) | 20.0 - 23.0 | Oxidation and corrosion resistance |
| Molybdenum (Mo) | 8.0 - 10.0 | Pitting and crevice corrosion resistance |
| Niobium + Tantalum (Nb + Ta) | 3.15 - 4.15 | Strengthening and stabilization against sensitization |
| Iron (Fe) | ≤ 5.0 | Solid solution strengthening |
| Manganese (Mn) | ≤ 0.50 | Deoxidizer and sulfur control |
| Silicon (Si) | ≤ 0.50 | Deoxidizer |
| Aluminum (Al) | ≤ 0.40 | Deoxidizer |
| Titanium (Ti) | ≤ 0.40 | Grain size control |
| Carbon (C) | ≤ 0.10 | Strength (kept low to prevent carbide precipitation) |
Chemistry Note: The niobium addition is critical—it stabilizes the alloy against sensitization during welding and provides solid solution strengthening without reducing ductility.
| Property | Metric | Imperial |
|---|---|---|
| Tensile Strength (Ultimate) | 827 MPa | 120,000 psi |
| Yield Strength (0.2% offset) | 414 MPa | 60,000 psi |
| Elongation at Break | 30% (in 50mm) | |
| Modulus of Elasticity | 208 GPa | 30.0 × 10⁶ psi |
| Rockwell Hardness | ≤ 40 HRC (typical) | |
| Brinell Hardness | ≤ 230 HB | |
| Shear Strength | 510 MPa | 74,000 psi |
| Shear Modulus | 79.3 GPa | 11.5 × 10⁶ psi |
| Poisson's Ratio | 0.31 | |
Note: Properties shown are for annealed condition. Cold working can significantly increase strength. Material maintains excellent strength retention at elevated temperatures.
Gas turbine engine components, ducting systems, thrust reversers, exhaust systems, afterburner parts, spray bars, fuel nozzles, turbine seals, and aircraft structural components requiring high-temperature strength and corrosion resistance.
Reaction vessels, heat exchangers, condensers, evaporators, transfer piping, valves, pumps, pressure vessels for aggressive chemicals, chloride service, acid gas processing equipment, and sour gas applications.
Downhole tubulars, wellhead components, subsea systems, blowout preventer (BOP) components, umbilicals, flowlines, risers, offshore platform equipment, sour gas service, and high-pressure high-temperature (HPHT) applications.
Seawater cooling systems, propulsion motor shafts, offshore drilling platform components, subsea equipment, marine engine parts, desalination plants, and saltwater service applications.
Nuclear reactor core components, steam generator tubing, control rod components, fuel processing equipment, reactor vessel internals, and high-radiation environment applications.
Flue gas desulfurization systems, waste treatment equipment, scrubber systems, incinerators, stack gas reheaters, and pollution control devices handling corrosive exhaust gases.
| Operation | Recommended Parameters |
|---|---|
| Turning | Speed: 40-90 SFM (12-27 m/min) carbide, Feed: 0.004-0.012 ipr, DOC: 0.050-0.150" |
| Milling (Roughing) | Speed: 50-100 SFM (15-30 m/min), Heavy feeds, depth 0.100-0.200" |
| Milling (Finishing) | Speed: 80-140 SFM (24-43 m/min), Light feeds, depth 0.010-0.030" |
| Drilling | Speed: 15-40 SFM (4.5-12 m/min), Feed: 0.002-0.008 ipr, peck drilling mandatory |
| Threading | Very slow speeds, carbide inserts, thread milling preferred over single-point |
| Coolant | High-pressure flood coolant MANDATORY, sulfurized or chlorinated cutting oils |
Critical Success Factor: Inconel 625 machining requires experienced operators and specialized equipment. The material work hardens ahead of the cutting tool, so constant chip load and feed must be maintained. Never let the tool dwell or rub on the work surface.
Inconel 625 has excellent weldability and can be joined using most conventional welding processes. The alloy's resistance to post-weld cracking and its ability to maintain corrosion resistance in the weld zone make it ideal for critical welded structures.
Inconel 625 exhibits outstanding resistance to a wide variety of corrosive environments, making it one of the most versatile corrosion-resistant alloys available.
Note: While Inconel 625 has excellent general corrosion resistance, it can be susceptible to stress corrosion cracking in highly oxidizing chloride environments at elevated temperatures. Consult corrosion specialists for extreme service conditions.
Get a quote for AS9100D certified Inconel 625 machining with full material traceability and aerospace certification.