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Nickel Inconel 625
Nickel Inconel 625 (UNS N06625, W.Nr. 2.4856) is a nickel-chromium-molybdenum superalloy with added niobium. It is strengthened by those elements dissolved in its nickel-chromium matrix, not by precipitation hardening. That gives it high strength and toughness from cryogenic temperatures up to 1800°F (982°C), without an aging heat treatment. It combines exceptional resistance to pitting, crevice corrosion and chloride stress-corrosion cracking with strong oxidation resistance, and it is non-magnetic.
Inconel 625 is readily hot and cold formed and machinable with carbide tooling, and it is one of the most weldable high-performance nickel alloys. The niobium addition stabilizes the alloy against sensitization during welding, so welds keep full corrosion resistance without a post-weld heat treatment. It is supplied either annealed, for maximum strength up to about 1200°F, or solution treated, for the best creep and rupture resistance above 1200°F.
The alloy is used across seawater and naval hardware, aerospace ducting, exhaust and fuel systems, chemical processing, pollution control, oil-and-gas and nuclear service.
Tech Steel & Materials offers the alloy Nickel Inconel 625 in 4 sub-type specifications, each in multiple and customized shapes/forms:
- AMS 5581 (Seamless or Welded Tubing, Custom Tube)
- AMS 5599 (Plate, Sheet, Strip: annealed)
- AMS 5666 (Bar, Forging, Ring, Custom Tube)
- AMS 5869 (Plate, Sheet, Strip: solution heat treated)
We also offer a fully customized line of tube drawing and seamless tubing in Nickel Inconel 625.
The Composition of Nickel Inconel 625
| 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 |
| Cobalt (Co) | — | 1.0 |
| Manganese (Mn) | — | 0.50 |
| Silicon (Si) | — | 0.50 |
| Aluminum (Al) | — | 0.40 |
| Titanium (Ti) | — | 0.40 |
| Carbon (C) | — | 0.10 |
| Phosphorus (P) | — | 0.015 |
| Sulfur (S) | — | 0.015 |
Fabrication
- Hot working: Heat to a maximum of 2150°F (1175°C) for heavy forging. Lighter reductions can continue down to about 1700°F (925°C). Avoid working between about 1200°F and 1600°F.
- Cold forming: Responds well to standard cold-forming methods. It work-hardens quickly, so allow for higher forming loads and anneal between heavy operations.
- Welding: Weldable by GTAW, GMAW, SMAW and submerged arc using matching filler: ERNiCrMo-3 wire (Inconel Filler Metal 625) or ENiCrMo-3 electrodes. No post-weld heat treatment is needed for corrosion resistance.
- Machining: About 35 sfm (10.7 m/min) with high-speed steel and 110 sfm (34 m/min) with carbide. Use rigid setups, positive-rake sharp tools and heavy flood coolant.
- Stress relief: Stress relieving at around 1600°F (870°C) relieves residual stresses from forming and welding.
Heat Treating Of Nickel Inconel 625
Inconel 625 is not age-hardenable. Its strength comes from molybdenum and niobium dissolved in the nickel-chromium matrix. The mill anneal it receives decides which of two conditions it is supplied in:
- Annealed (Grade 1): annealed at about 1700–1900°F (927–1038°C). This gives a fine grain and the highest room-temperature and moderate-temperature tensile and fatigue strength. It is recommended for service up to about 1200°F (650°C). Supplied as AMS 5599 sheet and plate, AMS 5666 bar and forgings, and AMS 5581 tubing.
- Solution treated (Grade 2): heated to about 2000–2200°F (1093–1204°C). This gives a coarser grain that maximizes creep and stress-rupture strength. It is recommended for service above 1200°F. Supplied as AMS 5869 sheet and plate.
Long exposure between about 1200°F and 1600°F can precipitate secondary phases that reduce ductility and impact toughness. Designers should account for this in components that spend long periods in that range.
Mechanical and Physical Properties
| Product / Condition | Tensile Strength | Yield Strength (0.2%) | Elongation | Hardness |
| Rod, bar, plate – annealed | 120–150 ksi (827–1034 MPa) | 60–95 ksi (414–655 MPa) | 60–30% | 145–220 HB |
| Sheet, strip – annealed | 120–150 ksi (827–1034 MPa) | 60–90 ksi (414–621 MPa) | 55–30% | — |
| Rod, bar – solution treated | 105–130 ksi (724–896 MPa) | 42–60 ksi (290–414 MPa) | 65–40% | — |
Typical room-temperature ranges. Values vary with section size and product form. For guaranteed minimums, refer to the applicable AMS specification.
Physical Properties Of Inconel 625
| Property | Value |
| Density | 0.305 lb/in3 (8.44 g/cm3) |
| Melting Range | 2350–2460°F (1290–1350°C) |
| Specific Heat (70°F) | 0.098 BTU/lb·°F (410 J/kg·°C) |
| Thermal Conductivity (70°F) | 68 BTU·in/ft²·h·°F (9.8 W/m·°C) |
| Coefficient of Thermal Expansion (70–200°F) | 7.1 x 10-6 in/in/°F (12.8 µm/m·°C) |
| Electrical Resistivity (70°F) | 50.8 µΩ·in (129 µΩ·cm) |
| Modulus of Elasticity (annealed) | 30.1 x 103 ksi (207.5 GPa) |
| Shear Modulus (annealed) | 11.8 x 103 ksi (81.4 GPa) |
| Poisson’s Ratio | 0.278 |
| Magnetic Permeability (200 oersted) | 1.0006 (non-magnetic) |
| Curie Temperature | Below −320°F (−196°C) |
Common Uses of Nickel Inconel Alloy 625
Inconel 625 is a premium-cost alloy, so it is chosen where corrosion, heat or fatigue would quickly defeat stainless steels and lower nickel alloys. It is also chosen where a failure would be costly or dangerous. Its combination of strength, weldability and resistance to seawater, acids and oxidation makes it one of the most versatile nickel alloys in service.
Seawater And Marine
- Wire rope and cores for mooring cables
- Propeller blades for naval patrol craft and submarine auxiliary propulsion motors
- Exhaust ducts for naval vessels
- Sheathing for undersea communication cables
- Submarine transducer controls and quick-disconnect fittings
- Seawater piping, pump shafts and instrument housings
Aerospace
- Aircraft ducting and engine exhaust systems
- Thrust-reverser assemblies
- Engine-compartment and control housings, including welded honeycomb structures
- Fuel and hydraulic line tubing
- Spray bars, bellows and turbine shroud rings
- Heat-exchanger tubing in environmental-control systems
Oil And Gas
- Clad and lined pipe, risers and flowlines for sour-gas service
- Subsea components, wellhead parts and valve internals
- Downhole tools and instrumentation tubing
Chemical Processing
- Reaction vessels and general plant equipment
- Distillation columns and bubble caps
- Heat exchangers, including honeycomb designs
- Transfer piping, tubing and valves
Pollution Control And Energy
- Flue-gas desulfurization scrubbers, dampers and stack liners
- Waste-to-energy boiler tubes and superheater protection
- Tubing for molten-salt and liquid-metal systems in solar-thermal and advanced power plants
Nuclear
- Reactor-core components
- Control-rod drive mechanism parts
Weld Overlay And Cladding
- ERNiCrMo-3 (625) filler used to overlay carbon-steel boiler walls, valves and pipe for corrosion protection
- Dissimilar-metal welds between nickel alloys, stainless and carbon steels
Other
- Additive manufacturing (3D-printed) components from 625 powder
- Motorsport and performance exhaust systems
- Pharmaceutical and food-processing equipment exposed to aggressive cleaning agents
Inconel 625 vs Inconel 718
| Property | Inconel 625 | Inconel 718 |
| UNS | N06625 | N07718 |
| Strengthening | Solid solution (no aging) | Precipitation hardened (aged) |
| Typical yield strength | 60–95 ksi annealed | ~150 ksi aged |
| Corrosion resistance | Superior (9% Mo, pitting and crevice) | Good |
| Weldability | Excellent, no post-weld treatment | Good, re-aging needed for full strength |
| Best for | Corrosive and marine service, welded fabrications | High-strength rotating and structural parts to 1300°F |
Inconel 625 Equivalent Designations
| Standard | Designation |
| UNS | N06625 |
| W.Nr / EN | 2.4856 (NiCr22Mo9Nb) |
| SAE AMS | 5581, 5599, 5666, 5869 |
| ASTM / ASME | B443 (plate/sheet), B444 (seamless tube), B446 (bar), B564 (forgings), B704/B705 (welded tube) |
| Welding filler | AWS ERNiCrMo-3 (wire), ENiCrMo-3 (electrode) |
| Common names | Alloy 625, Nickel 625 |
Select AMS
| AMS Number | Alloy | Type | UNS | Cross Ref. Spec | Misc./Shape | |
|---|---|---|---|---|---|---|
| AMS 5581 Custom Tube | Inconel 625 | Nickel | N06625 | - | Custom Tube |
|
| AMS 5581 Inconel 625 Tubing | Inconel 625 | Nickel | N06625 | - | Inconel 625 Tubing |
|
| AMS 5599 Inconel 625 Plate | Inconel 625 | Nickel | N06625 | - | Inconel 625 Plate |
|
| AMS 5599 Inconel 625 Sheet | Inconel 625 | Nickel | N06625 | - | Inconel 625 Sheet |
|
| AMS 5599 Inconel 625 Strip | Inconel 625 | Nickel | N06625 | - | Inconel 625 Strip |
|
| AMS 5666 Custom Tube | Inconel 625 | Nickel | N06625 | - | Custom Tube |
|
| AMS 5666 Inconel 625 Bar | Inconel 625 | Nickel | N06625 | - | Inconel 625 Bar |
|
| AMS 5666 Inconel 625 Forging | Inconel 625 | Nickel | N06625 | - | Inconel 625 Forging |
|
| AMS 5666 Inconel 625 Ring | Inconel 625 | Nickel | N06625 | - | Inconel 625 Ring |
|
| AMS 5869 Inconel 625 Plate | Inconel 625 | Nickel | N06625 | - | Inconel 625 Plate |
|
| AMS 5869 Inconel 625 Sheet | Inconel 625 | Nickel | N06625 | - | Inconel 625 Sheet |
|
| AMS 5869 Inconel 625 Strip | Inconel 625 | Nickel | N06625 | - | Inconel 625 Strip |
|
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