Nickel Alloy Alloy 908
UNS N09908 · also Incoloy 908
Alloy 908 (N09908, Incoloy 908) is an age-hardenable Fe-Ni-Nb controlled-expansion superalloy developed for superconducting magnet conduits, combining a low coefficient of thermal expansion at cryogenic temperature with useful strength and non-magnetic behaviour.
Reference datasheet — Alloy 908 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the SA condition
Alloy 908 tempers and conditions
Alloy 908 is supplied in 5 conditions, soft to hard. SA is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SADefault Solution annealed | The as-supplied mill condition for tube, strip and bar that will be formed/welded into conduit and later given the Nb₃Sn reaction heat treatment. | 390 | 800 | 40 | 195 HB | — |
As-welded deposit | Property set for qualifying conduit seam welds; weld metal is undermatched before aging and recovers most of the strength after the 650 °C reaction cycle. | 400 | 760 | 25 | 205 HB | 1.6 % IACS |
Cold worked | Choose for dimensional accuracy and higher as-formed strength in conduit tubing before the reaction heat treatment; reduced ductility for further forming. | 780 | 1,000 | 15 | 30 HRC | 1.6 % IACS |
solution annealed then Nb₃Sn reaction aged (≈650 °C / 200 h, inert or vacuum) | Final in-service condition of magnet conduit — γ′ precipitation during the superconductor reaction cycle gives full strength; must be run in vacuum or oxygen-free argon to avoid SAGBO cracking. | 1,080 | 1,280 | 18 | 39 HRC | — |
cold worked then reaction aged (≈650 °C / 200 h) | Highest-strength condition: cold-work substructure plus γ′ precipitation, used where conduit hoop stress at 4 K is critical; lowest ductility and toughness. | 1,230 | 1,400 | 12 | 43 HRC | 1.8 % IACS |
What is Alloy 908?
Alloy 908 (N09908, Incoloy 908) is an age-hardenable Fe-Ni-Nb controlled-expansion superalloy developed for superconducting magnet conduits, combining a low coefficient of thermal expansion at cryogenic temperature with useful strength and non-magnetic behaviour. Solution-annealed material runs 390 MPa yield, 800 MPa tensile, 40 % elongation and ~195 HB, with strip, bar and tube used for conduit and precision structures. Service is limited to about 600 °C, machinability is poor (score 25) and the alloy is susceptible to SAGBO / strain-age cracking if exposed to air at 550–700 °C; Alloy 718 is the higher-strength alternative when a larger CTE is acceptable. Alloy 908 has a density of 8.17 g/cm³ (0.295 lb/in³), lighter than 72% of nickel alloy grades. It melts at 1,330°C (2,426 °F). Alloy 908 has a yield strength of 390 MPa (56.6 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 51% of nickel alloy grades. Elongation at break is 40% and the elastic modulus is 162 GPa (23.5 Msi).
What is Alloy 908 used for?
- superconducting magnet jacketing
- cryogenic structural members
- precision low-expansion parts
Advantages
- Tough — resists crack growth — 180 MPa·√m (163.8 ksi·√in), better than 95% of nickel alloy grades
Limitations
- Needs corrosion protection — 45/100, worse than 93% of nickel alloy grades
- Low stiffness — 162 GPa (23.5 Msi), worse than 91% of nickel alloy grades
Alloy 908 properties
Typical room-temperature values for Alloy 908-SA; bars are the position among nickel alloy grades.
Physical3
Alloy 908 has a density of 8.17 g/cm³ (0.295 lb/in³), lighter than 72% of nickel alloy grades. It melts at 1,330°C (2,426 °F).
Mechanical14
Alloy 908 has a yield strength of 390 MPa (56.6 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 51% of nickel alloy grades. Elongation at break is 40% and the elastic modulus is 162 GPa (23.5 Msi).
Thermal5
Alloy 908 is rated for continuous service to 600°C (1,112 °F). It conducts heat at 12 W/m·K (6.93 BTU/hr·ft·°F), better than 65% of nickel alloy grades. Thermal expansion is 7.7 µm/m·K (4.28 µin/in·°F).
Electrical3
Alloy 908 conducts electricity at 1.6 % IACS, better than 70% of nickel alloy grades.
Chemical & Environmental3
Corrosion resistance is fair (45/100), worse than 93% of nickel alloy grades.
Sustainability4
Producing a kilogram of Alloy 908 takes about 185 MJ of energy and emits 14 kg of CO₂ — more than 73% of nickel alloy grades. Typical recycled content is 25%.
Manufacturability7
Alloy 908's machinability is poor (25/100, better than 76% of nickel alloy grades); weldability good (60/100); formability good (60/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the nickel alloy family
Yield strength against density for every nickel alloy grade FabDigit runs. Alloy 908 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Alloy 908
Is Alloy 908 easy to machine?
Machine like Alloy 718 — rigid setups, positive-rake carbide or ceramic tooling, low speed / heavy feed, flood coolant; work hardens rapidly and is far harder after the 650 °C age, so finish critical features before aging.
Can Alloy 908 be welded?
GTAW with matching filler, laser and electron-beam welds are all qualified for conduit seams; keep heat input low, use clean argon backing, and avoid air exposure at 550–700 °C to prevent SAGBO/strain-age cracking.
Can Alloy 908 be formed, bent or molded?
Cold form, roll and draw in the solution-annealed condition with interstage anneals at 980–1050 °C; hot work at 1050–1150 °C and finish above 950 °C.
Alloy 908 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Ni | 49 – 51 | 50 |
| Cr | 3.5 – 4.5 | 4 |
| NbNb+Ta | 2.7 – 3.7 | 3 |
| Ti | 1.3 – 1.8 | 1.5 |
| Al | 0.75 – 1.25 | 1 |
| Bgrain-boundary strengthening | 0.01 – 0.02 | 0.01 |
| C | ≤ 0.03 | 0.02 |
| Mn | ≤ 0.3 | 0.1 |
| Si | ≤ 0.15 | 0.08 |
| S | ≤ 0.01 | 0 |
| P | ≤ 0.02 | 0.01 |
| Cu | ≤ 0.2 | 0.05 |
| Febalance, nominally ~40 % | balance |
What surface finishes work on Alloy 908?
Not anodizable — pickle/bright-anneal or mechanically polish; electropolishing gives good vacuum-compatible surfaces for magnet hardware.
Surface treatments FabDigit runs on nickel alloy parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Nickel Alloy Alloy 908 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- N09908
- Trade names
- Incoloy 908
How much does Alloy 908 cost?
Alloy 908 is a high-cost nickel alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Alloy 908 — frequently asked
What is Alloy 908 used for?
Alloy 908 is typically used for superconducting magnet jacketing, cryogenic structural members and precision low-expansion parts. In short: low CTE at cryogenic temperature; magnet-conduit superalloy; age-hardenable, non-magnetic.
What is the yield strength of Alloy 908?
Alloy 908 has a typical yield strength of 390 MPa (56.6 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 51% of nickel alloy grades. Strength varies by condition: see the 5 listed tempers.
Is Alloy 908 easy to machine?
Not especially — machinability is rated poor (25/100, better than 76% of nickel alloy grades). Machine like Alloy 718 — rigid setups, positive-rake carbide or ceramic tooling, low speed / heavy feed, flood coolant; work hardens rapidly and is far harder after the 650 °C age, so finish critical features before aging.
Can Alloy 908 be welded?
Yes — weldability is rated good (60/100). GTAW with matching filler, laser and electron-beam welds are all qualified for conduit seams; keep heat input low, use clean argon backing, and avoid air exposure at 550–700 °C to prevent SAGBO/strain-age cracking.
What surface finishes work on Alloy 908?
Not anodizable — pickle/bright-anneal or mechanically polish; electropolishing gives good vacuum-compatible surfaces for magnet hardware.
Can Alloy 908 be formed, bent or molded?
Cold form, roll and draw in the solution-annealed condition with interstage anneals at 980–1050 °C; hot work at 1050–1150 °C and finish above 950 °C.
What is the maximum service temperature of Alloy 908?
Alloy 908 is rated for continuous use to about 600°C (1,112 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Alloy 908-SA and Alloy 908-CW?
SA is the default condition — the as-supplied mill condition for tube, strip and bar that will be formed/welded into conduit and later given the Nb₃Sn reaction heat treatment. CW: choose for dimensional accuracy and higher as-formed strength in conduit tubing before the reaction heat treatment; reduced ductility for further forming. Yield strength is 390 MPa in SA versus 780 MPa in CW.
How much does Alloy 908 cost?
Alloy 908 is a high-cost nickel alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- INCOLOY alloy 908 technical bulletin — Special Metals Corporation (2004)
- Handbook on Materials for Superconducting Machinery / cryogenic properties of Incoloy 908 — NIST / MIT Plasma Science and Fusion Center (1996)
- UNS N09908 alloy designation — SAE/ASTM Unified Numbering System (2020)
- ITER Material Properties Handbook — conduit alloys — ITER Organization (2013)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.