Nickel Alloy Alloy 908-SA (Solution annealed)
Heat-treated state · default condition
UNS N09908 · also Incoloy 908
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.
Values for the SA condition
Other Alloy 908 tempers and conditions
Alloy 908 is listed in 5 conditions; see the grade overview at Alloy 908.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SADefaultThis page 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-SA?
Alloy 908-SA is Alloy 908 heat treated to SA — 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. Alloy 908-SA 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). Alloy 908-SA 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).
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-SA properties
Typical room-temperature values for Alloy 908-SA; 13 are specific to this condition. Other listed values are Alloy 908 reference data and may not represent this condition. Bars are the position among nickel alloy grades.
Physical3
Alloy 908-SA 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-SA 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-SA 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-SA 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-SA 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-SA'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. Confirm any required mill or lot documentation when quoting.
Working with Alloy 908-SA
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.
What surface finishes work on Alloy 908?
Not anodizable — pickle/bright-anneal or mechanically polish; electropolishing gives good vacuum-compatible surfaces for magnet hardware.
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 | — |
Alloy 908-SA — frequently asked
What is Alloy 908-SA used for?
Alloy 908-SA 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-SA?
Alloy 908-SA 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-SA 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-SA 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-SA?
Not anodizable — pickle/bright-anneal or mechanically polish; electropolishing gives good vacuum-compatible surfaces for magnet hardware.
Can Alloy 908-SA 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-SA?
Alloy 908-SA 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.