Nickel Alloy Alloy 908 CW+Age
Precip hard
UNS N09908 · also Incoloy 908
Highest-strength condition: cold-work substructure plus γ′ precipitation, used where conduit hoop stress at 4 K is critical; lowest ductility and toughness.
Values for the CW+Age 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 |
|---|---|---|---|---|---|---|
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 | — |
CW+AgeThis page 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 CW+Age?
Alloy 908 CW+Age is Alloy 908 in the CW+Age condition — highest-strength condition: cold-work substructure plus γ′ precipitation, used where conduit hoop stress at 4 K is critical; lowest ductility and toughness. Alloy 908 CW+Age has a yield strength of 1,230 MPa (178 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 99% of nickel alloy grades. Elongation at break is 12% and the elastic modulus is 168 GPa (24.4 Msi). Alloy 908 CW+Age 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). SA is the default condition FabDigit quotes; CW+Age is available on request or by drawing note.
Advantages
- High strength — 1,230 MPa (178 ksi), better than 99% of nickel alloy grades
- High electrical conductivity — 1.8 % IACS, better than 81% of nickel alloy grades
Limitations
- Needs corrosion protection — 42/100, worse than 94% of nickel alloy grades
- Low stiffness — 168 GPa (24.4 Msi), worse than 91% of nickel alloy grades
- Limited ductility — 12%, worse than 83% of nickel alloy grades
- Limited formability — 12/100, worse than 83% of nickel alloy grades
- Difficult to weld — 30/100, worse than 78% of nickel alloy grades
Alloy 908 CW+Age properties
Typical room-temperature values for Alloy 908 CW+Age; 22 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 CW+Age 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 CW+Age has a yield strength of 1,230 MPa (178 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 99% of nickel alloy grades. Elongation at break is 12% and the elastic modulus is 168 GPa (24.4 Msi).
Thermal5
Alloy 908 CW+Age is rated for continuous service to 600°C (1,112 °F). It conducts heat at 13 W/m·K (7.51 BTU/hr·ft·°F), better than 71% of nickel alloy grades. Thermal expansion is 7.7 µm/m·K (4.28 µin/in·°F).
Electrical3
Alloy 908 CW+Age conducts electricity at 1.8 % IACS, better than 81% of nickel alloy grades.
Chemical & Environmental3
Corrosion resistance is fair (42/100), worse than 94% of nickel alloy grades.
Sustainability4
Producing a kilogram of Alloy 908 CW+Age 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 CW+Age's machinability is not recommended (14/100, worse than 81% of nickel alloy grades); weldability poor (30/100); formability not recommended (12/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Alloy 908 CW+Age
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 CW+Age — frequently asked
What is Alloy 908 CW+Age used for?
Alloy 908 CW+Age 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 CW+Age?
Alloy 908 CW+Age has a typical yield strength of 1,230 MPa (178 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 99% of nickel alloy grades. Strength varies by condition: see the 5 listed tempers.
Is Alloy 908 CW+Age easy to machine?
Not especially — machinability is rated not recommended (14/100, worse than 81% 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 CW+Age be welded?
Not readily — weldability is rated poor (30/100). 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 CW+Age?
Not anodizable — pickle/bright-anneal or mechanically polish; electropolishing gives good vacuum-compatible surfaces for magnet hardware.
Can Alloy 908 CW+Age 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 CW+Age?
Alloy 908 CW+Age 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.