Nickel Alloy CMSX-4-AC (Spheroidize annealed)
Heat-treated state
Pick only for process-development, orientation checks or castings that will be solutioned later; dendritic segregation and coarse eutectic γ′ limit properties.
Values for the AC condition
Other CMSX-4 tempers and conditions
CMSX-4 is listed in 4 conditions; see the grade overview at CMSX-4.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ACThis page Spheroidize annealed | Pick only for process-development, orientation checks or castings that will be solutioned later; dendritic segregation and coarse eutectic γ′ limit properties. | 830 | 950 | 8 | 38 HRC | 1.3 % IACS |
Solution heat treated | Intermediate condition: γ′ eutectic fully dissolved and dendrites homogenised, supplied when the customer performs its own coating diffusion + ageing cycle. | 870 | 1,030 | 15 | 39 HRC | 1.3 % IACS |
FHTDefault Fully heat treated: solution 1277–1321 °C + 1140 °C/4 h + 871 °C/20 h,… | Standard flight-hardware condition: uniform cuboidal γ′ ≈0.45 µm giving peak creep-rupture life at 950–1100 °C. | 920 | 1,100 | 12 | 41 HRC | — |
hot isostatic pressing (≈1290 °C / 100–170 MPa) followed by full heat treatment | Choose when casting micro-porosity must be closed for maximum LCF/HCF life and creep scatter reduction in critical blades. | 930 | 1,140 | 16 | 42 HRC | 1.3 % IACS |
What is CMSX-4-AC?
CMSX-4-AC is CMSX-4 heat treated to AC — pick only for process-development, orientation checks or castings that will be solutioned later; dendritic segregation and coarse eutectic γ′ limit properties. CMSX-4-AC has a yield strength of 830 MPa (120 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 88% of nickel alloy grades. Elongation at break is 8% and the elastic modulus is 125 GPa (18.1 Msi). CMSX-4-AC has a density of 8.7 g/cm³ (0.314 lb/in³), heavier than 75% of nickel alloy grades. It melts at 1,320°C (2,408 °F). FHT is the default condition FabDigit quotes; AC is available on request or by drawing note.
Advantages
- High strength — 830 MPa (120 ksi), better than 88% of nickel alloy grades
- High service temperature — 1,000°C (1,832 °F), better than 79% of nickel alloy grades
Limitations
- Poor heat conductor — 7.4 W/m·K (4.28 BTU/hr·ft·°F), worse than 100% of nickel alloy grades
- Low stiffness — 125 GPa (18.1 Msi), worse than 99% of nickel alloy grades
- Low electrical conductivity — 1.3 % IACS, worse than 99% of nickel alloy grades
- High embodied carbon — 22 kg CO₂/kg, worse than 99% of nickel alloy grades
- Limited formability — 3/100, worse than 97% of nickel alloy grades
CMSX-4-AC properties
Typical room-temperature values for CMSX-4-AC; 22 are specific to this condition. Other listed values are CMSX-4 reference data and may not represent this condition. Bars are the position among nickel alloy grades.
Physical3
CMSX-4-AC has a density of 8.7 g/cm³ (0.314 lb/in³), heavier than 75% of nickel alloy grades. It melts at 1,320°C (2,408 °F).
Mechanical14
CMSX-4-AC has a yield strength of 830 MPa (120 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 88% of nickel alloy grades. Elongation at break is 8% and the elastic modulus is 125 GPa (18.1 Msi).
Thermal6
CMSX-4-AC is rated for continuous service to 1,000°C (1,832 °F). It conducts heat at 7.4 W/m·K (4.28 BTU/hr·ft·°F), worse than 100% of nickel alloy grades. Thermal expansion is 11.6 µm/m·K (6.44 µin/in·°F).
Electrical3
CMSX-4-AC conducts electricity at 1.3 % IACS, worse than 99% of nickel alloy grades.
Chemical & Environmental3
Corrosion resistance is fair (45/100), worse than 93% of nickel alloy grades.
Sustainability4
Producing a kilogram of CMSX-4-AC takes about 300 MJ of energy and emits 22 kg of CO₂ — more than 99% of nickel alloy grades. Typical recycled content is 15%.
Manufacturability8
CMSX-4-AC's machinability is not recommended (9/100, worse than 95% of nickel alloy grades); weldability poor (15/100); formability not recommended (3/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with CMSX-4-AC
Is CMSX-4 easy to machine?
Effectively grind/EDM/ECM territory — creep-feed grinding for platforms and shrouds, EDM/ECM or laser for cooling holes; conventional carbide turning gives very low tool life and risks recrystallisation of the strain-hardened surface.
Can CMSX-4 be welded?
Fusion welding is avoided on load-bearing sections (liquation and strain-age cracking, loss of single-crystal epitaxy); repairs use tightly controlled epitaxial laser metal deposition, TLP/diffusion brazing with Ni-Hf-B or Ni-Pd fillers, followed by full re-solution and ageing.
Can CMSX-4 be formed, bent or molded?
Cast-only: Bridgman withdrawal directional solidification with a seed or spiral grain selector, tight thermal gradient control to avoid freckles, stray grains and high-angle boundaries; ceramic-core investment shells for internal cooling passages.
What surface finishes work on CMSX-4?
Grit blast + chemical/thermal core removal, then pack or CVD aluminide, Pt-aluminide or MCrAlY bond coat and EB-PVD/APS YSZ thermal barrier; no anodizing, and any surface work must stay below recrystallisation-inducing strain levels.
CMSX-4 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 |
|---|---|---|
| Cr | 6.2 – 6.8 | 6.5 |
| Co | 9 – 10 | 9.6 |
| Mo | 0.4 – 0.8 | 0.6 |
| W | 6 – 6.8 | 6.4 |
| Ta | 6.2 – 6.8 | 6.5 |
| Resecond-generation SX alloy addition; raises creep strength | 2.8 – 3.2 | 3 |
| Alγ′ former | 5.4 – 5.8 | 5.6 |
| Ti | 0.8 – 1.2 | 1 |
| Hfimproves coating adherence | 0.05 – 0.15 | 0.1 |
| Ckept very low; no grain boundaries to strengthen | ≤ 0.01 | 0 |
| Btrace | ≤ 0.01 | — |
| Zrtrace | ≤ 0.01 | — |
| Slow-sulphur melting for oxidation life | ≤ 5×10⁻⁴ | — |
| Nibalance, approx. 61.7% | balance | — |
CMSX-4-AC — frequently asked
What is CMSX-4-AC used for?
CMSX-4-AC is typically used for single-crystal turbine blades, high-pressure turbine vanes and advanced jet engine hot-section parts. In short: highest creep-rupture strength; single-crystal, rhenium-bearing; grind and EDM only.
What is the yield strength of CMSX-4-AC?
CMSX-4-AC has a typical yield strength of 830 MPa (120 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 88% of nickel alloy grades. Strength varies by condition: see the 4 listed tempers.
Is CMSX-4-AC easy to machine?
Not especially — machinability is rated not recommended (9/100, worse than 95% of nickel alloy grades). Effectively grind/EDM/ECM territory — creep-feed grinding for platforms and shrouds, EDM/ECM or laser for cooling holes; conventional carbide turning gives very low tool life and risks recrystallisation of the strain-hardened surface.
Can CMSX-4-AC be welded?
Not readily — weldability is rated poor (15/100). Fusion welding is avoided on load-bearing sections (liquation and strain-age cracking, loss of single-crystal epitaxy); repairs use tightly controlled epitaxial laser metal deposition, TLP/diffusion brazing with Ni-Hf-B or Ni-Pd fillers, followed by full re-solution and ageing.
What surface finishes work on CMSX-4-AC?
Grit blast + chemical/thermal core removal, then pack or CVD aluminide, Pt-aluminide or MCrAlY bond coat and EB-PVD/APS YSZ thermal barrier; no anodizing, and any surface work must stay below recrystallisation-inducing strain levels.
Can CMSX-4-AC be formed, bent or molded?
Cast-only: Bridgman withdrawal directional solidification with a seed or spiral grain selector, tight thermal gradient control to avoid freckles, stray grains and high-angle boundaries; ceramic-core investment shells for internal cooling passages.
What is the maximum service temperature of CMSX-4-AC?
CMSX-4-AC is rated for continuous use to about 1,000°C (1,832 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between CMSX-4-FHT and CMSX-4-AC?
FHT is the default condition — standard flight-hardware condition: uniform cuboidal γ′ ≈0.45 µm giving peak creep-rupture life at 950–1100 °C. AC: pick only for process-development, orientation checks or castings that will be solutioned later; dendritic segregation and coarse eutectic γ′ limit properties. Yield strength is 920 MPa in FHT versus 830 MPa in AC.
Sources
- CMSX-4 Alloy Data Sheet (single-crystal superalloy) — Cannon-Muskegon Corporation (2020)
- Superalloys 1996 — 'Development of the Rhenium-containing Superalloys CMSX-4 and CM 186 LC' — TMS (1996)
- ASM Handbook Vol. 1: Properties and Selection — Superalloys — ASM International (1990)
- Superalloys: A Technical Guide, 2nd ed. — ASM International (2002)
- Thermophysical and mechanical property compilations for single-crystal Ni-base superalloys — open literature / NIST-type compilations (2018)
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.