Nickel Alloy Nimonic 115 ST+A
Precip hard · default condition
UNS N07115 · EN 2.4662
ST+A = solution treated 1190 °C/1.5 h AC + aged 1100 °C/6 h AC
Standard supplied condition for wrought bar, billet and turbine forgings — maximum creep-rupture strength to ~1000 °C.
Values for the ST+A condition
Other Nimonic 115 tempers and conditions
Nimonic 115 is listed in 4 conditions; see the grade overview at Nimonic 115.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest practical condition, supplied when the customer will machine then age in-house. | 600 | 960 | 33 | 25 HRC | — |
As-forged / as-hot-rolled | Mill product form for re-forging or for parts that will receive the full ST+A cycle afterwards. | 720 | 1,100 | 20 | 32 HRC | 1.2 % IACS |
Investment cast, solution treated and aged | Equiaxed investment-cast blades/vanes: better creep life at temperature but lower ductility than wrought. | 800 | 1,030 | 9 | 37 HRC | — |
ST+ADefaultThis page Solution treated 1190 °C/1.5 h AC + aged 1100 °C/6 h AC | Standard supplied condition for wrought bar, billet and turbine forgings — maximum creep-rupture strength to ~1000 °C. | 865 | 1,240 | 25 | 39 HRC | — |
What is Nimonic 115 ST+A?
Nimonic 115 ST+A is Nimonic 115 in the ST+A condition — standard supplied condition for wrought bar, billet and turbine forgings — maximum creep-rupture strength to ~1000 °C. Nimonic 115 ST+A has a yield strength of 865 MPa (125 ksi) and a tensile strength of 1,240 MPa (180 ksi) — stronger than 92% of nickel alloy grades. Elongation at break is 25% and the elastic modulus is 224 GPa (32.5 Msi). Nimonic 115 ST+A has a density of 7.85 g/cm³ (0.284 lb/in³), lighter than 95% of nickel alloy grades. It melts at 1,290°C (2,354 °F).
Advantages
- High strength — 865 MPa (125 ksi), better than 92% of nickel alloy grades
Limitations
- Low electrical conductivity — 1.2 % IACS, worse than 99% of nickel alloy grades
- Difficult to weld — 8/100, worse than 99% of nickel alloy grades
- Difficult to machine — 10/100, worse than 93% of nickel alloy grades
- Limited formability — 8/100, worse than 87% of nickel alloy grades
- High embodied carbon — 15 kg CO₂/kg, worse than 87% of nickel alloy grades
Nimonic 115 ST+A properties
Typical room-temperature values for Nimonic 115 ST+A; 13 are specific to this condition. Other listed values are Nimonic 115 reference data and may not represent this condition. Bars are the position among nickel alloy grades.
Physical3
Nimonic 115 ST+A has a density of 7.85 g/cm³ (0.284 lb/in³), lighter than 95% of nickel alloy grades. It melts at 1,290°C (2,354 °F).
Mechanical15
Nimonic 115 ST+A has a yield strength of 865 MPa (125 ksi) and a tensile strength of 1,240 MPa (180 ksi) — stronger than 92% of nickel alloy grades. Elongation at break is 25% and the elastic modulus is 224 GPa (32.5 Msi).
Thermal6
Nimonic 115 ST+A is rated for continuous service to 980°C (1,796 °F). It conducts heat at 10.7 W/m·K (6.18 BTU/hr·ft·°F), worse than 68% of nickel alloy grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
Nimonic 115 ST+A conducts electricity at 1.2 % IACS, worse than 99% of nickel alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (78/100), better than 51% of nickel alloy grades.
Sustainability4
Producing a kilogram of Nimonic 115 ST+A takes about 210 MJ of energy and emits 15 kg of CO₂ — more than 81% of nickel alloy grades. Typical recycled content is 30%.
Manufacturability8
Nimonic 115 ST+A's machinability is not recommended (10/100, worse than 93% of nickel alloy grades); weldability not recommended (8/100); formability not recommended (8/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Nimonic 115 ST+A
Is Nimonic 115 easy to machine?
Extremely difficult in the aged condition — use rigid setups, positive-rake carbide or whisker-reinforced ceramic inserts, low surface speed with high feed, flood coolant and constant depth of cut to avoid work-hardened glaze; grinding and EDM are common for blade features.
Can Nimonic 115 be welded?
Essentially non-weldable by conventional fusion methods due to ~5 % Al + ~4 % Ti (strain-age/liquation cracking); repairs use vacuum brazing, wide-gap brazing or highly controlled preheated laser/EB processes with post-weld ST+A.
Can Nimonic 115 be formed, bent or molded?
Hot work only, in a narrow 1050–1160 °C window with rapid reheating; cold forming is impractical, and investment casting is the usual route for complex airfoils.
What surface finishes work on Nimonic 115?
Typically shot-peened and coated with pack/vapour aluminide or MCrAlY for hot-section service; polishes well but passivation/anodizing is not applicable.
Nimonic 115 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 |
|---|---|---|
| C | 0.12 – 0.2 | 0.15 |
| Cr | 14 – 16 | 14.3 |
| Co | 13 – 15.5 | 13.2 |
| Mo | 3 – 5 | 3.3 |
| Alprincipal γ′ former | 4.5 – 5.5 | 4.9 |
| Tiprincipal γ′ former | 3.5 – 4.5 | 3.7 |
| Fe | ≤ 1 | 0.5 |
| Mn | ≤ 1 | — |
| Si | ≤ 1 | — |
| Cu | ≤ 0.2 | — |
| Zrgrain-boundary strengthener | 0.02 – 0.1 | 0.04 |
| Bhigh B level as listed in ASM superalloy tables; some specs limit to ≤0.02 | 0.01 – 0.2 | 0.16 |
| S | ≤ 0.02 | — |
| Nibalance, ~60 % | balance | — |
Nimonic 115 ST+A — frequently asked
What is Nimonic 115 ST+A used for?
Nimonic 115 ST+A is typically used for turbine blades, hot-section fasteners and high-temperature discs. In short: highest gamma-prime Nimonic; service to 980 °C; essentially non-weldable superalloy.
What is the yield strength of Nimonic 115 ST+A?
Nimonic 115 ST+A has a typical yield strength of 865 MPa (125 ksi) and a tensile strength of 1,240 MPa (180 ksi) — stronger than 92% of nickel alloy grades. Strength varies by condition: see the 4 listed tempers.
Is Nimonic 115 ST+A easy to machine?
Not especially — machinability is rated not recommended (10/100, worse than 93% of nickel alloy grades). Extremely difficult in the aged condition — use rigid setups, positive-rake carbide or whisker-reinforced ceramic inserts, low surface speed with high feed, flood coolant and constant depth of cut to avoid work-hardened glaze; grinding and EDM are common for blade features.
Can Nimonic 115 ST+A be welded?
Not readily — weldability is rated not recommended (8/100). Essentially non-weldable by conventional fusion methods due to ~5 % Al + ~4 % Ti (strain-age/liquation cracking); repairs use vacuum brazing, wide-gap brazing or highly controlled preheated laser/EB processes with post-weld ST+A.
What surface finishes work on Nimonic 115 ST+A?
Typically shot-peened and coated with pack/vapour aluminide or MCrAlY for hot-section service; polishes well but passivation/anodizing is not applicable.
Can Nimonic 115 ST+A be formed, bent or molded?
Hot work only, in a narrow 1050–1160 °C window with rapid reheating; cold forming is impractical, and investment casting is the usual route for complex airfoils.
What is the maximum service temperature of Nimonic 115 ST+A?
Nimonic 115 ST+A is rated for continuous use to about 980°C (1,796 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Nimonic 115 ST+A and Nimonic 115-ST?
ST+A is the default condition — standard supplied condition for wrought bar, billet and turbine forgings — maximum creep-rupture strength to ~1000 °C. ST: softest practical condition, supplied when the customer will machine then age in-house. Yield strength is 865 MPa in ST+A versus 600 MPa in ST.
Sources
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys (superalloy data) — ASM International (1990)
- Superalloys: A Technical Guide, 2nd ed. — ASM International (2002)
- Nimonic alloy series technical data — Special Metals Corporation (2020)
- UNS N07115 / Werkstoff 2.4662 designation listings — SAE/ASTM DS-56 & DIN (2019)
- GH115/Nimonic 115 (2025)
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.