Nickel Alloy 718-STA (Solution treated and aged)
Heat-treated state · default condition
UNS N07718 · EN 2.4668, NiCr19Fe19Nb5Mo3 · GB GH4169
Default aerospace/oil-field condition: fine grain plus full γ″ hardening for maximum room- and mid-temperature strength.
Values for the STA condition
Other 718 tempers and conditions
718 is listed in 10 conditions; see the grade overview at 718.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Softest supply condition for forming, deep drawing, machining or welding before final aging. | 500 | 965 | 45 | 200 HB | — |
Hot Finished | As-forged or hot-rolled bar bought for re-forging or for parts that will be solution treated and aged by the customer. | 640 | 1,050 | 35 | 24 HRC | 1.4 % IACS |
Additive as-built | Printed condition with columnar grains and Laves phase; adequate for prototypes but anisotropic and low in yield strength until heat treated. | 700 | 1,030 | 27 | 30 HRC | 1.3 % IACS |
As cast | Complex-geometry housings, casings and valve bodies; strength and ductility below wrought due to dendritic segregation and Laves phase. | 880 | 1,030 | 9 | 35 HRC | — |
Cold drawn | Straight, close-tolerance bar and wire with work-hardened strength; use when tight size and moderate strength are needed without aging. | 930 | 1,140 | 18 | 33 HRC | 1.4 % IACS |
STA | Coarser grain, slightly lower tensile but better creep-rupture life, notch ductility and fracture toughness for hot rotating parts. | 1,050 | 1,275 | 21 | 38 HRC | — |
Additive + HIP + homogenize/solution + double age (AMS 5662-equivalent) | Fully densified and homogenized printed parts reaching wrought-like strength; the standard route for flight and downhole AM 718 hardware. | 1,160 | 1,380 | 16 | 43 HRC | 1.4 % IACS |
STADefaultThis page Solution treated and aged | Default aerospace/oil-field condition: fine grain plus full γ″ hardening for maximum room- and mid-temperature strength. | 1,170 | 1,375 | 18 | 42 HRC | — |
Direct aged | Retains hot-work substructure for the highest tensile/LCF strength; used for turbine discs, fasteners and downhole tools where fine grain and strength dominate. | 1,250 | 1,450 | 15 | 45 HRC | — |
Cold worked + aged strip/wire | Cold-rolled or drawn then aged for springs, seals, bellows and fasteners needing the highest hardness in thin sections. | 1,350 | 1,520 | 10 | 47 HRC | 1.4 % IACS |
What is 718-STA?
718-STA is 718 heat treated to STA — default aerospace/oil-field condition: fine grain plus full γ″ hardening for maximum room- and mid-temperature strength. 718-STA has a yield strength of 1,170 MPa (170 ksi) and a tensile strength of 1,375 MPa (199 ksi) — stronger than 98% of nickel alloy grades. Elongation at break is 18% and the elastic modulus is 204 GPa (29.6 Msi). 718-STA has a density of 8.19 g/cm³ (0.296 lb/in³), lighter than 68% of nickel alloy grades. It melts at 1,260°C (2,300 °F).
Advantages
- High strength — 1,170 MPa (170 ksi), better than 98% of nickel alloy grades
Limitations
- Limited formability — 15/100, worse than 81% of nickel alloy grades
- Limited ductility — 18%, worse than 77% of nickel alloy grades
718-STA properties
Typical room-temperature values for 718-STA; 18 are specific to this condition. Other listed values are 718 reference data and may not represent this condition. Bars are the position among nickel alloy grades.
Physical3
718-STA has a density of 8.19 g/cm³ (0.296 lb/in³), lighter than 68% of nickel alloy grades. It melts at 1,260°C (2,300 °F).
Mechanical16
718-STA has a yield strength of 1,170 MPa (170 ksi) and a tensile strength of 1,375 MPa (199 ksi) — stronger than 98% of nickel alloy grades. Elongation at break is 18% and the elastic modulus is 204 GPa (29.6 Msi).
Thermal6
718-STA is rated for continuous service to 650°C (1,202 °F). It conducts heat at 11.4 W/m·K (6.59 BTU/hr·ft·°F), better than 53% of nickel alloy grades. Thermal expansion is 13 µm/m·K (7.22 µin/in·°F).
Electrical3
718-STA conducts electricity at 1.4 % IACS, worse than 65% 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 718-STA takes about 175 MJ of energy and emits 12.5 kg of CO₂ — more than 65% of nickel alloy grades. Typical recycled content is 40%.
Manufacturability8
718-STA's machinability is poor (15/100, worse than 76% of nickel alloy grades); weldability good (65/100); formability poor (15/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 718-STA
Is 718 easy to machine?
Machine in the annealed state where possible; when aged use rigid setups, low speeds (10–30 m/min carbide, 150–300 m/min ceramic), heavy positive feeds to cut under the work-hardened layer and high-pressure coolant.
Can 718 be welded?
Best weldability of the age-hardenable superalloys (GTAW/EBW/laser with ERNiFeCr-2 filler); weld in solution-annealed condition, keep interpass heat low and post-weld solution + double age to restore properties.
Can 718 be formed, bent or molded?
Cold form only in the annealed condition with high forces and frequent intermediate anneals; hot work at 1010–1120 °C and finish above ~950 °C to avoid δ-phase-driven cracking.
What surface finishes work on 718?
Grind/EDM with care for recast layer removal; shot peen critical fillets for fatigue, passivate or electropolish for corrosion service — no anodizing, plating and PVD coatings are used instead.
718 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 |
|---|---|---|
| NiNi + Co | 50 – 55 | 53 |
| Cr | 17 – 21 | 19 |
| NbNb + Ta; γ″ former | 4.75 – 5.5 | 5.1 |
| Mo | 2.8 – 3.3 | 3 |
| Ti | 0.65 – 1.15 | 0.9 |
| Al | 0.2 – 0.8 | 0.5 |
| Co | ≤ 1 | 0.3 |
| C | ≤ 0.08 | 0.04 |
| Mn | ≤ 0.35 | 0.1 |
| Si | ≤ 0.35 | 0.1 |
| Cu | ≤ 0.3 | 0.05 |
| B | ≤ 0.01 | 0 |
| P | ≤ 0.02 | 0.01 |
| S | ≤ 0.02 | 0 |
| Febalance, typically ~18.5 % | balance | — |
718-STA — frequently asked
What is 718-STA used for?
718-STA is typically used for turbine disks, aerospace fasteners, gas turbine casings, oil & gas downhole components and cryogenic tanks. In short: best-weldable age-hardening superalloy; 1170 MPa yield when aged; workhorse turbine disk alloy.
What is the yield strength of 718-STA?
718-STA has a typical yield strength of 1,170 MPa (170 ksi) and a tensile strength of 1,375 MPa (199 ksi) — stronger than 98% of nickel alloy grades. Strength varies by condition: see the 10 listed tempers.
Is 718-STA easy to machine?
Not especially — machinability is rated poor (15/100, worse than 76% of nickel alloy grades). Machine in the annealed state where possible; when aged use rigid setups, low speeds (10–30 m/min carbide, 150–300 m/min ceramic), heavy positive feeds to cut under the work-hardened layer and high-pressure coolant.
Can 718-STA be welded?
Yes — weldability is rated good (65/100). Best weldability of the age-hardenable superalloys (GTAW/EBW/laser with ERNiFeCr-2 filler); weld in solution-annealed condition, keep interpass heat low and post-weld solution + double age to restore properties.
What surface finishes work on 718-STA?
Grind/EDM with care for recast layer removal; shot peen critical fillets for fatigue, passivate or electropolish for corrosion service — no anodizing, plating and PVD coatings are used instead.
Can 718-STA be formed, bent or molded?
Cold form only in the annealed condition with high forces and frequent intermediate anneals; hot work at 1010–1120 °C and finish above ~950 °C to avoid δ-phase-driven cracking.
What is the maximum service temperature of 718-STA?
718-STA is rated for continuous use to about 650°C (1,202 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 718-STA and 718-ANN?
STA is the default condition — default aerospace/oil-field condition: fine grain plus full γ″ hardening for maximum room- and mid-temperature strength. ANN: softest supply condition for forming, deep drawing, machining or welding before final aging. Yield strength is 1,170 MPa in STA versus 500 MPa in ANN.
Sources
- INCONEL alloy 718 Technical Bulletin — Special Metals Corporation (2007)
- AMS 5662/5663/5664 — Nickel Alloy Bars, Forgings and Rings, 718 — SAE International (2020)
- ASTM B637 — Precipitation-Hardening Nickel Alloy Bars, Forgings and Forging Stock — ASTM International (2018)
- ASM Handbook Vol.1 & Vol.19 — Superalloys, Fatigue and Fracture — ASM International (1996)
- MMPDS-17 Nickel Alloy Design Allowables — Battelle/FAA (2022)
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.