Nickel Alloy 718Plus-STA (Solution treated and aged)
Heat-treated state · default condition
UNS N07716 · also Allvac 718Plus
Standard sub-solvus fine-grain heat treatment — the default condition for discs, rings, shafts and fasteners needing maximum tensile/fatigue strength to 704 °C.
Values for the STA condition
Other 718Plus tempers and conditions
718Plus is listed in 6 conditions; see the grade overview at 718Plus.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest supplied condition for machining, cold forming and welding before the customer ages the part. | 500 | 950 | 50 | 22 HRC | — |
As-welded deposit | Condition of the joint before PWHT; useful for fit-up and leak-tight assemblies, but strength must be recovered by a post-weld solution + double age. | 630 | 980 | 25 | 28 HRC | 1.5 % IACS |
Super-solvus solution (1010–1038 °C) + double age | Coarse-grain version for creep- and dwell-crack-growth-limited hot sections; trades some tensile strength and LCF life for creep/rupture capability. | 1,130 | 1,380 | 14 | 42 HRC | — |
AM (L-PBF/EB-PBF) + HIP + solution + double age | Additively manufactured parts after HIP closure of porosity and full aging; slightly lower ductility and more property scatter than wrought forgings. | 1,150 | 1,400 | 14 | 43 HRC | 1.4 % IACS |
STADefaultThis page Solution treated and aged | Standard sub-solvus fine-grain heat treatment — the default condition for discs, rings, shafts and fasteners needing maximum tensile/fatigue strength to 704 °C. | 1,220 | 1,480 | 17 | 44 HRC | — |
Direct aged | Retains forging warm-work substructure for the highest yield strength and tensile properties in fasteners and small forgings; lowest ductility of the aged conditions. | 1,290 | 1,520 | 14 | 46 HRC | — |
What is 718Plus-STA?
718Plus-STA is 718Plus heat treated to STA — standard sub-solvus fine-grain heat treatment — the default condition for discs, rings, shafts and fasteners needing maximum tensile/fatigue strength to 704 °C. 718Plus-STA has a yield strength of 1,220 MPa (177 ksi) and a tensile strength of 1,480 MPa (215 ksi) — stronger than 98% of nickel alloy grades. Elongation at break is 17% and the elastic modulus is 197 GPa (28.6 Msi). 718Plus-STA has a density of 8.22 g/cm³ (0.297 lb/in³), lighter than 60% of nickel alloy grades. It melts at 1,260°C (2,300 °F).
Advantages
- High strength — 1,220 MPa (177 ksi), better than 98% of nickel alloy grades
Limitations
- Limited formability — 10/100, worse than 85% of nickel alloy grades
- Limited ductility — 17%, worse than 78% of nickel alloy grades
718Plus-STA properties
Typical room-temperature values for 718Plus-STA; 14 are specific to this condition. Other listed values are 718Plus reference data and may not represent this condition. Bars are the position among nickel alloy grades.
Physical3
718Plus-STA has a density of 8.22 g/cm³ (0.297 lb/in³), lighter than 60% of nickel alloy grades. It melts at 1,260°C (2,300 °F).
Mechanical16
718Plus-STA has a yield strength of 1,220 MPa (177 ksi) and a tensile strength of 1,480 MPa (215 ksi) — stronger than 98% of nickel alloy grades. Elongation at break is 17% and the elastic modulus is 197 GPa (28.6 Msi).
Thermal6
718Plus-STA is rated for continuous service to 704°C (1,299 °F). It conducts heat at 10.9 W/m·K (6.3 BTU/hr·ft·°F), worse than 64% of nickel alloy grades. Thermal expansion is 12.8 µm/m·K (7.11 µin/in·°F).
Electrical3
718Plus-STA conducts electricity at 1.4 % IACS, worse than 65% of nickel alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (72/100), worse than 71% of nickel alloy grades.
Sustainability4
Producing a kilogram of 718Plus-STA takes about 215 MJ of energy and emits 14.5 kg of CO₂ — more than 84% of nickel alloy grades. Typical recycled content is 35%.
Manufacturability8
718Plus-STA's machinability is not recommended (12/100, worse than 86% of nickel alloy grades); weldability good (55/100); formability not recommended (10/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 718Plus-STA
Is 718Plus easy to machine?
Machine soft in the annealed condition where possible; when aged use rigid setups, positive-rake carbide or SiAlON ceramic at low speed/high feed with heavy flood coolant, and avoid dwelling to prevent work-hardened glaze.
Can 718Plus be welded?
GTAW/EB/inertia welding with matching 718Plus filler is practical — the γ′ kinetics give better resistance to strain-age (PWHT) cracking than Waspaloy; weld in the annealed condition and follow with full solution + double age.
Can 718Plus be formed, bent or molded?
Hot forge in the ~950–1120 °C window with sub-solvus finishing to control grain size; cold forming only in the annealed state with interstage anneals due to rapid work hardening.
What surface finishes work on 718Plus?
Grit-blast and pickle or electropolish to remove Al/Ti-rich forging scale; not anodizable — use shot peening for fatigue life and aluminide or thermal-spray coatings for hot-gas surfaces.
718Plus 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 | 17 – 21 | 18 |
| Cokey addition vs Alloy 718 | 8 – 10 | 9 |
| Fe | 8 – 10 | 9.5 |
| Nbγ′/γ″ former | 5.2 – 5.8 | 5.45 |
| Mo | 2.5 – 3.1 | 2.75 |
| Wsolid-solution strengthener | 0.8 – 1.4 | 1 |
| Alraises Al/Ti ratio → γ′ dominant | 1.2 – 1.7 | 1.45 |
| Ti | 0.5 – 1 | 0.7 |
| C | 0.01 – 0.05 | 0.02 |
| Bgrain-boundary strengthener | 0 – 0.01 | 0.01 |
| Pdeliberate addition, improves creep | 0.01 – 0.02 | 0.01 |
| Mn | ≤ 0.35 | 0.05 |
| Si | ≤ 0.35 | 0.1 |
| S | ≤ 0.02 | 0 |
| Cu | ≤ 0.3 | 0.05 |
| Nibalance, nominally ~52% | balance | — |
718Plus-STA — frequently asked
What is 718Plus-STA used for?
718Plus-STA is typically used for turbine disks, compressor components, aerospace rotating hardware and high-temperature fasteners. In short: 55 °C above Alloy 718; weldable disk superalloy; better than Waspaloy fabricability.
What is the yield strength of 718Plus-STA?
718Plus-STA has a typical yield strength of 1,220 MPa (177 ksi) and a tensile strength of 1,480 MPa (215 ksi) — stronger than 98% of nickel alloy grades. Strength varies by condition: see the 6 listed tempers.
Is 718Plus-STA easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 86% of nickel alloy grades). Machine soft in the annealed condition where possible; when aged use rigid setups, positive-rake carbide or SiAlON ceramic at low speed/high feed with heavy flood coolant, and avoid dwelling to prevent work-hardened glaze.
Can 718Plus-STA be welded?
Yes — weldability is rated good (55/100). GTAW/EB/inertia welding with matching 718Plus filler is practical — the γ′ kinetics give better resistance to strain-age (PWHT) cracking than Waspaloy; weld in the annealed condition and follow with full solution + double age.
What surface finishes work on 718Plus-STA?
Grit-blast and pickle or electropolish to remove Al/Ti-rich forging scale; not anodizable — use shot peening for fatigue life and aluminide or thermal-spray coatings for hot-gas surfaces.
Can 718Plus-STA be formed, bent or molded?
Hot forge in the ~950–1120 °C window with sub-solvus finishing to control grain size; cold forming only in the annealed state with interstage anneals due to rapid work hardening.
What is the maximum service temperature of 718Plus-STA?
718Plus-STA is rated for continuous use to about 704°C (1,299 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 718Plus-STA and 718Plus-AN?
STA is the default condition — standard sub-solvus fine-grain heat treatment — the default condition for discs, rings, shafts and fasteners needing maximum tensile/fatigue strength to 704 °C. AN: softest supplied condition for machining, cold forming and welding before the customer ages the part. Yield strength is 1,220 MPa in STA versus 500 MPa in AN.
Sources
- ATI Allvac 718Plus Alloy Technical Data Sheet — ATI (Allegheny Technologies) (2020)
- Superalloys 2004 — 'Development of a New 700 °F Capable Nickel Base Superalloy' (Cao & Kennedy) — TMS (2004)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- AMS specifications for 718Plus bar, forgings and rings (nickel alloy, corrosion & heat resistant) — SAE International (2018)
- Superalloy physical/mechanical property compilations (VIM+VAR wrought Ni-Cr-Fe) — MMPDS / Special Metals comparative data (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.