Age (Inconel 718)
Solution treat & age · Precipitation hardening
Age (Inconel 718) is a precipitation-hardening condition for Inconel 718 (UNS N07718) and Alloy 718 AM.
718 age at a glance
Four scores, each 0–100 against every heat treatment in this catalog. Hardness is derived from the HRC target (20 HRC = 0, 70 HRC = 100) — treatments without a hardness target (anneals, stress relief, HIP, cryo) are not rated. Toughness, dimensional stability and cost are FabDigit's engineering assessment.
What is 718 age?
Age (Inconel 718) is a precipitation-hardening condition for Inconel 718 (UNS N07718) and Alloy 718 AM. It develops strength by solution treatment followed by controlled aging; the final condition, material specification, and acceptance test belong on the drawing.
How it works
Solution treatment dissolves strengthening constituents and establishes a controlled starting microstructure. Cooling retains a supersaturated or otherwise metastable matrix. During the prescribed age, diffusion forms a fine dispersion of strengthening precipitates that obstruct dislocation motion. Temperature and time control precipitate size, spacing, coherency, and grain-boundary chemistry: lower or shorter cycles generally favor peak strength, while overaging trades some strength for toughness, conductivity, or stress-corrosion resistance. The complete route, including the incoming material condition and cooling practice, is therefore part of the engineering definition.
Why specify it
- Produces 36–44 HRC across the stated grade set
- Provides 1240 MPa or greater tensile capability where the cited product condition defines it
- Adds strength through precipitation rather than a carbon-steel temper
- Can be applied after near-net machining with less movement than a severe steel quench
Where it falls short
- Properties depend on alloy, product form, section size, and incoming condition
- Overaging or underaging can miss both strength and corrosion targets
- Solution treatment or quenching may distort thin and asymmetric parts
- A condition name does not replace material heat-lot traceability
The 718 age cycle
Typical furnace parameters from the governing specifications and shop practice; the heat treater sets the exact recipe from the alloy, section size and required result.
| Temperature | 705–730 °C (1,301–1,346 °F) — Primary solution or age temperature window represented by the stages; use the alloy-specific specification. |
|---|---|
| Soak | 8–10 h — At-temperature time; load and section corrections may apply. |
| Cooling | Furnace cool |
| Atmosphere | Vacuum / argon |
| Door to door | 18–24 h — Typical furnace cycle excluding queue and laboratory testing. |
Stages
- 1Use solution-treated material per AMS 5662 or AMS 5663 route
- 2Age at 718 °C (1325 °F) for 8 h
- 3Furnace cool at 56 °C/h to 621 °C (1150 °F), hold to 18 h total, then air cool
What 718 age does to the part
| Hardness | 36–44 HRC (341–415 HB) — Condition and product-form range; Brinell is commonly reported as 341–415 HB. |
|---|---|
| Section affected | The whole section transforms. |
| Tensile strength | 1,240–1,450 MPa — AMS 5663 aged bar/forging requirements are commonly at or above 1,240 MPa, with product form and section limits. |
| Toughness | Retains useful ductility and creep strength to about 650 °C; excessive delta phase or overaging can reduce properties. |
| Distortion | Low risk. The slow two-step age is dimensionally stable; prior forging, welding, and solution treatment dominate movement. |
| Surface after treatment | Bright under clean vacuum or inert gas; air furnaces form adherent oxide scale. |
| Machining sequence | Machine in solution-treated condition where possible; finish grind and inspect after aging. |
Specifications for 718 age
The documents a drawing cites to define this treatment. Each links to a page explaining the standard, its classes and the tests it invokes.
| Standard | Role | Classes used | Status |
|---|---|---|---|
Heat Treatment of Wrought Nickel Alloy and Cobalt Alloy Parts | Governing | — | Active |
Nickel Alloy, Corrosion and Heat-Resistant, Bars, Forgings, and Rings, 52.5Ni - 19Cr - 3.0Mo - 5.1Cb - 0.90Ti - 0.50Al - 18Fe, Consumable Electrode or Vacuum Induction Melted, 1775 °F (968 °C) Solution and Precipitation Heat Treated | Governing | — | Active |
Test and related methods: ASTM E18 (Standard Test Methods for Rockwell Hardness of Metallic Materials), AMS 5662 (Nickel Alloy, Corrosion and Heat-Resistant, Bars, Forgings, and Rings, 52.5Ni - 19Cr - 3.0Mo - 5.1Cb - 0.90Ti - 0.50Al - 18Fe, Consumable Electrode or Vacuum Induction Melted, 1775 °F (968 °C) Solution Heat Treated, Precipitation-Hardenable).
Drawing call-out
ALLOY 718 PER AMS 5663; PRECIPITATION HEAT TREAT PER AMS 2774; UTS 1240 MPa MIN; HARDNESS 36–44 HRC PER ASTM E18Which alloys take 718 age?
Verdict per material family, with the grades that behave differently. Each family links to its datasheets in the material library. Typical grades: Inconel 718 (UNS N07718), Alloy 718 AM.
| Material family | Verdict | Notes |
|---|---|---|
| Yes | Designed for precipitation-hardenable nickel alloys, especially Inconel 718.
| |
| With care | Applicable to qualified AM Inconel 718 after homogenization, solution treatment, or HIP as required.
| |
| No | This alloy category does not use the Inconel 718 aging cycle. | |
| No | This alloy category does not use the Inconel 718 aging cycle. | |
| No | This alloy category does not use the Inconel 718 aging cycle. | |
| No | This alloy category does not use the Inconel 718 aging cycle. | |
| No | This alloy category does not use the Inconel 718 aging cycle. | |
| No | This alloy category does not use the Inconel 718 aging cycle. | |
| No | This alloy category does not use the Inconel 718 aging cycle. | |
| No | This alloy category does not use the Inconel 718 aging cycle. | |
| No | This alloy category does not use the Inconel 718 aging cycle. | |
| No | This alloy category does not use the Inconel 718 aging cycle. | |
| No | This alloy category does not use the Inconel 718 aging cycle. | |
| No | This alloy category does not use the Inconel 718 aging cycle. | |
| No | This alloy category does not use the Inconel 718 aging cycle. | |
| No | This alloy category does not use the Inconel 718 aging cycle. |
Design rules for 718 age
What to decide on the drawing before the part goes to the heat treater.
- Use calibrated furnaces and record the complete two-step aging ramp.The precipitation response depends on the material condition entering the age cycle.
- Account for prior solution condition and grain-boundary delta phase.Uniform temperature and controlled transfer reduce property variation and distortion.
- State the alloy, product specification, final condition, and hardness-test method on the drawing.A condition name alone does not define material pedigree or acceptance sampling.
- Protect finished dimensions and verify critical fits after treatment.Precipitation aging is low-distortion but can still produce measurable contraction or growth.
718 age versus the alternatives
Treatments engineers weigh against 718 age, and when each wins.
| Treatment | Hardness | Toughness | Stability | Cost | Choose it when |
|---|---|---|---|---|---|
718 age this page | 40 | 65 | 82 | $$$$ | — |
| — | 90 | 55 | $$$ | when forming or welding requires a soft solution-treated condition | |
| — | 75 | 65 | $$$$ | when cast or AM porosity must be closed before aging |
Cost, lead time and applications
Relative cost
Age (Inconel 718) is a high-cost treatment ($$$$) relative to the other heat treatments in this catalog.
Heat treatment is priced per lot with a furnace minimum. The exact figure appears on the instant quote once the part is uploaded.
Lead time
| Added lead time | 3–10 working days |
|---|---|
| Furnace time | 18–24 h |
What 718 age is used for
- Aerospace structural hardware
- Precision shafts, fittings, and actuators
- High-strength tooling and fixtures
- Corrosion-resistant mechanical components
718 age — frequently asked
What does 718 age mean?
718 age identifies a controlled solution-treatment and precipitation-aging condition, not a generic furnace temper. The drawing should also identify the alloy specification and acceptance hardness or tensile requirement.
Is this a quench-and-temper treatment?
No in the metallurgical sense. Strength comes primarily from fine precipitates formed during aging rather than tempering quenched carbon-steel martensite.
Will the part distort?
The expected risk is low. Aging is normally more stable than a hard steel quench, but residual stress, section changes, fixtures, and prior solution treatment still matter.
How should hardness be verified?
Use ASTM E18 for Rockwell hardness on a suitable flat section. The expected catalog range is 36–44 HRC; thin sections may require ASTM E384 microindentation and an approved conversion.
Can the condition be assigned after machining?
Usually yes when the starting material and process route are compatible. The purchase order must preserve traceability to the governing product specification and the heat treater must certify the complete cycle.