AMS 5663 (Alloy 718): Specifications, Heat Treatment, Composition

AMS 5663 defines the aerospace-grade condition of Nickel-Chromium alloy Alloy 718 supplied in bars, forgings and rings that have been solution treated and precipitation-aged to produce the high-strength, corrosion-resistant condition commonly specified in critical aerospace, power and oil & gas components. In practical terms: when a drawing or purchase order calls out AMS 5663, the purchaser expects Alloy 718 in the precipitation-hardened (aged) state with the composition, heat treatment, mechanical properties, and test requirements described in the AMS document — i.e., a ready-to-use high-strength superalloy with superior creep resistance and elevated-temperature performance.

What is ams5663 material?

AMS 5663 is an Aerospace Material Specification that covers corrosion- and heat-resistant nickel alloy (Alloy 718) in the forms of bars, forgings, flash-welded rings and stock intended for further forging or ring production. The AMS wording sets the permitted compositions, melting practices, required heat-treatment cycles, mechanical property minima, permitted product forms, and inspection/test requirements for items delivered in the aged (precipitation-hardened) condition. Suppliers and purchasers use AMS 5663 to ensure consistent performance and traceability for safety-critical parts.

Nomenclature, equivalents and UNS designation

• Common names: Alloy 718, Inconel 718 (trade name), sometimes seen as Nickel 718.

• UNS designation: N07718 (the common UNS for Alloy 718).

• AMS relationship: AMS 5662 commonly denotes solution-treated Alloy 718 (annealed/soft form) whereas AMS 5663 denotes the solution treated and precipitation-hardened (aged) form ready for service. Many mills and distributors will list both AMS 5662 (soft) and AMS 5663 (aged) as separate stock conditions.

Chemical composition

The composition ranges demanded by AMS 5663 align with classic Alloy 718 chemistry: a nickel-rich matrix strengthened by niobium (columbium), titanium, aluminum and supported by chromium and molybdenum. Below is a concise, industry-standard composition table (expressed as weight percent).

(Values are industry-standard ranges quoted by AMS/metal suppliers and datasheets; see official AMS document and mill datasheets for exact tolerances).

Notes on composition: niobium (Nb) and titanium are the primary precipitation hardening elements that form coherent γ″ (Ni₃Nb) and γ′ (Ni₃(Al,Ti)) precipitates; aluminum and titanium promote γ′; Nb (γ″) is the dominant hardening phase in 718. Excessive delta (δ) phase or Laves intermetallics (from improper melting or excessive local segregation) can reduce toughness and ductility. These microstructural phenomena are central to heat-treatment controls and forging practices.

Heat treatment, microstructure and metallurgy

AMS 5663 requires solution treatment followed by a controlled aging (precipitation) cycle to produce the final high-strength condition. A commonly referenced heat treatment (industry practice for AMS 5663 bars) is:

• Solution treat: ~1725–1775 °F (940–968 °C) — per AMS cycle specifics.

• Aging: multi-step aging such as 1325 °F (718 °C) for 8 hours, furnace cool at 100 °F/hr to 1150 °F (621 °C), hold 8 hours, then air cool — this produces the γ″ precipitation distribution targeted by AMS 5663. Exact temperatures, hold times and cooling rates are prescribed in the AMS text and may vary for specific product forms or special requirements.

Microstructure: the optimized aging produces a fine dispersion of γ″ (Ni₃Nb) and some γ′ which obstruct dislocation motion and give Alloy 718 its high strength up to intermediate high temperatures. Over-aging or improper thermal history can encourage δ-phase formation (Ni₃Nb orthorhombic) at grain boundaries — useful for grain stabilization in some contexts but detrimental if it reduces creep resistance or toughness. Melting practice (vacuum induction melting or consumable-electrode remelting) and hot-work/forging schedules must control segregation and inclusions to meet AMS testing criteria.

Mechanical properties

AMS 5663 states mechanical property requirements appropriate for aged Alloy 718. Practical, representative minima (room temperature) for fully aged AMS 5663 material are roughly in these ranges:

Specific numbers vary by product form, cross-section and testing standard; mills publish guaranteed minimums based on AMS test coupons and size-adjusted tables. For high accuracy on guaranteed minima for a given diameter or forging, consult the AMS text and supplier test certificates.

High-temperature behavior: Alloy 718 retains significant strength to ~650–700 °C (1200–1300 °F) and exhibits excellent creep-rupture resistance relative to many other nickel alloys in the same temperature band — which is why AMS 5663 718 is preferred for rotating and static structural parts operating in elevated-temperature service.

Fabrication, machining and joining considerations

Machinability: aged Alloy 718 (AMS 5663 condition) is much harder and work-hardens quickly compared to annealed 718 (AMS 5662). For complex machining it is common to machine most features in the solution-treated (soft) condition then perform the AMS 5663 aging cycle after final machining to achieve final dimensions and properties. If machining is performed in the aged condition, use sharp carbide tools, reduced depth of cut, and controlled feeds to manage work-hardening.

Welding and joining: Alloy 718 is generally weldable using common methods (TIG/GTAW, electron beam, laser) and responds well to post-weld heat treatments, but welded zones require attention to avoid segregation and cracking. For precipitation-strengthened grades, welding in the fully aged condition can create softened weld zones; post-weld solution and aging may be required depending on design intent.

Forming & forging: hot-work at recommended forging temperatures and controlled cooling is essential to avoid excessive precipitation before final solution/aging. AMS specifies acceptable forms and any special requirements for flash-welded rings and forgings.

Corrosion, oxidation resistance and service limits

Alloy 718 is not the most oxidation-resistant nickel alloy (compared with, for example, Alloy 625 or 600 at extreme temperatures) but presents excellent general corrosion resistance and good oxidation resistance up to moderate high temperatures due to chromium content and stable oxide formation. Its strength retention and creep resistance at intermediate high temperatures (≈ 600–700 °C) makes it highly suitable for rotating shafts, turbine discs, springs, fasteners and subsea components where combined mechanical and environmental demands exist. For extremely oxidizing or carburizing environments, other nickel alloys may be preferable.

Typical applications and industry sectors

AMS 5663 Alloy 718 is widely used where a combination of high static and cyclic strength and corrosion resistance are required:

• Aerospace: turbine discs, shafts, engine mounts, high-temperature fasteners and gas-path components.

• Oil & Gas: high-pressure valves, downhole tool components, connectors where high strength and sulfide stress-cracking (SSC) resistance are critical.

• Power generation: steam turbine components, heat exchangers in certain temperature bands.

• Nuclear & industrial: springs, fasteners, rotors and structural elements in aggressive or elevated-temperature service.

These sectors specify AMS 5663 to ensure repeatable performance, traceability and supplier accountability.

Quality control, testing, traceability and purchasing notes

Typical tests & documentation required by AMS 5663 include:

• Chemical analysis (heat/certificate level).

• Mechanical tests (tensile, yield, elongation) on representative coupons.

• Hardness checks.

• Microstructural etch and inclusion/segregation checks where specified.

• Melt practice documentation (VIM/VAR or consumable-electrode remelt cycles) and nondestructive testing if requested.

Purchasing tips:

• Always specify AMS 5663 on the PO when the purchaser requires the aged, ready-to-use condition and include required test reports, special heat treatment or secondary operations.

• For critical rotating or safety parts, require mill melt documentation and traceability to a single melt/heat.

• If tight dimensional tolerances are needed after the aging cycle, consider specifying machining allowances or asking the mill to supply in AMS 5662 (solutionized) with buyer control of the final aging.

Procurement, stock forms and common sizes

Suppliers commonly stock AMS 5663 material in:

• Round bars/rods (multiple diameters),

• Forgings (ring forgings up to the allowed cross-section),

• Flash-welded rings and stock for further forging.
  Typical diameters vary by mill; most distributors list both AMS 5662 and AMS 5663 bars. DFARS, NACE or other procurement clauses may be attached depending on end-use (oil & gas material compliance, etc.). Always request the seller’s specification declaration and test certificate referencing AMS 5663.

Comparative notes (AMS 5662 vs AMS 5663; other specs)

• AMS 5662 — Alloy 718 solution treated (soft) condition (commonly called annealed), easier to machine/form.

• AMS 5663 — Alloy 718 solution treated and aged (precipitation-hardened) condition, higher strength and hardness, delivered as a finished material for service.

Other standards and designations (API, ASTM, commercial mill specs) may reference 718 compositions or conditions, but when aerospace-level traceability and heat treatment control are required, AMS 5663 remains the canonical spec for the aged condition.

Frequently asked questions

1. What is AMS 5663?
   AMS 5663 is the SAE Aerospace Material Specification that prescribes composition, product forms and the solution + precipitation (aging) heat-treatment condition for Alloy 718 supplied as bars, forgings and rings.

2. Is AMS 5663 the same as Inconel 718?
   AMS 5663 specifies Alloy 718 in the aged condition — yes, it refers to Inconel/Alloy 718 but specifically in the precipitation-hardened form.

3. What are typical mechanical properties for AMS 5663?
   Fully aged AMS 5663 718 commonly shows tensile strengths in the range of ~1200–1300 MPa and yield strengths near or above 1000 MPa, depending on section size. Check the AMS text and supplier certificates for guaranteed minima.

4. Why buy AMS 5663 material instead of annealed 718?
   Buying AMS 5663 saves time: the material arrives already aged to the specified mechanical properties and is ready for service or final machining, eliminating the buyer’s need to perform a controlled aging cycle.

5. Can AMS 5663 be welded?
   Yes; Alloy 718 is weldable but welding strategies and post-weld heat treatment should be planned to manage softened weld zones and maintain mechanical integrity.

6. What industries use AMS 5663 718 most?
   Aerospace, oil & gas, power generation and heavy industrial sectors where combined strength and corrosion resistance at elevated temperatures are required.

7. What’s the difference between AMS 5662 and AMS 5663?
   AMS 5662 is the solution-treated (soft) condition; AMS 5663 is the solution-treated and precipitation-aged (hard) condition.

8. How does AMS 5663 control microstructure?
   AMS specifies melting practice, solution treatment and aging cycles to produce the desired γ″/γ′ precipitate distribution and to limit detrimental phases (Laves, δ) and segregation.

9. Are there standard test certificates with AMS 5663 deliveries?
   Yes — chemical analysis, mechanical test reports, heat/melt identification and any requested NDE or special tests should accompany AMS 5663 shipments per purchaser specification.

10. Where can I obtain the official AMS 5663 document?
    The SAE international standards store publishes AMS 5663; authorized distributors and standards libraries provide the full specification (purchase or institutional access may be required).

Practical procurement checklist

• Specify AMS 5663 on PO if aged Alloy 718 is required.

• Require full material test reports (MTRs) with heat number linkage.

• State any additional clauses (NACE MR0175, DFARS, customer QA flow-downs).

• If tight dimensions are required after aging, agree machining allowances or request solutionized supply (AMS 5662) and buyer-performed aging.

• Confirm melt practice (VIM/VAR or consumable electrode remelt) per application criticality.

Closing remarks

AMS 5663 remains the authoritative aerospace specification for precipitation-hardened Alloy 718 bars and forgings. It packages chemistry, melting practice, heat treatment, test methods and delivery conditions into a single supplier/purchaser agreement so that critical rotating and elevated-temperature components perform reliably in the field. When specifying or ordering, treat AMS 5663 as both a metallurgical and quality-assurance document: the details in the spec control how the alloy is melted, treated, tested and certified.

Authoritative references

• SAE AMS 5663 — Nickel Alloy, Corrosion and Heat-Resistant, Bars, Forgings, and Rings (SAE International)
• SAE AMS 5663P (PDF) — Full text (standards PDF copy for technical reference)
• Inconel — Wikipedia (overview of Inconel family and Alloy 718 / N07718)
• Righton-Blackburns — AMS 5663 Alloy 718 datasheet (composition and specification notes)