Alloy 718

Identity and material record

Haynes's room-temperature Alloy 718 sheet tables give 419 MPa yield solution annealed and 1,205 MPa 0.2% yield after mill annealing and aging. The separate plate results are 395 and 1,157 MPa, respectively. The aged cycle uses 8 h at 1325°F, furnace cooling to 1150°F, an 8 h hold and air cooling. These are characterization results. Haynes tensile and fabrication tables

Alloy 718 is an age-hardenable nickel-based alloy identified as UNS N07718. INCONEL and HAYNES identify producer trademarks rather than proof of provenance for any material called 718. Haynes describes its product as a nickel-iron-chromium-niobium-molybdenum-titanium-aluminum alloy. Haynes: HAYNES 718

Special Metals explains that heat treatment precipitates strengthening phases, including gamma prime and gamma double-prime. It emphasizes that the aging constituents must first be appropriately in solution; an aging label alone does not establish the complete metallurgical history. Special Metals: INCONEL alloy 718, heat-treatment discussion

Condition-specific wrought data

Haynes publishes these room-temperature characterization results by product form:

The aged table specifies 1325°F for 8 h, furnace cooling to 1150°F and an 8 h hold, followed by air cooling. Treat these as the producer's characterization data for the stated conditions, not universal purchasing minima. Haynes: tensile and fabrication tables

Heat-treatment instructions need a complete cycle

One Special Metals schedule uses solution annealing at 1700–1850°F, rapid cooling, aging at 1325°F for 8 h, furnace cooling to 1150°F, holding to reach 18 h total aging, then air cooling. The bulletin also gives an alternative higher-temperature solution/aging route. Neither is an instruction to mix selected stages from different schedules. Special Metals: heat-treating schedules

The phrase “total aging time” matters: do not reinterpret it as an additional 18 h hold at the final temperature. Likewise, preserve the distinction between a fixed hold and a total including the cooling stage. Use the governing material/process specification and qualified heat treater to resolve the actual part's cycle.

A fabrication plan should retain incoming condition, previous cold work, solution treatment, cooling route, aging, furnace/load records and required verification. Specify machining allowance and dimensional acceptance at the appropriate stage. A successful hardness reading alone cannot reconstruct an undocumented thermal history or demonstrate every required mechanical property.

Forming and welding

Haynes recommends welding with no preheat beyond normal shop conditions and keeping interpass temperature below 200°F (93°C). It notes that a full solution anneal before aging is often used after forming/welding, with best practice dependent on the fabrication's prior condition. These are product/process recommendations, not a universal joint qualification. Haynes: welding and postweld heat treatment

Qualify joint geometry, filler, shielding, cleanliness, heat input, distortion and required post-treatment for the actual assembly. Review dissimilar-metal joints separately. The parent alloy designation does not determine a suitable filler for every combination or establish that an existing procedure covers a changed condition.

Special Metals describes fabrication commonly beginning with mill-annealed or stress-relieved material, followed by the required final heat treatment. Preserve the actual route rather than treating all delivered 718 as ready for the same machining and joining operation. Special Metals: fabrication condition

Elevated-temperature service

Haynes describes its 718 component applications as normally limited to about 1200°F (650°C) and discusses the decline in relative creep-strength advantage around that range. This is manufacturer selection guidance; it does not establish a permissible load or lifetime at the stated temperature. Haynes: principal features and creep discussion

For a hot component, state continuous temperature, excursions, stress, dwell, cycles and environment. Distinguish tensile strength from creep, rupture and oxidation behavior. Include local stress, joints and any exposure capable of changing the aged microstructure. A furnace atmosphere or process stream also needs its own compatibility assessment.

Additive manufacturing is a separate property basis

EOS's NickelAlloy IN718 datasheet is organized by machine/process combination, including an EOS M 290, 40 µm section. It distinguishes as-manufactured and heat-treated tensile results and horizontal/vertical specimens. It also explains orientation effects on surface roughness. Those distinctions belong in an additive-part material record. EOS: NickelAlloy IN718 material datasheet

Do not transfer a wrought-plate table to a printed component or treat powder chemistry as proof of part properties. Record powder specification/history, system, parameter set, layer thickness, orientation, heat treatment and finishing. Qualify representative features and inspect internal and surface quality to the finished-part requirements.

An apparently matching alloy designation can therefore require different acceptance evidence after a manufacturing-route change. Resolve that evidence before approving a substitution between wrought, welded and additively manufactured components.

Purchasing and release

Retain the product identity and heat/lot traceability with the condition, material standard, process requirements and certificate. Connect those records to the drawing, actual fabrication history and final dimensional/mechanical inspections. Where the application needs creep, fatigue, corrosion or regulatory evidence, define the exact requirement rather than inferring it from an application list.

Special Metals prints SMC-045, ©2007 (September 2007). The Haynes brochure is identified as H-3055D, ©2020, despite its 2023 upload path. The EOS document contains multiple machine/process sections with their own identifiers; retain the relevant section rather than assigning one search-engine date to all data. Confirm the required current documents and standards when ordering.

Grades, tempers and conditions