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Incoloy A-286 (UNS S66286): A Cost-Effective Iron-Base Superalloy for High-Strength, Elevated-Temperature Applications
Material designation: Incoloy A-286 / A-286
UNS designation: S66286
European material number: 1.4980
Material classification: Iron-base, austenitic, precipitation-hardening superalloy
Nominal alloy system: Fe–25Ni–15Cr
Primary strengthening mechanism: γ′ precipitation strengthening
Commonly referenced specifications: AMS 5737, AMS 5732, ASTM A453 Grade 660, and other product-specific specifications, as applicable
Density: Approximately 7.93 g/cm³
Indicative long-term service range: Commonly associated with applications up to approximately 650–700°C, subject to stress, exposure duration, material condition, and design requirements
Primary applications: High-temperature fasteners, selected aerospace components, springs, forgings, and other load-bearing parts requiring a balance of strength, fabricability, and cost.
Incoloy A-286 is an iron-base, austenitic precipitation-hardening superalloy developed for components that require high mechanical strength, useful oxidation and corrosion resistance, and reliable performance under elevated-temperature conditions.
Unlike conventional nickel-base superalloys, A-286 uses iron as its principal matrix element while retaining approximately 24–27 wt.% nickel and 13.5–16.0 wt.% chromium. Titanium and aluminum contribute to the formation of the γ′ strengthening phase, while molybdenum and other alloying elements support the alloy's mechanical performance.
This alloy design provides a practical balance of strength, manufacturing flexibility, and material cost. A-286 is widely associated with high-temperature fasteners and selected aerospace and industrial components where its qualified mechanical properties meet the requirements of the intended service environment.
Its performance depends on more than nominal chemical composition. The product form, melting route, solution treatment, aging treatment, metallurgical cleanliness, and applicable material specification all influence the properties that can be achieved in service.
A-286 is commonly identified by the following designations:
Identification item | Reference |
Common alloy name | A-286 / Incoloy A-286 |
UNS | S66286 |
European material number | 1.4980 |
ASTM bolting specification | ASTM A453/A453M, Grade 660, where applicable |
Aerospace material specifications | AMS 5737, AMS 5732, and other applicable A-286 specifications |
Chinese comparison grade | GH2132, as a potential technical counterpart requiring verification |
These designations do not establish automatic interchangeability across all products. ASTM A453 Grade 660 is a high-temperature bolting specification, while AMS specifications define particular product forms, processing routes, and material conditions.
When purchasing A-286, the buyer should specify the complete governing standard and revision, product form, dimensions, heat-treatment condition, and required mechanical properties.
A-286 is attractive when conventional stainless steels cannot provide the required combination of elevated-temperature strength and durability, but a more highly alloyed nickel-base superalloy may not be necessary.
Its principal advantages include:
● Precipitation-strengthened mechanical performance: Aging produces a fine γ′ phase that contributes substantially to strength.
● Useful elevated-temperature properties: The alloy is suitable for selected load-bearing applications within its qualified temperature and stress envelope.
● Good fabrication potential: Established forging, machining, and fastener-manufacturing processes can be used with appropriate controls.
● Austenitic structure: The alloy offers useful toughness at low temperatures, subject to product-specific qualification.
● Competitive material economics: Its iron-base composition can provide a cost advantage over certain higher-nickel alternatives.
The main limitation is that A-286 is not a universal substitute for nickel-base superalloys. Its long-term strength, oxidation resistance, creep behavior, and microstructural stability must be evaluated for the actual operating conditions.
A-286 obtains its performance through the combined effects of nickel, chromium, titanium, aluminum, molybdenum, vanadium, boron, and a controlled iron-base matrix.
The following table summarizes commonly published composition limits for A-286. The exact limits depend on the governing specification, so this table should be used as a technical reference rather than as a universal acceptance standard.
Element | Commonly published range or limit (wt.%) | Principal function |
Iron (Fe) | Balance | Principal matrix element |
Nickel (Ni) | 24.0–27.0 | Stabilizes the austenitic matrix and supports toughness and high-temperature properties |
Chromium (Cr) | 13.5–16.0 | Improves oxidation resistance and contributes to corrosion resistance |
Titanium (Ti) | 1.90–2.35 | Primary contributor to γ′ precipitation strengthening |
Molybdenum (Mo) | 1.00–1.50 | Provides solid-solution strengthening |
Vanadium (V) | 0.10–0.50 | Contributes to the alloy's overall metallurgical and mechanical behavior |
Aluminum (Al) | ≤0.35 | Participates in γ′ formation |
Carbon (C) | ≤0.08 | Influences carbide formation and grain-boundary behavior |
Boron (B) | Commonly 0.003–0.010 | Supports grain-boundary cohesion and creep-rupture ductility |
Manganese (Mn) | ≤2.00 | Supports processing and deoxidation |
Silicon (Si) | ≤1.00 | Controlled minor element associated with processing |
Cobalt (Co) | ≤1.00 in commonly published specifications | Controlled minor alloying element |
Phosphorus (P) | Specification-dependent; commonly ≤0.025–0.030 | Controlled impurity |
Sulfur (S) | Specification-dependent; commonly ≤0.020 | Controlled impurity |
Copper (Cu) | Specification-dependent | Controlled minor element |
Composition verification note: The applicable standard may impose tighter limits or additional requirements. For example, the allowable phosphorus, sulfur, and copper contents should be taken from the actual specification rather than combined into a single assumed limit. The material test certificate should confirm the chemistry of the supplied heat.
Nickel stabilizes the austenitic face-centered cubic matrix and contributes to toughness over a broad temperature range. Chromium promotes the formation of a protective chromium-rich oxide scale, supporting resistance to oxidation at elevated temperatures.
The resulting combination makes A-286 suitable for selected components exposed to hot gases and elevated-temperature environments. However, oxidation resistance is not equivalent to universal corrosion resistance. The atmosphere, temperature, exposure time, deposits, and thermal cycling must be considered during material selection.
Titanium is the principal γ′-forming element in A-286, while aluminum also contributes to precipitation formation. The strengthening phase is commonly represented as Ni₃(Ti,Al).
During aging, fine γ′ precipitates form within the austenitic matrix and impede dislocation movement. This mechanism provides a major contribution to the alloy's elevated-temperature strength.
The resulting properties depend on precipitate size, distribution, volume fraction, and stability. These characteristics are controlled by chemical composition, prior processing, solution treatment, and aging conditions.
Molybdenum contributes to solid-solution strengthening by increasing resistance to dislocation movement within the matrix. Vanadium is also part of the alloy chemistry and contributes to its overall metallurgical behavior.
These elements complement the primary γ′ strengthening mechanism. Their effects should be evaluated together with heat treatment, grain structure, and long-term exposure conditions rather than considered independently.
Boron is present at a low concentration but can influence grain-boundary cohesion and creep-rupture ductility. The amount and distribution of boron must be controlled because trace-element behavior can have a disproportionate effect on high-temperature performance.
For critical aerospace applications, metallurgical cleanliness and impurity control may be as important as nominal chemistry. Requirements for remelting, gas content, inclusions, and restricted residual elements should be established by the applicable specification and component qualification requirements.
A-286 is strengthened primarily through precipitation hardening, supported by solid-solution effects and grain-boundary control.
The principal strengthening phase is γ′, generally described as Ni₃(Ti,Al). During aging, the phase forms as fine precipitates within the matrix.
These precipitates hinder dislocation motion and increase the alloy's resistance to plastic deformation. Properly controlled aging is therefore essential for obtaining the specified tensile strength and proof strength.
If the aging treatment is unsuitable, the intended precipitation structure may not develop. Prolonged exposure to elevated temperatures can also change precipitate size and distribution, potentially reducing mechanical performance.
Molybdenum and other dissolved alloying elements strengthen the matrix by interfering with dislocation movement. This mechanism complements precipitation strengthening and contributes to elevated-temperature strength.
The relative contribution of each mechanism varies with temperature and microstructural condition. Room-temperature tensile strength alone is not sufficient to establish long-term performance under sustained high-temperature loading.
Grain-boundary chemistry and microstructure influence ductility, crack initiation, and creep-rupture behavior. Boron can support grain-boundary cohesion when maintained within the specified range.
At elevated temperatures, extended exposure can promote γ′ coarsening and, under suitable conditions, the formation of η-type phases associated with Ni₃Ti. The rate and extent of these changes depend on temperature, exposure time, composition, and prior heat treatment.
For components operating near the upper end of the intended temperature range, long-term strength, stress relaxation, creep, and rupture life should be evaluated using relevant test data and design allowables.
Heat treatment is fundamental to the mechanical performance of A-286. The required processing route depends on the governing material specification and the product being manufactured.
Solution treatment establishes the matrix condition needed for subsequent precipitation hardening. The temperature and duration must be appropriate for the alloy specification, product dimensions, and manufacturing procedure.
A-286 specifications do not all use an identical solution-treatment temperature. For example, AMS 5737 identifies material solution-treated at approximately 899°C before precipitation heat treatment, while other A-286 specifications use different processing conditions.
The temperature range of approximately 980–1,000°C may be appropriate for certain A-286 processing routes, but it must not be treated as a universal requirement for every specification or product form.
Aging promotes the precipitation of the γ′ phase and develops the required strength.
A commonly referenced aging condition for some A-286 products is approximately 718°C for 16 hours, followed by cooling as specified. Other schedules may apply depending on the governing specification and intended material condition.
The frequently cited range of 700–720°C for 12–16 hours should therefore be treated as a reference framework, not a universal production instruction.
Specification or product route | Key consideration |
AMS 5737 bar, wire, forging, and covered tubing products | Includes specific remelting and solution-plus-precipitation heat-treatment requirements |
Other AMS A-286 specifications | Confirm the applicable product form, solution-treatment temperature, aging schedule, and acceptance criteria |
ASTM A453 Grade 660 bolting | Follow the specified grade, class, heat treatment, and mechanical acceptance requirements |
Non-aerospace commercial products | Confirm the actual governing specification and documented delivery condition |
A-286 can be forged and machined using established procedures appropriate to its material condition. However, hot-working temperature, deformation rate, section size, and intermediate thermal control must be managed carefully.
Machining parameters should be selected based on hardness, delivery condition, tool material, workpiece geometry, and the risk of work hardening. Welding requires a qualified procedure appropriate to the joint design, service environment, and applicable code.
The temperature range of 650–850°C should not be interpreted as a universal prohibited hot-working interval. Fabrication windows must be taken from approved alloy-specific processing guidance.
For critical components, retain the heat-treatment records and relevant manufacturing documentation. Final inspection should confirm compliance with the specified dimensional, mechanical, and metallurgical requirements.
Material properties vary with product form, heat treatment, section size, specimen orientation, and the applicable specification. The values below are representative reference data and must not be treated as universal design allowables.
Property | Representative information |
Density | Approximately 7.93 g/cm³ |
Melting range | Approximately 1,360–1,425°C in commonly published references; confirm the source and test basis |
Crystal structure | Austenitic face-centered cubic matrix with γ′ precipitates |
Magnetic behavior | Generally low magnetic response in the austenitic condition; verify where a defined magnetic limit is required |
Low-temperature capability | Used in selected cryogenic applications, subject to material and component qualification |
Elevated-temperature capability | Commonly used in applications up to approximately 650–700°C, depending on stress, exposure duration, and design requirements |
The melting range is not a recommended operating-temperature range. Similarly, oxidation resistance at a particular temperature does not demonstrate that the alloy can sustain a mechanical load at that temperature for the required service life.
The original reference values of at least 950 MPa tensile strength, 630 MPa 0.2% proof strength, and 15% elongation should only be used when supported by the applicable product specification or a representative test certificate.
Property | Reference value cited in some material summaries | Verification requirement |
Ultimate tensile strength, Rm | ≥950 MPa | Confirm product form, condition, and acceptance standard |
0.2% proof strength, Rp0.2 | ≥630 MPa | Confirm applicable minimum and test temperature |
Elongation, A | ≥15% | Confirm specimen geometry and test method |
Hardness | Specification-dependent | Confirm the applicable acceptance limit |
Stress-rupture life | No universal value | Specify temperature, stress, and duration |
Fatigue strength | No universal value | Specify the cyclic loading conditions and required life |
A-286 can achieve high strength following precipitation heat treatment. Nevertheless, the actual values for a particular product must be established through the relevant specification and material test certificate.
For engineering selection, distinguish among the following:
● Room-temperature tensile properties: Establish short-term tensile behavior under the specified test conditions.
● Elevated-temperature tensile properties: Describe short-term strength at a defined temperature.
● Creep and stress-rupture performance: Address deformation and failure under sustained loading at elevated temperature.
● Fatigue performance: Addresses cyclic loading and depends on the stress history, geometry, surface condition, and temperature.
● Stress relaxation: Particularly relevant to bolts, studs, and other components that must retain clamping force during prolonged exposure.
For critical applications, material selection should be based on the property that governs the actual failure mode rather than on the highest available tensile-strength figure.
A-286 is often selected where its qualified mechanical performance is sufficient without requiring the full capabilities of a more highly alloyed nickel-base superalloy.
Alloy | General selection context | Key considerations |
A-286 / UNS S66286 | Intermediate-temperature, high-strength load-bearing components | Good balance of strength, fabricability, and material cost |
GH2132 | Chinese iron-base precipitation-strengthened alloy commonly compared with A-286 | Verify the applicable Chinese standard, chemistry, product form, and mechanical requirements |
Inconel 718 / GH4169 | High-strength nickel-base applications, including demanding structural and rotating components | Compare temperature-dependent strength, fatigue, creep, processing, and cost |
Inconel X-750 | Springs, fasteners, and selected elevated-temperature components | Select according to the required precipitation-strengthened properties and service environment |
Waspaloy | More demanding high-temperature applications where its qualified performance is required | Processing and cost may be higher; confirm suitability using design data |
18-8 stainless steels | General corrosion-resistant components and less demanding structural applications | May not provide the required strength for highly loaded elevated-temperature service |
GH2132 is commonly cited as a Chinese counterpart to A-286 because the two alloys share a broadly similar iron-base, precipitation-strengthened alloy concept.
However, a similar alloy family does not guarantee equivalent performance. Chemical limits, trace elements, melting and forging practices, product standards, heat treatment, and acceptance criteria may differ.
For critical components, a substitution assessment should compare the governing specifications and required design properties. A-286 and GH2132 should not be treated as directly interchangeable solely on the basis of their designation.
Inconel 718 is a nickel-base precipitation-strengthened superalloy with a different alloy design and strengthening system.
A-286 may offer an economic advantage where its qualified strength and environmental resistance meet the design requirements. Inconel 718 may be preferable when its specific mechanical properties, fatigue behavior, or environmental performance are required.
The choice should be based on equivalent product conditions and comparable test requirements rather than nominal temperature limits alone.
Waspaloy is considered for applications that require the properties of a more highly alloyed nickel-base superalloy. X-750 is commonly used for springs, fasteners, and other components requiring elevated-temperature strength.
A-286 can be a practical alternative when its qualified performance is sufficient and the component does not require the characteristics of these alternative alloys. However, the correct selection depends on temperature, stress, fatigue, environmental exposure, manufacturing route, and design life.
A-286 offers precipitation-strengthened mechanical properties that can be advantageous in applications where conventional stainless steel does not meet the required strength or elevated-temperature performance.
However, A-286 should not automatically replace stainless steel in every application. Corrosion resistance, forming requirements, joining, operating temperature, and lifecycle cost must all be considered.
A-286 is used in applications that require a combination of strength, elevated-temperature capability, and manufacturing reliability.
High-temperature bolts, studs, nuts, and related fastening components are among the established applications of A-286.
For these products, ASTM A453 Grade 660 may be applicable when the specified product and service requirements fall within its scope. The exact grade, class, heat treatment, mechanical properties, and inspection requirements must be confirmed before purchase.
Fastener selection should consider not only tensile strength but also stress relaxation, thermal expansion, preload retention, fatigue, and environmental exposure.
A-286 can be considered for selected aerospace components where its qualified properties meet the component's design requirements.
Potential applications include specified structural parts, fasteners, and other load-bearing components operating within an appropriate temperature and stress envelope.
The use of A-286 in a particular turbine disk, compressor disk, or other rotating component should not be assumed without design qualification. Rotating components require detailed consideration of fatigue, stress-rupture performance, forging quality, inspection, and traceability.
A-286 may be used for springs and other mechanical components that require elevated-temperature strength and retention of mechanical performance.
The suitability of the alloy depends on the required spring force, operating temperature, cyclic loading, surface condition, and long-term stress relaxation.
In industrial gas turbines and related equipment, A-286 can be considered for selected structural or fastening applications where the material meets the required design and environmental criteria.
The austenitic matrix of A-286 supports its use in selected low-temperature applications. However, a stated minimum service temperature such as −253°C should not be interpreted as a universal guarantee for every product or component.
Cryogenic suitability must be evaluated against the actual medium, component geometry, stress state, toughness requirements, and relevant safety standards. Applications involving liquid oxygen or other reactive cryogenic fluids require additional compatibility and safety assessment.
Correct procurement requires a clearly defined specification rather than an alloy designation alone.
Before ordering A-286, specify:
1. Material designation: A-286 / UNS S66286, with any required trade designation.
2. Applicable specification and revision: For example, the relevant AMS specification or ASTM A453 Grade 660 where applicable.
3. Product form: Bar, wire, forging, mechanical tubing, fastener, or another permitted form.
4. Dimensions and quantity: Include dimensional tolerances and any special machining allowance.
5. Delivery condition: Define the required solution-treated, precipitation-hardened, or other specified condition.
6. Chemical analysis: Require the certified heat analysis and any additional trace-element limits.
7. Mechanical testing: Specify tensile, proof-strength, elongation, hardness, stress-rupture, or other requirements where applicable.
8. Melting route: Identify the required melting or remelting process if specified by the governing standard or customer requirements.
9. Inspection and traceability: Define the required nondestructive examination, dimensional checks, lot identification, and inspection documentation.
10. Acceptance criteria: Establish the applicable testing method, acceptance limits, and documentation requirements.
For quality-critical applications, request the material test certificate and confirm that the reported results correspond to the supplied heat or lot.
Depending on the order, supporting records may include:
● Chemical analysis
● Tensile and hardness test results
● Heat-treatment records
● Melting or remelting documentation
● Dimensional inspection reports
● Required nondestructive testing results
● Heat or lot traceability records
Additional documentation should be requested where required by the contract or the governing specification. Do not assume that every commercial A-286 product is supplied with an identical set of aerospace qualification records.
GH2132 is commonly considered a Chinese counterpart to A-286 because of their broadly similar iron-base precipitation-strengthened alloy systems. However, they are not automatically interchangeable. Confirm the applicable standards, chemical composition, product form, heat treatment, and mechanical acceptance requirements before substitution.
ASTM A453 Grade 660 is associated with A-286-type high-temperature bolting material. However, ASTM A453 specifies bolting grades and classes, including requirements for mechanical properties, heat treatment, and testing. It should not be used as a universal product specification for all A-286 plates, bars, or forgings.
Different AMS specifications can cover different product forms, melting routes, and material conditions. AMS 5737 specifically identifies A-286 material supplied in covered forms following consumable-electrode remelting and a specified solution-plus-precipitation heat-treatment route. The applicable specification should be selected according to the required product and engineering application.
A-286 typically requires solution treatment followed by precipitation aging, but the precise temperature and duration depend on the governing specification. A frequently referenced aging treatment is approximately 718°C for 16 hours; this must be verified for the particular product and specification. Do not apply a generic heat-treatment schedule without approval.
A-286 is associated with elevated-temperature applications extending to approximately 650–700°C in certain conditions. Continuous-service suitability depends on stress, exposure duration, microstructural stability, environmental conditions, and design-life requirements. The nominal temperature range is not a substitute for qualified design data.
A-286 is generally described as having an austenitic structure and a low magnetic response in suitable conditions. However, a strict magnetic requirement should be verified through an appropriate test method and acceptance limit for the supplied product.
Price differences can reflect product form, dimensions, material condition, manufacturing route, remelting requirements, certification, inspection, traceability, and order quantity. Aerospace-grade or other tightly controlled material may involve additional manufacturing and qualification costs. A specific percentage difference should not be assumed without current comparable quotations.
Confirm the exact specification and revision, product form, dimensions, delivery condition, chemical analysis, mechanical acceptance criteria, traceability requirements, and required inspection documentation. For critical components, verify that the supplied material is qualified for the intended service conditions.
Bozhong Alloy provides specialty-alloy sourcing support for industrial and engineering applications. For A-286 enquiries, buyers should specify the required product form, dimensions, quantity, governing specification, delivery condition, and inspection requirements.
Stock availability, processing capabilities, delivery schedules, and certification options should be confirmed against the actual product and order.
To request a quotation, provide:
● Material grade: A-286 / UNS S66286
● Product form and dimensions
● Required quantity
● Applicable AMS or ASTM specification and revision
● Required heat-treatment condition
● Testing, inspection, and certification requirements
● Destination and requested delivery schedule
This information enables the supplier to evaluate the requested material and confirm the available supply route and commercial terms.
Incoloy A-286 is an iron-base, austenitic precipitation-hardening superalloy that offers a useful balance of strength, fabrication capability, and material cost for selected elevated-temperature applications.
Its mechanical performance depends on γ′ precipitation strengthening, controlled chemistry, appropriate heat treatment, and the quality of the manufacturing process. The alloy is particularly relevant to high-temperature fasteners and selected aerospace and industrial components, provided that the material's qualified properties meet the design requirements.
For engineers and procurement teams, the correct approach is to verify the governing specification, product form, heat-treatment condition, mechanical test results, and traceability documentation before specifying or purchasing A-286.
Technical disclaimer: This guide provides general engineering information and is not a substitute for the current governing material specification, an approved manufacturing procedure, or qualified design data. Confirm all acceptance limits and processing requirements before production use.
