A-286 and Inconel 718 are precipitation-hardened alloys used for aerospace and high-temperature fasteners, rings and hardware. A-286 is an iron-nickel-chromium alloy that often delivers excellent value at moderate temperature. 718 is a nickel-base superalloy offering higher strength and a broader severe-service reputation—at greater cost and density.
Important: Fastener allowables depend on the exact AMS/ASTM specification, diameter, thread manufacture, heat treatment and test method. Typical datasheet properties cannot replace approved design data.
The Short Answer
Choose A-286 (UNS S66286) for cost-sensitive aerospace and industrial fasteners requiring high strength and oxidation resistance to roughly 700°C (1300°F), within its approved condition. Choose Inconel 718 (N07718) when higher strength, nickel-base corrosion resistance or program-specific approval justifies the premium. Never substitute solely from a room-temperature tensile table.
A-286 vs 718 Comparison
| Decision factor | A-286 | Inconel 718 |
|---|---|---|
| Alloy base | Iron-nickel-chromium | Nickel-chromium-iron |
| UNS | S66286 | N07718 |
| Strengthening | Precipitation hardening, titanium-bearing | Gamma-prime/gamma-double-prime precipitation hardening |
| Published temperature context | Useful strength/oxidation resistance to about 700°C (1300°F) | High strength commonly used to about 650°C (1200°F), condition dependent |
| Density | About 7.98 g/cm³ per ATI | About 8.19 g/cm³ per manufacturer handbook |
| Relative material cost | Generally lower | Generally higher |
| Typical parts | Bolts, studs, blades, vanes, shafts and springs | Turbine hardware, disks, shafts, fasteners, rings and oil/gas components |
Composition and Strengthening
A-286 is iron based with roughly 24–27% nickel, 13.5–16% chromium, titanium and molybdenum under ATI’s published composition. Controlled solution treatment and aging create a strong precipitation-hardened structure.
Alloy 718 contains substantially more nickel and uses niobium, titanium and aluminum to form strengthening precipitates. Its slow precipitation response supports fabrication and welding, while the aged condition provides high yield and fatigue strength.
The two alloys can occupy the same preliminary selection list, but they are not metallurgical equivalents.
Strength and Temperature
ATI lists representative specification minimums for precipitation-hardened A-286 around 965 MPa tensile strength, 655 MPa yield strength and 15% elongation for certain products. These figures illustrate capability, not a universal guarantee.
Alloy 718 can reach considerably higher strength in common aerospace aged conditions. Its useful design temperature depends on long-term microstructural stability, stress and the governing allowable dataset. Above the normal 718 range, other gamma-prime superalloys may be preferred.
A-286’s approximately 700°C/1300°F temperature statement refers to useful strength and oxidation resistance, not a single allowable load at that temperature. Creep, stress rupture and relaxation must be checked for duration.
For higher-temperature turbine comparisons, see Inconel 718 vs Waspaloy.
Fastener-Specific Selection
A bolt’s material is only one part of its performance. Specify:
- bar/wire starting condition;
- cold- or hot-heading route;
- solution and aging cycle;
- rolled-before-aging or rolled-after-aging threads;
- tensile, proof-load and wedge testing;
- stress-rupture or relaxation requirements;
- hardness and decarburization/surface controls;
- plating, coating or lubrication; and
- lot traceability.
Thread rolling sequence affects residual stress and fatigue behavior. A generic bar MTC cannot certify a finished aerospace fastener. Use the Nickel Alloy Fasteners Specification Guide for a complete order framework.
Corrosion and Oxidation
Both alloys derive oxidation resistance from chromium. 718’s nickel-base chemistry generally provides broader resistance in many severe environments, but it is not a dedicated high-molybdenum wet-corrosion alloy like 625.
A-286 can be suitable for engine and exhaust hardware where temperature and strength govern. If a fastener sees seawater, chloride crevices, sour gas or strong acids, environmental qualification may point to a different nickel alloy or coating system.
Weight and Cost
A-286’s density is slightly lower, and its lower nickel content often reduces raw-material cost. For a large fastener program, those differences can be meaningful. However, lifecycle cost includes:
- section size needed for the allowable load;
- heat-treatment and test complexity;
- tool wear and machining rate;
- approved-source availability;
- coating and corrosion protection; and
- failure consequence and replacement access.
If 718 permits a smaller, stronger component or is already program-approved, its premium may be justified. If A-286 meets all allowables, specifying 718 can be unnecessary overdesign.
Heat Treatment and Procurement
Both grades require precise solution and precipitation treatments, but the cycles and resulting structures differ. The purchase order should reference the exact AMS or ASTM document and revision for the product form. Do not copy a bar cycle into a finished-fastener drawing without confirming the fastener specification.
For 718 routes, see Inconel 718 Heat Treatment.
RFQ Checklist
- UNS S66286 or N07718 and exact material specification.
- Finished-fastener standard, drawing and revision.
- Diameter, thread, grip, head style and quantity.
- Melt/remelt and approved-source requirements.
- Heading, machining and thread-rolling sequence.
- Solution and aging condition.
- Service temperature, load, cycles and design life.
- Tensile, shear, fatigue, rupture or relaxation tests.
- Hardness, microstructure, NDE and surface inspection.
- Coating/lubricant compatibility and hydrogen controls.
- Lot definition, serialization and certification.
Frequently Asked Questions
Is Inconel 718 stronger than A-286?
In many common aged conditions, yes. The actual comparison must use the same product form, temperature, size and governing specifications.
Is A-286 an Inconel alloy?
No. A-286 is an iron-nickel-chromium precipitation-hardening alloy; Inconel 718 is a nickel-base superalloy.
Which alloy is lighter?
A-286 is slightly less dense—about 7.98 g/cm³ versus roughly 8.19 g/cm³ for 718. Part geometry usually matters more than the small density difference.
Which is better for aerospace bolts?
Both are established. Choose by approved specification, temperature, load, fatigue, corrosion, source approval and cost—not name recognition.
Can A-286 replace 718?
Only after engineering and program approval. Lower strength, different allowables and different environmental behavior may require redesign.
Final Recommendation
Use A-286 when its approved allowables meet the duty and cost/weight efficiency matters; use 718 when higher strength or program qualification earns its premium. Send J&A Alloy the drawing, standard, load-temperature spectrum, process sequence, tests, source approvals and certification requirements.
