Inconel 718 vs A-286 Bolts: Which Superalloy Fastener for Your Application?

Alloy Identification and Standards

Alloy	UNS No.	DIN / EN	Common ASTM/AMS fastener standards
Inconel 718	N07718	2.4668 / NiCr19NbMo	ASTM B637, AMS 5662 / 5663 / 5664
A-286	S66286	1.4980 / X5NiCrTiMoVB25-15-2	ASTM A453 Grade 660, AMS 5731 / 5732 / 5737

Chemical Composition, wt% (balance Fe)

Element	Inconel 718 UNS N07718	A-286 UNS S66286
Ni	50.0–55.0	24.0–27.0
Cr	17.0–21.0	13.5–16.0
Nb + Ta	4.75–5.50	—
Mo	2.80–3.30	1.00–1.50
Ti	0.65–1.15	1.90–2.35
Al	0.20–0.80	≤0.35
V	—	0.10–0.50
Co	≤1.0	—
C	≤0.08	≤0.08
Mn	≤0.35	≤2.00
Si	≤0.35	≤1.00
P	≤0.015	≤0.025
S	≤0.015	≤0.025
B	≤0.006	0.001–0.010

Minimum Room-Temperature Mechanical Properties

Property	Inconel 718	A-286
Condition	Solution annealed + aged	Solution treated + aged
Tensile strength, ksi / MPa	185 / 1275	130 / 895
Yield strength, 0.2% offset, ksi / MPa	150 / 1034	85 / 586
Elongation, %	12	15
Hardness, HB	331–444	248–341
Typical continuous service limit	1300°F / 704°C	1200°F / 649°C

Application Notes

Inconel 718 (UNS N07718)
Use for high-strength bolting in gas turbines, oil and gas, nuclear, and cryogenic service. Offers high creep-rupture strength and oxidation resistance to 1300°F (704°C) under load. NACE MR0175 / ISO 15156 sour-service qualified in aged condition. Select when tensile/yield above 160 ksi / 120 ksi is required, or when chloride SCC and sour corrosion resistance are critical.

A-286 (UNS S66286)
Precipitation-hardened austenitic stainless alloy for moderate-temperature fasteners, turbine frames, afterburners, and automotive turbocharger bolting. Good oxidation resistance to 1500°F (816°C) intermittent. Lower raw-material cost than Inconel 718 due to lower nickel content. Select when 85–100 ksi yield strength is sufficient, service temperature is below 1200°F (649°C), or cost is a primary driver.