Related Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
UNS N07718 / Alloy 718 / Precipitation-Hardening Nickel Superalloy
Inconel 718 Properties, Composition, Density, Hardness, Mechanical Data
Inconel 718 (UNS N07718, also branded Alloy 718) is a precipitation-hardening nickel-chromium-niobium superalloy that retains 185 ksi tensile to 705 °C (1300 °F). For bolting components, the controlling specification is ASTM A1014 / A1014M; aerospace bar stock procurement is governed by SAE AMS 5662 (solution-treated) and AMS 5663 (precipitation-hardened). This page consolidates the chemistry, mechanical, and physical properties of Inconel 718 as a single engineering reference for procurement, design, and quality teams.
Quick procurement: request a quote for Inconel 718 bolting in any ASME B18 dimensional standard, phone +91-22-66157017, WhatsApp +91-22-66157017, email info@torqbolt.com. MTC 3.1 / 3.2 certifications, NACE MR0175 compliance, ITAR-controlled aerospace orders supported.
Inconel 718 Chemical Composition (UNS N07718 per ASTM A1014 Table 1)
The chemistry of UNS N07718 is closely controlled to enable the precipitation of γ″ (gamma double-prime, Ni₃Nb) and γ′ (gamma prime, Ni₃(Al,Ti)) strengthening phases during age hardening. Niobium content is the discriminating element vs Inconel 625 and other nickel superalloys.
| Element | Composition (mass %) | Role |
|---|---|---|
| Nickel (Ni) | 50.0 – 55.0 | Austenite stabilizer, matrix |
| Chromium (Cr) | 17.0 – 21.0 | Corrosion + oxidation resistance |
| Molybdenum (Mo) | 2.80 – 3.30 | Solid-solution strengthening |
| Niobium plus Tantalum (Nb+Ta) | 4.75 – 5.50 | γ″ (Ni₃Nb) precipitation |
| Titanium (Ti) | 0.65 – 1.15 | γ′ precipitation |
| Aluminum (Al) | 0.20 – 0.80 | γ′ precipitation |
| Cobalt (Co), max | 1.0 | Solid-solution element |
| Carbon (C), max | 0.08 | Carbide control |
| Manganese (Mn), max | 0.35 | - |
| Silicon (Si), max | 0.35 | - |
| Phosphorus (P), max | 0.015 | - |
| Sulfur (S), max | 0.015 | - |
| Boron (B), max | 0.006 | Grain-boundary control |
| Copper (Cu), max | 0.30 | - |
| Iron (Fe) | Remainder | Cost-effective bulk |
Source: ASTM A1014 / A1014M-16ε1 Table 1. Iron is determined arithmetically by difference. If a product (check) analysis is performed, conformance is to ASTM B880 limits.
Inconel 718 Mechanical Properties (after Aging per ASTM A1014 Table 2)
The mechanical thresholds below apply to Inconel 718 bolting AFTER the mandated solution + double-age heat treatment cycle. Untreated or improperly treated stock will not meet these values.
Room-Temperature Tensile + Hardness
| Property | Minimum |
|---|---|
| Tensile strength | 185 ksi (1275 MPa) |
| 0.2% offset yield strength | 150 ksi (1035 MPa) |
| Elongation in 2 in. or 50 mm (or 4D) | 12 % |
| Reduction of area | 15 % |
| Brinell hardness | 331 – 444 HBW (≈ 36 – 47 HRC) |
Stress-Rupture (1200 °F / 100 ksi)
| Property | Minimum |
|---|---|
| Temperature | 1200 °F (650 °C) |
| Stress | 100 ksi (690 MPa) |
| Time to rupture | 23 hours |
| Elongation at rupture | 5 % |
Elevated-Temperature Tensile (1200 °F)
| Property | Minimum |
|---|---|
| Tensile strength | 145 ksi (1000 MPa) |
| 0.2% offset yield strength | 125 ksi (860 MPa) |
| Elongation | 12 % |
| Reduction of area | 15 % |
Inconel 718 Physical Properties
The physical properties below are not specified by ASTM A1014. Values are drawn from the Special Metals INCONEL alloy 718 technical bulletin and Inco Alloys Engineering Properties (commonly cited in the engineering literature).
| Property | Value |
|---|---|
| Density at room temperature | 8.19 g/cm³ (0.296 lb/in³) |
| Melting range | 1260 – 1336 °C (2300 – 2437 °F) |
| Coefficient of thermal expansion (20-100 °C) | 13.0 × 10⁻⁶ /°C (7.2 × 10⁻⁶ /°F) |
| Coefficient of thermal expansion (20-650 °C) | 14.4 × 10⁻⁶ /°C (8.0 × 10⁻⁶ /°F) |
| Thermal conductivity at 25 °C | 11.4 W/m·K |
| Specific heat at 25 °C | 435 J/kg·K |
| Modulus of elasticity at 25 °C | 200 GPa (29 × 10⁶ psi) |
| Electrical resistivity at 25 °C | 1.25 μΩ·m |
| Curie temperature | Below -112 °C (-170 °F), non-magnetic at all service temps |
Inconel 718 Heat Treatment Cycle (ASTM A1014 §5.2)
The mechanical thresholds in the tables above are only achieved after the precise solution-plus-double-age cycle specified in ASTM A1014 §5.2. Deviations from temperature or time will not develop full γ″ / γ′ precipitation strengthening.
Solution Treatment
- Temperature: 1725 – 1850 °F (940 – 1010 °C), ± 25 °F (± 14 °C)
- Hold time: commensurate with cross-sectional thickness
- Cooling rate: air cool or faster
Precipitation (Age) Treatment, Double Age
- First age: heat to 1325 °F (720 °C), hold 8 hours minimum, ± 15 °F (± 8 °C)
- Furnace cool: to 1150 °F (620 °C) at 100 °F (55 °C) per hour
- Second age: hold at 1150 °F for 8 hours
- Total cycle: minimum 18 hours, air cool to room temperature
Straightening of bolting components is permitted only AFTER solution treatment and BEFORE aging. Straightening after aging is prohibited because γ″ phase plasticity is exhausted.
Why Specify Inconel 718 for Bolting
Inconel 718 occupies a specific niche in the high-temperature bolting hierarchy:
- Strength + temperature: ASTM A1014's 185 ksi tensile at room temperature drops to only 145 ksi at 1200 °F, a 22% loss, vs 60-80% loss for stainless grades or low-alloy steels.
- Corrosion + oxidation: the high chromium (17-21%) gives oxidation resistance comparable to Inconel 600 and stress-corrosion resistance comparable to UNS S31600 (B8M Cl.2).
- Weldability: the slow γ″ precipitation kinetics give Inconel 718 the best weldability of any precipitation-hardening superalloy, important for assemblies that combine bolting and welded joinery.
- Cryogenic-to-high-temp: Inconel 718 is qualified by NASA for liquid-oxygen turbo-pump bolting (−253 °C) AND by gas-turbine OEMs for 700 °C compressor blade attachment. Service envelope: -423 °F to +1300 °F.
Related Standards + Aerospace Cross-Reference
| Standard | Scope |
|---|---|
| ASTM A1014 / A1014M | Precipitation-hardening bolting in UNS N07718 (this site's master spec) |
| ASTM B637 | Bar / forging stock for UNS N07718 (raw material for A1014 bolts) |
| SAE AMS 5662 | Aerospace UNS N07718 bar / forging, solution heat treated |
| SAE AMS 5663 | Aerospace UNS N07718 bar / forging, solution + precipitation hardened (final bolt heat-treat condition) |
| SAE AMS 5664 | Aerospace UNS N07718 bar / forging, solution + precipitation hardened, higher strength |
| SAE AS 7467 | Aerospace procurement spec for UNS N07718 bolts / screws, 185 ksi tensile, stress-rupture rated |
| ASME PVP Code Case 1993-7 | ASME pressure-vessel code case authorizing UNS N07718 bolting |
| MIL-DTL / NAS / MS specs | MS14181, AS3418, NAS1351 family, proprietary aerospace Inconel 718 bolt part numbers |
Inconel 718 Bolting Products by Dimensional Standard
TorqBolt manufactures Inconel 718 bolting to every ASME B18 family covered by ASTM A1014. Browse the dimensional reference for your specification:
- Imperial hex: Hex Bolts (B18.2.1), Heavy Hex Bolts, Hex Cap Screws, Heavy Hex Cap Screws, Heavy Hex Screws, Hex Lag Screws / Lag Bolts
- Imperial socket: Socket Head Cap Screws (B18.3), Shoulder Bolts, Countersunk Cap Screws, Spline Socket Cap Screws
- Metric: DIN 933 Hex Cap Screws (B18.2.3.1M), Metric Heavy Hex Screws, Metric Hex Bolts, DIN 912 Socket Cap Screws, Metric Machine Screws
- Studs + Nuts: B16.5 Flange Studs, Double-End Studs, Metric Clamping Studs, Metric Hex Nuts, Metric Heavy Hex Nuts
Satisfaction Survey
