Inconel 718
metalnickel superalloy — precipitation-hardened
UNS N07718Alloy 718IN718Nicrofer 5219Haynes 718Udimet 718AMS 5664 (wrought ref.)
Composition — UNS N07718 / ASTM F3055-14
| Element | Min % | Max % | Notes |
|---|---|---|---|
| Ni | 50.00 | 55.000 | Base element. High Ni content drives creep resistance and oxidation protection |
| Cr | 17.00 | 21.000 | Oxidation resistance via Cr₂O₃ scale; pitting and SCC resistance |
| Nb | 4.75 | 5.500 | Primary strengthener via γ'' (Ni₃Nb) precipitation; must stay in solution after anneal |
| Mo | 2.80 | 3.300 | Solid solution strengthening; creep resistance |
| Ti | 0.65 | 1.150 | Forms γ' (Ni₃Ti,Al) precipitates; controls γ'/γ'' ratio |
| Al | 0.20 | 0.800 | γ' former; oxidation resistance |
| Fe | 17.00 | 19.000 | |
| Co | — | 1.000 | |
| C | — | 0.080 | |
| Mn | — | 0.350 | |
| Si | — | 0.350 | |
| P | — | 0.015 | |
| S | — | 0.015 | |
| B | — | 0.006 | Grain boundary strengthening — low B is critical to prevent hot cracking in LPBF |
| Cu | — | 0.300 |
Mechanical & thermal properties — 5 conditions
| Property | LPBF as-built (XY) | LPBF as-built (Z) | LPBF SA+DA (XY) — primary service condition | LPBF SA+DA (Z) | LPBF + HIP + SA+DA (isotropic) |
|---|---|---|---|---|---|
| Elastic modulus | 185–210 GPa | — | 195–215 GPa | — | — |
| Yield strength (0.2%) | 650–920 MPa | 520–780 MPa | 1070–1180 MPa | 990–1110 MPa | 1050–1150 MPa |
| Ultimate tensile strength | 880–1120 MPa | 750–1000 MPa | 1310–1400 MPa | 1240–1360 MPa | 1270–1380 MPa |
| Elongation at break | 10.0–30.0 % | 8.0–28.0 % | 12.0–22.0 % | 10.0–19.0 % | 14.0–24.0 % |
| Hardness (HV) | 260–360 HV10 | — | 400–460 HV10 | — | — |
| Fatigue strength | — | — | 480–620 MPa | — | 580–720 MPa |
| Density | 8.19 g/cm³ | — | — | — | — |
| Thermal conductivity | 11.4 W/m·K | — | 11.4 W/m·K | — | — |
| CTE | 12.5–13.5 µm/m·K | — | — | — | — |
Values shown as min–max where a spread is reported, otherwise as typical ± unit. Ranges reflect inter-source variation, not single-sample scatter. All values are for AM-processed specimens unless noted.
Engineering considerations
- Always specify SA+DA post-processing: solution anneal at 980°C (not 1065°C — avoids δ-phase dissolution zone) + 720°C/8h FC to 620°C/8h. The exact temperature and time must be controlled to ±10°C.
- Laves phase verification: before shipping structural parts, verify Laves dissolution via SEM-EDS or hardness mapping. Residual Laves will appear as Nb/Mo-rich particles and corresponds to hardness excursions.
- Stress relief is mandatory before part removal: minimum 1000°C/1–2h in vacuum or argon. Removal without stress-relief will cause significant distortion in large or complex parts.
- Build orientation: for fatigue-critical applications, ensure primary load axis is in the XY plane in as-built condition. After SA+DA, anisotropy reduces but does not disappear — document orientation on traveller.
- HIP requirement: for NADCAP-controlled flight-critical parts, HIP (1163°C/100 MPa/4h) before SA+DA is standard practice at most Tier 1 aerospace AM suppliers. Budget 40–60% cost premium over SA+DA alone.
- Cracking risk: IN718 has lower hot-cracking susceptibility than many other Ni superalloys (no high Al+Ti) but liquation cracking at grain boundaries can occur with improper preheating or excessive energy density.
- Surface finish: as-built Ra 10–20 µm is too rough for many hot-section applications. Electrochemical machining (ECM) or abrasive flow machining (AFM) used for internal channel smoothing — specify finish method in design.
- Creep design: use the 100,000h larson-miller parameter data for wrought IN718 as a conservative baseline. LPBF SA+DA creep data is still sparse — avoid creep-critical applications without specific test data.
- Repair: LPBF IN718 can be laser-cladded or TIG-welded with IN625 or IN718 filler — widely used for cast/forged IN718 engine part repair. Process qualification required per OEM specifications.
Advantages
- Highest retained strength of common AM metals at elevated temperature — YS remains >700 MPa at 650°C
- Outstanding oxidation and hot corrosion resistance to 980°C
- Well-characterised post-processing route (SA+DA) produces wrought-equivalent or better properties
- LPBF enables complex internal cooling channels impossible in forging — critical for turbine thermal management
- Wide LPBF process window — relatively low crack susceptibility vs IN625, IN939, or CM247LC
- Comprehensive standards ecosystem: ASTM F3055, AMS 7009, NADCAP — clear qualification path
- Good weldability (low B, controlled S) — allows hybrid LPBF + TIG repair strategies
- Magnetic permeability of ~1.01 — effectively non-magnetic for sensor-critical applications
Limitations
- SA+DA heat treatment is mandatory for structural use — as-built properties are unacceptable for high-temperature service
- Laves phase formation during LPBF is intrinsic — Nb segregation cannot be fully prevented; only dissolved in post-processing
- Residual stress is extremely high in as-built LPBF IN718 — stress-relieve before removal from build plate or part will distort
- Very low thermal conductivity (11 W/m·K) — highest residual stress and cracking risk of the common LPBF metals
- Powder cost is 3–5× that of 316L stainless — cost-justify with functional requirement, not just temperature tolerance
- LPBF IN718 has lower oxidation resistance above 980°C than cast/wrought — chromia scale is not stable at higher temperatures
- High γ'' precipitation kinetics during LPBF cooling may lead to over-aging in slow-cooling regions — parameter uniformity critical
- Powder reactivity with moisture and oxygen — strict storage protocol; atmospheric control during process and powder handling mandatory
Typical applications
Turbine engine combustion chambers and linersTurbine blades and vanes (stationary airfoils)Fuel nozzles and injectorsExhaust housings and manifoldsRocket propulsion injectors and chambersOil & gas downhole tools and wellhead componentsCryogenic turbopump componentsStructural engine brackets and mountsHeat exchangers for high-temperature processesNuclear fasteners and pressure-boundary hardware
Industries
aerospacedefenceenergyindustrial
Standards & certifications
ASTM-F3055established
IN718 (UNS N07718) parts produced by powder bed fusion — composition, powder, and minimum mechanical property requirements
aerospacedefenceenergyindustrial
AMS-7009established
IN718 LPBF for aerospace structural applications — solution-annealed + double-aged (SA+DA) condition requirements
aerospacedefence
Required by most Tier 1 aerospace OEMs for structural and engine-adjacent IN718 LPBF parts. Sets UTS ≥1310 MPa, YS ≥1070 MPa, El ≥12%.
AMS-7000established
LPBF process requirements — machine qualification, atmosphere, process controls for aerospace production
aerospacedefence
ASTM-E466established
Force-controlled fatigue testing — critical for engine and rotating applications
aerospaceenergy
NADCAP-AC7110-14established
Third-party accreditation for AM metallic parts — required by most prime aerospace contractors
aerospacedefence
NADCAP accreditation required before supplying flight-critical IN718 AM parts to Airbus, Boeing, GE Aviation, Pratt & Whitney, Rolls-Royce, and Safran.
Compatible AM processes (4)
Other metal materials
Ti-6Al-4V Grade 5titanium alloy — alpha-beta316L Stainless Steelaustenitic stainless steel17-4PH Stainless Steelmartensitic precipitation-hardening stainless steelAlSi10Mgaluminium-silicon alloy (cast grade adapted for AM)AlSi7Mg Aluminium Alloyhypoeutectic Al-Si-Mg precipitation-hardenable aluminium alloyInconel 625nickel superalloy — solid-solution-strengthenedCoCrMocobalt-chromium alloy (biomedical and aerospace grade)Maraging Steel MS1 (18Ni-300)maraging steel (ultra-high-strength, precipitation-hardened)H13 Tool Steelchromium-molybdenum hot-work tool steel
Related calculators
HT AdvisorStandard stress-relief, solution, and aging cycles for AM metals (Ti-6Al-4V, IN718, 17-4PH, AlSi10Mg, 316L, CuCrZr) per AMS, ASTM F3301, and AMS 5664.DistortionEstimate residual stress and distortion risk index (σ/σ_y) for LPBF and DED builds. Mercelis-Kruth model with preheat sensitivity table.VEDCompute LPBF VED from power, scan speed, hatch, and layer thickness. Includes process windows for common alloys.Melt PoolLPBF / DED melt pool depth, width, and cooling rate from the Rosenthal moving heat source solution. Absorptivity, thermal diffusivity, and solidification velocity.HIPRecommended HIP temperature, pressure, and dwell time for AM metals per ASTM F3301, AMS 2801, and DEF STAN 02-835. Covers Ti alloys, Ni superalloys, steels.FatigueS-N curve estimation for AM metals using the Basquin law. Accounts for surface roughness stress concentration (Kt from Ra), build direction anisotropy, and porosity factor.
Last reviewed: 2026-05-04 · v1 · Sources: ASTM-F3055, AMS-7009, eos-in718-2023, jia-2014-in718, shipley-2018-in718-review, tucho-2017-in718, popovich-2017-in718, debroy-2018-review, yadollahi-2017-fatigue, ASTM-E8, ASTM-E466, NADCAP-AC7110-14