Inconel 939

metal

nickel superalloy — γ'-precipitation-hardened (high Al+Ti)

IN939UNS N13009AMS 5872 (wrought/cast ref.)Alloy 939

Density

8.23 g/cm³

YS (LPBF as-built (XY))

680–920 MPa

UTS (LPBF as-built (XY))

850–1100 MPa

Thermal conductivity

11.0 W/m·K

Composition — UNS N13009 / AMS 5872

Element	Min %	Max %	Notes
Ni	bal.		balance
Cr	21.00	23.000	Oxidation and hot corrosion resistance (Cr₂O₃ scale); higher than IN718
Co	18.00	20.000	Raises the γ solidus; reduces stacking fault energy to impede dislocation climb — critical for creep resistance
Al	3.40	4.000	Primary γ' former (Ni₃Al); with Ti creates high γ' volume fraction ~55%. High Al is the main driver of strain-age cracking risk in AM
Ti	3.40	4.000	γ' former (Ni₃Ti); Ti/Al ratio ~1:1 gives γ' (Ni₃(Al,Ti)) the optimal composition for high-temperature stability

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Mechanical & thermal properties — 4 conditions

Property	LPBF as-built (XY)	LPBF as-built (Z)	LPBF SA+FA (XY) — primary service condition	LPBF SA+FA (Z)
Elastic modulus	—	—	200–220 GPa	—
Yield strength (0.2%)	680–920 MPa	550–780 MPa	800–940 MPa	720–860 MPa
Ultimate tensile strength	850–1100 MPa	720–980 MPa	940–1080 MPa	860–1020 MPa
Elongation at break	—	2.0–9.0 %	5.0–12.0 %	2.5–8.0 %
Hardness (HV)	340–430 HV10	—	355–410 HV10	—
Fatigue strength	—	—	420–580 MPa	—
Density	8.23 g/cm³	—	—	—
Thermal conductivity	11.0 W/m·K	—	—	—
CTE	12.2–13.4 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

Heat treatment sequence is critical: solution anneal at 1160°C (not lower — incomplete γ' dissolution leads to coarse γ' after ageing). The full three-stage cycle (1160°C/4h + 1000°C/6h + 850°C/24h) is required; shortcutting the 850°C/24h stage reduces γ' uniformity.
Strain-age cracking prevention: stress-relieve in vacuum at 900°C/2h before removing from build plate, then solution anneal before final ageing. Direct ageing of as-built IN939 without solution anneal will cause part cracking due to constrained γ' precipitation on grain boundaries.
Build orientation: for turbine airfoil LPBF, orient blade chord (principal tensile stress direction) in the XY plane. Z-direction properties are substantially weaker — document orientation on material traceability certificate.
HIP recommendation: for rotating or fracture-critical parts, HIP at 1160°C/100 MPa/4h prior to SA+FA is strongly recommended. Closes solidification microcracks and sub-surface porosity. HIP temperature must match solution anneal temperature to avoid double-annealing grain growth.
Cracking inspection: 100% fluorescent penetrant inspection (FPI) after build and after stress-relief is required before heat treatment. Any surface-connected cracks are an immediate rejection; sub-surface cracks require HIP evaluation. X-ray CT recommended for complex internal geometries.
DED repair protocol: for cast IN939 blade tip or LE repair, pre-heat the substrate to ~200–300°C before deposition to reduce thermal shock. Post-deposit local solution anneal and re-age to restore γ' structure in the repair zone. Verify hardness match between deposit and parent metal.
Powder control: IN939 powder must be stored in sealed containers with desiccant and nitrogen backfill. Oxygen content of recycled powder must be verified (max 50 ppm increase per cycle). Al and Ti oxidation in powder degrades γ' precipitation response.
Competition with IN718: for applications below 700°C, IN718 LPBF is preferred — better characterised AM database, superior ductility, easier processing, lower cost. Specify IN939 only when creep resistance or hot corrosion resistance above 700°C is genuinely required.

Advantages

Superior elevated-temperature strength vs IN718 above 700°C — γ' volume fraction ~55% vs ~45% in IN718; remains load-bearing to ~900°C
Outstanding hot corrosion resistance — high Cr (22 wt%) provides superior type I hot corrosion resistance compared to IN718 (17–21 wt% Cr)
LPBF enables complex internal cooling channels in turbine airfoils that are impossible in cast IN939 (directionally solidified or equiaxed)
DED-Laser repair of worn cast IN939 turbine components is established practice — extends service life of expensive turbine hardware
Near-zero γ'' content (unlike IN718) — properties are thermally stable above 650°C; no δ-phase formation concerns
Good oxidation resistance to ~980°C due to protective Cr₂O₃+Al₂O₃ scale

Limitations

High strain-age cracking susceptibility — high Al+Ti content causes rapid γ' precipitation on reheating. Stress-relieving before solution anneal is critical; incorrect heat treatment sequence will crack the part
More difficult LPBF processability than IN718 — narrower process window; requires precise parameter control to avoid solidification cracking
Limited AM-specific data — LPBF IN939 published literature is sparse compared to IN718/IN625. Use caution when extrapolating data to design
Mandatory three-step heat treatment (SA + two-stage age) adds cost and time vs. IN718 two-step SA+DA
High raw powder cost — Co, Nb, Ta additions make IN939 powder ~40% more expensive than IN718 per kg
Welding/repair is more difficult than IN718 — higher cracking susceptibility; requires controlled preheat and inter-pass temperature management
NADCAP qualification path for LPBF IN939 is less mature than IN718 — no dedicated AMS standard exists yet (unlike AMS 7009 for IN718 LPBF)

Typical applications

Industrial gas turbine (IGT) first and second stage blades and vanesAero-engine hot-section airfoils (nozzle guide vanes, turbine blades)DED repair of cast/wrought IN939 turbine blade leading edges and tipsCombustion liner components requiring high oxidation resistance (>900°C)Power generation turbine ring segments and shroudsRocket combustion chamber hardware in high-temperature zones

Standards & certifications

ASTM-E8established

Tensile test method for acceptance testing of LPBF IN939 specimens

aerospaceenergy

ASTM-E466established

Force-controlled fatigue testing — for turbine blade fatigue qualification

aerospaceenergy

NADCAP-AC7110-14established

Third-party accreditation required for flight-critical IN939 AM parts

aerospace

IN939 is used in hot-section turbine parts where NADCAP accreditation is typically mandatory for supply to aero-engine OEMs.

Inconel 939

Composition — UNS N13009 / AMS 5872

Mechanical & thermal properties — 4 conditions

Engineering considerations

Advantages

Limitations

Typical applications

Industries

Standards & certifications

Compatible AM processes (2)

Other metal materials

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