Nickel Alloy IN-939-HT
Heat-treated state · default condition
HT = full four-step heat treatment
Standard commercial condition for IGT blades and vanes: optimum γ′ size distribution plus grain-boundary carbide morphology for creep and hot-corrosion life.
Values for the HT condition
Other IN-939 tempers and conditions
IN-939 is listed in 6 conditions; see the grade overview at IN-939.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As fabricated | Foundry delivery state for non-critical or to-be-heat-treated parts; lowest strength and coarse as-cast γ′. | 620 | 870 | 4 | 31 HRC | 1.4 % IACS |
Two-step treatment | Simplified/short-cycle heat treatment used for some vanes and repair parts; slightly lower creep life than the four-step cycle. | 760 | 1,050 | 5 | 36 HRC | 1.4 % IACS |
Directionally solidified casting, fully heat treated | Columnar-grain version for higher thermal-fatigue and creep life in long IGT blades; properties quoted along the growth direction. | 760 | 1,060 | 9 | 36 HRC | 1.4 % IACS |
HTDefaultThis page Full four-step heat treatment | Standard commercial condition for IGT blades and vanes: optimum γ′ size distribution plus grain-boundary carbide morphology for creep and hot-corrosion life. | 780 | 1,100 | 5.5 | 37 HRC | — |
Hot isostatic pressed then fully heat treated | Choose when internal casting porosity must be closed: best ductility, LCF and creep-rupture scatter reduction for critical rotating blades. | 800 | 1,130 | 8 | 37 HRC | 1.4 % IACS |
Laser powder-bed fusion, hot isostatic pressed and fully heat treated | Additive route for repair inserts and complex cooled components; fine grains give higher room-temperature strength but lower long-term creep than cast/DS material. | 850 | 1,150 | 9 | 38 HRC | 1.4 % IACS |
What is IN-939-HT?
IN-939-HT is IN-939 heat treated to HT — standard commercial condition for IGT blades and vanes: optimum γ′ size distribution plus grain-boundary carbide morphology for creep and hot-corrosion life. IN-939-HT has a yield strength of 780 MPa (113 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 83% of nickel alloy grades. Elongation at break is 5.5% and the elastic modulus is 205 GPa (29.7 Msi). IN-939-HT has a density of 8.16 g/cm³ (0.295 lb/in³), lighter than 73% of nickel alloy grades. It melts at 1,290°C (2,354 °F).
Advantages
- High strength — 780 MPa (113 ksi), better than 83% of nickel alloy grades
Limitations
- Limited ductility — 5.5%, worse than 91% of nickel alloy grades
- Limited formability — 5/100, worse than 91% of nickel alloy grades
- Hard to polish — 60/100, worse than 84% of nickel alloy grades
- Difficult to weld — 25/100, worse than 82% of nickel alloy grades
- Low fracture toughness — 75 MPa·√m (68.3 ksi·√in), worse than 81% of nickel alloy grades
IN-939-HT properties
Typical room-temperature values for IN-939-HT; 10 are specific to this condition. Other listed values are IN-939 reference data and may not represent this condition. Bars are the position among nickel alloy grades.
Physical3
IN-939-HT has a density of 8.16 g/cm³ (0.295 lb/in³), lighter than 73% of nickel alloy grades. It melts at 1,290°C (2,354 °F).
Mechanical13
IN-939-HT has a yield strength of 780 MPa (113 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 83% of nickel alloy grades. Elongation at break is 5.5% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
IN-939-HT is rated for continuous service to 850°C (1,562 °F). It conducts heat at 10.5 W/m·K (6.07 BTU/hr·ft·°F), worse than 73% of nickel alloy grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical2
IN-939-HT has an electrical resistivity of 1.25×10⁻⁶ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (80/100), better than 61% of nickel alloy grades.
Sustainability4
Producing a kilogram of IN-939-HT takes about 215 MJ of energy and emits 14.5 kg of CO₂ — more than 84% of nickel alloy grades. Typical recycled content is 30%.
Manufacturability8
IN-939-HT's machinability is not recommended (12/100, worse than 86% of nickel alloy grades); weldability poor (25/100); formability not recommended (5/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with IN-939-HT
Is IN-939 easy to machine?
Very difficult after aging — use rigid setups, ceramic or SiAlON inserts for roughing and coated carbide with heavy through-coolant for finishing at low speed/high feed; grinding, ECM and EDM are common for blade features.
Can IN-939 be welded?
Weld-crack sensitive (Al+Ti ≈ 5.6 %); repair by GTAW/laser with low-heat input in the solution-treated state, preheat, ductile Ni filler or wide-gap braze, followed by full re-heat-treatment and HIP where possible.
Can IN-939 be formed, bent or molded?
Vacuum investment casting (equiaxed or directionally solidified) with ceramic cores; no cold forming — grain-size, shrinkage porosity and shell reaction control are the key process levers.
What surface finishes work on IN-939?
Chemical/abrasive-flow deburring, shot peening for fatigue, then aluminide diffusion or MCrAlY / TBC coatings for hot-corrosion and oxidation protection; anodizing not applicable.
IN-939 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | 0.13 – 0.17 | 0.15 |
| Crhigh Cr for hot-corrosion resistance | 22 – 22.8 | 22.5 |
| Co | 18.5 – 19.5 | 19 |
| W | 1.8 – 2.2 | 2 |
| Nb | 0.9 – 1.1 | 1 |
| Ta | 1.3 – 1.5 | 1.4 |
| Tiγ′ former | 3.6 – 3.8 | 3.7 |
| Alγ′ former | 1.8 – 2 | 1.9 |
| Zrgrain-boundary strengthener | 0.08 – 0.12 | 0.1 |
| B | 0.01 – 0.02 | 0.01 |
| Feresidual | ≤ 0.5 | — |
| Siresidual | ≤ 0.2 | — |
| Mnresidual | ≤ 0.2 | — |
| Sresidual | ≤ 0.02 | — |
| Nibalance, ~48 % | balance | — |
IN-939-HT — frequently asked
What is IN-939-HT used for?
IN-939-HT is typically used for industrial gas turbine blades, nozzle guide vanes and hot corrosion-resistant castings. In short: high-chromium cast superalloy; hot corrosion service castings; requires post-weld heat treatment.
What is the yield strength of IN-939-HT?
IN-939-HT has a typical yield strength of 780 MPa (113 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 83% of nickel alloy grades. Strength varies by condition: see the 6 listed tempers.
Is IN-939-HT easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 86% of nickel alloy grades). Very difficult after aging — use rigid setups, ceramic or SiAlON inserts for roughing and coated carbide with heavy through-coolant for finishing at low speed/high feed; grinding, ECM and EDM are common for blade features.
Can IN-939-HT be welded?
Not readily — weldability is rated poor (25/100). Weld-crack sensitive (Al+Ti ≈ 5.6 %); repair by GTAW/laser with low-heat input in the solution-treated state, preheat, ductile Ni filler or wide-gap braze, followed by full re-heat-treatment and HIP where possible.
What surface finishes work on IN-939-HT?
Chemical/abrasive-flow deburring, shot peening for fatigue, then aluminide diffusion or MCrAlY / TBC coatings for hot-corrosion and oxidation protection; anodizing not applicable.
Can IN-939-HT be formed, bent or molded?
Vacuum investment casting (equiaxed or directionally solidified) with ceramic cores; no cold forming — grain-size, shrinkage porosity and shell reaction control are the key process levers.
What is the maximum service temperature of IN-939-HT?
IN-939-HT is rated for continuous use to about 850°C (1,562 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between IN-939-HT and IN-939-F?
HT is the default condition — standard commercial condition for IGT blades and vanes: optimum γ′ size distribution plus grain-boundary carbide morphology for creep and hot-corrosion life. F: foundry delivery state for non-critical or to-be-heat-treated parts; lowest strength and coarse as-cast γ′. Yield strength is 780 MPa in HT versus 620 MPa in F.
Sources
- Superalloys II — High-Temperature Materials for Aerospace and Industrial Power — Wiley (1987)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- IN-939 cast nickel-base superalloy data — Special Metals / Inco Alloys (2004)
- High-temperature alloy thermophysical and mechanical property compilations — NIMS / Cindas (2018)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.