Nickel Alloy IN-738LC-FHT
Heat-treated state · default condition
UNS N07738
FHT = full heat treatment: 1120 °C/2 h/AC + 843 °C/24 h/AC
Standard supplied condition for conventionally cast turbine blades and vanes — best balance of γ′ strengthening and creep life.
Values for the FHT condition
Other IN-738LC tempers and conditions
IN-738LC is listed in 4 conditions; see the grade overview at IN-738LC.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Raw investment casting before solution/age; used only as an intermediate state or for non-critical hardware. | 760 | 830 | 4 | 32 HRC | 1.3 % IACS |
Directionally solidified casting, solution + aged | Columnar-grain version for higher thermal-fatigue and creep capability along the blade stacking axis. | 880 | 1,000 | 10 | 35 HRC | 1.3 % IACS |
FHTDefaultThis page Full heat treatment: 1120 °C/2 h/AC + 843 °C/24 h/AC | Standard supplied condition for conventionally cast turbine blades and vanes — best balance of γ′ strengthening and creep life. | 945 | 1,030 | 6 | 36 HRC | 1.3 % IACS |
hot isostatic pressed (~1200 °C / 100–170 MPa / 4 h) then solution + age | Choose when casting microporosity must be closed for maximum LCF/creep life on high-duty rotating blades. | 960 | 1,090 | 8 | 36 HRC | 1.3 % IACS |
What is IN-738LC-FHT?
IN-738LC-FHT is IN-738LC heat treated to FHT — standard supplied condition for conventionally cast turbine blades and vanes — best balance of γ′ strengthening and creep life. IN-738LC-FHT has a yield strength of 945 MPa (137 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 94% of nickel alloy grades. Elongation at break is 6% and the elastic modulus is 201 GPa (29.2 Msi). IN-738LC-FHT has a density of 8.11 g/cm³ (0.293 lb/in³), lighter than 77% of nickel alloy grades. It melts at 1,230°C (2,246 °F).
Advantages
- High strength — 945 MPa (137 ksi), better than 94% of nickel alloy grades
Limitations
- Limited formability — 3/100, worse than 97% of nickel alloy grades
- Limited ductility — 6%, worse than 90% of nickel alloy grades
- Difficult to weld — 15/100, worse than 87% of nickel alloy grades
- High embodied carbon — 15 kg CO₂/kg, worse than 87% of nickel alloy grades
- Hard to polish — 60/100, worse than 84% of nickel alloy grades
IN-738LC-FHT properties
Typical room-temperature values for IN-738LC-FHT; 22 are specific to this condition. Other listed values are IN-738LC reference data and may not represent this condition. Bars are the position among nickel alloy grades.
Physical3
IN-738LC-FHT has a density of 8.11 g/cm³ (0.293 lb/in³), lighter than 77% of nickel alloy grades. It melts at 1,230°C (2,246 °F).
Mechanical16
IN-738LC-FHT has a yield strength of 945 MPa (137 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 94% of nickel alloy grades. Elongation at break is 6% and the elastic modulus is 201 GPa (29.2 Msi).
Thermal6
IN-738LC-FHT is rated for continuous service to 980°C (1,796 °F). It conducts heat at 11 W/m·K (6.36 BTU/hr·ft·°F), worse than 60% of nickel alloy grades. Thermal expansion is 11.6 µm/m·K (6.44 µin/in·°F).
Electrical3
IN-738LC-FHT conducts electricity at 1.3 % IACS, worse than 89% of nickel alloy grades.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), better than 74% of nickel alloy grades.
Sustainability4
Producing a kilogram of IN-738LC-FHT takes about 215 MJ of energy and emits 15 kg of CO₂ — more than 84% of nickel alloy grades. Typical recycled content is 30%.
Manufacturability8
IN-738LC-FHT's machinability is not recommended (12/100, worse than 86% of nickel alloy grades); weldability poor (15/100); formability not recommended (3/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with IN-738LC-FHT
Is IN-738LC easy to machine?
Very difficult: rigid setups, ceramic or coated-carbide tools, low speeds with high feed, flood coolant; grinding, EDM and ECM are standard for cooling holes and root forms.
Can IN-738LC be welded?
Highly crack-sensitive (γ′ >40 %): weld in solutioned/over-aged condition, use preheat or hot-box GTAW/laser cladding with ductile Ni fillers, followed by full solution + age; wide-gap brazing is the preferred repair route.
Can IN-738LC be formed, bent or molded?
Investment casting only (equiaxed, DS or LPBF); no cold forming — control shell temperature and gating to avoid hot tearing and shrinkage porosity, HIP to close residual porosity.
What surface finishes work on IN-738LC?
Grit blast and chemical clean, then aluminide diffusion or MCrAlY overlay coating plus optional YSZ thermal-barrier coat; polish or vibro-finish airfoils before coating.
IN-738LC 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 |
|---|---|---|
| Clow-carbon variant of IN-738 | 0.09 – 0.13 | 0.11 |
| Crhot-corrosion resistance | 15.7 – 16.3 | 16 |
| Co | 8 – 9 | 8.5 |
| Mo | 1.5 – 2 | 1.75 |
| W | 2.4 – 2.8 | 2.6 |
| Ta | 1.5 – 2 | 1.75 |
| Nb | 0.6 – 1.1 | 0.9 |
| Alγ′ former | 3.2 – 3.7 | 3.4 |
| Tiγ′ former | 3.2 – 3.7 | 3.4 |
| B | 0.01 | 0.01 |
| Zr | 0.03 – 0.08 | 0.05 |
| Fe | ≤ 0.5 | — |
| Si | ≤ 0.3 | — |
| Mn | ≤ 0.2 | — |
| S | ≤ 0.02 | — |
| Nibalance, ~61 % | balance | — |
IN-738LC-FHT — frequently asked
What is IN-738LC-FHT used for?
IN-738LC-FHT is typically used for industrial gas turbine blades, vanes and hot corrosion-resistant hot-section parts. In short: benchmark IGT blade alloy; strong hot corrosion resistance; castings only, weld-sensitive.
What is the yield strength of IN-738LC-FHT?
IN-738LC-FHT has a typical yield strength of 945 MPa (137 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 94% of nickel alloy grades. Strength varies by condition: see the 4 listed tempers.
Is IN-738LC-FHT easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 86% of nickel alloy grades). Very difficult: rigid setups, ceramic or coated-carbide tools, low speeds with high feed, flood coolant; grinding, EDM and ECM are standard for cooling holes and root forms.
Can IN-738LC-FHT be welded?
Not readily — weldability is rated poor (15/100). Highly crack-sensitive (γ′ >40 %): weld in solutioned/over-aged condition, use preheat or hot-box GTAW/laser cladding with ductile Ni fillers, followed by full solution + age; wide-gap brazing is the preferred repair route.
What surface finishes work on IN-738LC-FHT?
Grit blast and chemical clean, then aluminide diffusion or MCrAlY overlay coating plus optional YSZ thermal-barrier coat; polish or vibro-finish airfoils before coating.
Can IN-738LC-FHT be formed, bent or molded?
Investment casting only (equiaxed, DS or LPBF); no cold forming — control shell temperature and gating to avoid hot tearing and shrinkage porosity, HIP to close residual porosity.
What is the maximum service temperature of IN-738LC-FHT?
IN-738LC-FHT is rated for continuous use to about 980°C (1,796 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between IN-738LC-FHT and IN-738LC-AC?
FHT is the default condition — standard supplied condition for conventionally cast turbine blades and vanes — best balance of γ′ strengthening and creep life. AC: raw investment casting before solution/age; used only as an intermediate state or for non-critical hardware. Yield strength is 945 MPa in FHT versus 760 MPa in AC.
Sources
- IN-738 Alloy Technical Data (Inco/Special Metals) — International Nickel Co. / Special Metals (1981)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Superalloys II — High-Temperature Materials for Aerospace and Industrial Power — Wiley (1987)
- UNS N07738 alloy designation (Metals & Alloys in the Unified Numbering System) — SAE/ASTM (2017)
- Cast Ni-base superalloy property compilations (thermophysical and mechanical data) — NIMS / open literature (2020)
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.