Hangbo Alloy Group
Shanghai · Est. 2012
N07740 technical guide: nominal chemical composition, mechanical and physical properties, corrosion resistance, welding, product forms and ASTM standards...
Inconel 740 (UNS N07740) is a precipitation-hardenable nickel-chromium alloy. γ′-strengthened for 700 °C-class creep. Designed for ultra-supercritical power plants. This guide covers its nominal chemical composition, typical mechanical and physical properties, corrosion behaviour, welding, common applications, available product forms and the ASTM standards that apply — everything a specifier needs to evaluate Inconel 740 for a project.
Inconel 740 belongs to the precipitation-hardenable nickel-chromium alloy class of materials. It is γ′-strengthened for 700 °c-class creep. It is designed for ultra-supercritical power plants. It is good steam-side oxidation resistance.
Nominal (wt%) composition of Inconel 740 (UNS N07740):
| Element | Composition (wt%) |
|---|---|
| Nickel (Ni) | ≥ 45.0 |
| Chromium (Cr) | 23.0 – 27.0 |
| Cobalt (Co) | 15.0 – 22.0 |
| Molybdenum (Mo) | 0.5 – 2.5 |
| Aluminium (Al) | 0.2 – 1.0 |
| Titanium (Ti) | 1.0 – 2.0 |
| Niobium (Nb) | 1.3 – 2.3 |
| Iron (Fe) | ≤ 3.0 |
| Carbon (C) | 0.02 – 0.08 |
| Manganese (Mn) | ≤ 1.0 |
| Silicon (Si) | ≤ 1.0 |
| Sulphur (S) | ≤ 0.015 |
Typical physical properties:
| Property | Value |
|---|---|
| Density | 8.20 g/cm³ |
| Melting Range | 1300 – 1360 °C |
| Thermal Expansion (20–1000 °C) | 14.0 µm/m·K |
| Thermal Conductivity (100 °C) | 11.6 W/m·K |
| Modulus of Elasticity | 210 GPa |
Typical room-temperature mechanical properties (annealed / specified condition unless noted):
| Property | Typical Value |
|---|---|
| Tensile Strength (Rm), aged | 900 MPa (130 ksi) |
| Yield Strength, 0.2% (Rp0.2), aged | 620 MPa (90 ksi) |
| Elongation in 50 mm, aged | 25% |
| Hardness (Rockwell C), aged | 26 – 36 HRC |
| Property | Value |
|---|---|
| Creep rupture at 700 °C / 100 000 h | ≈ 150 MPa |
| Service temperature | Up to 750 °C (USC steam) |
740 is an age-hardenable Ni-Cr-Co alloy developed for ultra-supercritical (USC) and advanced-ultra-supercritical (A-USC) power plants. It combines 700 °C-class creep strength with good steam-side oxidation and fire-side corrosion resistance, enabling higher steam temperatures and plant efficiency.
Welded with matching or overalloyed fillers under a qualified procedure; post-weld heat treatment / aging is required to develop the γ′ strengthened properties. Fabrication follows the boiler code for the intended plant.
The grade is supplied to the following common specifications:
| Standard | Product Form / Scope |
|---|---|
| ASTM B983 | Seamless pipe & tube for USC service |
| ASTM B637 (equiv. cond.) | Bar & forgings reference |
Standards & References. Specifications cited on this page; confirm current revisions with the issuing body.
General references: Nickel Institute · AMPP (corrosion) · SAE International · ASTM International
740 is an age-hardenable Ni-Cr-Co alloy engineered for ultra-supercritical (USC) power boilers. It provides 700 °C-class creep strength with good steam-side oxidation resistance, allowing higher steam temperatures and better plant efficiency.
In the aged condition: ≈ 900 MPa tensile, ≈ 620 MPa yield, ≈ 25 % elongation, 26–36 HRC, with creep-rupture strength near 150 MPa at 700 °C / 100 000 h.
Mainly USC and A-USC boiler super-heater/reheater tubing, high-temperature headers and steam piping where efficiency gains depend on materials that survive 700 °C steam.
Yes, with matching or overalloyed fillers under a qualified procedure, followed by post-weld heat treatment / aging to develop the γ′ strengthened microstructure.
740 is stronger in long-term creep at 700 °C than solid-solution alloys like 617 or 230, because it is γ′-precipitation hardened, at the cost of more complex fabrication heat treatment.
Seamless pipe and tube for USC service are covered by ASTM B983, with bar/forging references under ASTM B637-type conditions.
As a dedicated nickel alloy manufacturer serving power generation, aerospace sectors, Hangbo Alloy Group supplies the grades discussed here across all standard product forms with full ASTM/ASME documentation and EN 10204 3.1 certification. Our material is specified for applications where corrosion resistance, high-temperature strength, and traceable quality are non-negotiable. See our production & testing facilities for more on how every heat is verified.