Bar and Rod
Plate and Sheet
Strip
Pipe and Tube
Wire
Welding
Powder Material
Cast Products
Forged Products
Fittings
Fastening
Round Bar:
φ2–500 mm, 1–6 m length
Flat/Square Bar:
4–100 mm thickness/width
Hex Bar:
A/F 3–100 mm
Hollow Bar:
OD 20–300 mm
Sheet:
0.3–6 mm thickness
Medium Plate:
6–25 mm thickness
Heavy Plate:
25–100 mm thickness
Standard Strip:
0.05–3 mm thick,
10–600 mm wide
Precision strip:
0.01–0.5 mm thick,
tight tolerance ±0.005 mm
Foil:
0.005–0.1 mm thick
Seamless Tube:
OD 6–450 mm,
WT 1–50 mm,
1–12 m length
Welded Tube:
OD 10–600 mm,
WT 1–20 mm
Capillary Tube:
OD 1–10 mm,
WT 0.1–2 mm
Wire Form:
Cold Drawn Wire,
Bright Wire,
Spring Wire,
Fine Wire,
Ultra-fine Wire
General Diameter:
φ0.1–10 mm
Coil Weight:
50–500 kg,
customizable tolerance
Solid Wire:
φ0.8–4.0 mm
Flux-cored Wire:
φ1.2–4.0 mm
Welding Rod:
φ2.0–5.0 mm
Powder Form:
AM 3D Printing Powder,
Spherical Powder,
Gas-atomized Powder,
Water-atomized Powder
Particle Size:
10–150 μm
Sphericity:
≥90% for AM grade
Cast Ingot:
φ200–800 mm
Precision Casting:
min wall 0.5 mm
Cast Pipe:
OD 100–600 mm,
WT 10–50 mm
Forged Bar:
Φ35–500 mm
Forged Ring:
OD 200–2000 mm
Forging Weight:
1–5000 kg
Fittings Form:
Elbow, Tee, Reducer, Flange, Cap, Outlet, Lap Joint
Size range:
1/2''–24'' (DN15–DN600)
Wall thickness:
Sch10–Sch160, STD, XS, XXS
Pressure Class:
150–2500 LB
Fastening Form:
Bolt, Nut, Screw, Stud, Washer, Pin, Rivet
Metric: M3–M64
Imperial: #4–2.5''
Length: 6–500 mm
Alloy 740H is an age-hardenable nickel-cobalt-chromium superalloy developed specifically for advanced ultra-supercritical (A-USC) coal-fired boilers. This datasheet presents the material within the American (ASTM / ASME / UNS) standard system.
A derivative of the aerospace alloy Nimonic 263 with a raised chromium content of about 24.5%, Alloy 740H combines excellent steam and coal-ash (fire-side) corrosion resistance with high creep strength, good microstructural stability and heavy-section weldability. It is age-hardened by precipitation of the gamma-prime (γ′, Ni₃(Al,Ti,Nb)) phase, with the niobium, aluminium and titanium balanced to give both thermal stability and high strength. It is the first — and to date the only — age-hardened nickel-base alloy approved by the ASME Boiler & Pressure Vessel Code for welded construction in the creep-limited temperature regime (Code Case 2702), with a maximum use temperature of 800 °C (1472 °F), and is designed for steam at about 760 °C. It is supplied in the solution-annealed and aged condition.
Typical applications include superheater and reheater tubing, headers and main steam piping for A-USC boilers, supercritical-CO₂ system components, and concentrated-solar-power receiver tubing.
| Property | Value | Unit |
|---|---|---|
| Density | 8.05 | g/cm³ |
| Melting range | 1288–1362 | °C |
| Elastic modulus | 221 | GPa |
| Coefficient of thermal expansion (20–100 °C) | 12.6 | µm/m·°C |
| Thermal conductivity (20 °C) | 11.0 | W/m·K |
| Specific heat (20 °C) | 448 | J/kg·K |
| Structure | Austenitic (FCC) | — |
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Nickel | Ni | Balance | — | Base element; γ′ matrix |
| Chromium | Cr | 23.5 | 25.5 | Steam / coal-ash corrosion resistance |
| Cobalt | Co | 15.0 | 22.0 | Solid-solution / γ′ stability |
| Niobium | Nb | 0.50 | 2.50 | γ′ (Ni₃(Al,Ti,Nb)) strengthening |
| Titanium | Ti | 0.50 | 2.50 | γ′ strengthening |
| Aluminium | Al | 0.20 | 2.00 | γ′ strengthening |
| Molybdenum | Mo | 0.50 | 2.00 | Solid-solution strengthening |
| Iron | Fe | — | 3.00 | Residual |
| Manganese | Mn | — | 1.00 | Deoxidiser |
| Silicon | Si | — | 0.50 | Deoxidiser |
| Carbon | C | 0.005 | 0.08 | Carbide formation |
Solution-annealed and aged condition, typical room-temperature values for UNS N07740.
| Condition | Property | Value |
|---|---|---|
| Solution annealed & aged | Tensile strength (UTS) | ≥1000 MPa (145 ksi) |
| Solution annealed & aged | 0.2% yield strength | ≥620 MPa (90 ksi) |
| Solution annealed & aged | Elongation at break | ≥20 % |
| Solution annealed & aged | Reduction of area | ≥25 % |
| — | Elastic modulus | 221 GPa |
Confirm against the mill test report. The alloy's primary advantage is its high creep-rupture strength, which exceeds that of alloy 617 in the A-USC temperature range.
| Environment | Performance | Notes |
|---|---|---|
| Steam oxidation | Excellent | Designed for ~760 °C A-USC steam |
| Coal-ash / fire-side | Excellent | High Cr (24.5%) resists fuel-ash corrosion |
| High-temperature oxidation | Excellent | To about 800 °C use temperature |
| Supercritical CO₂ | Very Good | Under evaluation for sCO₂ systems |
| Creep / thermal stability | Excellent | Primary design advantage |
The high chromium content gives outstanding steam-oxidation and coal-ash corrosion resistance, while the γ′ precipitation provides the creep strength needed for advanced ultra-supercritical service.
A γ′ precipitation-hardenable superalloy; strengthened by solution annealing followed by ageing, per ASME Code Case 2702.
Solution Treatment Solution anneal at a minimum of 1100 °C (2010 °F), holding about 1 hour per 25.4 mm of thickness (minimum 30 minutes); the range may extend to about 1160 °C. Water quench after solution annealing.
Precipitation Hardening (Ageing) Age between 760 °C (1400 °F) and 815 °C (1500 °F) for a minimum of 4 hours, precipitating γ′ (Ni₃(Al,Ti,Nb)). The minimum ageing time is extended for sections above 50 mm.
Weldable in heavy sections — a key design feature — though, as with all high-nickel γ′ alloys, welding is demanding. For A-USC service the alloy is normally welded in the solution-annealed and aged condition followed by post-weld heat treatment, per Code Case 2702.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Good (skilled) | Matching alloy 740H filler |
| GMAW / MIG | Acceptable | Matching filler |
| SMAW / stick | Acceptable | Matching electrode |
Follow Code Case 2702 welding rules and weld strength reduction factors; apply post-weld heat treatment to restore properties.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Preferred condition | Solution-annealed for machining, then age |
| Machinability | Difficult; rigid setups, carbide tooling, slow speeds |
| Coolant | Ample coolant |
Forming Processes
| Process | Notes |
|---|---|
| Cold forming | In the annealed condition; work-hardens |
| Hot forming | Performed hot; solution and age afterward |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| A-USC boilers | Superheater / reheater tubing, headers, steam piping | Creep strength + steam/coal-ash corrosion to ~760 °C |
| Power generation | High-temperature pressure parts | Creep strength + weldability |
| Supercritical CO₂ | sCO₂ system components | Oxidation + creep strength |
| Concentrated solar | Receiver tubing | High creep and fatigue strength |
| Product Form | Standard | Notes |
|---|---|---|
| Tube and pipe | ASME Code Case 2702 | UNS N07740 |
| Plate and sheet | ASME Code Case 2702 | — |
| Bar and forgings | ASME Code Case 2702 | — |
| Code construction | ASME B&PV Section I | To 800 °C max use temperature |
Nickel-cobalt-chromium γ′ precipitation-hardenable superalloy. UNS N07740.
| Alloy | Cr % | Co % | Strengthening | Best Used For |
|---|---|---|---|---|
| Alloy 740H | 23.5–25.5 | 15–22 | γ′ (Al, Ti, Nb) | A-USC boiler alloy; creep + steam/coal-ash corrosion to ~760 °C |
| Alloy 263 (Nimonic) | 19–21 | 19–21 | γ′ (Al, Ti) | Aerospace sheet; 740H parent alloy |
| Alloy 617 | 20–24 | 10–15 | Solid solution | High-temperature solid-solution alloy |
| Alloy 718 | 17–21 | ≤1 | γ′ + γ″ (Nb, Ti) | Most-used high-strength superalloy to ~700 °C |
| Alloy 625 | 20–23 | ≤1 | Solid solution | Corrosion + moderate high-temperature strength |
