Inconel 740H (UNS N07740) - A-USC Boiler Superalloy Supplier of Bars, Tubes & Forgings | Shanghai Hangbo Alloy Group
Date: 2026年8月14日 Categories: News Views: 218
By Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier | ISO 9001:2015 | Est. 2012
Contact: sales@hangboalloy.com | hangbo@nickel-alloy.com | WhatsApp (Lisa): +86 13611656360
Quick Answer: What Is Inconel 740H?
Inconel 740H (UNS N07740) is a γ′-strengthened nickel-cobalt-chromium superalloy developed for Advanced Ultra-Supercritical (A-USC) coal-fired boiler tubing operating at 700-760°C and 35 MPa steam — conditions beyond the capability of stainless steels and conventional nickel alloys. With 25% chromium, 20% cobalt, and 1.5% titanium + aluminum, it delivers the creep strength, fireside corrosion resistance, and steam-side oxidation resistance required for the next generation of high-efficiency coal plants. Shanghai Hangbo Alloy Group supplies Inconel 740H as tubes, bars, and forgings.
Industry Pain Point: A-USC boiler development (700°C class) has been stalled for two decades by a single material problem: no commercially available alloy simultaneously provides 100,000-hour creep strength of 100 MPa at 700°C AND resistance to coal-ash fireside corrosion AND steam oxidation. Inconel 740H — after a decade of EPRI-led alloy development and refinement — finally meets all three criteria, unlocking 700°C supercritical steam and the 8-10% efficiency gain that comes with it.
Key Properties at a Glance
| Property | Value |
|---|---|
| UNS Number | N07740 |
| Alloy Family | Ni-Co-Cr γ′ Strengthened |
| Density | 8.05 g/cm3 |
| Melting Range | 1310-1380C |
| Tensile (Aged) | >= 1000 MPa (145 ksi) |
| Yield (Aged) | >= 700 MPa (102 ksi) |
| Elongation (Aged) | >= 20% |
| Key Standards | ASTM B983 (pending), ASME Code Case 2702 |
Product Overview
Inconel 740H is the flagship alloy of the A-USC boiler program. Developed by Special Metals in cooperation with EPRI, it is an evolution of Inconel 740 optimized for:
- 700°C creep strength: 100 MPa for 100,000 hours — approximately 5x the allowable stress of the best stainless (Super 304H) at this temperature.
- Fireside corrosion: 25% Cr + 20% Co provides outstanding resistance to coal-ash/salt-deposit attack.
- Steam oxidation: The Cr₂O₃ scale remains protective in high-temperature steam — no exfoliation.
Key compositional features:
- 20% Cobalt: Raises γ′ solvus, stabilizing the strengthening phase to 760°C+.
- 1.5% Ti/Al: γ′ (Ni₃(Al,Ti)) precipitation hardening.
- Tight impurity control: B, Zr, P optimized for long-term microstructural stability.
Shanghai Hangbo Alloy Group supplies Inconel 740H in tubes (the dominant form for boiler waterwall/superheater service), bars, and forgings.
Executive Standards
| Product Form | Standard |
|---|---|
| Seamless Tube | ASME Code Case 2702 |
| Bar & Forging | ASTM B983 |
| Welding Filler | ERNiCrCoMo-3 |
Chemical Composition (wt.%)
| Element | Min | Max | Role |
|---|---|---|---|
| Ni | Balance | -- | Matrix |
| Cr | 23.5 | 26.5 | Fireside corrosion + steam oxidation |
| Co | 19.0 | 21.0 | γ′ solvus stabilization |
| Ti | 1.3 | 1.7 | γ′ former |
| Al | 0.8 | 1.2 | γ′ former |
| Mo | 0.2 | 1.0 | Solid-solution strengthening |
| Fe | -- | 2.0 | Control |
| Nb | 1.3 | 1.7 | γ′ former |
| C | 0.005 | 0.06 | Control |
| B | 0.001 | 0.006 | Creep ductility |
Mechanical & Physical Properties
Room-Temperature (Solution 1150C + Age 800C/16h)
| Property | Value |
|---|---|
| Tensile Strength | >= 1000 MPa (145 ksi) |
| Yield Strength 0.2% | >= 700 MPa (102 ksi) |
| Elongation | >= 20% |
700°C Creep-Rupture (Target)
| Stress | Life |
|---|---|
| 100 MPa | >= 100,000 h (design target) |
| 150 MPa | ~10,000 h (typical) |
Heat Treatment
Solution Anneal: 1120-1150C (2050-2100F), rapid cool.
Age: 760-800C (1400-1475F), 16 hours, air cool.
Industry Applications
| Industry | Component | Why 740H? |
|---|---|---|
| Power (A-USC) | Superheater/reheater tubes, headers | 700°C steam — 8-10% plant efficiency gain |
| Coal-Fired Boilers | Waterwall tubes, pendants | Fireside corrosion + creep |
| Steam Turbines | High-temp bolt materials | Strength + steam oxidation resistance |
| Petrochemical | High-temp hydrogen service | 700°C-class capability |
Quality Assurance: 7-Stage
- Raw Material: Ni, Co, Cr, Ti, Nb verified by OES/ICP.
- VIM Melt: Co +/-0.3%, Ti +/-0.1%, Nb +/-0.1%, B verified.
- Hot Working: 1120-1180C, finishing >=1000C, reduction >=4:1.
- Solution Anneal: 1120-1150C verified.
- Aging Verification: Hardness 30-38 HRC; tensile per lot.
- NDE: 100% UT bars; ET/hydro tubes. PMI every piece.
- Documentation: EN 10204 3.1 MTC. SGS/TUV/BV witness.
Frequently Asked Questions
Q1: What is Inconel 740H used for?
A-USC boiler superheater/reheater tubing at 700-760°C steam, coal-fired boiler waterwall tubes, and high-temperature steam turbine components.
Q2: 740H vs 617?
617: solid-solution strengthened, good to 650°C. 740H: γ′-strengthened, designed for 700-760°C — higher creep strength at A-USC conditions.
Q3: 740H vs Haynes 282?
282: newer, easier weldability, similar temperature class. 740H: more extensive A-USC qualification data.
Q4: Is it weldable?
Yes, with ERNiCrCoMo-3 (FM 263/740H class) filler. Requires careful HAZ control.
Q5: What is the price?
$80-130/kg EXW — premium alloy. Contact sales@hangboalloy.com.
Q6: Product forms?
Tubes (OD 25-114mm), bars (10-200mm), forgings. SGS available.
Q7: What heat treatment?
Solution 1120-1150°C + age 760-800°C/16h.
Q8: What is the density?
8.05 g/cm3.
Q9: Does Shanghai Hangbo ship internationally?
Yes — FOB/CIF/DAP to 40+ countries.
Q10: What is the max service temperature?
~760°C continuous (A-USC class).
Q11: Why cobalt at 20%?
Raises γ′ solvus, keeping the strengthening phase stable at 700°C+.
Q12: What standards apply?
ASME Code Case 2702, ASTM B983.
Q13: Is it magnetic?
Non-magnetic.
Q14: What efficiency gain does it enable?
8-10% plant efficiency vs conventional 600°C supercritical plants.
Q15: How long is the 700°C creep life?
Design target: 100 MPa for 100,000 hours.
Contact Shanghai Hangbo Alloy Group
| Channel | Details |
|---|---|
| Company | Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier |
| Website | www.nickel-alloy.com |
| Email (Sales) | sales@hangboalloy.com |
| Email (Technical) | hangbo@nickel-alloy.com |
| WhatsApp (Lisa) | +86 13611656360 |
| Address | Room 1508, No. 288 Shiyi Road, Baoshan District, Shanghai 200940, China |
Shanghai Hangbo Alloy Group - Complete Product Range
| Family | Available Grades |
|---|---|
| Pure Nickel | NI200, NI201, N4, N5, N6 |
| Monel | 400, 401, 404, 502, K-500, R-405 |
| Inconel | 600, 601, 617, 625, 690, 693, 706, 718, 740H, X-750, 725 |
| Incoloy | 800, 800H, 800HT, 825, 907, 925, 926, 945, A-286, 25-6HN, 27-7MO |
| Hastelloy | C-276, C-22, C-22HS, C-2000, C-4, G-30, G-35, G-50, X, B-2, B-3, B-4, HYBRID-BC1, N |
| Super Austenitic | 904L, Alloy 28, Alloy 31, 254SMO, 20Mo-6, AL-6XN |
| Chromium-Rich | Alloy 33 |
| High-Strength Stainless | Nitronic 50, Nitronic 60, PH13-8Mo |
| Chlorination-Resistant | Alloy 45 |
| Nimonic | 75, 80A, 90, 95, 105, 115, 263 |
| Haynes | 25, 188, 214, 230, 242, 282, 556, HR-120, HR-160 |
| RA Series | RA330, RA333 |
| Precision | 1J22, 1J46, 1J50, 1J79, 1J85, 3J21, 4J29, 4J32, 4J36, 4J45 |
| High-Strength | 18Ni250, 18Ni300, AerMet 100 |
| Heating | Cr20Ni80, Cr40Ni60 |
| Specialty | Alloy 20, Alloy 59, Inconel 686, 602CA |
Product Forms: Bars(6-500mm) | Tubes(OD 6-610mm) | Plates(0.1-100mm) | Forgings | Welded Pipes | Fittings | Wire(0.05-10mm) | Strip(0.02-4.0mm)
SGS/BV/TUV. Contact: sales@hangboalloy.com | WhatsApp (Lisa): +86 13611656360 | www.nickel-alloy.com
