Project Description
Hastelloy N / UNS N10003 is a nickel-molybdenum-chromium superalloy originally developed at Oak Ridge National Laboratories as the structural and container material for molten fluoride salt reactors. Its unique high-molybdenum, low-chromium chemistry delivers exceptional resistance to hot fluoride salts, hydrofluoric acid, and a wide spectrum of reducing media — making it indispensable in high-temperature chemical processing, oil refinery HF alkylation units, and advanced nuclear fuel cycle facilities where no other commercial alloy can offer equivalent service life.
Hastelloy N — Overview
Hastelloy N (UNS N10003) is the definitive nickel alloy for service in fluoride salt and hydrofluoric acid environments at elevated temperatures. Its nominal composition — 71% Ni, 16% Mo, 7% Cr — creates an austenitic matrix with outstanding resistance to molten fluoride salts in the 700–870°C range, where corrosion attack falls below one mil per year (25 µm/yr). No measurable oxidation occurs in air up to 649°C, and the alloy retains useful mechanical strength to 982°C for continuous service.
In the oil and gas and petrochemical industries, Hastelloy N is the specified material of construction for HF alkylation unit internals — the process used by over 50% of global gasoline refineries to produce high-octane alkylate blendstock. The concentrated hydrofluoric acid catalyst (≥86% HF) attacks virtually all stainless steels and Ni-Mo-Cr alloys at elevated temperature; Hastelloy N’s corrosion rate remains below 5 mpy in 48% HF at 79°C, far outperforming C-276 or 625 in this specific environment.
SHUNFU METAL procures Hastelloy N exclusively from VIM-refined heats, which is the only melt route that achieves the tight carbon control (≤0.06%) and elemental balance required for consistent HF resistance. Incoming heats are re-verified by our in-house OES spectrometer before any cutting or forging operation, ensuring no alloy substitution reaches the customer.
N10003 Equivalent Grades & Standards
Hastelloy N is a relatively specialized alloy; its international equivalents and applicable standards are listed below for engineering and procurement reference.
| Standard Body | Designation / Grade | Applicable Form |
|---|---|---|
| UNS (USA) | N10003 | All wrought forms |
| ASTM / ASME | B573 / SB573 (Rod & Bar) B434 / SB434 (Plate / Sheet / Strip) B366 / SB366 (Fittings) B619 / SB619 (Welded Pipe & Tube) |
Bar, Plate, Fittings, Pipe |
| AMS (USA, Aerospace) | AMS 5607 (Sheet / Plate / Strip) AMS 5771 (Bar / Forgings) |
Sheet, Plate, Bar, Forging |
| AWS (Welding) | SFA 5.14 / A 5.14 — ERNiMo-2 (filler wire) | Weld consumables |
| ASME Boiler & PV Code | Section VIII Div. 1 — approved to 704°C Section VIII Div. 2 — approved to 427°C Section XII — approved to 343°C B16.5 / B16.34 — approved to 704°C |
Pressure vessel & piping components |
| Military | Mil-N-24390B | Naval / defense applications |
| Trade Name | HASTELLOY® N (Haynes International) | All forms |
Note: Hastelloy N does not have a widely-used European EN/DIN or GOST equivalent — it is predominately specified by UNS N10003, ASTM, and AMS designations. EN W.Nr. equivalents have not been formally established for this alloy.
Oil, Gas & Petrochemical Applications of Hastelloy N
Hastelloy N bar stock is machined into the following specific components in oil refining, gas processing, chemical, and advanced energy applications:
- Reactor settler internals
- Acid re-run column trays
- Pump shafts & impellers
- Valve stems & seat rings
- Heat exchanger tube sheets
- HF storage vessel nozzles
- Fluorine gas manifold fittings
- Reactor agitator shafts
- Distillation column internals
- Transfer pump housings
- Molten salt reactor vessel internals
- Fluoride salt pump shafts
- Heat exchanger tube bundles
- Bearing & seal assemblies
- Valve body components
- HF scrubber spray headers
- Fluoride absorber packing supports
- Neutralization reactor agitators
- Vent scrubber internals
- Dip-tube injection quills
- Molten salt reactor structural bars
- UF₆ handling vessel components
- Criticality monitoring fixtures
- Fluoride volatility process hardware
- Fuel salt transfer pump bodies
- High-temp pressure vessel studs
- Flange bolting for HF service
- Bonnet bolts for HF valves
- Thermocouple well mandrels
- Instrument root valve stems
Supply Forms & Size Range — Hastelloy N Bar
SHUNFU METAL supplies Hastelloy N bar and forged forms with AMS 5771 and ASTM B573 certification. All material ships with full heat traceability from VIM-qualified melt sources; forged bars are solution-heat-treated and water-quenched at SHUNFU’s controlled-atmosphere furnace before dimensional inspection.
| Form | Size Range | Condition | Standard |
|---|---|---|---|
| Hot-Rolled Round Bar | Ø 6 – 250 mm | Solution Annealed & Pickled | ASTM B573 / AMS 5771 |
| Cold-Drawn Round Bar | Ø 3 – 80 mm | Bright Annealed | ASTM B573 / AMS 5771 |
| Forged Round Bar | Ø 80 – 600 mm | Forged + Solution Annealed + WQ | ASTM B573 / AMS 5771 |
| Hot-Rolled Flat Bar | T 6–150 mm × W 15–450 mm | Annealed & Pickled | ASTM B434 |
| Forged Flat Bar / Block | T 20–300 mm × W 60–800 mm | Forged + Solution Annealed | ASTM B573 / AMS 5771 |
| Hex Bar | AF 8 – 100 mm | Bright / Pickled | ASTM B573 |
Standard lengths: 1,000–6,000 mm. Cut-to-length and rough-machined blanks available. EN 10204 Type 3.1 MTC issued with every order. AMS 5771 first-article inspection reports available on request.
Chemical Composition — ASTM B573 / UNS N10003
Composition per ASTM B573 / UNS N10003 and Haynes International nominal data. SHUNFU METAL performs OES heat verification on every lot received; the deliberately low Cr (7%) and high Mo (16%) balance is confirmed before any cutting is authorized, as altering this ratio materially impacts fluoride corrosion performance.
| Element | Ni | Mo | Cr | Fe | Si | Mn | V | C | Co | Cu | W | Al+Ti |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Nominal % | Bal. (≈71) | 16.0 | 7.0 | ≤ 4.0 | ≤ 1.0 | ≤ 0.80 | ≤ 0.50 | 0.06 | ≤ 0.20 | ≤ 0.35 | ≤ 0.50 | ≤ 0.50 |
Defining characteristic: lowest Cr (7%) of any commercial Ni-Mo-Cr alloy, combined with the highest Mo (16%) in the Ni-Cr-Fe family — this inversion vs. C-276 or C-22 is by design. High Mo suppresses oxidation of the alloy surface by fluoride ions; lower Cr avoids chromium fluoride volatilization that would rapidly corrode high-Cr alloys in molten fluoride service. SHUNFU verifies the Mo/Cr ratio on every incoming heat without exception.
Mechanical Properties — Hastelloy N Bar (Solution Annealed)
Standard heat treatment: solution anneal at 1,177°C (2,150°F) for thin sections / 1,185°C (2,165°F) for sections ≥ 6 mm, followed by rapid air cool or water quench. Hastelloy N retains meaningful strength and ductility from cryogenic temperatures to above 982°C. SHUNFU METAL conducts full tensile and Charpy impact testing on each production lot per AMS 5771 requirements.
| Test Temperature | YS 0.2% (MPa) | UTS (MPa) | Elongation (%) | Hardness |
|---|---|---|---|---|
| RT (20°C) | 314 | 794 | 50.7 | ~96 HRB |
| 593°C (1,100°F) | 227 | 599 | 45.3 | — |
| 704°C (1,300°F) | 218 | 480 | 30.0 | — |
| 816°C (1,500°F) | 203 | 385 | 24.3 | — |
| 927°C (1,700°F) | 179 | 234 | 30.0 | — |
| Physical Property | Value |
|---|---|
| Density | 8.86 g/cm³ |
| Melting Range | 1,300–1,400°C |
| Elastic Modulus at RT | 219 GPa |
| Thermal Conductivity at 200°C | 13.1 W/m·K |
| Charpy Impact (Forged Bar, RT) | 80–88 ft-lb (108–119 J) |