Hastelloy X / (2.4665) / UNS N06002 / AMS 5536 / AMS 5754
DEFENCE METAL
Hastelloy X
UNS N06002 · W.Nr. 2.4665 · NiCr21Fe18Mo9 (ISO) · JIS NW6002 · Nickel-base, solid-solution strengthened: ~22% Cr – 18% Fe – 9% Mo – 1.5% Co – 0.6% W – 0.1% C, balance Ni (~47%). Specification ranges: Cr 20.5-23.0 · Mo 8.0-10.0 · Fe 17.0-20.0 · Co 0.5-2.5 · W 0.2-1.0 · C 0.05-0.15. NOT PRECIPITATION HARDENABLE.
Bought for gas turbine combustion-zone hardware (combustor liners, transition ducts, flame holders, exhaust cones, afterburner parts) and industrial furnace internals.
Forms
Bar/rod · plate · sheet · strip · seamless pipe/tube · welded pipe/tube · forgings · fittings · welding wire/electrode. (Product-form list taken from the defencemetal.com page.)
Standards
AMS 5536 (sheet, strip, plate) · AMS 5754 (bars, forgings, rings and forging/ring/heading stock) · AMS 5587 (seamless tubing) · AMS 5588 (welded tubing) · AMS 5798 (welding wire). ASTM: B435 (plate/sheet/strip) · B572 (rod) · B472 (billets and bars for reforging) · B622 (seamless pipe and tube) · B619 (welded pipe) · B626 (welded tube) · B366 (factory-made wrought fittings). ASME: SB-435 · SB-572 · SB-619 · SB-622 · SB-626 · SFA-5.14. AWS A5.14 ERNiCrMo-2 (filler wire). DIN 17742 (2.4665). Every AMS number was verified against the SAE specification title, which states the composition 47.5Ni-22Cr-1.5Co-9.0Mo-0.60W-18.5Fe — that composition is N06002. CAUTION: some sales pages list ‘AMS 5574’ for Hastelloy X round bar.
Advantage
It keeps its ductility after long hot exposure. After 16,000 hours at 650, 760 and 870 °C the room-temperature elongation drops but in no case falls below the 15-30% band (peer-reviewed study), and metal loss measured in flowing air at 980 °C for 1008 hours was only 0.29 mils per side (~7 µm).
Welding
Filler metal: AMS 5798 / AWS A5.14 ERNiCrMo-2 matching filler wire. Special Metals also lists INCONEL filler metal 617 and INCONEL electrode 117 for this alloy. No preheat is required; the part is warmed above ambient only enough to prevent moisture condensation.
Limits
This is not a precipitation-hardening alloy; strength is not developed by ageing. Long exposure in the 650-870 °C band precipitates carbides, sigma and mu phase: hardness rises while room-temperature ductility and impact toughness fall.
Compiled from manufacturer data sheets · confirm against the current specification before ordering
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Standards by Product FormWelding, Heat Treatment and MachiningWhich Alloy for Which Service?Frequently Asked Questions
Hastelloy X is a nickel-based superalloy known for its excellent oxidation resistance, high temperature strength and weldability. It sits on the high temperature side of the nickel alloy group; its UNS designation is N06002.
Thanks to the high chromium and molybdenum content of its composition it retains its oxidation and rupture resistance up to 1100 °C. Its microstructure is austenitic with minimal grain boundary precipitation — and that is what makes the alloy suitable for post-weld processing.
What separates Hastelloy X from the C-276 and C-22 grades in the same family is a matter of priority: the C series is optimised for aggressive acid environments, X for high temperature and oxidation. In hot, oxidising service such as a combustion chamber, X is the grade to use.
Jet engine combustion chambers, exhaust systems and burner cans; gas turbine components, heat exchangers and recuperators; and reforming reactors and oxidising gas lines in petrochemicals are the main applications. It can be supplied as sheet, plate, bar, forgings and tube.
Round bar · Flat bar · Plate · Sheet · Tube · Forgings All forms are supplied to order.
Standards by Product Form
STANDARDS BY PRODUCT FORM
DEFENCE METAL
Product form
Standards
Sheet / strip / plate
AMS 5536 · ASTM B435 · ASME SB-435
Bar, forgings, rings
AMS 5754 · ASTM B572 · ASME SB-572
Billets and bars for reforging
ASTM B472
Seamless pipe and tube
AMS 5587 · ASTM B622 · ASME SB-622
Welded pipe
ASTM B619 · ASME SB-619
Welded tube
AMS 5588 · ASTM B626 · ASME SB-626
Factory-made wrought fittings
ASTM B366
Welding wire
AMS 5798 · AWS A5.14 ERNiCrMo-2 · ASME SFA-5.14
Material number / DIN
W.Nr. 2.4665 · DIN 17742
The AMS numbers were verified against the composition in the SAE specification title (47.5Ni-22Cr-1.5Co-9.0Mo-0.60W-18.5Fe), which is N06002. AMS 5588 (welded tubing) could only be verified through the SAE/ANSI specification title; the 4-independent-source requirement was not met, so the row is kept but flagged here. Three sources were found for AMS 5587. For ASTM B472, the ASTM standard text itself (N06002 appears in its scope list) and the ASTM store record were found; the 4-source requirement was not met and the row carries this caveat. Some sales pages list ‘AMS 5574’ for Hastelloy X bar; AMS 5574 is a 309S stainless seamless tubing specification and has nothing to do with N06002. Rolled Alloys cites AMS 5799 for covered electrodes; that number was found in only one source and is therefore not placed on the map.
The most common mix-up when ordering Hastelloy X is which specification covers which product form. AMS 5536 covers sheet, plate and strip; AMS 5754 covers bar and forgings — the two are not interchangeable. Stating the product form and the specification together on the order prevents certificate mismatches.
1175 °C (2150 °F); practice range 1165-1190 °C (2125-2175 °F)
2 · COOL
3 · AGEING
see the table below
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Solution treatment
Temperature
1175 °C (2150 °F); practice range 1165-1190 °C (2125-2175 °F)
Time
Long enough for the full section to reach temperature; thickness dependent (no single soak time could be confirmed against 4 sources)
Cooling
Rapid cool — rapid air cool or water quench. Bright-annealed product is cooled in hydrogen.
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Bands to avoid
Step
Carbide / sigma / mu phase precipitation band
Range
650-870 °C (1200-1600 °F)
Effect
Age hardening, loss of room-temperature ductility and impact toughness; do not form in this band, and re-solution anneal material that has been exposed to it.
DEFENCE METAL
Bands to avoid
Step
Range to avoid for postweld heat treatment
Range
538-816 °C (1000-1500 °F)
Effect
Harmful secondary phases precipitate. Use a full solution anneal instead if a PWHT is needed.
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Hot working
Soak
At least 0.5 hour per 25 mm (1 in.) of thickness, 1175 °C (2150 °F) maximum
Finish
Finish around 955 °C (1750 °F); 25-40% reduction
DEFENCE METAL
Additional information
Alloy type
Solid solution — not precipitation hardenable. There is NO ageing (H900-type) schedule.
Schematic; the time axis is not to scale. No published TTT/CCT curve was found, so no curve is drawn. This alloy is not precipitation hardenable; the schematic has no ageing step. No product-form-specific solution anneal schedule could be confirmed against 4 independent sources; every source found gives the same temperature and cooling for all wrought product forms. The only difference is hydrogen cooling for bright-annealed product. Only two sources were found for soak time (Rolled Alloys: 15 minutes per 3.2 mm of thickness; Virgamet: 15-30 minutes). The 4-source requirement was not met, so no figure is given.
Welding
Hastelloy X is among the most weldable nickel-based superalloys. GTAW (TIG), GMAW (MIG), shielded metal arc (SMAW) and resistance welding are all applicable. Matching-composition ERNiCrMo-2 wire (AWS A5.14 / AMS 5798) is used as filler metal; for covered-electrode welding, ENiCrMo-2 (AWS A5.11). The low level of grain boundary precipitation keeps post-weld cracking risk low.
Heat treatment
The alloy is strengthened by solid solution rather than precipitation hardening, so no ageing treatment is applied. It is supplied in the solution annealed condition: typically annealed at around 1177 °C and rapidly cooled.
Machining
Because it retains its strength at elevated temperature, cutting forces are high and the material work hardens quickly. Rigid setups, sharp and regularly replaced tooling, low cutting speed and high feed are preferred. Letting the tool dwell and rub on the workpiece hardens the surface and makes the next pass harder.
Which Alloy for Which Service?
Nickel-based alloys are not interchangeable; each is optimised for a different priority. A short guide:
Selection Guide · Nickel-Based Alloys
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Hastelloy X
Oxidising hot gas above 900 °C — combustion chambers, exhaust systems, turbine components
High temperature oxidation; a more economical alternative to Hastelloy X
Frequently Asked Questions
What is the maximum service temperature of Hastelloy X?
A single figure would be misleading, because the limit depends on the application. Oxidation resistance is retained up to roughly 1100 °C. For pressure equipment, the design limit under ASME Section VIII Div. 1 is 899 °C. Mechanical strength falls off noticeably above 816 °C — for highly stressed parts that is the governing limit.
What is the difference between AMS 5536 and AMS 5754?
Same material, different product form. AMS 5536 applies to sheet, plate and strip; AMS 5754 to bar and forgings. Both require the material to be supplied in the solution annealed condition.
Can Hastelloy X be used in place of Inconel 625?
They are not direct substitutes. Inconel 625 excels in chloride and seawater environments and at moderate temperature, while Hastelloy X is optimised for oxidising gas environments at high temperature. In aerospace and power applications a grade substitution is only possible if the customer specification allows it.
→ Contact us for Hastelloy X stock availability, sizes and AMS 5536 / AMS 5754 certified supply.
In the chart, a value given as a range is drawn at its lower bound; the full range is in the table. This row is TYPICAL data, not a specification minimum. It cannot be used as an acceptance criterion. The minimum mechanical requirements of ASTM B435 / B572 / B622 / B619 and AMS 5536 / 5754 / 5587 / 5588 sit inside paywalled standard texts and could be found in only one independent source (tensile ≥ 655 MPa for ASME SB-435), so they are NOT shown in this diagram. When a per-product-form minimum table is required, the relevant ASTM/AMS text must be purchased and read. The spread between sources comes from product form (plate/sheet/bar) and producer; no average was taken, a range is given instead. No hardness data confirmed by 4 independent sources was found, so the HRC field is left empty.
