NiCr22Fe18Mo Forgings Alloy X · Hastelloy® X equivalent · GH3536

01NiCr22Fe18Mo at a glance

Reference data for writing a drawing callout or a purchase order.

Designation

NiCr22Fe18Mo (DIN 17744)

UNS number

N06002

Werkstoff number

2.4665

Also written

Alloy X, NiCr21Fe18Mo9, AISI 680, GH3536

Trade name

Hastelloy® X (Haynes International)

Alloy family

Ni-Cr-Fe-Mo, austenitic, solid-solution strengthened

Age hardenable

No. Solution anneal only

Forging standard

ASTM B564 / ASME SB-564; DIN 17744

Delivery condition

Solution annealed at approximately 1175 °C (2150 °F), rapid cooled

Oxidation limit in air

Approximately 1200 °C (2200 °F)

Density

8.22 g/cm³ (0.297 lb/in³)

Melting range

1260 to 1355 °C (2300 to 2470 °F)

Tensile strength, min

660 MPa (96 ksi)

Yield 0.2%, min

240 MPa (35 ksi)

Certification

EN 10204 3.1 or 3.2 (third-party witnessed)

Forged by

Jiangyin Jiangnan Metal Co., Ltd., Jiangyin, Jiangsu, China

Temperature ranges

The bands below summarise the behaviour of NiCr22Fe18Mo from room temperature to the solidus.

02What NiCr22Fe18Mo is, and when to specify it

NiCr22Fe18Mo belongs to the Ni-Cr-Fe-Mo family. Nominal chemistry is approximately 47% nickel, 22% chromium, 18% iron and 9% molybdenum, with about 1.5% cobalt and 0.6% tungsten. Chromium forms the oxide scale that provides oxidation and carburisation resistance. Nickel provides resistance to nitriding and chlorination and maintains the austenitic structure. Molybdenum, cobalt and tungsten strengthen the matrix so that load-bearing capacity is retained at high temperature. The iron content of 17 to 20% reduces the cost per kilogram compared with a fully nickel-base superalloy of similar temperature capability.

Strength is developed by solid solution rather than by precipitation. There is no gamma-prime phase, so no ageing treatment is required, no over-ageing occurs in service, and the heat-treatment window is wide. Room-temperature strength is correspondingly modest, with a specified minimum tensile strength of 660 MPa, below that of a precipitation-hardened grade such as Inconel® 718. The alloy is selected for oxidation resistance and long-term stability at temperature rather than for room-temperature strength.

Specify NiCr22Fe18Mo when

• Service is in hot oxidising, reducing or neutral atmospheres up to approximately 1200 °C, and the part must resist scaling rather than carry high stress.
• The component is fabricated and welded, as with combustion hardware, ducting and casings, so that weldability matters as much as strength.
• Long exposure at 650 to 870 °C is expected and the part must remain ductile and dimensionally stable.
• Carburising, nitriding or chloride-bearing atmospheres are present, as in petrochemical reformers and heat-treatment furnaces.
• Cost per kilogram is a factor and the iron content of this grade is an advantage over a cobalt-rich or fully nickel-base alternative.

Specify a different grade when

• Rupture strength above approximately 980 °C governs. Inconel® 617 and Haynes® 230 carry more load for longer at the top of the range.
• Room-temperature or intermediate strength governs. A precipitation-hardened grade such as Inconel® 718 or Waspaloy is more appropriate.
• Aqueous or acid corrosion governs. Alloy X is a heat-resisting alloy rather than a wet-corrosion alloy. Hastelloy® C-276, Alloy 59 or Alloy 625 should be considered instead.
• Sulfidising atmospheres dominate. High-nickel alloys are vulnerable to sulfur attack, and a higher-iron or cobalt-base grade may perform better.

03Chemical composition of NiCr22Fe18Mo

The limits below are the DIN 17744 limits for NiCr22Fe18Mo (2.4665), in weight percent. The ASTM B564, ASTM B572 and AMS 5754 limits for UNS N06002 agree on every major element, so a heat meeting one specification will normally meet the others. The four highlighted rows are the solid-solution strengtheners that define the grade.

Boron, aluminium and titanium residual limits are additionally specified in some standards, in particular the aerospace specifications AMS 5754 and AMS 5536. Where an order is placed to an aerospace or nuclear specification, state the standard and revision on the drawing so that the correct trace-element limits are applied to the heat.

Carbon content

Carbon is specified at 0.05 to 0.15%, which is high compared with a low-carbon wet-corrosion alloy in which carbon is suppressed to avoid grain-boundary chromium depletion. In a heat-resisting alloy the grain-boundary carbides are useful, since they pin the boundaries and contribute creep strength at temperature. For the same reason, NiCr22Fe18Mo should not be substituted for a low-carbon corrosion-resistant grade in aqueous service.

04Mechanical properties of NiCr22Fe18Mo forgings

Specified room-temperature minimums, solution annealed

These are the values a mill test certificate must meet. They are minimums rather than typical results.

Typical as-delivered values

Solution-annealed NiCr22Fe18Mo forgings normally test above the specified minimums. The ranges below are representative and vary with section size, reduction ratio and cooling rate.

Strength at temperature

Short-term tensile strength falls steadily with temperature. Above approximately 650 °C the design is normally governed by creep and stress rupture rather than by the tensile values below.

Ductility after long exposure

NiCr22Fe18Mo retains good ductility after prolonged exposure at 650, 760 and 870 °C (1200, 1400 and 1600 °F) for periods of the order of 16,000 hours. Carbides and µ-phase precipitate within this range and room-temperature ductility falls from the annealed value, but the material remains sufficiently ductile for combustion and furnace hardware subject to thermal cycling. This stability is the main reason the grade is used in preference to stronger alloys in such applications.

05Physical properties of NiCr22Fe18Mo

Values are nominal, at room temperature unless stated. Density is used for estimating forging weight and material cost, and is the value applied by the calculator in section 13.

Thermal conductivity is approximately one fifth that of carbon steel. Billets therefore require a slow heat and a full soak before forging, and heat concentrates at the cutting edge during machining.

06NiCr22Fe18Mo compared with alternative grades

The table compares NiCr22Fe18Mo with the grades most often considered alongside it for high-temperature service.

For combustion cans, ducting, furnace internals and casings that must resist scaling and withstand thermal cycling up to approximately 1200 °C, NiCr22Fe18Mo is normally both suitable and less expensive than the alternatives. Where the part carries sustained load above 980 °C, Alloy 617 or Haynes® 230 are the stronger choice. Where aqueous or acid corrosion governs, a corrosion-resistant grade such as Hastelloy® C-276 or Alloy 625 should be used instead.

07NiCr22Fe18Mo equivalent designations

The same alloy appears on drawings under a number of names. All of the following refer to UNS N06002.

08Applicable standards by product form

UNS N06002 carries maximum allowable stresses in the ASME Boiler and Pressure Vessel Code for elevated-temperature service. Where the forging is a pressure part, confirm the current code edition, the addenda and any applicable code case before finalising the design, and state the code requirement on the enquiry so that the correct testing and certification are applied.

09NiCr22Fe18Mo forgings produced

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory. Every item listed below is forged to the customer drawing or dimensional sketch. There is no fixed catalogue, no die cost and no piece minimum, which makes single pieces and prototypes practical in this grade.

Size and weight capability

Machining allowance is normally 6 to 20 mm per surface depending on section size unless the drawing states otherwise. Finish-machined parts are supplied to print. Maximum sizes in a nickel superalloy are further limited by the billet available in the grade, so large sections should be confirmed at enquiry.

10How NiCr22Fe18Mo forgings are made

1. Melting. Billet is melted by EAF with AOD or VOD refining. ESR remelting is added where the specification or the service requires improved cleanliness and reduced segregation, which is normal practice for aerospace and rotating hardware.
2. Heat verification. Heat chemistry is checked by spectrometer against the DIN 17744 and ASTM B564 limits for UNS N06002 before any material is heated, with particular attention to the Mo, Co, W and C ranges that carry the high-temperature strength.
3. Soaking and open-die forging. The billet is soaked at approximately 1175 °C (2150 °F) until the whole section reaches temperature. The alloy conducts heat poorly and an incompletely soaked core is liable to crack. Forging is carried out on hydraulic presses and hammers with controlled reduction to close porosity and develop grain flow following the part contour. Work is finished above approximately 950 °C, and the piece is reheated rather than worked below range.
4. Ring rolling. Rings are pierced and rolled seamless, which produces a circumferential grain flow that a cut-and-welded ring cannot reproduce.
5. Solution annealing. Held at approximately 1175 °C, then rapidly cooled or water quenched to retain the carbides in solution. No ageing treatment is applied, since the alloy is solid-solution strengthened.
6. Rough or finish machining. Turned, bored, drilled and faced to the drawing with an agreed machining allowance, or finish machined to final dimensions.
7. Non-destructive testing. Ultrasonic examination to EN 10228-3, SEP 1921, ASTM A388 or the customer nominated class, with liquid penetrant, hardness and dimensional inspection as required.
8. Certification and despatch. EN 10204 3.1 mill certificate as standard, or 3.2 witnessed by TUV, BV, LR, SGS or DNV. Hard stamped, preserved and packed for sea or air freight.

11Where NiCr22Fe18Mo forgings are used

NiCr22Fe18Mo is used mainly in gas-turbine combustion hardware and in industrial furnace internals. Furnace rolls in this alloy have been reported in serviceable condition after approximately 8,700 hours at 1177 °C.

These applications share the same requirement: a component that operates hot, is thermally cycled, and is welded or bolted into a larger fabrication. NiCr22Fe18Mo resists scaling, retains enough strength to hold its shape, welds without special procedure and does not embrittle over the service life of the equipment. Where the part carries high sustained stress at the top of the temperature range, a stronger grade should be specified. See the comparison in section 6.

12Testing, inspection and certification

• Chemical analysis. Spectrometric heat analysis and, on request, product analysis on the finished forging.
• Mechanical testing. Room-temperature tensile, yield and elongation per ASTM B564 and DIN 17744. Elevated-temperature tensile, stress-rupture and impact testing to customer specification.
• Grain size. Determined per ASTM E112 where the specification requires it.
• Ultrasonic testing. EN 10228-3, SEP 1921 class C, D or E, ASTM A388, or customer nominated class.
• Surface NDT. Liquid penetrant examination per ASTM E165 and ASME Section V Article 6.
• Corrosion testing. ASTM G28 or A262 practice as agreed where the application requires it.
• Certification. EN 10204 3.1 as standard. EN 10204 3.2 witnessed by TUV, BV, LR, SGS or DNV on request. Full heat traceability and hard stamping.

13NiCr22Fe18Mo engineering tools

Four calculators for this grade, using the density, temperature limits and designation set given above. All calculations run in the browser and no data is uploaded or stored.

14Frequently asked questions about NiCr22Fe18Mo

16Related grades and product forms