Hastelloy C-22 – UNS N06022
Versatile nickel-chromium-molybdenum-tungsten alloy
Ni-Cr-Mo-W alloy with ~21% Cr, 13.5% Mo and 3% W. It resists oxidizing media (Cr) and reducing media (Mo and W) and mixed environments such as wet chlorine, ferric/cupric chloride and nitric + hydrochloric acids. It has pitting and crevice resistance superior to C276 and 625. Its consumable is the most used as an 'over-alloyed' filler for welding other alloys.
Designations and equivalents
| System | Designation |
|---|---|
| UNS | N06022 |
| W.Nr./EN | 2.4602 – NiCr21Mo14W |
| DIN | NiCr21Mo14W |
| JIS | NW6022 |
| Trade names | Hastelloy C-22 (Haynes), Nicrofer 5621 hMoW (VDM), Inconel 622 (Special Metals), Alloy 22 |
Standards by product form
| Form | Standard |
|---|---|
| Bar | ASTM B574 |
| Forging | ASTM B564; B462 (flanges and fittings) |
| Plate | ASTM B575 |
| Tube | ASTM B622 (seamless), B619/B626 (welded) |
Tolerances and HS codes
- Forged bars (round and square): machining allowance from 2 mm (Ø 6–16 mm) to 24 mm (Ø 400–500 mm) on the diameter. E.g. Ø 100–125 mm finished: +7 mm, tolerance +6 / −0 (length up to 3,500 mm).
- Forged discs: allowance of 4 to 9 mm on the diameter and 3 to 11 mm on the height, plus-only tolerance.
- Cutting and machining: band saw −0 / +5 to +15 mm on length; waterjet +10 % of thickness on the diameter (min. 2 mm); machined parts −0 / +2 to +5 mm on the diameter. See the full tables (INF 002 and INF 003, the same for every alloy).
| Form | NCM (Brazil, 8 digits) | HS (international, 6 digits) | HTS (USA, 10 digits)* | CN (European Union, 8 digits)* |
|---|---|---|---|---|
| Forged bar | 7505.12.10 | 7505.12 | 7505.12.3000 | 7505 12 00 |
| Hot-rolled bar | 7505.12.10 | 7505.12 | 7505.12.3000 | 7505 12 00 |
| Plate (> 10 mm, width ≥ 600 mm) | 7506.20.00 | 7506.20 | 7506.20.3000 | 7506 20 00 |
| Seamless pipe | 7507.12.00 | 7507.12 | 7507.12.0000 | 7507 12 00 |
| Welded pipe | 7507.12.00 | 7507.12 | 7507.12.0000 | 7507 12 00 |
| Flange and fitting | 7507.20.00 | 7507.20 | 7507.20.0000 | 7507 20 00 |
Tariff class: nickel alloy (by chemical composition, under the Chapter 72 Notes and Section XV Note 5).
*: US and EU codes for reference. NCM per current legislation (General Rules of Interpretation, Notes to Chapters 72, 74 and 75 and Section XV Note 5). Confirm the final code with your customs broker according to the item size and finish. HS = first 6 digits of the NCM.
Chemical composition (%)
ASTM B574 / B564 (UNS N06022)
| Element | Range (%) |
|---|---|
| Ni | balance (≈ 56) |
| Cr | 20.0 – 22.5 |
| Mo | 12.5 – 14.5 |
| W | 2.5 – 3.5 |
| Fe | 2.0 – 6.0 |
| Co | ≤ 2.5 |
| Mn | ≤ 0.50 |
| V | ≤ 0.35 |
| Si | ≤ 0.08 |
| C | ≤ 0.015 |
| P | ≤ 0.02 |
| S | ≤ 0.02 |
Mechanical properties
solution annealed (ASTM B564 / B574)
| Property | Value |
|---|---|
| Yield strength (0.2%) | ≥ 310 MPa |
| Tensile strength | ≥ 690 MPa |
| Elongation | ≥ 45% |
Typical physical properties
| Property | Value |
|---|---|
| Density | 8.69 g/cm³ |
| Melting range | 1,357 – 1,399 °C |
| Modulus of elasticity | 206 GPa |
| Thermal conductivity (20 °C) | 10.1 W/m·K |
| Thermal expansion (20–100 °C) | 12.4 µm/m·K |
Heat treatment, welding and machining
| Item | Usual practice |
|---|---|
| Service temperature | An alloy for aqueous corrosion, from cryogenic up to 677 °C (bolting up to 427 °C) in the ASME (II-D) allowable stress tables, but corrosive service should stay well below that. Avoid prolonged exposure to 600 – 1,000 °C (precipitation of μ and P phases). |
| Heat treatment | Solution annealing at ≈ 1,120 °C with rapid cooling (water or forced air). Not age hardenable. |
| Welding | Good weldability. Consumables: AWS A5.14 ERNiCrMo-10 and AWS A5.11 ENiCrMo-10, also used to weld C276, 625, super-austenitics and super duplex when over-alloyed weld metal is wanted. |
| Machining | Difficult: work hardens; use carbide, low speed, constant feed and abundant coolant. |
Filler metal for welding
The wire composition is usually not identical to the material: each page explains why.
Typical applications
- Chemical processes with mixed oxidizing and reducing media
- Chlorination and wet chlorine handling
- Flue gas desulfurization (FGD)
- Pulp and paper bleaching
- Pharmaceuticals and fine chemicals
- Incineration and waste treatment
- Welding consumable and overlay
Alternatives: C276 in strongly reducing media (hot HCl, H₂SO₄); alloys 59 / 686 / C-2000 in borderline cases; 625 in moderate media, at lower cost.
Hastelloy C-22: complete guide
What Hastelloy C-22 is
Hastelloy C-22 belongs to the family of nickel alloys, in the nickel-chromium-molybdenum group. It is not "a steel alloy": nickel is about 56% of the composition and iron is between 2 and 6%. It was developed from C-276 with more chromium and less molybdenum, to extend resistance to oxidizing media without losing resistance to reducing ones, and with low carbon and silicon to keep the weld heat-affected zone as resistant as the base metal.
Chemical composition and role of the elements
Chromium (20 – 22.5%) protects in oxidizing media; molybdenum (12.5 – 14.5%) and tungsten (2.5 – 3.5%) protect in reducing media and against pitting and crevice corrosion; iron is limited to 6% and carbon to 0.015%. The equivalent PREN, Cr + 3.3 (Mo + 0.5 W), is around 65 to 70.
Mechanical properties
Solution annealed, ASTM B574 requires a minimum yield strength of 310 MPa, minimum tensile strength of 690 MPa and minimum elongation of 45%. The alloy is not hardenable by heat treatment; strength increases only by cold work.
Corrosion and limits of use
C-22 resists nitric acid, wet chlorine, ferric and cupric chlorides, hypochlorites, oxidizing acid mixtures with chlorides, seawater, brines and also dilute hydrochloric and sulfuric acid, which makes it the choice for processes where the medium alternates between oxidizing and reducing. In hot concentrated hydrochloric acid, alloy B-2 is superior.
Applications
Waste incinerators and gas scrubbers, desulfurization absorbers, chemical and pharmaceutical reactors and exchangers, pulp bleaching equipment, effluent treatment, valve and pump components in oxidizing chloride media and protective weld overlays.
Supply forms and Dustre services
Round bars and blocks forged in open die, cut to size on a band saw, with rough or finish machining, solution annealing or annealing in our own furnaces and hardness, tensile and impact testing. All material is supplied with a 3.1 inspection certificate and heat traceability.
Frequently asked questions
What is the chemical composition of Hastelloy C-22?
Per ASTM B574 / B564 (UNS N06022): Ni balance (≈ 56); Cr 20.0 – 22.5; Mo 12.5 – 14.5; W 2.5 – 3.5; Fe 2.0 – 6.0; Co ≤ 2.5.
Which standards cover Hastelloy C-22?
Bar: ASTM B574. Forging: ASTM B564; B462 (flanges and fittings). Plate: ASTM B575. Tube: ASTM B622 (seamless), B619/B626 (welded).
Up to what temperature can Hastelloy C-22 be used?
An alloy for aqueous corrosion, from cryogenic up to 677 °C (bolting up to 427 °C) in the ASME (II-D) allowable stress tables, but corrosive service should stay well below that. Avoid prolonged exposure to 600 – 1,000 °C (precipitation of μ and P phases).
Which materials can replace Hastelloy C-22?
C276 in strongly reducing media (hot HCl, H₂SO₄); alloys 59 / 686 / C-2000 in borderline cases; 625 in moderate media, at lower cost.
