Hastelloy^® B-2 / Alloy B-2 (UNS N10665 · W.Nr. 2.4617) Forgings: Rings, Flanges, Bars, Discs and Tube Sheets

Hastelloy^® B-2 and Alloy B-2: the same alloy under two names

Engineers use both names for one material. Hastelloy B-2 is the brand name under which the alloy was first commercialised; Alloy B-2 is the generic name for the identical chemistry, registered as UNS N10665. Chemistry, mechanical properties, heat treatment and corrosion behaviour are the same whichever name appears on the drawing.

What is Hastelloy^® B-2 / Alloy B-2 (UNS N10665)?

Hastelloy B-2 / Alloy B-2 is a wrought nickel-molybdenum alloy in which roughly 28 % molybdenum is held in solid solution in a face-centred-cubic nickel matrix. There is no deliberate chromium addition (1.0 % maximum). That is what makes it good in reducing acids and unsuitable in oxidising ones.

Molybdenum in solid solution suppresses the cathodic hydrogen-evolution reaction that drives corrosion of nickel in hydrochloric acid. The alloy therefore survives boiling HCl at concentrations where austenitic stainless steels, and even Ni-Cr-Mo grades such as C-276, corrode measurably. Resistance to hydrochloric acid across the full concentration range is why the grade gets specified at all, and it is the first thing to check when someone proposes it.

Alloy B-2 — the grade also sold as Hastelloy B-2 — is the low-carbon, low-silicon development of the original Alloy B. Carbon is capped at 0.02 % and silicon at 0.10 % specifically to reduce grain-boundary carbide precipitation in weld heat-affected zones, which caused knife-line and heat-affected-zone attack in the earlier grade. Alloy B-2 is therefore usually supplied and used in the as-welded condition for many services, whereas Alloy B required post-weld solution annealing.

The alloy is not age hardenable. Strength comes entirely from solid-solution strengthening and from cold or hot work; the only heat treatment applied to a finished forging is a solution anneal followed by a rapid quench. Purchase orders calling for "solution treatment plus ageing" on Alloy B-2 are technically incorrect. We query them before production starts.

Hastelloy B-2 equivalent designations: UNS N10665, 2.4617, NiMo28, NS3202

This alloy reaches us under a dozen different names: Hastelloy B-2 on American drawings, Alloy B-2 or UNS N10665 in specifications, 2.4617 or NiMo28 on European documentation, NS3202 in China. All of them describe the same chemistry. Jiangyin Jiangnan Metal Co., Ltd. accepts purchase orders under any of them and issues a multi-designation mill test certificate where the chemistry and mechanical results satisfy several specifications at once.

What is the chemical composition of Hastelloy B-2 / Alloy B-2?

The composition below is per ASTM B335 / ASTM B564 for UNS N10665. Every heat we forge is verified in-house by optical emission spectrometry and reported on the mill test certificate against the ordered specification.

What are the mechanical properties of Hastelloy B-2 forgings?

Alloy B-2 is supplied solution annealed. The values below are the specification minima to ASTM B564 that we certify against; typical production results comfortably exceed them, and actual heat-specific results appear on every mill test certificate.

What are the physical properties of Alloy B-2 / Hastelloy B-2?

The high molybdenum content makes Alloy B-2 denser than stainless steel. Converting an existing stainless design to B-2 raises piece weight by roughly 18 % for the same geometry, which affects lifting, machining time and freight cost.

What does Hastelloy B-2 resist, and what attacks it?

Alloy B-2 performs well in reducing acids and badly in oxidising ones. A few parts per million of the wrong contaminant will move an environment from one category into the other, so the stream analysis matters more than the name of the acid.

Why is Alloy B-2 / Hastelloy B-2 limited to about 425 °C?

Drawings frequently leave this limit out.

Between roughly 650 °C and 815 °C (1200-1500 °F) the Ni-Mo solid solution is thermodynamically unstable and forms ordered intermetallic phases, Ni₄Mo (β) and Ni₃Mo. These are brittle and form both on grain boundaries and within grains. Room-temperature ductility and impact toughness drop sharply and corrosion resistance falls. Exposure can happen in service, during a slow furnace cool, or in a weld heat-affected zone. A part affected this way can still pass its tensile test and then crack during handling.

Two rules follow from this:

• Limit continuous service to about 425 °C (800 °F). Short excursions above this are tolerable; sustained exposure in the 650-815 °C band is not.
• Cool rapidly through the band. After solution annealing at 1066 °C, the quench must be fast enough to pass through 815-650 °C without holding. Heavy sections are the risk: a 300 mm-thick forging cools slowly at the core no matter how vigorous the quench, which is why section thickness must be part of the enquiry.

How is Hastelloy B-2 / Alloy B-2 forged and heat treated?

Alloy B-2 has a narrower hot-working window than stainless steel, higher flow stress, and it work-hardens fast. The parameters below are the ones we run in our own shop.

How is Alloy B-2 / Hastelloy B-2 welded and machined?

Which forged products are available in Hastelloy B-2?

Jiangyin Jiangnan Metal Co., Ltd. produces Alloy B-2 by open-die forging, seamless ring rolling and upset forging, selected by geometry and quantity. Every route ends in the same solution anneal and rapid quench.

Hastelloy B-2 / Alloy B-2 production capability at Jiangyin Jiangnan Metal

Our works at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province is an open-die forging factory established in 2008, employing about 460 people including 9 senior engineers and 32 intermediate engineers, and exporting to more than 40 countries under ISO 9001:2015.

Process flow for a Hastelloy B-2 / Alloy B-2 order

1. Raw material and heat verification ESR-remelted N10665 billet; chemistry confirmed by optical emission spectrometry against ASTM B335/B564 before cutting.
2. Heating Charge to 1150-1180 °C in a controlled-atmosphere furnace; soak time matched to section, recorded on the chart.
3. Forging or ring rolling Open-die press or radial-axial ring mill, light incremental passes with reheats, finish above 900 °C, forging ratio ≥ 3:1.
4. Rough machining Machining stock left for the final profile; descaling without nitric acid.
5. Solution annealing 1066 °C ± 15 °C, 30 min per 25 mm, followed by rapid water quench through the 815-650 °C ordering band.
6. Non-destructive examination Ultrasonic testing to ASTM A388, EN 10228-3 or SEP 1921; liquid penetrant to ASTM E165 on machined surfaces.
7. Mechanical and corrosion testing Tensile, hardness, optional Charpy; ASTM G28 Method A intergranular corrosion test where specified.
8. Certification, marking and dispatch EN 10204 3.1 or 3.2 certificate, heat-number marking, export packing.

Equipment used for nickel-alloy forgings

Standards, testing and certification for Alloy B-2 / Hastelloy B-2 forgings

Quality gates and non-conformance handling

Every Alloy B-2 order passes six mandatory hold points at which production cannot continue without QA sign-off: raw-material chemistry, forging temperature compliance, post-forging ultrasonic testing, solution-annealing chart approval, mechanical and corrosion test acceptance, and final NDE with dimensional inspection. Customer-witnessed hold points can be added at any of these stages at no extra charge. Any out-of-specification finding raises a formal non-conformance report within 24 hours; the customer receives the report and the proposed disposition before any rework, regrade or concession is actioned.

Where are Hastelloy B-2 forgings used?

Hastelloy B-2 / Alloy B-2 is used where hydrochloric acid or another strongly reducing acid is made, concentrated, stored or used as a reagent.

Hastelloy B-2 vs B-3 vs C-276 vs C-22: which should you specify?

Related grade pages: Hastelloy B-3 · Hastelloy B-4 · Hastelloy C-276 · Hastelloy C-22 · Hastelloy C-2000 · Alloy 59 · Hastelloy G-3

Eight common mistakes when ordering Hastelloy B-2 / Alloy B-2 forgings

1. Calling for solution treatment plus ageing Alloy B-2 is a solid-solution alloy and cannot be age hardened. Specify solution anneal at 1066 °C plus rapid quench, nothing more.
2. Ignoring ferric and cupric contamination The commonest cause of premature failure. Give us the full stream analysis, not just "HCl 20 %", so we can tell you if C-276 is the right answer instead.
3. Ordering by trademark alone Hastelloy B-2 and Alloy B-2 are the same alloy, but a purchase order naming only the trademark can be read as requiring material from one specific producer — which narrows your bidder list without changing the metallurgy. Write UNS N10665 per ASTM B564 (Hastelloy® B-2 equivalent) and you keep both the familiar name and an open market.
4. Omitting the intergranular corrosion test on heavy sections A thick forging can pass tensile testing while its slow-cooling core has begun to precipitate intermetallics. Add ASTM G28 Method A on a core-representative coupon.
5. Allowing nitric-acid pickling downstream Standard stainless passivation baths attack B-2. State "no nitric acid contact" on the drawing and pass it to the machine shop.
6. Designing for service above 425 °C Sustained exposure in the 650-815 °C band embrittles the alloy. If excursions are credible, specify Alloy B-3.
7. Reusing a stainless-steel weight estimate At 9.22 g/cm³, Alloy B-2 is roughly 18 % heavier than 316L for the same geometry, which changes lifting, machining and freight costs.
8. Not stating the section thickness at enquiry Quench effectiveness is section-dependent. A design that is straightforward at 60 mm may need a different approach at 300 mm.

How to specify a Hastelloy B-2 / Alloy B-2 forging order

1. State the generic designation UNS N10665 per ASTM B564 for forgings, or ASTM B335 for bar. Add (W.Nr. 2.4617 / NiMo28) for European review.
2. Define the product form and dimensions Ring, flange, disc, shaft, sleeve, tube sheet or bar, with finished dimensions, machining allowance and tolerances, or attach the drawing.
3. Specify the delivery condition Solution annealed at 1066 °C followed by rapid quench. No ageing.
4. State the process environment Acid, concentration, temperature, and any oxidising contaminants. This is what lets us confirm the grade choice rather than just fill the order.
5. Define non-destructive examination UT to ASTM A388, EN 10228-3 or SEP 1921 with acceptance class; PT to ASTM E165 on machined surfaces.
6. Specify certification and extra testing EN 10204 3.1 or 3.2, plus ASTM G28 Method A intergranular corrosion test and PMI where required.
7. Give quantity, marking and delivery terms Quantity, heat-number marking, Incoterms, destination port and required date.

Recommended drawing callout

MATERIAL:      UNS N10665 per ASTM B564
                (also satisfies ASME SB-564, W.Nr. 2.4617, NiMo28)
CONDITION:     Solution annealed 1066 deg C (1950 deg F),
                rapid water quench. NOT age hardened.
MECHANICAL:    Rm >= 760 MPa; Rp0.2 >= 350 MPa; A >= 40 %;
                hardness <= 100 HRB
CORROSION:     ASTM G28 Method A on coupon representing
                slowest-cooling section
NDE:           UT per ASTM A388 (state class) or EN 10228-3
                PT per ASTM E165 on all machined surfaces
SURFACE:       No nitric acid contact at any stage.
                Mechanical descaling or nitric-free pickle only.
                No carbon-steel tooling contact.
CERT:          EN 10204 3.1  (3.2 with third-party witness if required)
MARKING:       Heat number, specification, drawing number,
                low-stress stamp on non-functional surface

Glossary of terms used on this page

Hastelloy® B-2

Registered trademark of Haynes International, Inc., and the name by which this nickel-molybdenum alloy is most widely known in industry. Used on this page to identify the alloy; material we supply is certified under the generic designations.

Alloy B-2

The generic name for the same alloy, designated UNS N10665, containing 26-30 % Mo with nickel as balance. Interchangeable with Hastelloy B-2 in engineering usage.

UNS N10665

Unified Numbering System designation for Alloy B-2, and the preferred way to specify it on drawings and purchase orders.

W.Nr. 2.4617 / NiMo28

German material number and EN chemical-symbol designation for the same chemistry.

Solid-solution strengthening

Strengthening produced by dissolving alloying atoms, here molybdenum, in the base metal lattice, as opposed to precipitation or age hardening.

Solution annealing

Heating to 1066 °C to dissolve secondary phases into a single-phase solid solution, then quenching rapidly to hold them in solution.

Ni₄Mo / Ni₃Mo ordering

Formation of ordered intermetallic phases between about 650 °C and 815 °C, which embrittles Alloy B-2 and reduces its corrosion resistance.

Reducing acid

An acid environment with no strong oxidising agent present, for example deaerated hydrochloric acid. The regime in which Alloy B-2 performs best.

Oxidising contaminant

A species such as Fe³⁺, Cu²⁺, dissolved oxygen, nitric acid or chlorine that shifts the corrosion potential and rapidly attacks Alloy B-2.

ASTM G28 Method A

Boiling ferric sulphate-sulphuric acid test used to detect harmful intermetallic precipitation in nickel alloys.

EN 10204 3.1 / 3.2

Inspection-document types: 3.1 is issued by the manufacturer's own independent inspection function; 3.2 is countersigned by a third-party or customer inspector.

Seamless rolled ring

A ring produced by piercing a forged billet and expanding it on a ring mill, giving circumferential grain flow and no weld seam.

Forging ratio

The ratio of starting to finished cross-sectional area, a measure of how thoroughly the as-cast structure has been broken down.

ERNiMo-7 / ENiMo-7

Matching welding consumables for Alloy B-2, per AWS A5.14 (bare filler) and AWS A5.11 (covered electrodes).

Frequently asked questions about Hastelloy B-2 / Alloy B-2 (UNS N10665)

Technical references

Chemistry, mechanical property, heat-treatment and corrosion data on this page derive from the published standards and engineering references below. Test results on any individual order are independent and traceable to our own calibrated equipment.

1. ASTM B335, Standard Specification for Nickel-Molybdenum Alloy Rod, ASTM International, West Conshohocken, PA.
2. ASTM B564, Standard Specification for Nickel Alloy Forgings, ASTM International.
3. ASTM B333, Standard Specification for Nickel-Molybdenum Alloy Plate, Sheet, and Strip, ASTM International.
4. ASTM B622, Standard Specification for Seamless Nickel and Nickel-Cobalt Alloy Pipe and Tube, ASTM International.
5. ASTM B462, Standard Specification for Forged or Rolled UNS N06030, N06022 … Alloy Pipe Flanges, Forged Fittings, and Valves and Parts for Corrosive High-Temperature Service, ASTM International.
6. ASTM B366, Standard Specification for Factory-Made Wrought Nickel and Nickel Alloy Fittings, ASTM International.
7. ASME Boiler and Pressure Vessel Code, Section II Part B (SB-564, SB-335, SB-333) and Section VIII Division 1, American Society of Mechanical Engineers.
8. ASTM G28, Standard Test Methods for Detecting Susceptibility to Intergranular Corrosion in Wrought, Nickel-Rich, Chromium-Bearing Alloys, ASTM International.
9. ASTM A388, Standard Practice for Ultrasonic Examination of Steel Forgings, ASTM International.
10. ASTM E165, Standard Practice for Liquid Penetrant Testing for General Industry, ASTM International.
11. EN 10228-3, Non-destructive testing of steel forgings - Part 3: Ultrasonic testing of ferritic or martensitic steel forgings, CEN, Brussels.
12. SEP 1921, Ultrasonic testing of steel forgings, Stahl-Eisen-Prüfblatt, Verein Deutscher Eisenhüttenleute.
13. EN 10204:2004, Metallic products - Types of inspection documents, CEN, Brussels.
14. AWS A5.14, Specification for Nickel and Nickel-Alloy Bare Welding Electrodes and Rods, American Welding Society.
15. AWS A5.11, Specification for Nickel and Nickel-Alloy Welding Electrodes for Shielded Metal Arc Welding, American Welding Society.
16. ASM Handbook, Volume 13B: Corrosion - Materials, ASM International, Materials Park, OH.
17. ASM Specialty Handbook: Nickel, Cobalt, and Their Alloys, J.R. Davis (ed.), ASM International.
18. ASM Handbook, Volume 14A: Metalworking - Bulk Forming, ASM International (nickel-alloy forging practice).
19. Haynes International, technical data sheet for HASTELLOY® B-2 alloy, haynesintl.com.
20. GB/T 15007, Designation and code of corrosion-resisting alloys, Standardization Administration of China.

Standards cited are the revisions current at the time of this page review. For procurement, always reference the revision in force at the contract date. All trademarks are the property of their respective owners.