Hastelloy B-2 – UNS N10665
Nickel-molybdenum alloy for reducing acids
Ni-Mo alloy (~28% Mo), practically chromium-free, with exceptional resistance to hydrochloric acid at all concentrations and temperatures and to other reducing media (non-aerated H₂SO₄, H₃PO₄ and acetic acid). It does not tolerate oxidizers: Fe³⁺ or Cu²⁺ ions, oxygen or chlorine cause accelerated corrosion. It loses ductility when exposed to 540 – 870 °C and has largely been replaced by B-3 (N10675).
Designations and equivalents
| System | Designation |
|---|---|
| UNS | N10665 |
| W.Nr./EN | 2.4617 – NiMo28 |
| DIN | NiMo28 |
| Trade names | Hastelloy B-2 (Haynes), Nimofer 6928 (VDM), Alloy B2 |
| Others | Successor: Hastelloy B-3 (N10675) |
Standards by product form
| Form | Standard |
|---|---|
| Bar | ASTM B335 |
| Forging | ASTM B564 |
| Plate | ASTM B333 |
| 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 B335 / B564 (UNS N10665)
| Element | Range (%) |
|---|---|
| Ni | balance (≈ 69) |
| Mo | 26.0 – 30.0 |
| Fe | ≤ 2.0 |
| Cr | ≤ 1.0 |
| Co | ≤ 1.0 |
| Mn | ≤ 1.0 |
| Si | ≤ 0.10 |
| C | ≤ 0.02 |
| P | ≤ 0.04 |
| S | ≤ 0.03 |
Mechanical properties
solution annealed (ASTM B564 / B335)
| Property | Value |
|---|---|
| Yield strength (0.2%) | ≥ 350 MPa |
| Tensile strength | ≥ 760 MPa |
| Elongation | ≥ 40% |
| Hardness (plate) | ≤ 100 HRB |
Typical physical properties
| Property | Value |
|---|---|
| Density | 9.22 g/cm³ |
| Melting range | 1,332 – 1,382 °C |
| Modulus of elasticity | 217 GPa |
| Thermal conductivity (20 °C) | 11.1 W/m·K |
| Thermal expansion (20–100 °C) | 10.8 µm/m·K |
Heat treatment, welding and machining
| Item | Usual practice |
|---|---|
| Service temperature | An alloy for aqueous corrosion. Avoid exposure between ~540 and 870 °C (Ni₄Mo/Ni₃Mo ordering, with severe loss of ductility). Do not use in oxidizing media. |
| Heat treatment | Solution annealing at ≈ 1,065 °C with rapid cooling (water). Pass quickly through the 540 – 870 °C range on heating and cooling. Not age hardenable. |
| Welding | GTAW, GMAW or SMAW with low heat input and rigorous cleaning. Consumables: AWS A5.14 ERNiMo-7 and AWS A5.11 ENiMo-7. For joints with B-3: ERNiMo-10 / ENiMo-10. |
| Machining | Difficult: work hardens very quickly; use carbide, low speed, firm feed and abundant coolant. |
Filler metal for welding
The wire composition is usually not identical to the material: each page explains why.
Typical applications
- Hydrochloric acid equipment (all concentrations)
- Reactors, columns and exchangers for HCl, HBr and hydrogen chloride
- Processes with non-aerated sulfuric, phosphoric and acetic acids
- Pumps and valves in fine chemicals and pharmaceuticals
- Aluminum chloride (catalyst) processes
Alternatives: Hastelloy B-3 (N10675) for safer fabrication (greater thermal stability); C276 or C22 when oxidizers are present (Fe³⁺, Cu²⁺, O₂, chlorine); tantalum or zirconium in extremely aggressive HCl.
Hastelloy B-2: complete guide
What Hastelloy B-2 is
Hastelloy B-2 belongs to the family of nickel alloys, in the nickel-molybdenum group. Unlike the Hastelloy C series, which are Ni-Cr-Mo alloys, B-2 is practically binary: about 69% nickel and 28% molybdenum, with iron and chromium limited to 2 and 1%. It is the reference alloy for hydrochloric acid.
Chemical composition and role of the elements
Molybdenum, from 26 to 30%, gives the resistance to reducing acids; carbon (≤ 0.02%), silicon (≤ 0.10%) and iron (≤ 2%) are kept very low to avoid the precipitation of carbides and intermetallic phases in the weld heat-affected zone, a problem of the old alloy B.
Mechanical properties
Solution annealed, ASTM B335 requires a minimum yield strength of 350 MPa, minimum tensile strength of 760 MPa and minimum elongation of 40%. The alloy work hardens strongly and is not hardenable by heat treatment.
Corrosion and limits of use
Resistance to hydrochloric acid at all concentrations up to boiling is the reason for choosing the alloy, which also resists sulfuric, phosphoric and acetic acid under reducing conditions. The limitation is equally clear: any oxidizer in the medium, such as ferric or cupric ions, dissolved air, free chlorine or nitric acid, severely accelerates corrosion. For mixed or oxidizing media, the choices are C-276 and C-22.
Applications
Reactors, heat exchangers, piping, pumps and valves for hydrochloric acid and reducing chlorides, acetic acid and chemical intermediate production equipment, and components exposed to deaerated sulfuric and phosphoric acid.
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 B-2?
Per ASTM B335 / B564 (UNS N10665): Ni balance (≈ 69); Mo 26.0 – 30.0; Fe ≤ 2.0; Cr ≤ 1.0; Co ≤ 1.0; Mn ≤ 1.0.
Which standards cover Hastelloy B-2?
Bar: ASTM B335. Forging: ASTM B564. Plate: ASTM B333. Tube: ASTM B622 (seamless), B619/B626 (welded).
Up to what temperature can Hastelloy B-2 be used?
An alloy for aqueous corrosion. Avoid exposure between ~540 and 870 °C (Ni₄Mo/Ni₃Mo ordering, with severe loss of ductility). Do not use in oxidizing media.
Which materials can replace Hastelloy B-2?
Hastelloy B-3 (N10675) for safer fabrication (greater thermal stability); C276 or C22 when oxidizers are present (Fe³⁺, Cu²⁺, O₂, chlorine); tantalum or zirconium in extremely aggressive HCl.
