Hastelloy B is a solid-solution nickel–molybdenum alloy — the original member of the "B" family of corrosion-resistant alloys — with outstanding resistance to hydrochloric acid and other strongly reducing media. This datasheet presents the material within the Hastelloy trade-name designation system.
Like all B-family alloys it contains essentially no chromium; the high nickel and molybdenum contents provide superior resistance to hydrochloric acid at all concentrations and temperatures, and to sulphuric, acetic and phosphoric acids and other non-oxidising acids. Iron and chromium are held low to reduce processing brittleness and to limit precipitation of the ordered Ni₄Mo (β) phase between about 700 °C and 870 °C.
The original alloy B has a higher carbon and iron content than the later low-carbon alloy B-2 (UNS N10665); because of this it can be susceptible to carbide precipitation and intergranular attack in the weld heat-affected zone, and for most new fabrications the low-carbon B-2 or the more thermally stable B-3 are preferred. Being chromium-free, alloy B should not be used in oxidising environments or in reducing acids contaminated with oxidising salts (e.g. ferric or cupric chloride), and should not be used with iron or copper piping in hydrochloric-acid systems. It is listed in NACE MR0175 / ISO 15156 for sour service.
Typical values, solution-annealed condition.
| Property | Value | Unit |
|---|---|---|
| Density | 9.24 | g/cm³ |
| Melting range | 1330–1380 | °C |
| Young's modulus (20 °C) | 217 | GPa |
| Specific heat capacity (20 °C) | 373 | J/kg·K |
| Thermal conductivity (20 °C) | 11.3 | W/m·K |
| Electrical resistivity (20 °C) | 1.35 | µΩ·m |
| Coefficient of thermal expansion (20–100 °C) | 10.2 | µm/m·°C |
| Maximum service temperature (oxidising) | ~540 | °C |
| Structure | Austenitic (FCC) | — |
Limiting composition per ASTM B333 (UNS N10001).
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Nickel | Ni | Balance | — | Base element; reducing-acid resistance |
| Molybdenum | Mo | 26.0 | 30.0 | Primary alloying element; HCl + reducing-acid resistance |
| Iron | Fe | 4.0 | 6.0 | Present (higher than alloy B-2) |
| Cobalt | Co | — | 2.5 | Residual |
| Chromium | Cr | — | 1.0 | Essentially chromium-free (defining feature) |
| Carbon | C | — | 0.05 | Higher than B-2 (0.02); HAZ sensitisation risk |
| Vanadium | V | 0.20 | 0.60 | Carbide former |
| Manganese | Mn | — | 1.0 | Deoxidiser |
| Silicon | Si | — | 1.0 | Deoxidiser |
| Phosphorus | P | — | 0.04 | Residual impurity |
| Sulphur | S | — | 0.03 | Residual impurity |
Typical room-temperature properties, solution-annealed condition.
| Property | Value | Source |
|---|---|---|
| Ultimate tensile strength | 760–860 MPa | Typical / ASTM B333 |
| 0.2% proof strength (yield) | ~350–400 MPa | Typical |
| Elongation at break | ~40 % | Typical / ASTM B333 |
| Hardness | ~95–100 HRB | Typical |
The alloy is solid-solution-strengthened (not age-hardenable) and can be strengthened by cold work. It has a relatively low coefficient of thermal expansion. Values are typical; confirm against the mill test certificate for each delivery.
| Environment | Performance | Notes |
|---|---|---|
| Hydrochloric acid (all conc. / temps) | Outstanding | Among the highest of any nickel alloy |
| Hydrogen chloride gas | Outstanding | Exceptional resistance |
| Sulphuric acid (medium conc.) | Excellent | Resists non-oxidising H₂SO₄ |
| Acetic / phosphoric / organic acids | Excellent | Strong reducing-acid resistance |
| Reducing environments | Outstanding | High Ni + Mo |
| Chloride SCC | Very Good | Good resistance |
| Weld HAZ (as-welded) | Caution | Higher C than B-2; can sensitise — prefer B-2 for as-welded service |
| Oxidising media / ferric or cupric salts | Poor | No chromium — avoid oxidising contaminants, Fe/Cu salts |
A solid-solution nickel–molybdenum alloy; not age-hardenable. Heat treatment is solution annealing only.
Solution Anneal Temperature: ~1060–1080 °C, followed by rapid air cool or water quench Purpose: dissolves secondary phases, restores corrosion resistance and ductility.
Service caution: avoid prolonged exposure to ~700–870 °C, which promotes ordered Ni₄Mo (β) phase and embrittlement; in oxidising atmospheres limit to ~540 °C.
Weldable with controlled heat input. Note: the original alloy B has a higher carbon content than B-2, so the weld heat-affected zone can be susceptible to carbide precipitation and intergranular attack; a post-weld solution anneal is advisable for aggressive acid service, or the low-carbon B-2 should be specified for as-welded service.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Good | AWS A5.14 ERNiMo-1 (matching alloy B filler) |
| GMAW / MIG | Good | AWS A5.14 ERNiMo-1 (matching alloy B filler) |
| SMAW / stick | Good | AWS A5.11 ENiMo-1 |
Keep the joint clean and free of iron/copper contamination, which is detrimental in subsequent acid service.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Work hardening | High rate (typical of Ni-Mo alloys); rigid setup, sharp tooling, positive rake |
| Cutting | Low speed, sufficient feed/depth to cut below work-hardened layer |
| Coolant | Ample flood coolant |
| Preferred condition | Solution-annealed |
Forming Processes
| Process | Notes |
|---|---|
| Hot forming | Followed by solution anneal + rapid cool |
| Cold forming | Cold-formable; high work-hardening rate; intermediate anneals for heavy reductions |
| Cleanliness | Keep tooling free of iron contamination to protect acid-service performance |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Chemical processing | HCl reactors, acid storage tanks, heat exchangers, piping | HCl + reducing-acid resistance |
| Sulphuric / acetic / phosphoric acid | Process vessels and piping | Non-oxidising acid resistance |
| Pharmaceutical | Reactors, pressure vessels | Corrosion resistance |
| Petrochemical | Reducing-environment process hardware | Reducing-acid resistance |
| High-temperature (reducing/vacuum) | Components needing low thermal expansion | Low CTE; reducing-atmosphere stability |
| Product Form | ASTM Standard | ASME Code |
|---|---|---|
| Rod and bar | ASTM B335 | ASME SB-335 |
| Plate, sheet and strip | ASTM B333 | ASME SB-333 |
| Seamless pipe and tube | ASTM B622 | ASME SB-622 |
| Welded pipe | ASTM B619 | ASME SB-619 |
| Welded tube | ASTM B626 | ASME SB-626 |
| Fittings | ASTM B366 | ASME SB-366 |
| Welding consumables | AWS A5.14 ERNiMo-1 · AWS A5.11 ENiMo-1 | — |
Listed in NACE MR0175 / ISO 15156 for sour service. UNS N10001.
| Hastelloy Grade | Ni % | Cr % | Mo % | Other | Best Used For |
|---|---|---|---|---|---|
| Hastelloy B | bal | ≤1.0 | 26–30 | Fe 4–6, C ≤0.05 | Original Ni-Mo; HCl + reducing acids |
| Hastelloy B-2 | bal | ≤1.0 | 26–30 | Fe ≤2, C ≤0.02 | Low-C improvement; as-welded service |
| Hastelloy B-3 | bal | 1.0–3.0 | 28.5 | Fe 1–3 | Best thermal stability; HCl service |
| Hastelloy C-276 | bal | 14.5–16.5 | 15–17 | W 3–4.5 | Oxidising + reducing; broad corrosion |
| Hastelloy C-22 | bal | 20–22.5 | 12.5–14.5 | W 2.5–3.5 | Best pitting/crevice; mixed acids |




