If you work with strong acids or high-temperature processes, you need a material that won’t corrode or break down. UNS N10665 Hastelloy B2—a nickel-molybdenum alloy—stands out for its unbeatable resistance to harsh chemicals like hydrochloric acid. This guide walks you through its properties, uses, how it’s made, and how it compares to other materials—so you can make the right choice for your project.
1. Material Properties of UNS N10665 Hastelloy B2
Hastelloy B2’s power comes from its unique mix of elements and standout characteristics. Let’s break them down clearly.
1.1 Chemical Composition
The alloy’s ingredients are carefully balanced to fight corrosion. Here’s its typical makeup (by weight):
| Element | Content Range (%) | Key Job |
| Nickel (Ni) | 65–70 | The base metal—gives ductility and stops stress cracking |
| Molybdenum (Mo) | 26–30 | The star—blocks corrosion in strong acids (like hydrochloric acid) |
| Iron (Fe) | 2–6 | Adds strength without making the alloy brittle |
| Carbon (C) | Max 0.01 | Kept low to prevent carbide formation (which causes corrosion) |
| Manganese (Mn) | Max 1.0 | Helps with manufacturing (e.g., welding) |
| Silicon (Si) | Max 0.1 | Reduces oxidation at high temperatures |
| Phosphorus (P) | Max 0.04 | Controlled to avoid weak spots in the alloy |
| Sulfur (S) | Max 0.03 | Kept low to stop corrosion in acidic environments |
| Copper (Cu) | Max 0.5 | Boosts resistance to certain acids (like sulfuric acid) |
1.2 Physical Properties
These traits make Hastelloy B2 easy to design with for tough jobs:
- Density: 9.2 g/cm³ (a bit heavier than stainless steel, but worth it for durability)
- Melting Point: 1330–1380°C (2425–2525°F) – handles high-heat processes
- Thermal Conductivity: 13.5 W/(m·K) at 20°C (68°F) – transfers heat evenly
- Thermal Expansion Coefficient: 12.8 μm/(m·K) (20–100°C) – doesn’t warp much when heated
- Electrical Resistivity: 135 Ω·mm²/m at 20°C – works for electrical parts in harsh areas
- Magnetic Properties: Non-magnetic – great for medical or electronic equipment where magnetism is a problem
1.3 Mechanical Properties
Hastelloy B2 is strong and flexible—even at high temperatures. All values below are for the annealed (heat-treated) version:
| Property | Value (Room Temperature) |
| Tensile Strength | Min 690 MPa (100 ksi) |
| Yield Strength | Min 310 MPa (45 ksi) |
| Elongation | Min 40% (in 50 mm) |
| Hardness | Max 220 HB (Brinell) |
| Fatigue Resistance | 230 MPa (10⁷ cycles) |
| Creep Resistance | Maintains strength up to 600°C (1110°F) |
1.4 Other Properties
- Corrosion Resistance: Outstanding in pure hydrochloric acid (even at high concentrations) – way better than stainless steel.
- Oxidation Resistance: Good up to 650°C (1200°F) in air – but avoid prolonged exposure to high oxygen levels (it can form a weak layer).
- Stress Corrosion Cracking (SCC) Resistance: No SCC in chloride solutions (a big issue for many other alloys).
- Pitting Resistance: Resists small holes (pitting) in salty or acidic liquids.
- Hot/Cold Working Properties: Easy to forge (hot working at 1040–1170°C) and bend (cold working) – doesn’t lose strength when shaped.
2. Applications of UNS N10665 Hastelloy B2
Thanks to its acid resistance, Hastelloy B2 is used in industries where other materials fail. Here are the most common uses, with real examples:
2.1 Chemical Processing Equipment
- Use Case: A chemical plant in India used Hastelloy B2 for hydrochloric acid storage tanks. The old tanks (made of carbon steel) rusted through in 6 months—this one has lasted 4 years with no issues.
- Other Uses: Acid mixers, heat exchangers, and pipework for strong acids.
2.2 Oil and Gas Industry
- Use Case: An oil refinery in Texas uses Hastelloy B2 for “acidizing” tools. These tools inject hydrochloric acid into wells to boost oil flow— the alloy resists corrosion, cutting tool replacement costs by 40%.
2.3 Acid Handling Systems
- Use Case: A water treatment plant in Germany uses Hastelloy B2 for pumps that move sulfuric acid. The alloy’s resistance to acid wear means the pumps run 2x longer than those made of stainless steel.
2.4 Pulp and Paper Industry
- Use Case: A Swedish pulp mill uses Hastelloy B2 for “digester” parts. The digester uses sulfuric acid to break down wood— the alloy avoids corrosion, reducing downtime by 25%.
2.5 Pharmaceuticals & Food Processing
- Why It Works: Non-toxic and easy to clean (meets FDA rules). Used for mixing tanks that handle acidic ingredients (like citrus extracts).
3. Manufacturing Techniques for UNS N10665 Hastelloy B2
To get the best performance from Hastelloy B2, manufacturers use specific methods:
- Casting: Investment casting (using a wax mold) is best for complex shapes (e.g., valve bodies). The low carbon content prevents defects during casting.
- Forging: Hot forging (at 1040–1170°C) shapes the alloy into strong parts like pump impellers. Cold forging (at room temp) is used for small parts (e.g., bolts) to make them harder.
- Welding: Gas Tungsten Arc Welding (GTAW) works best. Use matching filler metals (e.g., ERNiMo-7) to keep corrosion resistance high. Clean the metal first (remove oil/dirt) to avoid weak welds.
- Machining: Use carbide tools (they stay sharp longer). Add coolant (like mineral oil) to prevent overheating—Hastelloy B2 can “work-harden” (get harder) if cut too fast.
- Heat Treatment: Annealing (heat to 1065–1120°C, then cool fast) softens the alloy for shaping. It also restores corrosion resistance after welding.
- Surface Treatment: Passivation (soak in nitric acid) creates a thin protective layer—this boosts pitting resistance. No painting needed— the alloy’s surface resists rust on its own.
4. Case Study: Hastelloy B2 in a Hydrochloric Acid Reactor
A chemical company in Brazil needed a reactor to make PVC (polyvinyl chloride). The reactor uses 31% hydrochloric acid at 80°C—their old reactor (316 stainless steel) failed after 1 year.
They switched to a Hastelloy B2 reactor. Here’s what happened:
- Lifespan: The reactor has run for 6 years with no corrosion.
- Cost Savings: Maintenance costs dropped by 70% (no more frequent part changes).
- Performance: The alloy’s even heat transfer improved PVC production by 10%.
This case shows why Hastelloy B2 is the top choice for hydrochloric acid applications.
5. Comparative with Other Materials
How does UNS N10665 Hastelloy B2 compare to other common materials? The table below breaks it down:
| Material | Corrosion Resistance (HCl Acid) | Tensile Strength (MPa) | Max Service Temp (°C) | Cost (Relative) |
| Hastelloy B2 | Excellent (31% HCl) | 690 | 600 | High |
| Stainless Steel 316 | Poor (corrodes quickly) | 515 | 870 | Low |
| Titanium Alloy Ti-6Al-4V | Good (dilute HCl) | 860 | 400 | Very High |
| Inconel 625 | Fair (not for strong HCl) | 930 | 980 | High |
| Monel 400 | Poor (HCl attacks it) | 550 | 480 | Medium |
| Hastelloy C22 | Good (mixed acids) | 690 | 650 | High |
| Carbon Steel | Very Poor (rusts instantly) | 400 | 425 | Very Low |
Key Takeaways:
- Hastelloy B2 is the best for pure hydrochloric acid—no other material matches its resistance.
- It’s cheaper than titanium alloys but more expensive than stainless steel (worth it for long-term savings).
- Inconel 625 works better at higher temps, but Hastelloy B2 crushes it in acid resistance.
Yigu Technology’s Perspective
At Yigu Technology, we see UNS N10665 Hastelloy B2 as a go-to for clients in chemical and oil industries dealing with strong acids. Its ability to resist hydrochloric acid saves our customers time and money—no more frequent part replacements. We offer custom machining for Hastelloy B2 components, ensuring they fit exact project needs. For anyone working with harsh acidic environments, Hastelloy B2 isn’t just an option—it’s a smart investment.
FAQ
1. Can UNS N10665 Hastelloy B2 handle concentrated hydrochloric acid?
Yes! It’s designed for this—even 31% concentrated hydrochloric acid at high temps (up to 80°C) won’t corrode it. This makes it way better than stainless steel or carbon steel for acid tasks.
2. Is Hastelloy B2 hard to weld?
No, but you need the right method. Use Gas Tungsten Arc Welding (GTAW) with ERNiMo-7 filler metal. Also, clean the metal first to remove oil or dirt—this keeps welds strong and corrosion-resistant.
3. What’s the lifespan of Hastelloy B2 parts in chemical processing?
In harsh acid environments (like hydrochloric acid), Hastelloy B2 parts last 5–10 years. That’s 5–10x longer than stainless steel parts, which usually fail in 1–2 years. Proper maintenance (like annealing) can make it last even longer.