# Alloy B-2 (UNS N10665) Properties and Applications

## Introduction to Alloy B-2

Alloy B-2, also known as UNS N10665, is a nickel-molybdenum alloy renowned for its exceptional resistance to reducing environments. This material is particularly effective in handling hydrochloric acid and other non-oxidizing acids, making it a preferred choice in chemical processing industries.

## Chemical Composition

The chemical composition of Alloy B-2 plays a crucial role in its performance characteristics:

– Nickel (Ni): ~65-70%
– Molybdenum (Mo): ~26-30%
– Iron (Fe): ≤2.0%
– Chromium (Cr): ≤1.0%
– Cobalt (Co): ≤1.0%
– Manganese (Mn): ≤1.0%
– Silicon (Si): ≤0.10%
– Carbon (C): ≤0.02%
– Phosphorus (P): ≤0.04%
– Sulfur (S): ≤0.03%

## Physical Properties

Alloy B-2 exhibits several notable physical properties:

– Density: 9.22 g/cm³ (0.333 lb/in³)
– Melting Range: 1330-1380°C (2425-2515°F)
– Electrical Resistivity: 128 μΩ·cm at 20°C
– Thermal Conductivity: 10.1 W/m·K at 100°C
– Coefficient of Thermal Expansion: 11.5 μm/m·K (20-100°C)

## Mechanical Properties

The mechanical properties of Alloy B-2 vary depending on its condition:

### Annealed Condition

– Tensile Strength: 690 MPa (100 ksi)
– Yield Strength (0.2% offset): 310 MPa (45 ksi)
– Elongation: 40%
– Hardness: 90 HRB

### Cold Worked Condition

– Tensile Strength: 965 MPa (140 ksi)
– Yield Strength (0.2% offset): 690 MPa (100 ksi)
– Elongation: 15%
– Hardness: 25 HRC

## Corrosion Resistance

Alloy B-2 offers outstanding corrosion resistance in various environments:

– Excellent resistance to hydrochloric acid at all concentrations and temperatures
– Superior performance in sulfuric, phosphoric, and acetic acids
– Good resistance to pitting and crevice corrosion
– Limited resistance to oxidizing environments (requires caution with nitric acid or other oxidizers)

## Applications of Alloy B-2

Due to its unique properties, Alloy B-2 finds applications in numerous industries:

### Chemical Processing

– Reactors and vessels for hydrochloric acid production
– Heat exchangers in sulfuric acid service
– Piping systems for phosphoric acid

### Pharmaceutical Industry

– Equipment for drug synthesis
– Reaction vessels requiring high purity

### Pollution Control

– Scrubbers for acid gas removal
– Waste treatment systems

### Other Applications

– Flue gas desulfurization systems
– Pickling equipment
– Acid recovery plants

## Fabrication and Welding

Alloy B-2 can be fabricated using standard techniques, though some precautions are necessary:

– Hot working should be performed between 870-1175°C (1600-2150°F)
– Cold working requires intermediate annealing
– Welding should be done using matching filler metal (ERNiMo-7)
– Post-weld heat treatment is generally not required

## Comparison with Other Nickel Alloys

While Alloy B-2 excels in reducing environments, other nickel alloys may be more suitable for different conditions:

– Alloy C-276: Better for mixed acid environments with oxidizing species
– Alloy 625: Superior in chloride-containing environments at higher temperatures
– Alloy 400: More economical for less severe conditions

## Conclusion

Alloy B-2 (UN