# Alloy B-2 UNS N10665: Properties and Applications

## Introduction to Alloy B-2 UNS N10665

Alloy B-2, also known by its UNS designation N10665, is a nickel-molybdenum alloy that offers exceptional resistance to reducing environments. This alloy is part of the Hastelloy family of nickel-based alloys and is particularly known for its outstanding performance in highly corrosive conditions.

## Chemical Composition

The chemical composition of Alloy B-2 UNS N10665 plays a crucial role in its corrosion resistance properties:

– Nickel (Ni): ~65-70%
– Molybdenum (Mo): ~26-30%
– Iron (Fe): ~2% max
– Chromium (Cr): ~1% max
– Carbon (C): ~0.02% max
– Manganese (Mn): ~1% max
– Silicon (Si): ~0.1% max
– Phosphorus (P): ~0.04% max
– Sulfur (S): ~0.03% max

## Key Properties of Alloy B-2

### Corrosion Resistance

Alloy B-2 exhibits excellent resistance to hydrochloric acid at all concentrations and temperatures. It also performs well in sulfuric, acetic, and phosphoric acids, making it ideal for harsh chemical processing environments.

### Thermal Stability

The alloy maintains its mechanical properties at elevated temperatures, with good resistance to stress-corrosion cracking in chloride-bearing solutions.

### Mechanical Properties

Typical mechanical properties of Alloy B-2 include:

– Tensile Strength: 110 ksi (758 MPa) min
– Yield Strength: 51 ksi (352 MPa) min
– Elongation: 40% min

## Applications of Alloy B-2 UNS N10665

Due to its unique combination of properties, Alloy B-2 finds applications in various demanding industries:

### Chemical Processing

– Reactors and vessels handling hydrochloric acid
– Heat exchangers in corrosive environments
– Piping systems for aggressive chemicals

### Pharmaceutical Industry

– Equipment for drug production
– Storage tanks for corrosive pharmaceutical compounds

### Pollution Control

– Scrubbers and stack liners
– Waste treatment systems

### Oil and Gas

– Downhole components
– Offshore platform equipment

## Fabrication and Welding Considerations

Alloy B-2 can be fabricated using standard techniques, but requires special considerations:

– Hot working should be performed between 1600°F and 2250°F (871°C to 1232°C)
– Cold working requires intermediate annealing

– Welding should be done with matching filler metal (ERNiMo-7)
– Post-weld heat treatment is generally not required

## Comparison with Other Nickel Alloys

While Alloy B-2 offers superior resistance to reducing environments, it has less resistance to oxidizing conditions compared to alloys like C-276 or C-22. The choice between these alloys depends on the specific service environment.

Alloy B-2 UNS N10665 remains a critical material for industries requiring reliable performance in extremely corrosive environments. Its unique combination of properties continues to make it the material of choice for many challenging applications where other materials would fail prematurely.