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July 10, 2025| | 0 Comment

Alloy 625 (UNS N06625): Properties, Applications, and Performance Characteristics

# Alloy 625 (UNS N06625): Properties, Applications, and Performance Characteristics

## Introduction to Alloy 625

Alloy 625, also known by its UNS designation N06625, is a nickel-chromium-molybdenum superalloy renowned for its exceptional strength and corrosion resistance. This material has become a cornerstone in industries requiring high-performance materials capable of withstanding extreme environments.

## Chemical Composition

The unique properties of Alloy 625 stem from its carefully balanced chemical composition:

– Nickel (Ni): 58% minimum
– Chromium (Cr): 20-23%
– Molybdenum (Mo): 8-10%
– Niobium (Nb): 3.15-4.15%
– Iron (Fe): 5% maximum
– Carbon (C): 0.10% maximum
– Manganese (Mn): 0.50% maximum
– Silicon (Si): 0.50% maximum
– Phosphorus (P): 0.015% maximum
– Sulfur (S): 0.015% maximum
– Aluminum (Al): 0.40% maximum
– Titanium (Ti): 0.40% maximum

## Mechanical Properties

Alloy 625 exhibits impressive mechanical characteristics across a wide temperature range:

Property | Value
Tensile Strength | 120-160 ksi (827-1103 MPa)
Yield Strength | 60-120 ksi (414-827 MPa)
Elongation | 30-45%
Hardness | 150-250 HB
Modulus of Elasticity | 31 x 10^6 psi (214 GPa)

## Physical Properties

The physical characteristics of Alloy 625 contribute to its performance:

– Density: 0.305 lb/in³ (8.44 g/cm³)
– Melting Range: 2350-2460°F (1290-1350°C)
– Thermal Conductivity: 6.5 BTU·in/(hr·ft²·°F) at 70°F
– Electrical Resistivity: 48.5 μΩ·in at 70°F
– Magnetic Permeability: <1.02 (non-magnetic)

## Corrosion Resistance

Alloy 625 offers outstanding resistance to various corrosive environments:

– Excellent resistance to pitting and crevice corrosion
– Superior performance in chloride-containing solutions
– Resistance to oxidizing and reducing acids
– Good performance in seawater and brackish water
– Resistance to stress corrosion cracking

## Heat Treatment and Workability

The alloy can be processed through various thermal treatments:

– Annealing: 1900-2100°F (1038-1149°C) followed by rapid cooling
– Stress Relieving: 1200-1400°F (649-760°C)
– Solution Annealing: 2050°F (1121°C) minimum

Alloy 625 can be formed using standard techniques, though its high strength requires more force than conventional steels. It machines best in the annealed condition using rigid setups and positive rake tools.

## Applications of Alloy 625

The unique combination of properties makes Alloy 625 suitable for numerous demanding applications:

### Aerospace Industry

– Jet engine components
– Ducting systems
– Afterburner components
– Rocket motor casings

### Marine Engineering

– Propeller blades
– Submarine components
– Seawater piping systems
– Offshore platform components

### Chemical Processing

– Reactor vessels
– Heat exchangers
– Pumps and valves
– Distillation columns

### Oil and Gas Industry

– Downhole components
– Wellhead equipment
– Flare stacks
– Pipeline systems

### Nuclear Applications

– Fuel element spacers
– Control rod components
– Reactor core components

## Performance at Elevated Temperatures

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