# Alloy K-500 UNS N05500: Properties and Applications

## Introduction to Alloy K-500

Alloy K-500, also known as UNS N05500, is a precipitation-hardenable nickel-copper alloy that combines the excellent corrosion resistance of Alloy 400 with added strength and hardness. This alloy is widely used in various industries due to its unique combination of properties.

## Chemical Composition

The chemical composition of Alloy K-500 plays a crucial role in its performance:

– Nickel (Ni): 63.0% minimum
– Copper (Cu): 27.0-33.0%
– Aluminum (Al): 2.3-3.15%
– Titanium (Ti): 0.35-0.85%
– Iron (Fe): 2.0% maximum
– Manganese (Mn): 1.5% maximum
– Carbon (C): 0.25% maximum
– Silicon (Si): 0.5% maximum
– Sulfur (S): 0.01% maximum

## Mechanical Properties

Alloy K-500 offers impressive mechanical properties, especially after precipitation hardening:

– Tensile Strength: 1100-1400 MPa (160-200 ksi)
– Yield Strength: 690-1100 MPa (100-160 ksi)
– Elongation: 20-40%
– Hardness: 25-40 HRC (after aging)
– Modulus of Elasticity: 179 GPa (26 x 10^6 psi)

## Physical Properties

The physical characteristics of Alloy K-500 include:

– Density: 8.44 g/cm³ (0.305 lb/in³)
– Melting Range: 1315-1350°C (2400-2460°F)
– Electrical Resistivity: 49.0 μΩ·cm
– Thermal Conductivity: 21.9 W/m·K (151 BTU·in/hr·ft²·°F)
– Coefficient of Thermal Expansion: 13.9 μm/m·°C (20-100°C)

## Corrosion Resistance

Alloy K-500 exhibits excellent corrosion resistance similar to Alloy 400, with additional benefits:

– Outstanding resistance to seawater and marine atmospheres
– Good resistance to sulfuric, hydrochloric, and hydrofluoric acids
– Excellent resistance to stress corrosion cracking
– Superior performance in chloride-containing environments
– Resistance to biofouling and microbiologically influenced corrosion

## Heat Treatment

The precipitation hardening process for Alloy K-500 typically involves:

– Solution Annealing: 982°C (1800°F) followed by rapid cooling
– Aging Treatment: 593°C (1100°F) for 4-16 hours, depending on desired properties
– Stress Relieving: 538-593°C (1000-1100°F) for 1-4 hours

## Applications of Alloy K-500

Due to its unique combination of properties, Alloy K-500 finds applications in various industries:

### Marine Engineering

– Pump shafts and impellers
– Marine fasteners and fittings
– Propeller shafts
– Valve components
– Seawater piping systems

### Oil and Gas Industry

– Downhole equipment
– Wellhead components
– Valve stems and trim
– Fasteners for offshore platforms
– Chemical injection systems

### Aerospace and Defense

– Aircraft bearings
– Missile components
– Rocket motor cases
– High-strength fasteners
– Turbine blades

### Chemical Processing

– Pump shafts and impellers
– Mixer shafts
– Valve components
– Heat exchanger tubing
– Process vessels in corrosive environments

## Fabrication and Machining

Alloy K-500 can be fabricated using standard techniques, though some considerations apply:

– Hot Working: Performed between 871-1149