# Alloy K-500 UNS N05500: Properties and Applications

## Introduction to Alloy K-500

Alloy K-500, also known by its UNS designation N05500, is a nickel-copper alloy that combines the excellent corrosion resistance of Monel 400 with the added benefits of increased strength and hardness. This alloy is precipitation hardenable, making it suitable for applications requiring high mechanical properties in corrosive environments.

## Chemical Composition

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

– Nickel: 63% minimum
– Copper: 27-33%
– Aluminum: 2.3-3.15%
– Titanium: 0.35-0.85%
– Iron: 2.0% maximum
– Manganese: 1.5% maximum
– Carbon: 0.25% maximum
– Silicon: 0.5% maximum
– Sulfur: 0.01% maximum

## Mechanical Properties

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

– Tensile Strength: 1100-1500 MPa (160-220 ksi)
– Yield Strength: 760-1200 MPa (110-175 ksi)
– Elongation: 20-35%
– Hardness: 25-40 HRC (after heat treatment)
– 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: 51.0 μΩ·cm
– Thermal Conductivity: 21.8 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 maintains excellent corrosion resistance similar to Monel 400, with particular strengths in:

– Seawater and marine environments
– Hydrofluoric acid and fluorine gas
– Alkaline solutions
– Sulfuric and hydrochloric acids
– Various salt solutions

The alloy is particularly resistant to stress corrosion cracking and pitting in marine applications.

## Heat Treatment

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

1. Solution annealing at 982°C (1800°F) followed by rapid cooling
2. Aging at 538-649°C (1000-1200°F) for 4-16 hours
3. Air cooling

This treatment sequence develops the optimal combination of strength and corrosion resistance.

## Applications of Alloy K-500

Due to its unique combination of properties, Alloy K-500 finds use in numerous demanding applications:

### Marine Engineering

– Pump shafts and impellers
– Marine propeller shafts
– Fasteners and bolting
– Valve components
– Offshore drilling equipment

### Oil and Gas Industry

– Downhole tools and equipment
– Wellhead components
– Valve stems and trim
– Pump components in sour service

### Aerospace and Defense

– Aircraft fuel pump components
– Rocket motor cases
– High-strength fasteners
– Turbine blades and components

### Chemical Processing

– Mixer shafts and agitators
– Heat exchanger tubes
– Reactor vessels
– Piping systems for corrosive media

## Fabrication and Machining

Alloy K-500 can be fabricated using standard techniques, though it requires more power than mild steel:

– Machining: Similar to austenitic stainless steels but with better chip breaking
– Welding: Can be welded using GTAW or GMAW processes with matching filler metal
– Forming: Requires

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