Nickel Aluminum Bronze (NAB) is a high-performance copper-based alloy containing aluminium (typically 8–12%), nickel, iron, and other elements. It is known for exceptional corrosion resistance, high strength, and excellent wear performance, especially in marine and seawater environments.
This alloy offers a unique combination of durability, toughness, and anti-fouling properties, making it a preferred material for demanding applications where ordinary bronzes or stainless steels may fail.
Chemical Composition
The composition varies by specific grade and standard, but a typical NAB alloy contains:
| Element | Typical Content (%) | Function |
|---|---|---|
| Copper (Cu) | Balance (~78–82 %) | Base metal, provides ductility & conductivity |
| Aluminium (Al) | ~8.5–11 % | Forms protective oxides, strengthens alloy |
| Nickel (Ni) | ~3.5–6 % | Increases strength, toughness & corrosion resistance |
| Iron (Fe) | ~2.5–5 % | Strengthens & improves wear resistance |
| Manganese (Mn) | ~0.8–1.5 % | Improves hot workability and deoxidation |
| Zinc (Zn) | ~≤ 1 % | Minor adjustments/impurity control |
Physical Properties
| Property | Typical Value |
|---|---|
| Density | ~7.5–7.8 g/cm³ (lower than many steels) |
| Melting Range | ~1000–1080 °C (cast alloys) |
| Thermal Conductivity | ~34–50 W/m·K (moderate) |
| Electrical Conductivity | ~7 % IACS (lower than pure copper) |
| Thermal Expansion | ~16–17×10⁻⁶/°C |
Mechanical Properties
NAB combines high strength, good ductility, and toughness:
| Property | Typical Metrics |
|---|---|
| Ultimate Tensile Strength | ~550–830 MPa (varies by grade & heat treatment) |
| Yield Strength | ~200–420 MPa |
| Elongation | ~15–25 % |
| Hardness | High (varies by condition) |
| Fatigue Resistance | Excellent relative to many bronzes |
Strengthening & Metallurgical Behavior
🧰 Alloying Effects
The combined effects of aluminium, nickel, and iron produce a complex microstructure with:
α (alpha) phase: Copper-rich ductile matrix
β & κ intermetallic phases: Hard particles that confer strength and wear resistance
The intermetallic phases — especially κ phases (iron and nickel rich) — reinforce the structure without making it brittle.
Heat Treatment
Although NAB is primarily used in cast condition, it can be heat treated to optimize properties:
Annealing at ~675–775 °C improves ductility and ease of forming
Stress relief (~250–400 °C) decreases residual stresses after machining
Quenching & tempering can increase strength while retaining toughness in some grades
Heat treatment influences phase distribution and mechanical toughness.
Key Characteristics
🌊 Corrosion & Environment Resistance
NAB is renowned for corrosion resistance, especially in:
Seawater and saline environments
Marine biofouling conditions
Acidic or alkaline industrial environments
The protective alumina (Al₂O₃) film on the surface is self-healing, preserving performance over time.
Strength & Wear
High strength and toughness for dynamic loads
Wear resistance for bearings, shafts, and gears
Fatigue resistance for cyclic stresses
Non-Sparking & Low Magnetism
Many NAB grades are non-sparking and have low magnetic permeability, useful in safety-critical and precision applications.
Refining & Processing Properties
Excellent castability with good fluidity for complex shapes
Controlled cooling affects microstructure and final properties
Machining & Welding
Generally machinable with proper tooling (can be similar to some stainless steels)
Welding possible with suitable techniques (e.g., MIG/TIG with filler metals) but requires expertise to avoid defects
Hot & Cold Working
Hot working is favorable for shaping before machining
Cold working is limited relative to some steels but can fine-tune mechanical properties
Available Forms
Nickel aluminium bronze is supplied in many industrial forms, including:
Castings (investment, sand, centrifugal)
Bars & rods
Plates & sheets
Billets & ingots
Fasteners and custom shapes
Forged components
Applications
Marine & Offshore
Propellers, hubs, and shafts
Pump housings and impellers
Valves and fittings
Excellent seawater corrosion resistance makes NAB ideal for ship components
Industrial & Machinery
Gears, bearings, bushings
Valve bodies
Wear-resistant components
High strength and wear resistance support heavy industrial use.
Aerospace
Landing gear bushings
Bearings and pistons
Strength-to-weight ratio and fatigue performance are beneficial.
Oil & Gas
Non-sparking tools
Corrosion-resistant components for aggressive environments
Chemical & Energy
Pump parts, heat exchanger components, fasteners
Durable under corrosive chemicals and thermal cycling.
Advantages of Nickel Aluminium Bronze
📌 Outstanding Corrosion Resistance: Particularly in seawater and harsh chemical environments.
📌 High Strength & Toughness: Maintains performance under heavy loads and dynamic stresses.
📌 Wear & Abrasion Resistance: Longer service life for moving parts and components.
📌 Self-Healing Oxide Layer: Continuous surface protection in aggressive environments.
📌 Non-Sparking & Safe: Useful in environments with ignition risks.
📌 Stable Over Wide Temperatures: Good strength retention at elevated temperatures.
Why Choose Nickel Aluminium Bronze?
Choose NAB when you need a balance of high mechanical strength, corrosion resistance, wear resistance, and durability — especially in marine, aerospace, industrial machinery, and chemical environments where failure is costly or dangerous. Its self-protecting surface, toughness under load, and versatility in manufacturing make it a top alloy choice in demanding engineering applications.