Nickel Aluminium Bronze Alloy

Alloys of copper and aluminum are known as aluminum bronze and, together with other alloying additions, produce a range of properties that are beneficial to a diverse range of industries. Of these, the nickel aluminum bronze group of alloys is the most widely used. They have been adapted with time to optimize performance and can provide a combination of properties that can offer an economic alternative to other types of alloy systems. End uses range from landing gear bushing and bearings for all of the world’s commercial aircraft to seawater pumps and valves, propellers for naval and commercial shipping, non-sparking tools in the oil and gas industry, and pleasing facades in architecture.

Nickel aluminum bronzes are available in both cast and wrought product forms and have a unique combination of properties:

• Excellent wear and galling resistance
• High strength Density (10% lighter than steel)
• Non-sparking
• Low magnetic permeability (of <1.03 µ in selected grades)
• High corrosion resistance
• Good stress corrosion properties
• Good cryogenic properties
• High resistance to cavitation
• Damping capacity twice that of steel
• High resistance to biofouling
• A protective oxide surface film that has the ability to self-repair.

Nickel Aluminium Bronze Alloy Specifications

Broadly, the nickel aluminum bronzes can be classified as alloys containing 6-13% aluminum and up to 7% iron and 7% nickel. The more common alloys normally contain 3-6% of these two elements. Manganese up to approximately 1.5% is added as a deoxidant and a strengthening element.

Nickel Aluminium Bronze Alloy Applications

Aerospace

The main application for nickel aluminum bronze in the aerospace sector is landing gear bearings for the world’s fleet of commercial aircraft.

The excellent bearing properties against steel, corrosion resistance in salt conditions during de-icing of runways in winter, and high mechanical properties make it an ideal alloy for this application. The main specifications are AMS 4640, AMS 4880, AMS 4881, AMS 4590, BS2 B 23, NFL14-702, NFL14-705, and NFL14-706. The aircraft companies and main subcontractors also have their own specifications, for example, Airbus ASN-A 3406, ASN-A 3315, ASN-A6127A, and Rolls Royce MSR 8503.

Architecture

Aluminum bronzes are used in a wide spectrum of architectural applications. Their natural ability to form a protective oxide layer in oxygen-rich environments opens up applications, both for inland and marine atmospheric conditions. Nickel aluminium bronze has a rich golden oxide and, with its unique properties, can provide additional benefits.

The Parliamentary building in London, Portcullis House, is a prime example of architectural use as it contains 450 tonnes of nickel aluminum bronze incorporated in the window frames, cladding and roof (artificially darkened), built to withstand bomb blasts and with a life expectancy of 120 years.

Marine

There is a large market for nickel aluminium bronze in naval applications, particularly for the submarine fleets of the world. The main applications are in seawater piping and valve systems, weapons handling, flexible couplings, sonar equipment, seawater external hatches, hydraulic valves and bearings, fasteners and sealing flanges, low-noise propellers, propulsion equipment, and periscope assemblies. These applications make use of some of the important properties of nickel aluminum bronzes: good corrosion resistance, non-sparking, wear resistance, high strength, and good impact properties.

The alloys also exhibit good anti-damping properties, twice that of steel, which is important in submarines in suppressing sound for silent operations. Non-sparking and wear resistance become particularly important in weapons' handling systems. The various grades with lower iron and nickel contents can be manufactured with magnetic permeability below 1.03 µ.

Nickel aluminum bronze is one of the main alloys used for ship propellers on commercial vessels and cruise liners. Its high resistance to cavitation, coupled with reasonable cost and the ease of repair when damaged, makes it a leading contender for this application. The hubs for variable-pitched propellers are also made from nickel aluminium bronze. The alloy exhibits good anti-galling properties against itself, which is important as the propeller blades rotate within the cylindrical openings. Nickel aluminum bronze is also used in the winch gear mechanisms of ocean-going yachts, where anti-galling, high strength, and corrosion resistance to salt spray play an important part.

Offshore Oil/Gas and Petrochemical

The offshore oil/gas industry makes use of nickel aluminum bronze in many applications, where the alloy is used for pipework, valves, and pumps in seawater pumping systems, particularly for fire-fighting equipment. It is compatible with copper-nickel piping systems and is used for associated pumps and valves. It is also used in seawater pumping systems to convey water for injection back into the well.

Actuator valves are an important application, both on land-based pipelines and subsea where oil is being transported.

On land-based applications, pipelines can be situated in isolated areas, as well as in hostile locations. Actuator valves form a vital link in the safety of the oil line, as well as protecting the environment against oil spillage. The valves need to work under extremes of temperature ranging from -50°C in extremely cold conditions, such as those encountered in the Arctic regions, to +50°C at the height of the summer in the Middle East desert areas. They have to withstand the ingress of sand in the desert and be able to work after many years of inactivity. For this reason, nickel aluminum bronze is chosen in many of the designs for its corrosion resistance and bearing properties. Nickel aluminium bronze also forms the main component which closes off the valves within the piping system. Offshore, actuator valves are used on oil rig platforms, where valves are sometimes inaccessible and need to be activated by radio waves.

Desalination and Water Condenser Systems

This industry is an important outlet for nickel aluminum bronze for pumps, valves, water boxes, impellers, condenser tube plates, and housings. It is used for elevated temperatures up to approximately 325°C in high-pressure condenser systems. It can be used for pumping seawater to a recommended level of 4.3 m/sec, which exceeds that tolerated by 90-10 and 70-30 copper nickel. Although the aluminum bronzes do not have the biofouling resistance of the copper-nickels, they still have a high resistance to marine growth.