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Hardfacing alloys include Cobalt base, Nickel base, Iron base and Tungsten Carbide compounds which offer outstanding wear resistance at both room and high temperatures. They aer deposited onto metal surfaces which then become resistant to wear, corrosion and heat, giving increased life ecpectancy in service. To keep costs to a minimum, these are only deposited at selected areas subejcted to extreme heat or wear in marine or vehicle applications. Oil and Gas, Nuclear, plastics, steel, glass bottle and ceramics manufacture, mining, construction and metal processing industries rely on these hardfacing alloys for their essential day to day equipment reliability and long term productivity.
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Aluminium bronze are copper alloys with up to 14% aluminium.
Combination of strength and corrosion resistance makes them on of the most important engineering materials for highly stressed components in corrosive environments.
They have increasing use in chemical, petrochemical and desalination plant, marine, offshore and shipboard plany, power generation, aircraft, automotive and railway engineering, iron and steelmaking, electrical manufacturing and building industries.
A typical list of products include impellers, bearings, shafts, pumps and valves, water cooled compressors, gear selection forks, synchronising rings, non-sparking tools, glass moulds (Foundary products) and wrought products and drop forgings, tubeplates, tubes and shells, pressure vessels, reaction and distillation vessels, chain, compressor blades, shafting and gears.
In addition to aluminium, the major alloying elements are nickel, iron, manganese and silicon.
There are 4 major types of alloy available:
single phase alpha alloys containing less than 8% of aluminium eg ca 102. they have good ductility and are suitable for extensive cold working. ca 109 are single phase up to over 9% aluminium.
- Duplex alloys containing from 8% to 11% alluminium and usually additions of iron and nickel to give higher strength are eg casting alloys : ab1, ab2, cual10fe3, cual10feni5, and wrought alloys: ca 105, ca 104, dgs 1043, cual10fe3 and cual10fe5ni5.
- Copper aluminium silicon alloys have lower magnetic permeability cast ab3, cual6si2fe, wrought ca 107, cual6si2 and dgs1044.
- Mainly alpha alloys with good strength and ductility are copper manganese aluminum alloys developed for manufacture of propellers cma1 cumn13al8fe3ni3. They have comparable strength to low carbon steel and stronger than most stainless steel. they retain a substantial proportion of their strength at elevated temperature and gain strength slightly at low temperature while retaining ductility.
They have good corrosion resistance and are free from oxide flakin due to the formation of an intrinsic, thin but tough adherent film of aluminium oxide which is self healing and once formed, prevents further oxidation and consequently eliminiates flaking. they have excellent resistance to stress corrosion and corrosion fatigue.
Welding is possible with aluminium bronze to repair damaged or locally defective castings and forgings. it is also possible to rectify machining errors. to avoid the possible effects of different microstructure present in weld bead and heat affected zone, post weld treatment may be recommended for the complex alloys to soak at 660 deg celsisu and cooling in still air.
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