Nickle and its Alloys

Nickel and its alloys
The most important ore for nickel is iron sulphides, which contain about 3% of nickel. About 90% of the total production of nickel is obtained by this source. Its extraction process consists of first roasting the ore, followed by smelting in a small blast furnace. Limestone and quartz are added as flux. They form slag with impurities. Coke is used as fuel. Crude molten nickel is tapped off periodically from the bottom of the furnace. This crude metal is further refined in a Bessemer converter followed by treating with sulphuric acid to extract pure nickel. Copper is separated as copper sulphate.

Properties
• Silvery shiny appearance
• High toughness and ductility
• Good high and low temperature strength
• High oxidation resistance
• Good corrosion resistance
• Ferro-magnetic
• Relatively high cost
• Not mixed with cheap
Crystal structure FCC
Atomic number 28
Atomic weight 58.71
Density (g.cm-3) 8.89
Melting point (oC) 1455

Limitations
• Relatively high cost
• Not mixed with cheap alloying elements.

Applications
• Applications required necessary corrosion or heat- resisting properties and for special engineering applications.
• Chemical plant, heat exchanger, reaction furnace, rotary kiln,turbine blades.
• Used as alloying elements in stainless steels, and in other elements such as copper, cobalt, chromium, etc.
Production of nickel
There are three major types of nickel deposits (sources):
1) Nickel-copper sulphide
2) Nickel silicates
3) Nickel laterites and serpentines
Classification of nickel alloys
There are different types of nickel and nickel alloys;
1) Commercially pure nickel
2) Nickel-copper alloys (Monels)
3) Nickel-chromium alloys
4) Nickel-base superalloys
5) Nickel-iron superalloys

1) Commercially pure nickel
• High purity nickel contains 99.99% Ni.
• Commercially pure nickel contains 99.5% Ni (+Co).
• Microstructure consists of solid solution phase in annealed condition.
Cold drawn Nickel 200 annealed at 829oC
Properties
• Good mechanical properties and retains its strength at elevated temperature.
• Excellent resistance to most corrosive environment.
Applications
• Food processing equipment
• Electrical & electronic parts
• Caustic handling equipment
.