Nickel and its Alloy
Nickel and its Alloy: Nickel and its alloys are discussed as under.
Nickel: Nickel is a silvery shining white metal having extremely good response to polish. The most important nickel’s ore is iron sulphides which contain about 3% of nickel. About 90% of the total production of nickel is obtained by this source. This ore is mainly found in Canada and
Manufacture: The ore of Nickel is initially roasted to reduce the sulphur content and then smelted to separate the gangue from it. Matte (impure product of the smelting of sulphide ore especially those of nickel or copper, is known as matte) delivered by the smelting furnace is then put
in a Bessemer converter to oxidize the iron. The iron oxide thus combines with a limestone and quartz and form the slag. The Bessemer’s matte consists chiefly of copper and nickel sulphides.
Properties: Nickel is as hard as steel. It possesses good heat resistance. It is tough and having good corrosion resistance. Its melting point is 1452°C and specific gravity is 0.85. At normal temperature, nickel is paramagnetic. Nickel alloys are sometimes used for their high potential field strengths, some for their permeability and some for their high coercive force. When it contains small amount of carbon, it is quite malleable. It is somewhat less ductile than soft steel, but small amount of magnesium improves ductility considerably.
Applications: Nickel is used in kitchen utensils and appliances, and in laundry and dairy machinery. It is extensively useful for electroplating plating work for protecting surfaces of iron and brass from corrosion. It is also utilized as an important alloying element in some type of cast iron
and steel. It is helpful for making stainless steel. Its alloys are discussed as under.
Nickel Alloys: The important nickel alloys are haste alloy, Monel metal, inconel, nomonic and ni-chrome.
Haste Alloy or high Temprature Alloy: Haste alloy or high temperature alloy is mainly a nickel base alloy. It contains
Ni = 45%,
Cr = 22%,
Mo = 9%,
Co = 1.5%,
W = 0.5%,
C = 0.15% and
Fe = Remaining
Properties:(i) It can be hot and easily cold worked, casted and welded.
(ii) It has high resistance corrosion especially to acids and salts except nitric acid (HNO3).
(iii) It can be machined also.
(iv) This alloy is used where the resistance to corrosion is of consideration.
Applications: The high temperature alloys are those alloys which can withstand high temperatures about 1100°C. These alloys are used in components of nuclear plants, jet and rocket engines etc.
Monel Metal: Monel metal is an important alloy of nickel and copper. It contains 68% Ni, 30% Cu, 1% Fe and small amount of other constituents like iron, manganese, silicon and carbon.
Properties: Monel metal is superior to brass or bronze in resisting corrosion and in retaining its strength at high temperature. It is magnetic at ordinary temperatures. Its mechanical properties are improved by cold working. It can be cast, cold and hot worked, forged and welded. It
resembles nickel in appearance and is strong, ductile and tough. It has good mechanical properties and can retain them even at elevated temperatures. It has high excellent corrosion resistance.
Applications: Monel metal is also used for pump fittings, condenser tubes, sea water exposed parts etc. It is widely used for making turbine blades, containers, parts for chemical plants, food handling machinery parts, marine parts, pump impellers, propellers, evaporators and heat exchangers in chemical works.
Inconel: Inconel contains
Ni = 80%
Cr = 14%
Fe = 6%
Properties: Inconel has high resistance to corrosion and oxidation at elevated temperatures. It can be readily cold-worked and hot-worked, but does not respond to heat treatment. It contains high mechanical properties coupled corrosion and heat resisting properties. It can be cast, forged, rolled and cold drawn. Its specific gravity is 8.55 and melting point is 1395°C. Its Brinell Hardness is about 160BHN. It can be soft soldered or can be welded by oxyacetylene welding.
Applications: Inconel is used for making springs, exhaust manifold of aircraft engines, machinery for food processing industries, especially milk and milk products. It is widely used for processing uranium and for sheathing for high temperature heating elements.
Nomonic alloy: The composition of nomonic alloy is given as under.
Cr = 15 to 18%
Co = 15 to 18%
Ti = l.2 to 4.0%
Al = l.5%
Ni = Remaining
(i) Nomonic is a special type of nickel alloy having good strength
(ii) It can be easily heat treated to attain excellent properties for very high temperature service.
Applications: Nomonic is widely used for making gas turbine engines
Ni = 60%
Cr = 15%
Fe = 20%
Properties: Ni-chrome is non-corrosive. It can easily withstand high temperatures without oxidation.
Applications: Ni-chrome is commonly used for making electrical resistance wire for electric furnaces and heating elements.