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Turbines are used in many different ways produce and generate electricity. They are used as gas turbines, coal turbines and steam turbines. Each one has a different property, which makes it unique. Airlines and cars generally run on gas turbines. Steam engines, ships and railway engines run on coal turbines as coal produces a high amount of energy that enables them to run for long length of time before adding more coal.
In order for these turbine’s to operate well and efficiently with as little maintenance as possible, it is necessary for the turbine’s to have well-constructed, well designed turbine blades. They have to have certain properties that enable them to withstand high temperature and also be able to operate under extremely cold conditions when used in aeroplanes. They have to be light in weight and density in order to be driven by the steam or the gas, yet be strong enough to support the strong forces and pressure applied on it.
Materials used in turbine blades undergo several treatments to reinforce the strength. There are many challenges put forward to the producers of these turbines, as they have to design them to be environmentally friendly, yet be powerful. In order to cope with the pressures of having to implement the need to be lightweight and environmentally friendly, they have to improve the mechanical and thermal strength in order to match keep up with the rising technology and competition.
Turbine blades have to be able to endure temperatures around and greater then 500OC, in order for them to be useful. A reasonably lightweight alloy commonly used in the production of turbine blades is an often a long SiC-fibre reinforced titanium alloy for the highly mechanically loaded parts. By using “sputtering” techniques followed by hot isostatic pressing cycles, the components then become strengthened in comparison to conventional materials, which are manufactured.
These alloys are heavily researched to adapt to long-term behaviour which the turbines and blades undergo. These researches focuses on the durability of the turbines and degrading reactions at fibre-matrix interfaces as well as internal protective layers. This means that they test the materials under extreme conditions e.g. high temperatures or duration periods, which will enable them to find the stress points which will be more prone to damage than other areas as well as disintegration points.
By conducting these research experiments, engineers have been able to produce a fibre reinforced material that is oxidation resistant (rusting) and damage tolerant for a long duration of time and for temperature up to 1400OC, which accommodates the thermal resistance. In order to improve the efficiency of the engine, introduction of metallic and ceramic coatings can be added as well as thermal protection layers. The fibre-reinforced materials are used for thermal protection in the coating of the blades and inside the combustion chamber of the thrust engines. Special ceramic coatings have to be adjusted when considering increasing the resistance to high temperatures the metallic turbine blade.
The materials which turbine blades are made from are titanium alloys. Titanium alloys have good corrosion resistance to most conditions substances including nitric acid in all concentrations to boiling point; sea water; and to alkalis in all concentrations to boiling point. Stress corrosion can occur in some alloys if chlorine salts are added onto stressed parts. These parts are therefore subjected to high temperatures. Titanium alloys also provides well understood processing and handling characteristics.
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Engines, Aerospace materials, Turbine blade, Steam turbine, Gas turbine, Turbine, Titanium alloy, Ceramic, Corrosion, Titanium, Superalloy, Thermal barrier coating
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