How super alloys are the spirit of modern industries
The elevated temperature applications of super alloys are wide, such as components for aircrafts, chemical plant systems and petrochemical units.
Additionally super alloys are extensively used in Aerospace and Marine industries, Nuclear plants, heat exchangers and industrial gas turbines. F119 engine that is the latest in a series of military engines to power high functional aircraft. The gas temperatures in these engines in the hot sections may increase to levels above 2000oF or 1093oC. Quenching techniques decrease the real component metal temperatures to lower levels and super alloys that can serve at these temperatures are the major parts of the warm sections of these engines.
The importance of super alloys in modern industry is signified by the fact that in 1950 only 10% of the total aircraft gas turbine engine was made from super alloys that has increased by 50% in 1985. Although, not all applications need high temperature strength capability, their high strength combined with corrosion resistance has made specific super alloys standard materials for biomedical equipments. Superalloys are also used in cryogenic applications.
Applications of super alloys are grouped following: bulk of tonnage is used in gas turbines:
· Aircraft gas turbines: — Disks, combustion chambers, shafts, casings, exhaust systems, cases, blades, vanes, burner cans, afterburners, thrust reversers.
· Steam turbine power plants: Bolts, blades, stack gas reheaters
· Reciprocating engines: Turbochargers, exhaust valves, hot plugs, valve seats
· Metal Processing: Hot work tools, dies and casting dies
· Medical applications: Dentistry and prosthetic equipments
· Space Equipments: Aerodynamically heated skins, rocket engine components
· Heat Processing equipments: Trays, fixtures, conveyor belts, fans, furnace mufflers, baskets
· Nuclear Power plants: Control rod drive mechanisms, valve stems, springs, ducts
· Chemical and petrochemical plants- bolts, fans, valves, reaction vessels, pipes, pumps
· Pollution control systems- Scrubbers
· Metals processing mills- ovens, afterburners, exhaust fans
· Coal gasification and liquefaction units- Heat exchangers, reheaters and pipes
Corrosion resistant and high performance super alloys are perfect to high temperature creep and fatigue resistant applications where stress is lower than in rotating components. Therefore turbine vanes and other static components are widely made from these materials. Low coefficient of thermal expansion and high heat conductivity make nickel based super alloys fit for applications where thermal fatigue is a serious design problem. For prolong service needs, land based casting specifications are becoming more complex.
Nickel based super alloys are also used by implant manufacturers for low carbon level. They have good ductility and excellent corrosion resistance.
Gas turbine engines
Superalloys are widely used in gas turbine engines in the areas of high temperatures and which need high strength, good creep resistance and corrosion and oxidation resistance. In the turbine engines this is in the high pressure turbine where blades are exposed t temperatures reaching if not more than their melting points. Advanced jet engines are more efficient for higher service temperatures which is made possible with the use of nickel based super alloys such as Inconel 625 wire and others. Various nickel super alloys are used from 1200oF to 1300oF