High Temperature Nickel alloys Applications
The superalloys are iron and nickel, nickel, nickel and cobalt base alloys that are normally made for service at temperature higher than 540oC or 1000oF and lower than melting point of alloys that is often at or above 1204oC or 2200oF. The superalloys are also used in the space applications where subzero and cryogenic temperatures cause problems.
Wrought nickel and iron-nickel base alloys generally have temperature limitations about 816oC or 1500oF. At temperatures more than this limit, cast alloys are recommended for use. Most of superalloys are reinforced through the formation of secondary phases and higher temperature limit for alloy applications.
It is usually considered in superalloy industry that specific alloys are utilized for the particular temperatures of application such as many wrought nickel and iron-nickel base superalloys are employed at temperatures from 1200oF to 1300oF or 649oC to 704oC. The cast alloys are employed around these temperature limits but specifically at the highest temperatures such as in gas turbine engines.
The high temperature applications of superalloys are broad such as parts for aircraft, chemical plant apparatus and petrochemical device. These materials are excellent for use in a series of military engines to power high functional aircrafts. The gas temperatures in these engines in the hot sections may increase up to 2000oF or 1093oC. The quenching techniques decrease the actual metal part temperatures to lower values, superalloys that can successfully be used at these temperature limits are employed in the major parts of the hot sections of these engines.
The worth of superalloys in the present market is generalized by the fact that in 1950 only 10% of whole structure of jet engines was made of superalloy, in 1985 this percentage reaches to 50%.
Nickel based super alloys are progressively being used in oil and gas applications. The conditions occurred in oil and natural gas formation are highly corrosive and complicated. Usually noticeable magnitudes of hydrogen sulfide, carbon dioxide, chlorides and free sulfur are available. In few conditions, high pressure and temperature about 450of or232oC may occur. Treatment of natural gas and oil in these natural conditions needs special metals. Nickel based alloy 718 is broadly used in oil and natural gas sectors. It contains chromium and molybdenum that increase corrosion resistance. Nickel alloy 718 was originally made for using in gas turbines and aerospace engineering, however it has become the recommended metal for production of well head parts, auxiliary and downhole apparatus and partial surface protection valves.
Other application sectors for high temperature nickel alloys are nuclear power plants, electricity generation units, pollution control, automotive, chemical processing industry, waste treatment etc.