The quality of materials is considered essential to the function of an object. The limitation of the material depends on the structure and properties of the material. Materials engineering consists of studying the composition of the material. This is useful to identify its properties in order to know the qualities, limits and use of the material.
The advancement of technology includes several applications that would require materials which would meet certain requirements. Advance engineering materials are used because of their mechanical properties and are used for applications that can sustain the conditions when it is exposed to certain conditions such as temperature, pressure, strength and others. Analyzing the material properties enables us to identify their uses and functions.
SUPERALLOYS
Alloys that have significant levels of mechanical properties above 600-700oC, and which endure significantly when exposed to high temperatures for considerable times are called superalloys. Superalloys are considered one of the advanced materials used in the field of engineering. They can sustain high temperature greater than 540oC, usually at most 0.7 times its absolute melting temperature, which may be up to around 1000oC. Most superalloys at 760oC have yield strength of 500MPa (retrieved from GlobalSpec, 2010).
Properties
Superalloys are also resistant to corrosion (Grieve, 2005). The resistance to corrosion is because of its property that resists oxidation (retrieved from GlobalSpec, 2010). The composition of superalloys includes non-ferrous metals which are Nickel, nickel alloys, cobalt, and cobalt alloys. These metals have high strength and toughness, excellent corrosion and oxidation resistance, and high superior temperature strength. Other composition of the superalloys are ferrous metals and alloys such as carbon steels, alloy steels, stainless steels, cast iron, maraging steel and other iron-based alloys.
Types of Superalloys
Superalloys are categorized according to its based component such as Iron Nickel based, Nickel based and Cobalt. The first type, Iron Nickel based, contain contain 20-40 Ni, 15-20 Cr, 30-50 Fe, with Mo, Al, Ti. It is developed from the technology of stainless steel and always wrought. The second type is the Nickel based this superalloy can be cast or wrought. It has higher Nickel content than the first type. It is composed of 40 Ni, 10-20 Cr, at most 10 Al and Ti, 5-10 Co with B, Zr and C. Other chemicals such as Mo, W and Nb are also often used. The third type of superalloy is the Cobalt based can also be wrought or cast. It consists of 35-60 Co, 20-30 Cr, at most 35 Ni and added with W and Mo (Grieve, 2005).
Processes
High temperature strength of superalloys is developed by solid solution hardening. The oxidation and corrosion property is because of the formation of a protective oxide layer that is formed when there is exposure to oxygen and covers the material. This layer protects the rest of the component. There is a significant strengthening mechanism is through the development of secondary phase precipitates through precipitation strengthening (Sims, 1987).
All types of superallloys are capable of being forged, rolled or formed. Most superaloys are forged, wrought, hot-rolled, cast, extruded, cold-finished, or formed through compressing powdered metals or alloys (retrieved from GlobalSpec, 2010). The more highly alloyed compositions are normally processed as castings. Highly alloyed compositions containing a huge amount of hardening phase are difficult to weld while fabricated structures may be built up by welding and brazing (Grieve, 2005).
Application and Uses
Applications of superalloys in the industry are mostly used in gas turbine engines including commercial and military aircraft, marine propulsion, and power generation (Sims, 1987). These turbines are exposed to high temperatures which require high temperature strength, oxidation and corrosion resistance. Other uses of superalloys are found in submarines, nuclear reactors, heat exchanger tubing, military electric motors, submarines and chemical processing vessels. Seventy five percent of superalloys are used in aerospace such as space vehicles. Fifty percent of a typical modern jet engines weight is from the superalloys. Superalloys are also used for fixtures and jigs that are used in furnaces (Grieve, 2005).
Further Research
The further research and development of superalloys continues to progress through time. One of the researches resulted in increasing the entry temperatures in turbines. Radiolysis, a new method in making superalloys, is being studied to be an effective way of creating and improving superalloys. This new method involves the study of the formation of nanoparticle. This can still expand the research into other features of superalloys that can be studied. Understanding the some important concepts in material science helps in making this research and be able to see other areas of possible improvements. However, other applications of superalloys are exposed to temperature near its melting point which can result in an unacceptable creep level. This is because of the common use of singe crystals and polycrystalline alloys are produced (Sims, 1987).
The choice of material is important to its purpose. The limitation of the objects use depends on the material. Material engineering makes it easier for us to decide which appropriate material to use. Identifying conditions which will determine the requirements in the property of the material will determine what material can be best suited. Material engineering is a tool for us to meet requirements under certain conditions.
There are significant contributions of superalloys to the industry. These materials are commonly found in objects that require its excellent properties. It is considered as a very good advance engineering material since it is used for technological advancement also. Imagining the industry without it would be very difficult.
The advancement of technology includes several applications that would require materials which would meet certain requirements. Advance engineering materials are used because of their mechanical properties and are used for applications that can sustain the conditions when it is exposed to certain conditions such as temperature, pressure, strength and others. Analyzing the material properties enables us to identify their uses and functions.
SUPERALLOYS
Alloys that have significant levels of mechanical properties above 600-700oC, and which endure significantly when exposed to high temperatures for considerable times are called superalloys. Superalloys are considered one of the advanced materials used in the field of engineering. They can sustain high temperature greater than 540oC, usually at most 0.7 times its absolute melting temperature, which may be up to around 1000oC. Most superalloys at 760oC have yield strength of 500MPa (retrieved from GlobalSpec, 2010).
Properties
Superalloys are also resistant to corrosion (Grieve, 2005). The resistance to corrosion is because of its property that resists oxidation (retrieved from GlobalSpec, 2010). The composition of superalloys includes non-ferrous metals which are Nickel, nickel alloys, cobalt, and cobalt alloys. These metals have high strength and toughness, excellent corrosion and oxidation resistance, and high superior temperature strength. Other composition of the superalloys are ferrous metals and alloys such as carbon steels, alloy steels, stainless steels, cast iron, maraging steel and other iron-based alloys.
Types of Superalloys
Superalloys are categorized according to its based component such as Iron Nickel based, Nickel based and Cobalt. The first type, Iron Nickel based, contain contain 20-40 Ni, 15-20 Cr, 30-50 Fe, with Mo, Al, Ti. It is developed from the technology of stainless steel and always wrought. The second type is the Nickel based this superalloy can be cast or wrought. It has higher Nickel content than the first type. It is composed of 40 Ni, 10-20 Cr, at most 10 Al and Ti, 5-10 Co with B, Zr and C. Other chemicals such as Mo, W and Nb are also often used. The third type of superalloy is the Cobalt based can also be wrought or cast. It consists of 35-60 Co, 20-30 Cr, at most 35 Ni and added with W and Mo (Grieve, 2005).
Processes
High temperature strength of superalloys is developed by solid solution hardening. The oxidation and corrosion property is because of the formation of a protective oxide layer that is formed when there is exposure to oxygen and covers the material. This layer protects the rest of the component. There is a significant strengthening mechanism is through the development of secondary phase precipitates through precipitation strengthening (Sims, 1987).
All types of superallloys are capable of being forged, rolled or formed. Most superaloys are forged, wrought, hot-rolled, cast, extruded, cold-finished, or formed through compressing powdered metals or alloys (retrieved from GlobalSpec, 2010). The more highly alloyed compositions are normally processed as castings. Highly alloyed compositions containing a huge amount of hardening phase are difficult to weld while fabricated structures may be built up by welding and brazing (Grieve, 2005).
Application and Uses
Applications of superalloys in the industry are mostly used in gas turbine engines including commercial and military aircraft, marine propulsion, and power generation (Sims, 1987). These turbines are exposed to high temperatures which require high temperature strength, oxidation and corrosion resistance. Other uses of superalloys are found in submarines, nuclear reactors, heat exchanger tubing, military electric motors, submarines and chemical processing vessels. Seventy five percent of superalloys are used in aerospace such as space vehicles. Fifty percent of a typical modern jet engines weight is from the superalloys. Superalloys are also used for fixtures and jigs that are used in furnaces (Grieve, 2005).
Further Research
The further research and development of superalloys continues to progress through time. One of the researches resulted in increasing the entry temperatures in turbines. Radiolysis, a new method in making superalloys, is being studied to be an effective way of creating and improving superalloys. This new method involves the study of the formation of nanoparticle. This can still expand the research into other features of superalloys that can be studied. Understanding the some important concepts in material science helps in making this research and be able to see other areas of possible improvements. However, other applications of superalloys are exposed to temperature near its melting point which can result in an unacceptable creep level. This is because of the common use of singe crystals and polycrystalline alloys are produced (Sims, 1987).
The choice of material is important to its purpose. The limitation of the objects use depends on the material. Material engineering makes it easier for us to decide which appropriate material to use. Identifying conditions which will determine the requirements in the property of the material will determine what material can be best suited. Material engineering is a tool for us to meet requirements under certain conditions.
There are significant contributions of superalloys to the industry. These materials are commonly found in objects that require its excellent properties. It is considered as a very good advance engineering material since it is used for technological advancement also. Imagining the industry without it would be very difficult.
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