Turbines and their Importance in Airplane Functioning
Turbines play an important part in airplane functioning. According to Hünecke, turbines are a vital part of the jet engine that works to produce the push which enables the plane to lift itself off the ground, as well as its remaining afloat when in the air (35) As a result of its relevance, it is critical for aeronautical engineering students to grasp the basic materials utilized to manufacture jet turbines. . It is worth noting that turbines represent the hot component of a jet engine, so the materials employed must meet specific requirements. This paper, therefore, focuses on discussing the materials used for making jet turbines in aspects of the materials' properties, manufacturing processes, and costs.
Materials and Properties
Jet turbines are made specifically of two distinct materials, including the unconventional metal alloys and ceramics. The unconventional metal alloys are composed of nickel, cobalt, chromium, tungsten, and tantalum based materials. General observation of the unconventional alloys includes the material being of high strength in terms of static, fatigue, and creep-structure, able to withstand high temperatures ranging from 850 to 1100 degrees Celsius or 1600 – 2000 Fahrenheit, the material has to be resistant to corrosion and be of low weight (Everhart 77). Nickel or cobalt based materials are preferred to other engineering alloys for specific properties. For example, the alloy can bear loads of up to 0.8Tm which is a fraction that is higher than any other engineering alloys, the specific gravity is 8.8, and it is over fifty percent of the engine weight not limited to having high stiffness (Rajput 44). The unconventional alloys enhanced with thermal barrier coatings increase the corrosion and oxidation resistance abilities of the materials, as well as reduce the temperature at the surface of the material with approximately 40 degrees Celsius. Comparatively, unconventional alloys have high ductility, toughness, impact, and critical flow size to qualify them as the mostly used materials.
The Use of Ceramics in Jet Turbines
The ceramic materials used in making jet turbines include silicon, nitrogen, and carbon. The ceramics, like unconventional alloys, have certain properties that make them be of preference to other metals. For instance, they are reinforced with fiber to form a ceramic matrix for improved toughness and improved defect of tolerance. The carbon-carbon composites have the potential to function under temperatures higher than 2000 degrees Celsius. However, it requires protection with silicon from oxidation. According to Rajput, the use of carbon-carbon composite is exemplified in space shuttles where it is used to make nose-cone when temperatures' reentry ranges between 1650 degrees Celsius (64).
Manufacturing Processes of Unconventional Alloys, Ceramics, and Costs
The manufacturing process of nickel based alloys begins with the identification of the purest available raw materials. This is essential for the manufacture of alloys with the required chemical compositions and various desired characteristics. Basically, the manufacturing process of nickel-based alloys passes through nine distinct steps encompassing melting, hot rolling, acid pickling, annealing, wire drawing, cold rolling/slitting, annealing, quality control, and packing (Campbell 110).
The first step in the manufacturing of alloys is melting that is done under clean conditions and contamination free intense heating sources. As such, pure argon, as well as mixtures of reactive gases, is used to create the desired furnace for melting. The melt raw materials are then melted rapidly through radiation and conduction which promote high alloy recoveries, maintain the melt cleanliness, and produce excellent material properties. For specified properties as for materials used to make jet turbines, a combination of plasma arc melting is often taken into consideration.
The second process is hot rolling. In the process, the material melt is further subjected to intense heating above its crystallization temperature. The material then deforms between rollers to create thin cross-sectional sheets. Compared to cold rolling, the sheets created are thinner, yet the stages are the same. Nonetheless, cold rolling is done to reduce the average grain size while maintaining the material's equiaxed microstructure.
Acid pickling is the third process for the manufacture of nickel alloys. A solution of strong acid known as pickle liquor is used for the process. The process is essential for the treatment of alloys' surface. For instance, it ensures the removal of various impurities, including stains, rust, inorganic contaminants, and scales from ferrous and copper metals, as well as aluminum alloys.
The fourth process is annealing. Here, the alloy is heated to a specific temperature and then cooled very slowly at a controlled flow rate. The purpose is to soften the alloy for cold working, improve its machinability, restore ductility, and enhance its electrical conductivity. Notable is that annealing further encourages cold working without cracking being a risk. This follows the release of mechanical stress. A similar process is repeated in the manufacturing process to constitute stage number seven.
Wire drawing is the fifth process whereby the alloy material is lubricated, and a powered capstan is used to draw it through the desired die, hence, modeled into specified dimensions. The process, nonetheless, increases the tensile and yield property of the material while, on the other hand, reduces the material's ductility.
Cold rolling or slitting is the sixth process which is quite the opposite to hot rolling highlighted above. For instance, unlike hot rolling, cold rolling involves passing the metal billets' rollers at a temperature that is below the crystallization temperature. The purpose is to increase the yield strength and harden the material through introducing defects into the material's crystal structure, hence, preventing further slip.
The eighth step is the quality control in which the alloy material is examined and evaluated to meet the desired specifications. This also ensures that the manufactured alloy corresponds to the desired properties for the right use. The last process is packing in which the materials depending on the shapes are packed in containers that carry them to the destination for safe delivery. Lastly, the cost of the manufacture of the material is noted to vary, for example, the approximate costs depend on the availability of the raw materials, labor, and quantity.
Works Cited
Campbell, F C. Elements of Metallurgy and Engineering Alloys. Materials Park, Ohio: ASM International, 2008.
Everhart, John L. Engineering Properties of Nickel and Nickel Alloys. Boston, MA: Springer US, 1971.
Hünecke, Klaus. Jet Engines: Fundamentals of Theory, Design and Operation. Shrewsbury, England: Airlife, 1997.
Rajput, R K. Internal Combustion Engines: (including Air Compressors and Gas Turbines and Jet Propulsion). Bangalore, India: Laxmi Publications, 2007.
