Coatings for High-Temperature Structural Materials Trends and Opportunities (1996) / Chapter Skim
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2 APPLICATION NEEDS AND TRENDS
2 APPLICATION NEEDS AND TRENDS
Pages 10-18
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From page 10... ...
Aircraft Turbine Needle Two government programs, the High-Speed Civil Transport program led by NASA and the Integrated High-Perfonnance Turbine Engine Technology program led by DOD, are aimed at developing prototype turbines within the next ten years that will operate at firing temperatures at least 150°C (270°F) higher than the current generation of high-performance gas turbines.
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From page 11... ...
I Trucks (off-road trucks with motorized wheels) Land-Baserl Turbine Needs Industrial gas turbines for power generation are distinguished from aircraft gas turbines by many characteristics Hat include larger size, lower rotational speeds, longer life expectancy, longer time between overhauls, high time at full power, few on/off duty cycles, lower quality and lower heating-value fuels, wide variety of fixed locations (e.g., arctic to Topic, oceans to deserts, clean to polluted)
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From page 12... ...
Coal gasification produces a raw syngas consisting mainly of carbon monoxide and hydrogen, along with substantial quantities of hydrogen sulfide, ammonia, and hydrogen chloride, and a few parts per million of alkali metals (NRC, 1986~. To meet environmental requirements, commercial gasification systems include clean-up systems that remove virtually all of the hydrogen sulfide, ammonia, and hydrogen chloride; in Base: Fighter engine 1525°C Civil transport 1425°C Power generation t250°C general, the alkali metals are also removed.
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From page 13... ...
Design engineers seek to mitigate the impact of operating conditions on component integrity by two approaches, both of which have become absolutely essential to the design of hot-section components. The first approach relies directly on coating technology to extend the service life of both nickelbase and cobalt-base superalloys, as discussed in chapter 3.
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14 ~ o loo ,-: ~ ~ a ~ ~ a ~ O D ~ Z Z C~ ~ == _ E~ O O ~ O CO O L~ Cr)
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From page 15... ...
Both silicon carbide and silicon nitride oxidize to form silicon oxide surface scales, which may limit their high-temperature use unless adequate protective coatings can be applied. Under the operating conditions envisioned for these materials, surface recession caused by active oxidation (SiO formation instead of SiO2)
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From page 16... ...
Obstacles include low creep strength at high temperature and poor ductility at low temperatures (Dimiduk et al., 1992~. Despite these drawbacks, a number of research programs have improved the properties of these materials, and intermetallics now offer the promise of lessdemanding, lower-temperature applications.
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From page 17... ...
If these efforts ultimately prove successful, a coating will probably still be necessary to provide the long-term environmental resistance required for all As-turbine engines. growth occurs in cracks, porosity, and grain boundaries, the large volume increase results in fracture and eventually catastrophic failure of Me matenal (Doychak, 1994)
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From page 18... ...
. b Intemational Nickel Company (1977)
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