Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > The alloy learn with a variety of properties of alloys > Special physical properties of alloys > Special thermal properties of alloys > Melting point alloys , refractory alloy , high temperature alloys

Research of Microstructure and Property on Air Nozzle Alloy of Circulating Fluidized Bed Boilers

Author DaiYanBin
Tutor LiuShaoGuang; XuYuSong
School Jiangsu University of Science and Technology
Course Materials Science
Keywords wind cap air nozzle superalloy high-temperature oxidation high-temperature corrosion high-temperature erosion
CLC TG132.32
Type Master's thesis
Year 2012
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The serious high-temperature corrosion and erosion problems of the circulatingfluidized bed boiler wind caps have shortened the service life of wind caps and directlyimpacts the running of boilers, finally will causes severely economic loss. So,it will be avery meaningful subject to solve the high-temperature corrosion and erosion problems ofthe wind caps. New AN superalloys for CFB boiler wind caps have been developed viamultiple alloying methods. superalloy’s microstructure, microhardness, corrosion anderosion-wear behavior under high temperature condition have been studied and comparedwith those of steel25-20and steel316by using optical microscope, Vicker-Hardnessmeasurements, X-ray refra,ctionobservation, scanning electron microscope, energy dispersion spectrum analysis.The results indicate that the as-cast microstructure of AN superalloys was dendritewhich consists of γ(Ni-Cr-Fe-C) dendrite and carbides such as Cr23C6and NbC in dendriteintervals, and the microhardness of AN1and AN2as-cast samples were HV0.1335andHV0.1341respectively. after solution treatment, the dendrite features almost disappeared andfine carbine particles can be dispersively distributed into theγmatrix. The microhardness ofAN1and AN2solid-solution samples were HV0.1424and HV0.1431respectively. Afterhaving been exposed to1000℃for100h, the isothermal mass gain of AN1and AN2superalloys, steel25-20and steel316were respectively0.5391mg/cm2,0.4282mg/cm2,0.9527mg/cm2和1.61mg/cm2, show excellent high-temperature oxidation resistance. Thecorrosion dynamics curve at1000℃of AN superalloys had parabolic law. After100hourstest, high-temperature corrosion resistance of AN superalloys were913and34times thatof steel25-20and steel316respectively. Swash caused erosion of AN superalloys appear inthe form of furrowing, cutting, and slicing. The first two appear most significantly when theattack angles are small, while the last one at large attack angles. The maximum erosive rateof both AN1and AN2superalloy samples appeared when the impact angle is about at30°due to the plastic erosion mechanism for AN superalloys. The erosion rate of AN1, AN2superalloys, steel25-20and steel316was0.015mm3/g,0.012mm3/g,0.048mm3/g and0.06mm3/g respectively when the impact angle is about60°.Accounting to the tests and analysis results on the structure and properties of ANsuperalloys, conclusions show as follow: no matter the hardness, high-temperature oxidationresistance, high-temperature corrosion resistance and high-temperature erosion resistance,AN2superalloy sample is a little more better than AN1superalloy which can be used on the site as CFB wind caps and can be greatly popularized after trying on the site.

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