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Overheating Damage Analysis on Turbo-disk and Turbo-blades Used in Locomotive Turbocharger Heated by High-temperature and Short-time

Author: LiuXuan
Tutor: YuZhiWei
School: Dalian Maritime University
Course: Vehicle Operation Engineering
Keywords: K418 high-temperature alloy GH2036 high-temperature alloy High-temperature and short-time aging Overheated Structure Overheat damage analysis
CLC: TG115.5
Type: Master's thesis
Year: 2009
Downloads: 82
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Abstract


Morphology development of K418 and GH2036 high-temperature alloys during high-temperature and short-time aging was investigated by SEM,OPM and XRD to evaluate the overheating damage microstructure features.The failure analysis was conducted on the overheating-damaged turbo-blades and turbo-disk used in locomotive turbocharger.The main results were concluded as follows:(1) High-temperature and short-time aging process:①The phases constitutes of K418 alloy have no changes during aging,which are still composed ofγ-austenite,γ′-Ni3(Al,Ti) and MC-carbide.However,the lattice parameter ofγ′phase increases slightly with aging temperature.②γ′phase would aggregated gradually and grew-up with aging temperature. Re-solution ofγ′phase would take place and the amount ofγ′phase would decrease when aging temperature attained to the solvus temperature ofγ′-phase.The burn-off microstructure,such as re-melting eutectic phases(γ+γ′),re-meting boundary and degraded carbide would appear in the located region when aging at 1200℃.The hardness of K418 alloy increases slightly with aging temperature.③The area of carbide precipitation zone of GH2036 alloy decreases gradually with aging temperature and intergranular carbide grow-up obviously.The micro-hardness in carbide precipitation zone is higher than one in no-carbide precipitation zone.And the micro-hardness decreases in two zones with aging temperature.(2) Overheat damage analysis on the failed turbo-blade and turbo-disk:①Melting of the boundary,degraded interdendritic carbides and re-melting of eutectic phases(γ+γ′),typical of overheat damage occurred on the mid-airfoil of blades, which decrease fatigue strength of the blade.The multiple-origins fatigue fracture took place on the blades.The fractured blades have similar microstructure to the specimen aged at 1200℃,and the hardness of the fractured blade corresponds to the hardness of the specimen aged at 1200℃. ②Overheating during the operation of turbo-disk resulting from the intense friction between the air-seal and the back face of disk was found,which was reflected by microstructure features.The yield strength and fracture strength of the rubbed disk surface decreased resulting from overheating.The microstructure of disk surface intensely worn has similar features to the specimen aged at 1150℃,and the hardness of failed blades corresponds to the specimen aged at 1150℃.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallurgy ( Physical Metallurgy ) > Analytical tests of the metal (Metal Testing and Materials ) > Mechanical properties ( mechanical properties ) test
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