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1、Jet Engine MaterialsA quick overview of the materials requirements,the materials being used,and the materials being developedMotivation for Materials DevelopmentuHigher Operating TemperaturesuHigher Rotational SpeedsuLower Weight Engine ComponentsuLonger Operating LifetimeuDecreased Failure Occurren
2、ceuThis all adds up to:uBetter PerformanceuLower Life Cycle CostsMaterials Requirementsuthousands of operating hours at temperatures up to 1,100C(2000 F)uhigh thermal stresses caused by rapid temperature changes and large temperature gradientsuhigh mechanical stresses due to high rotational speeds a
3、nd large aerodynamic forcesulow-and high-frequency vibrational loadinguoxidationucorrosionutime-,temperature-and stress-dependent effects such as creep,stress rupture,and high-and low-cycle fatigue.Regions of the EngineuCold SectionsuInlet/FanuCompressoruCasinguHot SectionsuCombustoruTurbine/OutletC
4、old Section Materials RequirementsuHigh Strength(static,fatigue)uHigh StiffnessuLow WeightuMaterials:uTitanium AlloysuAluminum AlloysuPolymer CompositesuTitanium intermetallics and compositesApplications of Polymer CompositesFiber Reinforced Polymer Composite Properties-Graphite/KevlaruVery high str
5、ength-weight ratiosuVery high stiffness-weight ratio(graphite)uVersatility of design and manufactureuSpecific gravity:1.6 (compared to 4.5 for titanium&2.8 for aluminum)uCan only be used at low temperatures 150 ksi,E=18 MsiuSpecific gravity of 4.5(58%that of steel)uTitanium alloys can be used up to
6、temperatures of 590 C(1100 F)uGood oxidation/corrosion resistance(also used in medical implants)uHigh strength alloys hard to work-therefore many engine components are castMetallurgy of disks critical to achieve desired properties and to eliminate defectsuAccident occurred JUL-19-89 at SIOUX CITY,IA
7、Aircraft:MCDONNELL DOUGLAS DC-10-10,Injuries:111 Fatal,47 Serious,125 Minor,13 Uninjured.uA FATIGUE CRACK ORIGINATING FROM A PREVIOUSLY UNDECTECTED METALLURGICAL DEFECT LOCATED IN A CRITICAL AREA OF THE STAGE 1 FAN DISK THAT WAS MANUFACTURED BY GENERAL ELECTRIC AIRCRAFT ENGINES.THE SUBSEQUENT CATAST
8、ROPHIC DISINTEGRATION OF THE DISK RESULTED IN THE LIBERATION OF DEBRIS IN A PATTERN OF DISTRIBUTION AND WITH ENERGY LEVELS THAT EXCEEDED THE LEVEL OF PROTECTION PROVIDED BY DESIGN FEATURES OF THE HYDRAULIC SYSTEMS THAT OPERATED THE DC-10S FLIGHT CONTROLS.Aluminum alloys can reduce weight over titani
9、umuConventional alloys have lower strength/weight ratios than Ti but more advanced alloys approach that of Ti.uSpecific gravity:2.8(62%that of Ti)uLower cost than TiuMax temp for advanced alloys:350 C(600 F)uLower weight&rotating part inertiaTitanium Aluminide Ti3AluAn intermetallic alloy of Ti and
10、AluExtends the temperature range of Ti from 1100 F to 1200-1300 FuSuffers from embrittlement due to exposure to atmosphere at high temperature-needs to be coated.Titanium Composites(MMC)uTitanium matrix with SiC fibersuDecreases weight while increases strength and creep strengthTYPICAL Ti/SiC COMPOS
11、ITE100XHot Section Materials RequirementsuHigh Strength(static,fatigue,creep-rupture)uHigh temperatureresistance 850 C-1100 C(1600 F-2000 F)uCorrosion/oxidation resistanceuLow WeightHigh Temperatures-1100 C(2000 F)uCreep becomes at factor for conventional metals when the operating temperature reache
12、s approximately 0.4 Tm(absolute melting temp.)uConventional engineering metals at 1100 C:uSteel 0.9 TmuAluminum1.4 TmuTitanium 0.7 TmuConclusion:We need something other than conventional materials!uUnconventional metal alloys-or superalloysuCeramicsHigh Temperatures-1100 C(2000 F)What Materials Can
13、Be Used?SuperalloysuNickel(or Cobalt)based materialsuCan be used in load bearing applications up to 0.8Tm-this fraction is higher than for any other class of engineering alloys!uHigh strength/stiffnessuSpecific gravity 8.8(relatively heavy)uOver 50%weight of current enginesTypical Compositions of Su
14、peralloysCHEMICAL COMPOSITION,WEIGHT PERCENTChromium yields corrosion resistanceMicrostructure of a SuperalloyuSuperalloys are dispersion hardeneduNi3Al and Ni3Tiin a Ni matrixuParticles resistdislocation motion andresist growth at hightemperaturesCreep-RuptureuStrain increases over time under a sta
15、tic load-usually only at elevated temperatures(atoms more mobile at higher temperatures)uThe higher energy states of the atoms at grain boundaries causes grain boundaries-particularly ones transverse to load axis-to creep at a rate faster than within grainsuCan increase creep-rupture strength by eli
16、minating transverse grain boundariesControlled grain structure in turbine blades:Equi-axedDirectionally solidified (DS)Single Crystal(SX)Performance of superalloy parts enhanced with thermal barrier coatingsuThin coating-plasma sprayeduMCrALY coating materialsuIncreased corrosion/oxidation resistanc
17、euCan reduce superalloy surface temperature by up to 40 C(100 F)Non-metallics-CeramicsCobaltNickelChromiumTungstenTantalumSiliconNitrogenCarbonSUPERALLOYCERAMICCeramics-AdvantagesuHigher TemperaturesuLower CostuAvailability of Raw MaterialsuLighter WeightuMaterials:uAl2O3,Si3N4,SiC,MgO Ceramics-Chal
18、lengesSuperalloysCeramicsDUCTILITYTOUGHNESSIMPACTCRITICAL FLAW SIZECeramic CompositesuCeramic Fiber Reinforced Ceramic MatrixuImprove toughnessuImprove defecttoleranceuFiber pre-form impregnated with powder and then hot-pressed to fuse matrixCarbon-Carbon compositeuCarbon fibers in a carbon matrixuH
19、as the potential for the highest temperature capability 2000 C(4000 F)uMust be protected from oxidation(e.g.SiC)uCurrently used for nose-cone for space shuttle which has reentry temperatures of 1650 C(3000 F)Trends in turbine materialsTURBINE ROTOR INLETTEMP,FMaterials for F109 engineF109 FAN MODULE
20、 MATERIALSF109 HP COMPRESSOR MATERIALSTi 6-4INCO 718Ti 6-2-4-2INCO 625(side plates)INCO 718(vanes)201-T6 Aluminum17-4 PHHAST XF109 COMBUSTOR/MIDFRAME MATERIALSINCO 600HAST XHAST SINCO 718INCO 718INCO 718HS 188+TBCHS 188300 SSHS 188WASP BINCO 718HAST XHAST XMAR-M 247DSHAST SMAR-M 247DSINCO 738MAR-M 2
21、47DSMAR-M 247INCO 738F109 HP TURBINE MATERIALSWASPALOYWASPALOYWASPALOYWASPALOYWASPALOYHAST X BACK WITH HAST X0.032 CELL.HONEYCOMBEQUIAXED MAR-M 247COATED WITH RT-21EQUIAXED MAR-M 247HASTELLOY XHAST X BACK WITH HAST X0.032 CELL.HONEYCOMBINCONEL 625 HAST X BACK WITHHAST X0.032 CELL.HONEYCOMBEQUIAXED MAR-M 247 COATED WITH RT-21INCONEL 625 HAST X BACK WITH HAST X0.032 CELL.HONEYCOMBF109 LP TURBINE MATERIALS
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