热障涂层破坏理论与评价技术(英文版)

Chapter 1 Introduction 　　The aeroengine is the “heart” of an aircraft， and these national treasures are an important indicators of national core competitiveness. The turbine inlet tempera-tures in both third-and fourth-generation aeroengines exceed the melting points of high-temperature metallic materials.A new generationof materials can yielda new generation of equipment. As the most feasible technology for improving the service temperature of gas turbine engines， thermal barrier coatings (TBCs) have becomeanindispensablethermalprotection materialfor hot-end components(e.g.， high-pressure turbinebladesin aeroenginesandgasturbines)and，toaremarkable extent， determine engine performance anddevelopmentlevels. All theworld’savia-tionpowershave listedTBCsasakey coretechnologyin theirmajoradvancement plans.Likewise， China has categorized TBCs asakeytechnology urgently needed for aeroengines andgasturbines. 　　Operating in hot-end components such as engine turbine blades， TBCs are subjected to long-termextreme conditions such as impactsfrom 2000Kgas near the critical Mach number， centrifugal forces generated by rotations at 10，000– 50，000 rpm，fatigue， creep， calcium-magnesium-aluminosilicate(CMAS) corrosion， solid particle erosion，and oxidation， accompaniedbychemical reactions.Asaresult ofextremeadverse conditions， coatingsspallandfailbyavarietyofcomplexmech-anisms， posinga multitudeofnew challengesto research onfailure theories.For example， oxidation， thermal mismatch， growth stress， and high temperature， which are involved in the interfacial oxidation failure of TBCs， affect one another. The oxidation process and the resulting coating spallation are both a typical thermo-mechano-chemical couplingphysical nonlinear problem anda geometric nonlinear problemwithstrainupto10%.As anotherexample，TBCmelts(CMAS) corrodeat high temperatures， and theirrelevant in.ltration and performanceevolution patterns and thermo-mechano-chemical coupling mechanismsare allnewfailure phenomena exhibitedbyTBCs，the mechanical natureofwhich has been poorlyexplained sofar. 　　Turbine blades are geometrically complex， and TBCs with defects and multi-layer systemshaveacomplexmicrostructure. During service， coatings and interfaces evolve in terms of composition， microstructure， and performance. Their nonlinear physical and geometricpropertiescreatenew problemsfor mechanical performance characterization and numerical simulation techniques. In addition， high tempera-turesare inevitableservice conditions for TBCs.The characterizationofthe coating performance at high temperatures and the accurate descriptionofthe loading condi-tions in complex high-temperature environments are issues to be considered in the failure analysis of TBCs. 　　Performanceevaluationand service lifepredictionarethemosturgent issuesof the TBC applicationsector.The associationofthe service lifewith thematerial and service-environment parametersoffersthe most direct basis forthe TBC production sector.Understanding this associationisthe ultimategoalofinvestigationintofailure mechanisms and， more importantly， is the most dif.cult scienti.c problem at the forefrontof theresearchin this .eld. Moreover， simulation andevaluationdevices canofferthe most reliable， directexperimental basis.They are thetopical andkey areasof researchonTBCfailure mechanism analysisandevaluationtechniques，but technological embargos are often imposed by relevant countries. 　　Thus，spallationfailure theories， numerical computational methods， mechanical performance characterizations， performance and service life evaluations， and pre-test-run simulation and evaluation devices all merit investigation in the study of TBCfailure mechanisms and performanceevaluation. 　　1.1 TBCs and the Corresponding Preparation Methods 　　1.1.1 TBC Materials and Structures 　　To meetthe demandforincreasingservice temperaturesingasturbine engines，the National Aeronautics and Space Administration(NASA)of the UnitedStates put forwardthe conceptof TBCsin 1953 [1–3]. TBCsofferthermalprotection based on thefollowing principle. Ceramicmaterials are characterizedby high-temperature resistance， high thermalstability，lowthermal conductivity，and high corrosion resis-tance. Because of these properties， ceramic materials are combined with metallic substrates in the form of coatings to insulate high-temperature metallic substrate materialsfromhigh-temperaturegas，withthegoalof reducingsurface temperatures in hot-end metallic components and simultaneously enhancing their resistance to high-temperature oxidation and hot corrosion [4，5]. TBCs have been satisfactorily appliedinhot-end componentssuch as turbine blades in aeroengines and gas turbines. 　　A typical TBC has a two-layer structure [8]. Figure 1.1 shows the geometry an structureof a TBC onaturbine blade. Theblade substrateis generally madeofa Ni-based high-temperaturealloy(adirectionally solidi.ed alloy ora single-crystal alloy).The TBC containsa metallic bond c