Analysis of Plasma-Sprayed Thermal Barrier Coatings With Homogeneous and Heterogeneous Bond Coats Under Spatially Uniform Cyclic Thermal Loading

摘要: Abstract. This report summarizes the results of a numerical investigation into major failuremechanism in plasma-sprayed thermal barrier coatings observed under spatially-uniform cyclicthermal loading which mimics furnace durability test. In particular, factors leading to spallation ofthetopcoatcausedbythetop/bondcoatthermalexpansionmismatchconcomitantwithdeposition-induced interfacial roughness, oxide film growth and creep-induced normal stress reversal at therough interface’s crest are analyzed. Further, recent attemps increase coating throughthe reduction top/bond coat expansion mismatch achieved by embedding aluminaparticles bond also critically examined. The analysis focuses on evolution localstress inelastic strain fields vicinity rough interface during thermalcycling, how these influenced presence an spatially uniformand nonuniform (graded) distributions alumina particles metallic coat. impact ofthese potential local horizontal delamination crest,thought initiate this location, is included investigation. feasibilityof grading properties reduce driving forces criticallyexamined. conducted using Higher-Order Theory for Functionally GradedMaterials accounts high-temperature creep/relaxation effects within individualTBC constituents. two-phase microstructures, both actual andhomogenized employed order highlight limitationsof prevalent homogenization-based approach applied graded materials. revealthe important contributions shear components delaminationgrowth film, suggest mixed-mode crack propagationcharacterized deflections. use heterogeneous, coats, with spatiallyuniform or microstructure, shown byincreasing magnitude component ahead tip.