Ceramic thermal barrier coatings (TBCs), attributed to their inherent brittle nature, are highly susceptible to damage by impacting foreign particles when the impacting kinetic energy exceeds certain limits. The damage is termed foreign object damage (FOD) in related turbine components and results in various issues/problems to coatings as well as to substrates from delamination to spallation to cracking to catastrophic failure depending on the severity of impact. The FOD testing was performed using a ballistic impact gun for turbine airfoil components coated with 7% yittria stabilized zirconia (7YSZ) by electron beam physical vapor deposit (EB-PVD). A range of impact velocities up to Mach 1 was applied with three different projectile materials of steel, silicon nitride, and glass balls. The damage was assessed and characterized in terms of impact velocity, projectile material, and remaining life of turbine components. An energy-balance approach was made to develop a model to predict delamination of the TBCs upon impact.

Thermal harrier coatings (TBCs), attributed to their inherent brittleness, are vulnerable to damage by impacting foreign objects when kinetic energy of the objects surpasses cer tain limits. The damage is termed foreign object damage (FOD) and results in various issues to coatings as well as to substrates, from plastic impression to delamination to spallation to cracking, depending on the severity of impact. The FOD experiments were conducted utilizing a ballistic impact gun for vane airfoil components coated with 220 pm-thick, 7% yttria-stabilized zirconia (7YSZ) by electron beam physical vapor de posit (EB-PVD). The testing was performed with impact velocities ranging from 150 mis to Mach 1 using 1.6-mm hardened chrome-steel ball projectiles. The resulting FOD was in the forms of impact impressions, cone cracking, and delamination of the coatings!sub strates. Prediction of delamination crack size as a function of impact velocity was made based on an energy-balance approach through a quasistatic, first-order approximation. The prediction was in reasonable agreement with experimental data considering a pre sumable compaction of the TBCs upon impact. Experimental ProceduresMaterials/Airfoil Components. The airfoils used in this work were hot-section vanes (nozzles) coated with 7YSZ EB-PVD TBCs. The thickness of the top coats was about 220 pm. The

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