Thermally Grown Oxide Stress in PS-PVD and EB-PVD Thermal Barrier Coatings Observed at Various Lifetimes Via Synchrotron X-ray Diffraction

The current standard application method for thermal barrier coatings (TBCs) on turbine blades for jet engines is electron-beam physical vapor deposition (EB-PVD) due to its high strain tolerance and low thermal conductivity. An emerging deposition method, plasma-spray physical vapor deposition (PS-PVD), presents an opportunity for a tailorable microstructure, and non-line-of-sight deposition that is faster and less expensive. To compare the lifetime behavior of both PS-PVD and EB-PVD coatings, samples subjected to 300 and 600 thermal cycles were measured during a 1 h thermal cycle to determine the strains, which were converted to stress, in the thermally grown oxide (TGO) layer of the TBCs using synchrotron X-ray diffraction (XRD). Room temperature XRD measurements indicated among samples that PS-PVD coatings experienced greater variation in in-plane room temperature strain in the TGO after cycling than the EB-PVD coatings. In-situ XRD measurements indicated similar high-temperature strain and no spallation after 600 thermal cycles for both coatings. Microscopy imaging after cycling showed greater rumpling in PS-PVD coatings that led to different failure modes between the two coatings' TGO layers. The tailorability of PS-PVD coatings allows for adjustments in the processing parameters to improve their overall performance after aging and bridge the differences between the two deposition methods.

Automated summary

The current standard application method for thermal barrier coatings (TBCs) on turbine blades for jet engines is electron-beam physical vapor deposition (EB-PVD). An emerging deposition method, plasma-spray physical vapor deposition (PS-PVD), offers a faster and less expensive alternative with a tailorable microstructure. By comparing lifetime behavior of both coatings, it was found that PS-PVD coatings showed greater variation in in-plane room temperature strain in the thermally grown oxide (TGO) layer after cycling, while both coatings exhibited similar high-temperature strain and no spallation after 600 thermal cycles. Microscopy imaging showed that PS-PVD coatings had more rumpling and different failure modes in the TGO layer compared to EB-PVD coatings. The tailorability of PS-PVD coatings enables adjustments to improve overall performance and bridge the differences between the two deposition methods.