Crystallographic and TEM Features of a TBC/Ti2AlC MAX Phase Interface after 1300 ° C Burner Rig Oxidation

A FIB/STEM interfacial study was performed on a TBC/Ti2AlC MAX phase system, oxidized in an aggressive burner rig test (Mach 0.3 at 1300 degrees C for 500 h). The 7YSZ TBC, alpha-Al2O3 TGO, and MAXthal 211(TM) Ti2AlC base were variously characterized by TEM/STEM, EDS, SADP, and HRTEM. The YSZ was a mix of clean featureless and faulted high contrast grains. The latter exhibited ferro-elastic domains of high Y content tetragonal t variants. No martensite was observed. The TGO was essentially a duplex alpha-Al2O3 structure of inner columnar plus outer equiaxed grains. It maintained a perfectly intact, clean interface with the Ti2AlC substrate. The Ti2AlC substrate exhibited no interfacial Al-depletion zone but, rather, numerous faults along the basal plane of the hexagonal structure. These are believed to offer a means of depleting Al by forming crystallographic, low-Al planar defects, proposed as Ti2.5AlC1.5. These characterizations support and augment prior optical, SEM, and XRD findings that demonstrated remarkable durability for the YSZ/Ti2AlC MAX phase system in aggressive burner tests.

Automated summary

A FIB/STEM interfacial study was conducted on a TBC/Ti2AlC MAX phase system after it underwent aggressive burner rig testing. The study characterized the 7YSZ TBC, alpha-Al2O3 TGO, and MAXthal 211(TM) Ti2AlC base using various techniques such as TEM/STEM, EDS, SADP, and HRTEM. The results revealed clean and faulty YSZ grains, a duplex alpha-Al2O3 structure for the TGO, and a Ti2AlC substrate with basalse plane faults. These findings support previous research demonstrating the durability of the YSZ/Ti2AlC MAX phase system.