Corrosion behavior under near-service conditions of YSZ TBCs subject to CMAS and NaCl in a burner rig test

The corrosion behavior of yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) under the synergistic effect of calcium-magnesium-alumina-silicate (CMAS) and NaCl under near-service conditions (the flame temperature can reach 1900°C and the flame speed can reach 0.5Mach) was investigated using a burner rig. The results indicated that when the surface temperature of the top coating (TC) (∼1200°C) was lower than the melting point of the CMAS, after thermal shock in a water environment, the phase of the CMAS on the TC surface remained stable, and the CMAS did not penetrate the TC interior. However, after thermal shock in a NaCl environment, the presence of NaCl disrupted the silicate network structure of CMAS, lowering its melting point and viscosity; meanwhile, the high-speed flame (0.5 Mach) promoted the penetration of CMAS melt into the TC, resulting in a porosity decrease in TC from 8.4 ± 0.88% to 6.92 ± 0.53%. The dominant mechanism of CMAS infiltration into TC changed from capillary-driven to a combined capillary-dynamic process. Meanwhile, the transformation of the chain-structured diopside (Ca(Mg, Al)(Si, Al) 2 O 6 ) in the CMAS to the island-structured magnesium feldspar (Ca 2 MgSi 2 O 7 ). Additionally, NaCl accelerated the formation of the non-protective oxide Cr 2 O 3 in the thermally grown oxides layer. This study provides new insights into the corrosion protection and performance optimization of TBC systems under near-service conditions.