Comprehensive investigation on CMAS and steam corrosion resistance of quaternary rare earth oxide co-doped zirconia thermal barrier coating material

The development of advanced gas turbines has placed higher demands on high-temperature thermal barrier coatings (TBCs). Multi rare earth oxide doped zirconia has been demonstrated with low thermal conductivity, and improved high-temperature stability. This study evaluated the durability and corrosion behavior of La ₂O ₃, Gd ₂O ₃, Yb ₂O ₃, and Y ₂O ₃ co-doped ZrO ₂, referred to as 1La-xGd-2Yb-3.5YSZ (x = 2, 4, and 6), under high-temperature steam and molten calcium-magnesium-alumino-silicate (CMAS) conditions. The effects of co-doping on high-temperature corrosion were investigated, elucidating the corrosion mechanisms of solid solution materials with varying dopant compositions. High-temperature steam corrosion tests at 1300°C demonstrated that co-doping significantly enhanced the phase stability of the solid solution and provided excellent resistance to steam corrosion. Under CMAS corrosion conditions, the addition of gadolinium oxide markedly suppressed the formation of the monoclinic phase, reduced the Ca/Si ratio in the melt, and facilitated the formation of a recrystallized apatite phase, which is critical for improving the CMAS corrosion resistance of the ceramic topcoat.