Design of Ti ₂AlC/YSZ TBCs for more efficient in resisting CMAS attack

Abstract

Ti 2 AlC has been demonstrated as the promising protective layer material for thermal barrier coatings (TBCs) against calcium-magnesium-alumina-silicate (CMAS) attack. In this study, the reliability of Ti 2 AlC coatings against the CMAS corrosion was explored, and new Ti 2 AlC/YSZ TBCs more efficiently resistant to CMAS were designed. The fabricated Ti 2 AlC coatings inevitably contain some impurity phases (TiC and Al 2 Ti 3 ), the contents of which were minimized by optimizing the spraying distance. Corrosion tests revealed that Ti 2 AlC/YSZ TBCs yielded higher resistance to the CMAS attack than YSZ TBCs, but with long-term exposure to CMAS, the Ti 2 AlC protective coating exhibited microstructure degradation due to the presence of the impurity phases, which caused the formation of a layer mixed with Al 2 O 3 and TiO 2 rather than a continuous compact Al 2 O 3 layer on the surface. Pre-oxidation schemes were designed in air or with a controlled oxygen partial pressure, which revealed that the pre-oxidation at an oxygen partial pressure of ~630 Pa could promote a continuous Al 2 O 3 layer formed on the Ti 2 AlC protective coating surface. Furthermore, a vacuum heat treatment at 867 ℃ for 10 h before pre-oxidation was beneficial for the formation of the compact Al 2 O 3 layer. Through the above scheme design, new Ti 2 AlC/YSZ TBCs were obtained, which had reduced impurity phase contents and a pre-oxide layer with an ideal structure on the surface. New TBCs exhibit higher microstructure stability exposed to CMAS and more efficient CMAS resistance.

High toughness and CMAS resistance of REAlO 3/RE 2Zr 2O 7 (RE = La, Nd, Sm, Eu, Gd, and Dy) composites with eutectic composition for thermal barrier coatings

“…In addition, YSZ is powerless under silicate melt (CaO-MgO-Al2O3-SiO2, CMAS) attack. At high temperature, the CMAS melt can infiltrate into coatings and reduce the overall porosity of YSZ, resulting in low strain tolerance and a decrease in lifetime by nearly two orders of magnitude [6][7][8]. Thus, there is an urgent need for new TBC materials that not only possess excellent thermal and mechanical properties but show high resistance to CMAS corrosion.…”