Fabrication and characterization of Yb2Si2O7-based composites as novel abradable sealing coatings

Abstract

Ceramic matrix composites (CMCs) have gradually replaced superalloys for use in hot sections of aero-engines to meet the requirements for increasingly high engine temperatures. However, the abradable sealing coatings (ASCs) commonly applied to superalloys are not suitable for CMCs owing to factors such as the difference in the coefficient of thermal expansion, therefore it is necessary to develop a new system suitable for CMCs. Yb2Si2O7 exhibits good high-temperature phase stability and relatively low hardness and may be a suitable material for ASCs. In the present study, Yb2Si2O7-based composite coatings with different hexagonal boron nitride (hBN) contents (0, 5, 10, and 15 wt%) were deposited by air plasma spray (APS), and the microstructure, mechanical properties, and abradability of the coatings were characterized. The results showed that the system of Yb2Si2O7 combined with hBN exhibits lower hardness, lower friction coefficient, higher wear rate, and smaller IDR value than the pure Yb2Si2O7 coating and is appropriate for use in ASCs. However, excessive hBN caused severe wear of the coatings. The relevant wear mechanisms of the coatings were analysed, and this study may provide guidelines for the development of ASCs suitable for CMCs.