Corrosion behavior and failure mechanism of SiC whisker and c-AlPO4 particle-modified novel tri-layer Yb2Si2O7/mullite/SiC coating in burner rig tests

Abstract

The corrosion behavior of environmental barrier coatings (EBCs) directly affects the service life and stability of ceramic matrix composite (CMC) structural parts in the aero-engines. The silicon carbide (SiC) whisker toughening phase and c-AlPO4 bonding phase are firstly used to improve the service life of novel tri-layer Yb2Si2O7/mullite/SiC EBCs in the burner rig test. The formation of penetrating cracks in Yb2Si2O7/mullite/SiC coating caused the failure of coating at 1673 K. The SiC whiskers in mullite middle coating significantly inhibited the formation of penetrating cracks in Yb2Si2O7/mullite/SiC coating, and efficiently prevented the oxidation of carbon fiber reinforced silicon carbide (Cf/SiC) samples for 360-min thermal cycles (24 times) with a weight loss of 6.19×10−3 g·cm−2. Although c-AlPO4 particles further improved the service life of SiCw-mullite (SM) coating, the overflow of POx gas aggravated the formation and expansion of cracks in the Yb2Si2O7 outer coating, and caused the service life of overall Yb2Si2O7/c-AlPO4-SiCw-mullite (ASM)/SiC coating to be slightly lower than that of Yb2Si2O7/SM/SiC coating. This study guides the design of modified tri-layer EBCs with long service life in high-temperature and high-speed gas environment.