Bonding strength of environmental barrier coatings on surface of SiC-based ceramic matrix composites

Abstract

SiC-based ceramic matrix composites (SiC-CMC) are an ideal material for aeroengines with high thrust/mass ratio.In order to prevent the corrosion of SiC-CMC by gas (rich in H2O and O2) in the engine, it is necessary to prepare environmental barrier coatings (EBCs) with excellent water and oxygen corrosion resistance, gas erosion resistance and thermal shock resistance. Among many factors that evaluate the performance of EBCs, the bonding strength between EBCs and SiC-CMC matrix is an important indicator, but the limit value of the bonding strength has not been clearly explored.In this paper, main factors to control the bonding strength were studied in order to reach the highest value, including the SiC-CMC matrix state, the tensile strength limit of single crystal Si, and the preparation process of the Si bonding layer, etc. In the SiC-CMC/EBCs system, the interface between the SiC fiber cloth is the weakest part of the bonding strength, followed by the Si bonding layer. The bonding strength limit is 15 MPa, which is the tensile strength limit of single crystal Si in the [400] crystal direction. The bonding strength of the Si layer using atmospheric plasma spraying (APS) or high velocity oxygen-fuel(HVOF) is similar, which is lower than that of mullite or Yb2Si2O7 layer sprayed by the same process.

Keywords

• sic
• composite
• environmental barrier coatings
• bonding strength