A self-healing environmental barrier coating: TiSi2-doped Y2Si2O7/barium strontium aluminosilicate coating

In order to increase the component lifetime of SiC based materials in combustion environments, environmental barrier coatings (EBCs) based on ceramic oxides are used to improve corrosion resistance of SiC, due to their high chemical stability. In this work, mullite and barium-strontium-aluminosilicate (BSAS) coatings were deposited by slurry dip coating on SiC substrates. Slurries were prepared by suspending commercial powders in water or ethanol, using appropriate dispersants. Substrates were dipped into the slurry and subsequently dried and heat treated at high temperature to promote densification. SEM observations were carried out to investigate the microstructure of the obtained coatings and to evaluate crack formation, porosity and adhesion.

Download Full-text

Rear Earth Oxide Multilayer Deposited by Plasma Spray-Physical Vapor Deposition for Envisaged Application as Thermal/Environmental Barrier Coating

Coatings ◽

10.3390/coatings11080889 ◽

2021 ◽

Vol 11 (8) ◽

pp. 889

Author(s):

Jie Zhong ◽

Dongling Yang ◽

Shuangquan Guo ◽

Xiaofeng Zhang ◽

Xinghua Liang ◽

...

Keyword(s):

Composite Coating ◽

High Temperatures ◽

Physical Vapor Deposition ◽

Ceramic Matrix Composites ◽

Ceramic Matrix ◽

Matrix Composites ◽

Environmental Barrier ◽

Chemical Attack ◽

Environmental Barrier Coating ◽

Barrier Coating

SiC fiber-reinforced SiC ceramic matrix composites (SiCf/SiC CMCs) are being increasingly used in the hot sections of gas turbines because of their light weight and mechanical properties at high temperatures. The objective of this investigation was the development of a thermal/environmental barrier coating (T/EBC) composite coating system consisting of an environmental barrier coating (EBC) to protect the ceramic matrix composites from chemical attack and a thermal barrier coating (TBC) that insulates and reduces the ceramic matrix composites substrate temperature for increased lifetime. In this paper, a plasma spray-physical vapor deposition (PS-PVD) method was used to prepare multilayer Si–HfO2/Yb2Si2O7/Yb2SiO5/Gd2Zr2O7 composite coatings on the surface of SiCf/SiC ceramic matrix composites. The purpose of this study is to develop a coating with resistance to high temperatures and chemical attack. Different process parameters are adopted, and their influence on the microstructure characteristics of the coating is discussed. The water quenching thermal cycle of the coating at high temperatures was tested. The results show that the structure of the thermal/environmental barrier composite coating changes after water quenching because point defects and dislocations appear in the Gd2Zr2O7 and Yb2SiO5 coatings. A phase transition was found to occur in the Yb2SiO5 and Yb2Si2O7 coatings. The failure mechanism of the T/EBC composite coating is mainly spalling when the top layer penetrates cracks and cracking occurs in the interface of the Si–HfO2/Yb2Si2O7 coating.

Download Full-text