Thermal Shock Resistance and Thermal Erosion Resistance at 1 350 ℃ of Si/Yb₂Si₂O₇ Coatings on Surface of SiC_f/SiC Composites

Abstract

In order to study the thermal shock resistance and thermal erosion resistance of Si/Yb2 Si2 O7 coatings at 1 350 ℃， Si/Yb2 Si2 O7 coatings were prepared on SiCf/SiC composites by vacuum plasma spraying technology.Subsequently，the structure and performance of the samples were characterized by metallography， physical phase， SEM， EDS， gas thermal shock equipment and gas thermal flushing equipment.Results showed that the bonding strength between the coating and SiCf/SiC composite material was 25.01 MPa.After 1 350 ℃gas thermal shock for 1 000 times and 1 350 ℃，550 m/s gas thermal scouring for 1 h， the surface phases of the Yb2Si2O7 coating were mainly Yb2Si2O7，Yb2SiO5， Yb2O3 and SiO2， and the test results of thermal shock resistance and thermal erosion resistance both met the design requirements.Furthermore， the coating had high bonding strength.The composite materials， Si layer and Yb2Si2O7 layer were resistant to high temperature and had good thermal matching performance， and the surface layer had strong resistance to gas corrosion， which was the main reason for the good thermal shock and thermal erosion performance of the coating.Besides， the gas combustion time of gas thermal scouring was shorter than the total time of gas thermal shock， and the thermal scouring was a constant temperature continuous scouring without drastic alternation of hot and cold.Therefore， no obvious cracking was observed at the edge of the coating near the tooling after gas scouring，and the black ablation area after continuous scouring was smaller than the area of gas thermal shock.    

Keywords

• sicf/sic composites； si/yb2si2o7 coating； vacuum plasma spraying； thermal shock resistance； thermal erosion resistance