Oxidation and thermal shock resistant properties of Si/Yb2SiO5/NdMgAl11O19 coating deposited on Cf/SiC composites

Abstract Yb 2 SiO 5 and NdMgAl 11 O 19 (NMA) powders were synthesized by solid-state reactions. Triple-layer ceramic coatings based on the Si bond layer, Yb 2 SiO 5 interlayer and NMA top layer were prepared on carbon fiber reinforced silicon carbide ceramic matrix (C f /SiC) composites by atmospheric plasma spraying (APS). The coatings were subjected to thermal shock tests at 1300 °C, 1400 °C and 1450 °C, respectively. The results showed that the Si/Yb 2 SiO 5 /NMA coating significantly improved the oxidation resistance of C f /SiC composites. The failure mechanism of the Si/Yb 2 SiO 5 /NMA coating was closely related to the thermal shock temperature. Below 1400 °C, the failure of the coating was connected with the mismatch of thermal expansion coefficient (CTE) between the coating and substrate, the reaction between Yb 2 SiO 5 and NMA at the interface, the poor sintering property of Yb 2 SiO 5 and NMA and the substrate itself. Above 1450 °C, the coating failed after only one thermal shock cycle due to the temperature higher than the melting point of the silicon.