Thermal cycling behavior and hot corrosion performance of the plasma sprayed Er2Si2O7 coatings deposited on Cf/SiC composites

Abstract

Rare-earth based disilicates are promising coating materials for Cf/SiC composites. In this study, Er2Si2O7 coating was deposited on the Cf/SiC substrate by atmospheric plasma spraying using the solid-state reaction synthesized powders. Sintered Er2Si2O7 coupons derived from the synthesized powders were subjected to dilatometric studies showing the average value of 4.3 ppm/°C for the coefficient of thermal expansion. The coated Cf/SiC coupons were thermally cycled between 400 °C and 1500 °C on a burner rig facility until failure of coating. Meanwhile, hot corrosion performance of the free standing plasma sprayed Er2Si2O7 coating coupon was evaluated by using molten vanadate salt with loading of 15 mg/cm2 at 800 °C. Analytical techniques such as X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy were applied to study the microstructural characteristics of the powders and coatings before and after thermal cycling and hot corrosion tests. Coatings’ degradation as a result of thermal cycling and hot corrosion tests was investigated in terms of microstructure and microchemistry transformations.

Keywords

• Disilicate
• Cf/SiC composites
• Microstructure
• Thermal cycling
• Hot corrosion