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

Peer review under responsibility of The Ceramic Society of Japan and the Korean Ceramic Society.

Figures & data

Table 1 Plasma spraying parameters for the manufacture of Er₂Si₂O₇ coatings.

Spray distance/mm	Voltage/V	Current/A	Plasma gas/SLPM^a	Carrier gas Ar/SLPM	Powder feed/g/min
110	62	650	Ar = 46, H2 = 8	2.6	30

a SLPM – standard liters per minute.

Fig. 1 XRD patterns of (a) Er₂Si₂O₇ powders fabricated by solid-state reaction at 1450 °C for 22 h and (b) as-sprayed Er₂Si₂O₇ coating deposited on C_f/SiC composites coupon.

Fig. 2 Variation in the coefficient of thermal expansion (CTE) and thermal expansion rate (ΔL/L₀) with temperature for Er₂Si₂O₇ bar by dilatometry. The bar was sintered at 1500 °C for 5 h prior to dilatometric measurements.

Fig. 3 (a) Macrograph of as-sprayed Er₂Si₂O₇ coating on the C_f/SiC coupon, (b) SEM image on the surface of as-sprayed Er₂Si₂O₇ coating and (c–d) EDS analysis for point 1 located in the flattened splat and point 2 located in the accumulated incongruent molten media within the as-sprayed Er₂Si₂O₇ coating, respectively.

Fig. 4 (a) SEM image on the cross-section of as-sprayed Er₂Si₂O₇ coating on C_f/SiC coupon, (b) EDS line scan starting from the interlayer and terminating at the surface of the coating, and (c–d) EDS spectra along with elemental percentages for point A near the interface and point B near the surface of the coating, respectively.

Fig. 5 (a) SEM image on the surface of the thermal shock tested Er₂Si₂O₇ coating on C_f/SiC coupon, (b) camera photograph of the thermal shock tested Er₂Si₂O₇ coating on C_f/SiC coupon, and (c–e) EDS analysis for point A located in the flattened splat, point B in the accumulated media and point C in the sponge-like media in (a), respectively.

Fig. 6 (a) SEM image on the cross-section of the thermal cycled Er₂Si₂O₇ coating on C_f/SiC coupon and (b and c) EDS spectra along with elemental percentages for point A near the interface and point B near the surface, respectively.

Fig. 7 XRD patterns of (a) as-sprayed Er₂Si₂O₇ coating and (b) the thermally cycled Er₂Si₂O₇ coating with 327 cycles with a flame temperature of 2000 °C. For each cycle, the coating was thermal cycled between surface temperatures of 400 °C and 1500 °C. (a) repeated for the sake of ease in comparison to the readers.

Fig. 8 (a) SEM image on the surface of plasma sprayed Er₂Si₂O₇ coating after exposure to molten V₂O₅ for 6 h at 800 °C and (b and c) EDS analysis for points 1 and 2 in (a), respectively.

Fig. 9 XRD patterns of (a) the as-sprayed Er₂Si₂O₇ coating and (b) the coating after exposure to molten V₂O₅ salt for 6 h at 800 °C. (a) repeated again for the sake of ease in comparison to the readers.