Interaction of Yb2Si2O7 environmental barrier coating material with Calcium-Ferrum-Alumina-Silicate (CFAS) at high temperature

Experimental investigations of Yb2Si2O7 pellet exposed to Calcium-Ferrum-Alumina-Silicate (CFAS) at 1400 degrees C in ambient air were carried out to reveal corrosion reaction between molten silicate deposit and Yb2Si2O7. Phase transformation, microstructure evolution and reaction mechanism were evaluated. Results indicated that the corrosion process was accompanied by the infiltration of CFAS melt, the dissolution of Yb2Si2O7 and the reprecipitation of Yb2Si2O7 and Ca2Yb8(SiO4)6O2 apatite as reaction product. The formation of apatite decreased the concentration of Ca2+ in the melt. After CFAS exposure at 1400 degrees C for 30 h, the thickness of the apatite layer stopped increasing due to insufficient Ca2+ content, and remained at about 115.4 mu m. However, the infiltration depth of CFAS melt increased with the extending corrosion duration and increasing deposit content. And the infiltration rate was preliminarily found to first decrease and then increase with time. Most of the residual CFAS were crystallized into garnet (Ca3Fe2(SiO4)3 and Yb3Fe5O12) and mayerite (Ca12Al14O33), while a small volume of amorphous glass was dispersed among the garnet and mayerite grains.

Automated summary

Experimental investigations were conducted on the corrosion reaction between Yb2Si2O7 pellet and CFAS at 1400 degrees C, revealing the formation of apatite layer. The infiltration depth of CFAS melt increased with time, while the thickness of apatite layer reached a plateau after 30 hours of exposure.