Preparation of SiCw/Yb2Si2O7 composite powders for environmental barrier coatings

Abstract

In order to prolong the lifetime of environmental barrier coatings (EBCs) produced by thermal spraying, Yb2Si2O7 powders doped with SiC whisker(SiCw/Yb2Si2O7) as feed stocks was prepared by ball milling, spray drying and vacuum sintering. The morphology, phase composition, particle size, flowability and densification of the powder were analyzed by TG-DSC, XRD, SEM and other methods. The SiC whisker was wrapped into the nanometer agglomerated powder by spray drying. The particle size varied by different spray drying parameters. Powders used for atmospheric plasma spraying were prepared by spray drying, optimal particle size can be obtained under 250 °C inlet temperature, 0.05 MPa atomization pressure, and a peristaltic pump rate of 60 r/min. With the increase of vacuum calcination temperature, the density and flowability of powders are improved, and the composition of the powder changed from Yb2O3 to Yb2SiO5 and finally to Yb2Si2O7. The optimal compactness and flowability of the powders were obtained at the sintering temperature of 1300 °C with minimal surface porosity. SiC whisker was not oxidized during the vacuum sintering and still maintained the original whisker morphology. The densification process of recombinant particles and its mechanism were analyzed in terms of surface morphology and cross section.