Figure 3.

(a) BSE−SEM image of a typical YAS coating layer and (b) its corresponding EDS mapping image. No pores were found in the deposited coatings, indicating a dense microstructure. The image shows grains with two distinct contrasts and morphologies: dark gray and light gray, with varying sizes. According to the EDS mapping results, the light gray region with larger grain sizes is rich in Y, Al and O elements, while the light gray region with smaller grain sizes is rich in Y, Si and O elements.