Deposition mechanisms of yttria-stabilized zirconia coatings during plasma spray physical vapor deposition

As a new processing technology, plasma spray physical vapor deposition (PS-PVD) offers the possibilities to deposit coatings with microstructures varied in a wide range, including fully dense structure, columnar structure and hybrid structure. In this paper, the deposition mechanisms related to the above three microstructures were investigated by looking into the morphologies and phase compositions of the initial deposits during several seconds spraying. The dense coating was stacked up mainly by liquid droplets, un-melted/semi-melted particles and vapor phases. The columnar coating was mostly deposited from vapor phases which were transported to the substrate surface in the state of vapor atoms and clusters, growing in a new growth mechanism different from that in EB-PVD process. The hybrid coating was formed by co-deposition of vapor phases and liquid droplets.