Deposition Characteristics of SrZrO3 Thermal Barrier Coating Prepared by Solution Precursor Plasma Spray Process

The crystallization kinetics of the dried SrZrO3 precursor powders were investigated by DSC measurements. The crystallization activation energy of ZrO2 in the SrZrO3 precursor powders is 54.9 kJ/mol. And the Avrami parameter value is 2.16, indicating a two-dimensional, diffusion-controlled nucleation and growth mechanism of ZrO2 nuclei in the SrZrO3 precursor powders. The SrZrO3 thermal barrier coating (TBC) was prepared by solution precursor plasma spray (SPPS) process. The coating deposition characteristics were investigated by designing different spray models (single-scan spray, multiple-scan spray, and raster-scan spray) with optimized spray parameters. The surface and cross-sectional morphology of the SrZrO3 coatings were characterized by scanning electron microscope (SEM). The experimental results showed that the atomization pressure of liquid feedstock has strong influence on the trajectory of the precursor droplets in the plasma jet. The inter-pass boundary (IPB) microstructure in the SrZrO3 coating is mainly attributed to the secondary melting of the powdery deposits formed in the cold region of the plasma jet. The influence of the raster-scan step size of plasma torch on the SrZrO3 coating microstructure depends on the stay time of plasma torch on the substrate; the small raster-scan step size is favorable for the formation of IPB structure in this work.