Effect of Different Thermal Spray Process Parameters on the Microstructure and Properties of PS-PVD- PVD 8YSZ Coatings

Plasma spray-physical vapor deposition (PSPVD) technology, invented at the beginning of this century, has been widely studied because of its non-line-of-sight deposition and high efficiency in the preparation of columnar and quasi-columnar structure coatings. Coatings prepared using this technology show characteristics of high thermal insulation and long life cycles. A jet with high PSPVD energy and speed causes coating deposition during turbulent effects, which significantly influence the microstructure and performance of the coating. The coating performance depends on the interface control and microstructural coating characteristics. To verify the influence of the spraying deposition process on the coating microstructure and reduce the influence of cylindrical tooling, different PSPVD process parameters, such as the spraying current, powder feed rate, spray gun swing, and sample rotation parameters, were studied using a planar tooling system. Additionally, the influence of different process parameters on the microstructure and microhardness of the coating was verified, particularly for relatively small turbulence conditions during cylindrical tool rotations. By using the autonomous PS-PVD powder with a particle size range of 1-20 g m-at a low-deposition-current range of 1.6-2.1 kA and a wide deposition distance of 0.9-2.0 m-it was systematically verified that the powder had a wide process window, as well as the ability to obtain a quasi-columnar structure coating with different microstructures. The effects of the deposition parameters on the microstructure and microhardness of the coating were systematically analyzed, and the formation mechanism of the coating under the low-current deposition mode was revealed. The results showed that the powder-feed rate and relative movement parameters of the spray gun sample had a considerable influence on the coating microstructure, contributing to its rapid control. The increase in the spray gun swing rate may be due to jet dragging when producing a certain mass of particle filtering, thereby reducing the content of condensing particles in the coating. A change in the spraying current affects the microstructure of the coating through the dimensions of the columnar crystals and the content of condensing nanoparticles. The increased spray deposition current increased the vapor-phase concentration in the jet, which increased the deposition rate of the coating and reduced the content of condensing nanoparticles in the columnar gap. This refined the size of the columnar crystals and reduced the microhardness of the coating. With an increase in spraying distance, the deposition rate decreased significantly, whereas the coating microhardness first decreased and then increased. As the spraying distance increased, the deposition efficiency and divergent growth of the columnar crystals decreased, and the content of condensed nanoparticles increased. However, the microhardness of the coating initially decreased and then increased. JL-11NP powder shows the ability to acquire a quasi-columnar structure over a wide process range, which further reveals the deposition mechanism based on gas-solid-liquid, three-phase, low-deposition-current composites. The above influence laws and mechanisms lay the foundation for precise control of the microstructure and properties of PSPVD coating deposition with a low current. Systematic evaluation of the thermal insulation, cycle life, and high-temperature erosion resistance of coatings with different microstructures is one of the key focus areas of future research. Comprehensive regulation of the gas-solid-liquid, three-phase ratio can be used to study the influence of microstructural coatings-such as dendrite crystals, continuous growth, condensed particle content, and columnar crystal density-on the coating properties, as well as further promote the development of technological applications for PSPVD engineering.