Influence of plasma jet temperature on the synthesis and structure of YSZ coatings

Abstract

The paper describes a process for preparation of yttria stabilized zirconia (YSZ) coatings by plasma spray technique employing non-equilibrium plasma spray technology at atmospheric pressure. Yttria-stabilized zirconia (10–15 wt.% Y₂O₃) powders (10–105 μm in diameter) have been used. Plasma sprayed coatings have been characterized using scanning electron microscope (SEM) and X-ray diffractometer (XRD) for the microstructural study and phase analysis as a part of a process optimisation study. The dependence of microstructure of coatings on initial powder characteristics and the influence of deposition temperature in the range of 3000–3350 ^∘C on the structural characteristics of plasma sprayed coatings were investigated. By the data of XRD analysis, all samples were obtained with cubic crystal orientation. It has been found that crystallite size has tendency to decrease with increasing the deposition temperature. YSZ deposited at 3150–3350 ^∘C are found to have a nanocrystalline structure with average crystallite size of 75 nm. The samples sprayed using coarse-grained powder feed are characterized by larger grain size and crystallite size. The main parameters influencing the coating formation are the properties of the initial powder and the plasma process temperature. The SEM analysis showed that the best temperature region for the deposition of YSZ coatings was about 3200–3350 ^∘C.
Keywords: coatings, plasma spraying, microstructure-final, XRD, ZrO₂
PACS: 52.77.Bn, 68.55.J-, 68.90.+g