Effect of Processing Parameters and Powder Size on Microstructures and Mechanical Properties of Y₂O₃ Coatings Fabricated by Suspension Plasma Spray

Abstract

The suspension plasma spray (SPS) technique has been used to obtain dense Y 2 O 3 coatings and to overcome the drawbacks of the conventional air plasma spray (APS). SPS uses suspensions containing micrometer or sub-micrometer sized powders dispersed in liquid media. In this study, microstructure developments and mechanical properties have been investigated as functions of particle size of source material and plasma processing parameters such as plasma power and stand-off distance. The microstructure of the coating was found to be highly related to the particle size and the plasma processing parameters, and it was directly reflected in the hardness and the adhesion strength. When fine powder (BET 16.4 m 2 /g) was used as a raw material in the suspension, there was, with increasing stand-off distance, a change from a dense structure with a slightly bumpy surface to a porous structure with a cauliflower-like surface. On the other hand, when a coarse powder (BET 2.8 m 2 /g) was used, the coating density was lower, with microscopic splats on the surface. Using fine Y 2 O 3 powders, the coating layer with an optimum short stand-off distance showed a high hardness of approximately 90% of that of sintered Y 2 O 3 and an adhesion strength several times higher than that of the coating by conventional APS.

Environmental Barrier Coatings Made by Different Thermal Spray Technologies

“…Suspension plasma spraying is one of the rather new thermal spray techniques, which has a liquid feed stock and relatively higher plasma power compared with conventional ones. Especially, SPS could supply a great diversity in microstructural features from columnar and porous to bulk-like dense ones [39,40]. Main processing parameters, such as gun power, spraying distance, roughness, and particle size distribution in suspension, would play an important role in controlling the microstructures fabricated by SPS.…”

The Effects of Water Addition on the Color and Crystalline Phase of Y2O3 Coatings Fabricated by Plasma Suspension Spray

“…s transistor size has scaled down, Y 2 O 3 ceramics have been widely used in the semiconductor industry in order to reduce particulate contamination inside the wafer processing chamber. [1][2][3][4][5][6][7][8][9][10] Y 2 O 3 ceramics are applied as a sintered bulk or as coatings in various components because these materials have very high plasma resistance in fluorine-based plasma. To achieve Y 2 O 3 ceramics as coatings, various techniques such as physical vapor deposition, aerosol deposition, and plasma spray have been used.…”

“…To achieve Y 2 O 3 ceramics as coatings, various techniques such as physical vapor deposition, aerosol deposition, and plasma spray have been used. [6][7][8][9][10] Of these, suspension plasma spray (SPS) has become a new candidate method to obtain a highly dense microstructure. 8,9) SPS coating generally uses submicrometer-or a few micrometer-sized powders dispersed in a liquid media as a feeding material for the plasma spray; these sizes are compared to those in materials used in the conventional plasma spray, which have a few tens of micrometer-sized granules.…”

“…[6][7][8][9][10] Of these, suspension plasma spray (SPS) has become a new candidate method to obtain a highly dense microstructure. 8,9) SPS coating generally uses submicrometer-or a few micrometer-sized powders dispersed in a liquid media as a feeding material for the plasma spray; these sizes are compared to those in materials used in the conventional plasma spray, which have a few tens of micrometer-sized granules. 10,11) The suspension is injected radially or axially into the plasma jet and is fragmented into small droplets; then, after evaporation of the liquid media, the particles are melted and deposited on the substrate.…”

“…10,11) Thus, the coatings fabricated by SPS consisted of finer splats or particles than those in coating by conventional plasma spray; also, the produced materials generally showed denser micro-structure and smaller pores. 8,9) For commercialization of coatings, color control is a key technology, though the effect of color on the production of particulate contamination is not clear. The semiconductor industry usually requires bright-colored coatings, as well as a dense microstructure.…”