Fabrication and Characterization of Zirconia Thermal Barrier Coatings by Spray Drying and Atmospheric Plasma Spraying

Abstract

In this study, we prepared yttria stabilized zirconia granules for thermal barrier coatings using a spray drying process. First, we characterized the properties of granules such as flow rate and packing density for utilizing the air plasma spray process. The flow rate and packing density data showed 0.732 g/sec and 2.14 g/cm 3 , respectively, when we used larger and denser particles, which are better than hollow granules or smaller spherical granules. Second, we chose larger, spherical granules fabricated in alcohol solvent as starting powders and sprayed it on the bondcoat/nimonic alloy by an atmospheric plasma spray process varying the process parameters, the feeding rate, gun speed and spray distance. Finally, we evaluated representative thermal and mechanical characteristics. The thermal expansion coefficients of the coatings were 11~12.7 × 10 −6 / o C and the indentation stress measured was 2.5 GPa at 0.15 of indentation strain.

A study of the influence of TiO2 addition in Al2O3 coatings sprayed by suspension plasma spray

“…However, in order to produce ceramic coatings onto a substrate by utilizing powders as feedstock, the most employed technique is Atmospheric Plasma Spraying (APS) [11,12]. This technique consists in injecting powder into a plasma plume.…”

Preparation of Granule Powders for Thermal Spray Coating by Utilization of Pyrophyllite Minerals

“…The flow rate was shown to have a value of 2.5 g/sec. In another study on thermal spray coating similar to the present study, 20) plasma thermal spray coating was conducted by utilizing YSZ (Yttria Stabilized Zirconia) granule powders having an apparent density of 1.66 g/cm 3 and a flow rate of 0.732 g/sec, and production of dense coating structures without macroscopic defects or cracks being observed was reported to be feasible. When compared with the above study results, utilization of the pyrophyllite granule powders as the powders for thermal spray coating is shown to be possible as they exhibited the fluidity allowing sufficient spray even at a low gas pressure, accompanied by a satisfactory density.…”

Evaluation of Thermal Durability of Thermal Barrier Coating and Change in Mechanical Behavior

“…Heat treatments were conducted at 1250 ∘ C for 10 minutes after removing the binder and dispersant at a temperature of 600∼800 ∘ C. The heat-treated granules were classified using an auto-sieve machine with a stack of sieves, 38, 45, 75, 106, and 125 m. The starting granules for APS coatings were selected in the size range of 45∼106 m. The properties of the feedstock for the coatings were reported in the previous literature [20]. A nickel-based alloy (Nimonic 263, Ni-20Cr-20Co-5.9Mo-0.5Al-2.1Ti-0.4Mn-0.3Si-0.06C in wt.%, ThyssenKrupp VDM, Germany) was prepared and sandblasted to enhance the adhesion force.…”