| Abstract: |
ZrO2-7-8wt%Y2O3 (YSZ) thermal barrier coatings (TBCs) were manufactured via conventional air plasma spray (APS), suspension plasma spray (SPS) and an additional technology hereby named finely-dispersed-particle air plasma spray (FAPS). The FAPS processing employs the exact same classification of finely dispersed particles as used in SPS; however, whereas SPS uses a liquid medium, in the case of FAPS the particles are fed conventionally via a carrier gas into the plasma spray torch by using a newly developed powder feeder for fine (suspension-like) particles (National Research Council of Canada (NRC) patent-granted technology). These finely dispersed YSZ particles consist of irregularly shaped (fluffy-like) agglomerates made from individual nano-sized particles. The conventional APS YSZ TBC was sprayed via a Metco 3MB torch, whereas, both SPS and FAPS YSZ TBCs were sprayed using the Mettech Axial III torch. The conventional APS YSZ TBC microstructure exhibits the traditional lamellar morphology, whereas, that of the SPS YSZ TBC shows porous and columnar features. Conversely, the FAPS YSZ TBC exhibits a porous but vertically cracked microstructure, which is not typical in thermally sprayed coatings. It is hypothesized that these porous and vertically cracked FAPS TBCs may combine the benefits of low thermal conductivity values (pores) with the compliance provided by the vertical cracks. Therefore, FAPS TBCs may represent an additional important technology in TBC manufacturing. The as-sprayed microstructures of these coatings were evaluated via scanning electron microscopy (SEM). In addition to the microstructures, this presentation will also include details on the phase composition of the coatings evaluated via X-ray diffraction (XRD), as well as, their elastic modulus (E) and hardness (H) values. Finally, the thermal conductivity values of these coatings measured from room temperature (RT) up to 1300oC will be included in the presentation.
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