In order to obtain thermal barrier coatings by Suspension Plasma Spraying (SPS) process with potential new self-healing ability multicomponent submicronic Y-TZP/Al2O3/SiC suspensions were prepared. For this purpose, concentrated aqueous suspensions of individual components as well as the multicomponent mixture were studied and characterised in terms of colloidal stability and rheological behaviour to determine the best conditions for processing and preparation of the coatings. In the study, different dispersant contents and sonication times were tested. Subsequently, low concentrated suspensions were prepared to obtain preliminary thermal barrier coatings with the optimised feedstock. Thus, ceramic coatings were deposited by SPS and then characterised in order to assess the microstructure and phase distribution, in particular, the degree of preservation of the sealing agent, SiC, in the final coating as a previous indicator of its self-healing ability.

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In this research, Suspension Plasma Spraying (SPS) technique was used for the thermal deposition of a multicomponent mixture made up of an Y-TZP/Al2O3 matrix with SiC particles. Two suspensions of Y-TZP and Al2O3 with different SiC particle content (6 wt% and 12 wt%) were tested as feedstocks in the SPS process. Three stand-off distances were varied in order to assess coating microstructure and quantify SiC particles preservation in the final coatings. Coatings were characterised in terms of porosity, microstructure and phase distribution. The estimate of the amount of SiC particles present in the coating was carried out by XRD technique. Findings showed typical cauliflower-like SPS microstructure which intensifies with stand-off distance. Coatings porosity values varied significantly between 8 to 25% whereas minimum porosity was found for the intermedium stand-off distance of 40 mm. Microstructure analysis also revealed the presence of SiC particles in the coatings which was confirmed by EDX analysis, overall XRD test as well as TG analysis compared with SiC powder. Finally, quantification of SiC content in the final coatings by means of XRD analysis showed that most of SiC particles (c.a 80 %) of the feedstocks were preserved in the final coatings.