Effect of solids content and stand-off distance on thermal behaviour of zircon particles in suspension plasma spraying

The aim of this work is to assess the thermal behaviour of zircon (ZrSiO₄) particles in plasma spraying during their flight inside the plasma jet by injecting them as an aqueous suspension. From a commercial zircon powder of a mean particle size of 1 µm, suspensions were prepared using two different solids contents, i.e. 10 vol.% and 30 vol.% (33 wt% and 66 wt% respectively). Different proportions of an ammonium poly(acrylate) were added to both suspensions to stabilise them. The optimum amount of dispersant was determined through zeta potential and rheological measurements. The liquid feedstocks were deposited by suspension plasma spraying (SPS) on metallic substrates testing different spraying distances. The topography of the coatings was observed by scanning electron microscopy, the different crystalline phases were determined by X-ray diffraction and the thermal conductivity was measured by means of a laser flash equipment. From the results, it can be seen a clear effect of both the feedstock solids content and the spraying distance on the thermal decomposition of zircon particles, giving rise to different microstructures and proportion of crystalline phases in the resulting coatings.

This work has been supported by the Spanish Ministry of Science, Innovation and Universities (RTI2018-099033-B-C3, MCIU/AEI/FEDER, UE).