Effects of Processing Parameters on the Deposition of Yttria Partially Stabilized Zirconia Coating During Suspension Plasma Spray

Abstract

The process–microstructure relationship in suspension plasma spray ( SPS ) of yttria partially stabilized zirconia ( YSZ ) has been studied experimentally. An ethanol‐based suspension with a powder loading of 25 wt% was plasma sprayed with radial injection under four different plasma conditions, to examine the effects of plasma gas composition (Ar/He ratio), secondary gas (Ar/He and Ar/H 2 ), and the nozzle diameter of the plasma gun. The suspension feeding rate was optimized firstly and coatings were prepared for microstructural observation. Capturing of in‐flight particles into water as well as collection of splats formed on heated flat metal substrates were utilized in order to better understand the more complicated intermediate process steps in SPS . It was found that a plasma jet with higher momentum allowed a higher suspension flow rate and both columnar and deep vertically cracked structure could be created depending on the plasma parameters as well as the substrate surface roughness.