Numerical investigation of influence of precursors on transport properties of the jets used in solution precursor plasma spraying

Abstract

The solution precursor plasma spraying is a modification of the conventional plasma spraying technique where the feedstock is a liquid precursor instead of a powder. The phenomena which occur in both techniques are different since the feedstock is liquid and consequently, the jet fragmentation, the solvent evaporation and the chemical reaction or pyrolysis must occur before solid melting and impact onto the substrate. The evaporation of the precursor changes the chemical composition of the plasma plume, hence it implies an important modification in the thermodynamic properties. In the present study, the influence of the solution precursor on these properties, concretely the thermal conductivity and dynamic viscosity of the plasma plume, has been addressed. Then, the ability of heating factor of the plasma plume was estimated and different effects of the precursor on the mentioned transport properties were evaluated.The effect of the type of precursor, the feedstock flow rate and the solution concentration has been evaluated in the present work. It is concluded that all of these variables affect slightly the viscosity but considerably the thermal conductivity and the ability of heating factor. Hence, the selection of the precursor characteristics allows to heat transfer between plasma plume and starting feedstock and consequently the resultant coatings exhibit a lower presence of porous or unmelted material.