Tailoring the porosity level of the suspension plasma sprayed coatings using a dual suspension injection system

This study investigated the feasibility of tailoring the porosity in suspension plasma sprayed (SPS) coatings using a dual suspension injection system. Two titanium dioxide water-based suspensions with different particle sizes were injected into the plasma jet through two injectors located at different radial distances from the exit of the plasma torch. By varying the spray parameters, the fraction of unmelted particles in the coatings coming from the injector located farther from the torch changed. The total porosity was evaluated to range from approximately 16 % to 36 %, and the variation was related principally to the gaps between the unmelted particles. Among the selected spray parameters, the suspension feed rate and distance between the injectors were found to have the most significant effect on increasing the porosity. The samples were analyzed using SEM, XRD, and Raman spectroscopy.