Post-deposition heat treatment effect on microstructure of suspension plasma sprayed bioactive glass coatings

This research addresses a simple and easy method to improve the microstructure of suspension plasma sprayed bioactive glass coatings. Based on previous research of the group, a SPS bioactive glass coating was deposited under optimised variables employing a stable suspension feedstock. After the microstructural characterisation, the coatings were subjected to a heat treatment at 400, 500 and 600 °C peak temperatures. These temperatures have been chosen according to the shrinkage curve of the working glass which results from a hot stage microscope. Results show an improvement of the coatings microstructure (reduction in both porosity and thickness and increment of the adhesion) after a heat treatment at 500 °C with respect to the original coating. However, for a temperature of 400 °C the coating microstructure is not altered (porosity, thickness and adherence are the same as those of the original sample) while at 600 °C the entire coating is completely delaminated. •The obtained suspension had a suitable viscosity to be sprayed and high stability.•The coatings developed had an impaired microstructure composed of two layers.•Hot stage microscopy made possible to select the temperatures to perform a post–deposition heat treatment.•A heat treatment at a peak temperature close to the glass transition, improved the coating microstructure.