On reactive suspension plasma spraying of calcium titanate

Abstract

This study shows possibility of preparation of calcium titanate powder and coatings by reactive suspension plasma spraying. Suspension of mixture of calcium carbonate (CaCO3) and titanium dioxide (TiO2) powders in ethanol was fed into hybrid plasma torch with a DC-arc stabilized by a water–argon mixture (WSP®-H 500). Various feeding distances and angles were used in order to optimize suspension feeding conditions. In the next step, the coatings were deposited on stainless steel substrates and the effect of substrate temperature on microstructure and chemical and phase composition of the coatings was studied. Captured in-flight particles and deposits were analysed by X-ray diffraction (XRD) and scanning electron microscopy SEM equipped with EDX detector. Obtained results confirm that chemical reaction of CaCO3 and TiO2 forming CaTiO3 perovskite takes place during the interaction of suspension with plasma jet. The conditions of rapid cooling during spraying process result in the presence of metastable CaTiO3 high-temperature tetragonal and cubic phases. Increase in the substrate temperature increases the content of the calcium titanate in the deposit and the coatings microstructure becomes more compact. Obtained results show that WSP®-H technology may be used for deposition of the CaTiO3 powders and coatings by reactive plasma spraying.