Thermal spraying to coat traditional ceramic substrates: Case studies

Thermal spray is a group of continuous, line of sight, deposition methods, where usually particles (1–50 μm) are melted and accelerated, through either a combustion or a plasma flame. The molten droplets impinge on a substrate and rapidly solidify to form thin layers (“splats”). Among these techniques, plasma spraying is particularly fit for spraying ceramics and applied in many industrial applications on metallic surfaces. However, it has seldom been used for spraying glasses and even less to coat ceramic substrates, in particular traditional ones. In this paper, layered refractory ceramics coatings on sintered refractories have been deposited to improve the substrate resistance to molten glass. Some examples of plasma sprayed high-performance or waste glasses applied on porcelanized stoneware and porous single-firing bodies are presented, too. The coatings have been subsequently thermally treated and microstructural, chemical, mechanical analysis have been carried out both on as-sprayed and treated samples.