BAS, CMAS and CZAS glass coatings deposited by plasma spraying

In this study, three different industrial frits BaO–Al 2O 3–SiO 2 (BAS), CaO–MgO–Al 2O 3–SiO 2 (CMAS), CaO–ZrO 2–Al 2O 3–SiO 2 (CZAS) have been deposited on porcelainized stoneware tiles by plasma spraying. In the as-sprayed conditions, the microstructure of the coatings is defective because of pores, microcracks and low intersplat cohesion. Hot stage microscope and differential thermal analysis measurements made on the glass powders allowed to characterize the frits thermal behaviour. Post process thermal treatments have been arranged, following these indications as well as preliminary tests, in order to achieve the lowest porosity and the highest resistance to abrasion. At the chosen temperatures, a microstructural improvement has been induced, but in the BAS specimens, an optimal sintering has not been accomplished because of the unavoidable full overlapping of the sintering and crystallization processes.