Ceramic/fluoropolymer composite coatings by plasma spraying

Al2O3–TiO2/perfluorinated vinylether (PFA) composite coatings are produced by plasma spraying. Because of the different thermo-physical characteristics of both materials, two systems of powder injection were studied: injection of mixed powders and separated injection (co-injection). The effect of the powder injection on the coating microstructure and on the PFA content was investigated using different methods, i.e., micrographic examination, image analysis and energy-dispersive spectrometry (EDS). From micrographic examination, it was observed that a composite structure can be obtained whatever the considered injection system. The coatings consist of a ceramic matrix in which rounded PFA particles are dispersed homogeneously. The content values of the polymer within the coatings evaluated by image analysis show a PFA increase. This trend is not observed for coatings realized by co-injection. On the other hand, powder injection system has no influence on the content of the polymer located at the coating surface. EDS analyses carried out for fluor and aluminium elements prove that PFA particles are homogeneously dispersed at the coating surface. The use of an appropriated thermal post-treatment allows polymer melting and its spreading.