Characterization of Sealing Treatments on the Behavior of Aluminium Phosphate Sealed Plasma – Sprayed Alumina Coatings Operating in Extreme Environment

The impregnation of an aluminum phosphate deposit optimizes the properties of the plasma coating of alumina and seals open and / or interconnected porosities produced during the thermal spraying in order to compensate for the failure of the ceramic seal and to obtain an insulating barrier power. This study focuses on the structural characterization of alumino-phosphates materials obtained by the thermal process of a mono-aluminum phosphate solution (MAlP). The training protocol is characterized by the molar ratio of phosphorus / aluminum and depends on the heating rate, temperature and isothermal duration. These parameters may result into different kind of compounds. Initially, a study on the MAlP solution was conducted to determine the effects of the training protocol parameters. In a second step, a study was conducted on samples of alumina projected plasma and impregnated with a MAlP solution. In order to qualify and quantify in aggressive conditions the physicav and chemical properties of these deposits, thermal and electrical test benches are used as well as technical characterization of ³¹P/²⁷Al nuclear magnetic resonance.