Laser innovation of YSZ electrophoretic deposition overlay on plasma sprayed thermal barrier coating system

Abstract

In this study, laser surface treatment was used on electrophoretically deposited YSZ overlay coatings on APS YSZ to enhance and improve the TBCs system. First, preliminary preparation of TBC YSZ samples were produced by APS over superalloy substrates and the co-deposition to protecting of TBCs by applying overlay EPD coating followed by sintering was characterized. An electrophoretic deposition process was carried out on the TBC YSZ samples at the optimum coating parameters 40 V in 5 min with a solid concentration of 10 g/L of YSZ. After deposition the samples were dried at room temperature for 24 h and Subsequently, the electrophoretic deposition was followed by sintering in a vacuum furnace at 1200 °C for 2 h. coating samples after sintering were further treated by using Pulsed Nd: YAG laser beam. The surface morphology and microstructure of the samples were studied by a field emission scanning electron microscope (FESEM), Optical microscope, microroughness, and phase purity of the coating material were investigated by XRD. Results indicated that the YSZ oxide overlay produced by electrophoretic deposition (EPD) was successfully performed as an environmental barrier overlay in protecting the APS YSZ TBCs against environmental degradation. The analysis of the XRD pattern of the sintered coating showed the presence of only equilibrium tetragonal phase (t) while in laser state the phase was only nontransformable tetragonal ZrO2 phase (t -ZrO2). Which is regarded to be a desirable ZrO2 phase to beneficial for TBC. It is found from microroughness inspection, decreasing surface roughness after laser treatment. Which indicated improvement in coating surface properties.