The Effect of Surface Roughness of Inconel 738 Superalloy on the Adhesive Properties of 8YSZ Coatings Deposited by Electrophoretic Deposition (EPD)

Abstract

The electrophoretic deposition coating method has recently received attention as a new method for thermal barrier coating due to its advantages such as the simplicity of the method, controllability of the process, and the need for simple equipment. In this study 8 wt % yttria- stabilized zirconia was deposited on Inconel 738 substrate at room temperature by electrophoretic deposition. Before deposition, the substrates were treated by sand blasting treatment (by silica sands with different sizes) and roughness in the range of R_a=1 and R_a=3 was achieved on the substrate surfaces. The coated samples were sintered at 1100 °C temperature under controlled atmosphere (Ar atmosphere). X-Ray diffraction, scanning electron microscopy and thermal shock resistance technics were used to investigating of structural and phase properties and adhesiveness between coatings and substrates. Results from thermal shock resistance test show that by increasing roughness number, the thermal shock resistance ability first increased and then decreased. In addition, according to SEM images, increasing of roughness number, causes decrease the microcracks that creating in the coating surface. The best result was observed for coatings deposed on substrate with R_a=2.