Preparation of ZrB<inf>2</inf>coatings by electrophoretic deposition in NaCl-KCl-AlCl<inf>3</inf>molten salts

Abstract

Fabrication of transition metal diboride coatings via electrophoretic deposition in molten salts has been recently proposed, however, the influence of the process parameters on the coating has not yet been studied extensively. In this paper, the effects of cell voltage as well as deposition time on the produced ZrB2 coatings by electrophoretic deposition of ZrB2 nanoparticles in NaCl–KCl–AlCl3 molten salts at 710 °C were investigated. The micromorphologies of the surface and the cross-section of the ZrB2 coatings were characterized by SEM. It was found that with the increase of cell voltage from 1.3 V (i.e., electric field 0.87 V/cm) to 1.8 V (1.2 V/cm), the thickness of the ZrB2 coating increased under the cell voltages from 1.3 V to 1.5 V and decreased from 1.5 V to 1.8 V. We assume that during the electrophoretic deposition process, the viscosity of molten salt containing high concentration ZrB2 nanoparticles close to the depositing electrode, which is influenced by the motion rate of nanoparticles governed by the electric field, probably plays an essential role for electrophoretic deposition process of nanoparticles on the electrode. In addition, under the cell voltage of 1.5 V the growth of ZrB2 coating was studied as a function of deposition time. As the deposition time was increased, the thickness and coherence of the coating were elevated.