Fabrication of TiB2 coatings by electrophoretic deposition of synthesized TiB2 nanoparticles in molten salts

Abstract

This paper presents a novel process for preparation of TiB2 coatings, which is a combination of synthesis of TiB2 nanoparticles by borothermal reduction of TiO2 in molten NaCl–KCl–AlF3 system and subsequent electrophoretic deposition of the as-synthesized TiB2 nanoparticles in the same molten salts system. The electrophoretic deposition under various cell voltages was carried out, which resulted in preparation of dense and relatively flat TiB2 coatings. The effect of applied cell voltages on the electrophoretic deposition rate and mechanical properties of produced TiB2 coatings has been presented. The thickness of the coatings increased with the rise of cell voltages due to elevated migration and deposition rate of TiB2 nanoparticles. The hardness of the fabricated TiB2 coatings was assessed by nanoindentation, indicating that the values of hardness and elastic modulus increased with elevated electrophoretic voltages, which probably has an influence on the structure of the TiB2 coatings. Under the cell voltage of 1.2 V, the values of hardness and elastic modulus could reach 32.4 ± 1.2 GPa and 420.2 ± 23.9 GPa, respectively. This proposed process should also be applied for preparation of additional types of transition metal diboride coatings.