Morphology and Mechanical Properties of TiB2 Coatings Deposited from Chloride-Fluoride Melts by Pulse Electroplating

Electrodeposition of TiB 2 coatings in molten chloride-fluoride electrolyte (NaCl-KCl-NaF-K 2 TiF 6 -KBF 4 ) at 700°C was investigated. PP techniques in forms of periodically reversed (PRC) and periodically interrupted current (PIC) were applied, instead of traditional dc procedure, which was also used for comparison, for the efficient deposition of the coatings onto molybdenum, stainless steel, and tungsten carbide substrates with different geometries and surface areas. The effect of current density, frequency, and pulse shape on the coatings properties was studied. It was found that the morphology and roughness of the deposit depend strongly on the deposition method and conditions. The coating with the lowest roughness (Ra = 102 ± 5 nm) was obtained by PRC PP. The values of microhardness were in the range of 1800-2400 MPa, depending on the pulse frequency in PIC electrolysis. The residual stresses are related to the frequency of deposition and vary in the range of -0.7 to - 1.3 GPa, being the minimum at pulse frequency of 20 and 100 Hz. It was also found that the TiB 2 coating decreases wetting of the steel surfaces by molten glass, which is of practical importance for tools working in these media.