Morphologies and textures of rhenium coatings electrodeposited in chloride molten salts

Abstract

Rhenium (Re), with excellent comprehensive high-temperature properties, is an ideal high-temperature coating material. Electrodeposition technology has attracted much attention in recent years due to its relatively low fabrication cost and superior mechanical properties of Re. In this work, the morphologies and textures of Re coatings electrodeposited in NaCl-KCl-CsCl ternary melts were systematically studied at 20–250 mA/cm2 in the temperature ranging from 700 to 880 °C. With increasing polarization (i.e., increasing current density or decreasing temperature), the growth mechanism of the ED Re coating changes from lateral growth with preferred growth crystal plane of (002) to outward growth with preferred growth crystal plane of (110). The morphologies of the Re coatings change in the order of faceted grains, pyramid-like surface, spired starfish-like surface, intertwined roots-like surface and dendritic powder. The optimal deposition process range for dense and smooth Re coatings is as follows: the temperature 800–850 °C and current density 50–100 mA/cm2. The average microhardness of the Re coatings deposited at 50 mA/cm2 in the temperature range of 800–850 °C was ~377 kg/mm2.