Facile formation of a thin chromium carbide coating on diamond particles via quaternary molten salt

In this paper, we introduced NaF into a NaCl-LiCl-KCl molten salt to reduce the thickness of chromium carbide coating on diamond particles. The effect of temperature of the quaternary salts (from 600 ? to 750 ?) on the chromium carbide coating was investigated by XPS, SEM, EDS, and XRD. The result indicates that a uniform and continuous Cr7C3 coating of about 160 nm in thickness forms when NaF is mixed with molten salt at 650 ?. Lower temperatures (< 650 ?) do not contribute to a continuous coating in the quaternary molten salt. As the temperature rises, the coating thickness gradually increases. Adding NaF reduces the reaction temperature, thereby preventing diamond surface graphitization. The cause of a thin Cr7C3 coating formation is discussed in terms of the viscosity of molten salt and Gibbs free energy. This study provides a low-cost method for forming a continuous thin carbide coating on diamond particles. (c) 2022 Elsevier B.V. All rights reserved.