Surface roughness effects on electrochemical anodization behavior of binderless tungsten carbide and oxide boundary generation

Electrochemical anodization has been utilized to reduce the surface hardness of Tungsten Carbide (WC) so that to increase its machinability. In this study, experiments have been conducted to illustrate the impact of surface roughness on electrochemical anodization of binderless WC. Anodization was performed on binderless WC that had different surface roughness by applying a constant voltage and utilizing Sodium Hydroxide (NaOH) as the electrolyte. Oxide generation mechanism during the anodization process has been analyzed in detail, through the investigation of current behavior, surface characterization, surface hardness reduction, surface profile change. It has been observed that during the anodization process, multiple peaks in current curves were produced as a result of discharge channels, induced by the cavities at oxide-substrate interface. When the electric barrier is broken, there was an increase in the formation of oxide layers. Hardness decreased significantly across all substrate conditions. Pristine WC substrate had a robust hardness of 33.34 GPa, while non-polished, semi-polished, and polished substrates had 8.26, 9.545, and 9.411 GPa, respectively. These findings demonstrate the significant impact of anodization on WC's mechanical characteristics, resulting in a 71.6 % decrease in hardness across substrate states. A hypothesis has been presented to describe the overall anodization behavior and boundary oxide generation mechanism of binderless WC. Polished WC substrates have lower surface roughness, indicating more controlled and homogeneous anodization as compared to non-polished and semi-polished WC substrates. The present study enhances the understanding of the impact of surface roughness on the electrochemical anodization of binderless WC, which will further facilitate its incorporation with machining techniques.