New method of electrochemical pretreatment for CVD diamond coating: Cobalt removal and polishing of cemented carbide tools

Abstract

The deposition of diamond coatings on cemented carbide (WC–Co) tool surfaces using chemical vapor deposition (CVD) is an effective method for improving tool life. However, it is necessary to perform a cobalt removal pretreatment on the WC–Co tools to mitigate the catalytic graphitization effect. In this study, a pretreatment process based on electrochemical selective dissolution is proposed. By controlling the voltage and treatment time, this process enables the efficient removal of cobalt from the tool surface and simultaneous polishing of the cutting edge. Experimental results show that increasing the voltage improves the surface polishing effect, but excessive voltage leads to severe edge passivation. As treatment time increases, cobalt removal becomes faster, but once a limit is reached, further extension of the time no longer enhances cobalt removal efficiency. COMSOL Multiphysics simulations reveal that the electrochemical potential difference between cobalt and WC drives selective cobalt dissolution. After pretreatment, the tools were coated with diamond using CVD method. The resulting diamond coatings were dense, crack-free, and had a high proportion of diamond phase, demonstrating the high quality of the coatings. This proposed electrochemical pretreatment method provides an efficient, controllable, and innovative solution for the surface pretreatment of WC–Co tools.