Study on cobalt removal process of polycrystalline diamond compact with high efficiency and environmental protection

Abstract

Polycrystalline diamond compact (PDC) is a widely used superhard material that needs to be treated with cobalt removal to enhance its thermal stability. However, the traditional acid soaking process has some shortcomings, such as low cobalt removal efficiency, high cost and unfriendliness to the environment. To solve the above problems, this paper uses a self-made electrolytic system to study the electrolytic cobalt removal process of PDC and uses the control variable method to explore the influence of current density, electrolyte concentration and pH on the electrolytic cobalt removal process. The optimum process is as follows: current density of 1A/dm2, Na2SO4 concentration of 0.6 mol/L and electrolyte pH of 2. Under these conditions, an average de‑cobalt depth of approximately 235 μm can be achieved after 4 h of electrolysis, during which the de‑cobalt efficiency is close to 59 μm/h. SEM and ultra depth field microscopy observations revealed that many pores appeared on the surface of the PDC sample after electrolytic cobalt removal. After processing and calculating its surface image, the surface porosity was about 13.5%. At the same time, the detection results of EDS show that the cobalt removal process in this paper can achieve a cobalt removal rate of 90.4%. In summary, this paper introduces an efficient and environment-friendly cobalt removal scheme of PDC and analyzes several factors affecting its efficiency.