Effect of room temperature cobalt removal on the microstructure and mechanical properties of PCD

Abstract

In order to improve the thermal stability of PCD during practical application, the mixed solution of sulfuric acid and hydrogen peroxide was selected to remove cobalt from PCD. The effect of decobaltization on microstructure and mechanical property of PCD as well as its mechanism were studied. According to the SEM results, several deep corrosion pits were observed on the surface of PCD after the 48 h decobaltization process under room temperature, indicating that the cobalt phase was almost removed. Besides, the depths of decobaltization on the upper and lower surfaces were 176 μm and 162 μm, respectively. Based on the EDS results, the remaining mass fraction of cobalt in the decobaltized layer was determined to be 0.93%, while that in the non-decobaltized layer was 7.64%. This suggested that 87.83% of cobalt was dissolved and removed in the mixed solution of sulfuric acid and hydrogen peroxide. The residual stress of PCD samples was also measured. The residual stress before and after decobaltization was 483.91 MPa and 330.35 MPa, respectively. The reduction of 31.73% indicated that decobaltization could effectively reduce the residual thermal stress in PCD.

Keywords

• polycrystalline diamond (pcd)
• decobaltization
• h2so4-h2o2
• residual stress