Experimental study on electro-Fenton chemical mechanical polishing of polycrystalline diamond

Polycrystalline diamond (PCD) possesses outstanding properties, including ultra-high hardness, excellent wear resistance, a high elastic modulus, and high thermal conductivity. However, its extremely high surface hardness and complex structure make it challenging to obtain an atomically smooth surface. Conventional chemical mechanical polishing (CMP) is insufficient for achieving high-quality surface finishing. Therefore, electro-Fenton chemical mechanical polishing (EF-CMP) was proposed for the surface finishing of PCD. An EF-CMP apparatus was established, and systematic single-factor experiments were carried out to investigate the effects of abrasive size, abrasive concentration, polishing platen speed, polishing pressure, applied current, H 2 O 2 concentration, and Fe 3 O 4 concentration. The results showed that the optimal abrasive size was W1, at which the surface roughness and material removal rate (MRR) were 2.55 nm and 379.7 nm/h, respectively; the optimal abrasive concentration was 2 wt%, corresponding to a surface roughness of 2.44 nm and an MRR of 357.8 nm/h; the optimal polishing platen speed was 60 r/min, yielding a surface roughness of 2.18 nm and an MRR of 378.9 nm/h; the optimal polishing pressure was 0.27 MPa, under which the surface roughness and MRR were 2.20 nm and 451.2 nm/h, respectively; the optimal applied current was 20 mA, giving a surface roughness of 2.08 nm and an MRR of 371.6 nm/h; the optimal H 2 O 2 concentration was 10 wt%, at which the surface roughness and MRR were 2.27 nm and 354.1 nm/h, respectively; and the optimal Fe 3 O 4 concentration was 2 wt%, corresponding to a surface roughness of 2.15 nm and an MRR of 385.7 nm/h. On the basis of the single-factor experiments, further process parameter optimization and analysis indicated that polishing pressure had the most significant effect on Sa, with the influence order of B < C < D < A and a range value of 1.2. The regression model showed good fitting performance (R 2 = 0.9454, adjusted R 2 = 0.9054), and the optimal combination D2C3B2A3 produced a lower surface roughness. The mechanism of EF-CMP for PCD was also revealed. This study provides a theoretical basis for the high-efficiency, low-damage, and planarization processing of PCD, and offers a new route for high-quality polishing.