Experimental study of chemical mechanical polishing of polycrystalline diamond based on photo-Fenton reaction

Polycrystalline diamond (PCD) is widely used in cutting tools, optical devices, and heat dissipation tools due to its exceptional hardness, wear resistance, and thermal conductivity. However, these excellent properties also make polishing the PCD surface a challenge. Traditional polishing methods struggle to achieve both high material removal efficiency and high-quality surface finishes simultaneously. This paper proposes a chemical mechanical polishing (CMP) method for PCD based on the photo-Fenton reaction. The method utilizes the reaction between H₂O₂ and Fe₃O₄ under ultraviolet (UV) light to generate highly oxidative hydroxyl radicals (·OH), effectively oxidizing the PCD surface to reduce the difficulty of processing. The concentration of ·OH and Fe²⁺/Fe³⁺ in different reaction solutions was measured using spectrophotometry. Results indicate that the concentration of ·OH is highest in the photo-Fenton solution, and UV light promotes the conversion of Fe³⁺ to Fe²⁺, sustaining the ongoing photo-Fenton reaction. Through single-factor polishing experiments, the effects of various processing parameters on the CMP performance of PCD were investigated. The results show that the material removal rate of PCD increases with increasing concentrations of H₂O₂, abrasive particle size, polishing pressure, and polishing disc speed. In contrast, the removal rate first increases and then decreases with increasing UV light intensity and Fe₃O₄ concentration. Additionally, the surface roughness (Ra) of PCD decreases initially and then increases with increasing UV light intensity, abrasive particle size, polishing pressure, and polishing disc speed, while it decreases with increasing Fe₃O₄ and H₂O₂ concentrations. Under the conditions of 100 mW/cm² UV light intensity, 2 wt% Fe₃O₄, 10 wt% H₂O₂, 5 wt% abrasive concentration, 0.5 μm abrasive particle size, 0.89 MPa polishing pressure, and a polishing disc speed of 60 r/min, the material removal rate of PCD reaches 698.7 nm/h, and the surface roughness Ra is 3.78 nm. The photo-Fenton reaction-based CMP method proposed in this paper provides a new approach to polishing hard-to-process materials.