Sharpening of CVD diamond coated tools by 0.5−10 keV Ar+ ion beam

CVD diamond coated tungsten carbide tools have been used for cutting and drilling of soft materials such as aluminum and copper alloys. However, it is very difficult to obtain a tool having a sharp tip of the order of sub-μm by mechanical abrasive polishing methods. Therefore, we applied ion beam processing for sharpening the cutting edge of diamond coated tungsten carbide tools. Result shows that it is possible to obtain a 20–80 nm order tip width of a CVD diamond coated knife processed by a 0.5–10 keV Ar+ ion beam, and the sharpening speed of a tip of the knife depends on the ion beam energy. Namely, a tip width of a knife processes by a 1.0 keV Ar+ ion beam at an ion dose of 2.7 × 1020 ions/cm2 becomes 20 nm, and a tip width of a knife processed by a 10 keV Ar+ ion beam at an ion dose of 5.4 × 1019 ions/cm2 becomes 40 nm. However, a facet with an apex angle in the range of 60–100° was formed on the cutting edge of a knife with an initial apex angle of 55°, and we found that the facet angle can be controlled by choosing ion beam energy of 0.5–10 keV. Moreover, results show that the processed knife machined by a 0.5 keV Ar+ ion beam has very smooth rake and flank faces, and also has a small line edge roughness of the cutting edge compared to those of the sharpened knife by a 1.0–10 keV Ar+ ion beam.

Research highlights
► The facet angle of cutting edge of CVD diamond coated knives can be controlled by changing ion energy of Ar+ ion beam.
► With 7 to 10 keV Ar+ ion, the processed CVD diamond coated knife's apex angle is 55° to the order of 100 nm.
► Tip width of the CVD diamond coated knife processed by 0.5–10 keV Ar+ ion beam decreases with increasing ion dose.
► Sharpened CVD diamond coated knives by 0.5 keV Ar+ ion beam has very smooth rake and flank faces and small line edge roughness.
► Surface roughness Rrms of the insert-chip with fine grain decreases with increasing ion dose and becomes 20 nm rms.