High-rate ultrasonic polishing of polycrystalline diamond films

•Polishing of polycrystalline CVD diamond with big rate is achieved using an ultrasonic machining (USM) with a diamond slurry.•The surface roughness Ra can be reduced from ≈ 5 μm down to ≈ 0.5 μm just for 5 min treatment.•Defects are formed in a sub-surface layer (< 6 μm) upon erosion damage by diamond particles impacts.•A combination of the USM with other finishing methods could rationalize the entire polishing process

We report on fast polishing of polycrystalline CVD diamond films by ultrasonic machining in a slurry with diamond particles. The material removal mechanism is based on diamond micro-chipping by the bombarding diamond particles subjected to action of an ultrasonic radiator. The treated samples were characterized with optical profilometry, SEM, AFM and micro-Raman spectroscopy. The developed method demonstrates the polishing rate higher than those known for mechanical or thermo-mechanical polishing, particularly, the surface roughness of 0.5 mm thick film can be reduced in a static regime from initial value Ra ≈ 5 μm to Ra ≈ 0.5 μm for the processing time as short as 5 min. No appearance of amorphous carbon on the lapped surface was revealed, however, formation of defects in a sub-surface layer of a few microns thickness was deduced using Raman spectroscopy. The polishing of a moving workpiece confirmed the possibility to treat large-area diamond films.

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