Journal of Advanced Mechanical Design, Systems, and Manufacturing (May 2020)
Micromachining of polycrystalline CVD diamond-coated cutting tool with femtosecond laser
Abstract
To enhance the cutting performance of chemical vapor deposit (CVD) diamond-coated tool, a short pulse laser grinding technique is applied. However, the thermal impact of a nanosecond laser damages the diamond crystallinity of the processed surface. To reduce this thermal impact, a femtosecond laser is innovatively used in this study to conduct the pulse laser grinding (PLG) of a CVD diamond-coated cutting tool, to achieve a sharpened tool edge with high quality. Furthermore, the CVD diamond tool edges processed by femtosecond and nanosecond lasers are compared based on sharpness, smoothness, and microstructure changes. The results show that a sufficient laser fluence higher than the threshold and a reduction in the pulse overlapping rate of the laser fluence of the femtosecond laser PLG could ensure a better tool edge shaping. A laser power of 7 W, processing angle of 20°, and scanning speed of 60 mm/s with roughness reduced to approximately half, are the suitable processing conditions of the femtosecond laser. From the observation of a scanning electron microscope, the tool edge processed by femtosecond laser PLG has a relatively sharp edge, with a radius of curvature around 1 μm, similar to that of a nanosecond laser. The further magnified images reveal a distinct processed surface characteristic. The nanosecond laser-processed surface has obvious longitudinal machining marks while that of the femtosecond laser has ablated debris. Moreover, the surface microstructure change of CVD diamond by femtosecond and nanosecond laser PLG are compared using Raman spectroscopy, further confirming that femtosecond laser could successfully suppress unfavorable structural effects in CVD diamond. Based on the results, femtosecond laser has a great potential for processing higher-quality CVD diamond tool edges.
Keywords
