Surface micro/nanostructuring of cutting tool materials by femtosecond laser

The creation of periodic micro/nanostructures on a variety of cutting tool materials using a femtosecond laser is reported in this paper. The materials include four types of common cutting tool materials: high speed steel (HSS), tungsten carbide (WC), silicon nitride (Si3N4), and polycrystalline cubic boron nitride (PCBN). The ferntosecond laser is a Ti:sapphire laser that has a pulse width of 25 fs, a wavelength of 790 nm, and a repetition rate of 1 kHz. The ferntosecond laser micromachining experiments were conducted at normal atmospheric pressure. The main operating parameters include laser fluence, polarization and cutting speed. SEM examinations reveal that ripple patterns are generated on HSS and WC. The average period of the ripples is approximately equal to the laser wavelength. The ripples are oriented perpendicular to the electric field vector of the laser irradiation. The orientation of the ripples can be controlled by changing the polarization state of the laser beam. Surface scratches can also influence ripple orientation. Nano dot matrix was created using a circularly polarized beam. However, ripple structures were not found on Si3N4 and PCBN under the same conditions. This brings in the possibility of material composition and property playing a role in the formation of the ripples. Potential applications of the micro/nanostructures on cutting tools are suggested.