The fabrication of microstructures, such as microgrooves, on ferrous metal surfaces enables the control of various surface functions, such as improvement of hydrophobicity. However, conventional microgrooving methods using single-crystal diamond V-shaped tools have serious issues ranging from severe tool wear to low machining efficiency. Here, we propose a method for efficient fabrication of microgrooves on ferrous metals using laser-processed cBN tools. Using this method, a large number of microgrooves were successfully machined on pure iron surfaces with high efficiency. Moreover, by instantly terminating the cutting process, the cutting mechanism for this new tool was elucidated by direct observation of the cutting points.

We have developed a method for slicing of diamond, which utilizes the internal modified regions and cracks induced by a focused picosecond laser. The linear laser focus scanning formed a wire-shaped modified region, and then planar-modified regions were formed by arranging many wire-shaped modified regions. The conditions for stable formation of the modified region and continuous induction of cracks along the focus scanned plane were elucidated. The previously formed wire-shaped modified region absorbed the laser beam during the next laser scan. To prevent absorption, the sample scanning direction was tilted to the laser optical axis. Furthermore, cracks propagated between the wire-shaped modified regions and spread in a planar shape with selection of appropriate line intervals. Based on these results, slicing an area of 300 × 400 mm of a diamond was performed, and the maximum roughness of the surface, Sz, was approximately 30 mm.