Influence of pulsed laser ablation on the surface integrity of PCBN cutting tool materials

摘要

Polycrystalline cubic boron nitride (PCBN) is widely used in industry as a cutting tool material for the machining of hardened steels, cast, or nickel-based super alloys. For the generation of geometrical features of such tools, laser ablation is a novel and promising technology, which offers wear-free processing, high automation potential, and geometrical flexibility. In this study, the ablation mechanism is experimentally investigated for a wide range of laser pulse durations (fs-ns regime) and laser-induced effects on the surface properties are presented. It could be shown by using Raman spectroscopy that laser-induced transformations of cubic boron nitride to the hexagonal lattice structure (hBN) or boron oxide (B2O3) are strongly determined by the single pulse and areal fluence of the laser source. Furthermore, a pulse duration of few picoseconds or below reduces the thermally induced phase transformations. Moreover, it was shown that the use of ns-laser leads to significant melting and recrystallization processes of the binder material, which reduces surface hardness. This mechanism was not found for the use of fs- and ps-laser sources.