Improving dry machining performance of TiAlN hard-coated tools through combined technology of femtosecond laser-textures and WS2 soft-coatings

In this paper, we investigated the effects of WS2 solid lubricant film and femtosecond laser-textures on improving the cutting performance of PVD TiAlN coated tools, which is crucial for dry cutting applications. To do this, nano-scale textures were fabricated on the rake face of WC/Co-based TiAlN coated tools using femtosecond laser technology, WS2 solid lubricant film was then deposited on to the conventional and nano-scale textured TiAlN coated surfaces by medium-frequency magnetron sputtering technique. The microstructures and fundamental properties of the laser textured and WS2 coated surfaces were assessed utilizing the analytical tools. Dry cutting experiments were carried out on hardened steel with the developed TiAlN coated tools, and the resulting friction and wear data were compared with those from the conventional one. These tests show that, as WS2 film has much smaller shear strength than TiAlN coatings, the lubrication of contact between the tool/chip interface is enhanced. This leads to a significant improvement in the dry cutting performance of WS2 coated specimens, showing reductions in cutting forces, cutting temperatures, friction coefficient and tool wear compared with that of the conventional TiAlN coated tool. Another, important, finding is nano-scale textures on the TiAlN coating surfaces can improve the effective life of the initial WS2 layer for a longer period than the untextured one due to the higher adhesive strength between the WS2 and textured TiAlN films. The possible mechanisms for the effects of WS2 solid lubricant film and femtosecond laser-textures are discussed.