Laser micromachining of bionic transport structures on cemented tungsten carbide for passive directional transport of lubricants

Abstract

Several 10 ℓ/min of cooling lubricants are used to cool and lubricate the cutting edges during conventional mechanical milling of lightweight metals. Different concepts of minimum quantity lubrication (between 5 mℓ/h and 50 mℓ/h) have been developed in the past since the recycling and disposal of the cooling lubricants is energy-intensive and costly. One promising approach for minimum quantity lubrication during milling processes with closed cutting edges is the passive directional transport of the lubricant along the chip guiding surfaces to the milling area.

Laser micromachining with ultrashort laser pulses was used for the fabrication of bionic transport structures on tools made from cemented tungsten carbide. An analytical model for the prediction of the dimensions of the transport structures was derived and experimentally verified. The microscopic surface structures that form on the surface of the transport structures were investigated and their wetting behavior for different lubricants and deionized water was characterized by contact angle measurements. A low contact angle <6° was achieved with laser wavelength-sized ripples on the surface. Finally, passive directional transport of lubricants on tools made from cemented tungsten carbide could be demonstrated with bionic transport structures over a distance of up to 60 mm.