Periodical micro-nano-structuring of metallic surfaces by interfering laser beams

The motivation for this work is originated from nature. Insects and plants, for instance, possess some optimised surface fixing configurations against vibration and certain micro-structural composite effects combining the properties of two phases or materials to enhance strength. Inspired from these observations, surface tribological properties can be optimised by combining the surface topographical structuring and phase micro-structuring. Two or more beams of a high-power pulsed Nd:YAG laser are used to generate a two-dimensional interference pattern. With such an interference pattern, the topography and the phase micro-structure of various metals are manipulated periodically. We have estimated the thermal history of one laser pulse by simulation. The structured materials include three materials. Firstly, a gold layer on a silicon wafer to demonstrate a periodical topography effect. Secondly, a Ni:Al layer with atomic ratio 3:1 on a silicon wafer to improve the periodical initiation of an intermetallic phase reaction to Ni3Al. Finally, a hot dipped tin CuSn-4 alloy (4 wt.% Sn) to show the possibility of a phase transformation from Cu6Sn5 to Cu3Sn.