Femtosecond laser rotary drilling for SiCf/SiC composites

Abstract

SiCf/SiC ceramic matrix composites (SiCf/SiC composites) are difficult to drill small holes due to their heterogeneity, high hardness, and low electrical conductivity. In order to solve the difficulties of poor quality and low efficiency when drilling small holes, a novel femtosecond laser rotary drilling (FLRD) technique is proposed. Beam kinematic paths and experimental studies were carried out to analyze the effects of processing parameters on the drilling results in the two-step drilling process. In the through-hole drilling stage, the material removal rate increases with increasing laser power, decreasing feed speed and decreasing pitch. As for the finishing stage of drilling, the exit diameter increased with increasing laser power and decreasing feed speed. The drilling parameters were selected by taking the processing efficiency of through-hole and the quality of finished hole as the constraint criteria. Holes with a diameter of 500 μm were drilled using FLRD in 3 mm thick SiCf/SiC composites with a drilling time < 150 s. The hole aspect ratio was 6, the taper < 0.2°, and there was no significant thermal damage at the orifice or the wall of the hole. The FLRD provides a solution for precision machining of small holes in difficult-to-machine materials by offering the advantages of high processing quality and short drilling times.