In the field of aerospace defense

2.5D C/SiC composites are crucial materials for high-temperature resistant components. The high hardness and wear resistance of these materials render the high-quality micro-hole machining exceptionally challenging. A picosecond laser drilling process for 2.5D C/SiC composites based on magnetic field/liquid-assisted machining (MLM) was proposed. By extracting the characteristics of micro-hole inlet/outlet diameter

taper

oxidation

and recast layer

a comparative study was conducted between MLM and three processes: picosecond laser machining (PM)

magnetic field-assisted machining (MM)

and liquid-assisted machining (LM). The results demonstrate that the picosecond laser machining based on MLM can effectively reduced the inlet diameter of the micro-holes while increasing the outlet diameter

achieving a micro-hole taper of 1.3° and 1.1° under two different sets of experimental parameters

the taper is reduced by 18.75% and 45% compared with PM process

reduced by 13.33% and 31.25% compared with MM process

reduced by 91.22% and 79.63% compared with LM process

respectively. Furthermore

microstructural analyses of the drilled micro-holes were performed using EDS spectroscopy

Raman spectroscopy

and XPS techniques. It was found that the MLM process more effectively reduced the graphitization defects on the hole walls. Among them

liquid-assisted machining avoids oxidation at the inlet of micro-holes

while clearly observing exposed fibers and matrix

effectively avoiding thermal damage and recast layer defects. In picosecond laser drilling

the primary mechanisms of MLM are attributed to the cooling effect of the liquid

its ability to isolate oxygen

and the longitudinal stretching of the plasma by the magnetic field

which reduces the plasma shielding effect.