Improving cutting quality by analysis of microstructure characteristics and solidification behaviour of recast layer formation on laser cut ceramic

We studied the microstructure characteristics and solidification behaviour of the recast layer on a 1 mm Al2O3 electronic ceramic substrate processed by CO2 laser cutting to improve the cutting quality. SEM (scanning electron microscope) and CLSM (confocal laser scanning microscope) observations showed that the upper and lower regions of the recast layer consist of equiaxed grains, while columnar grains dominate in the middle region, downgrading cutting quality. We used finite element modelling (FEM) to understand the solidification mechanism and explain profile and microstructure variation along the kerf. Using this analysis, we performed experiments to study the influences of assist gas pressure and laser cutting speed on the grain size and recast layer thickness. A thin, dense recast layer of uniform thickness and microstructure resulted from the following optimal parameters: 8 bar N2 assist gas pressure, cutting speed of 1500 mm/min, and laser fluence of 200 W.