Formation of the breaking surface of alumina in laser cutting with a controlled fracture technique

Abstract

Laser cutting using the controlled fracture technique is based on the thermal breaking principle. The laser beam is applied to the surface of a ceramic substrate; the substrate is then controllably separated along the moving path of the laser beam. The fractography and cutting surface formation are studied in this work. It is found that the breaking surface can be divided into four regions. The first region is the laser evaporation region produced by the heat concentration. The second region is the columnar grain region produced by resolidification of the melted material. The third region is the intergranular fracture region produced by anisotropic thermal expansion. The fourth region is the transgranular fracture region characterized by unstable fractures. These experiments are conducted on alumina ceramics using a CO2 laser. The fracture mechanism is analysed using stress analysis and fractographic observation. The tensile stress generated on the surface due to the laser beam separates the material along its path. The effects of the cutting parameters such as the laser power, cutting speed, laser spot diameter and specimen geometry on the machining quality are obtained from the experimental analysis. It is concluded that the best cutting quality is obtained using a large laser spot size.