Thermal controlled fracture of Al₂O₃ substrate by inducing microwave discharge in graphite coat

Compared with traditional cutting methods, the thermal fracture method (TCFM) has gained considerable attention for its numerous advantages such as low energy costs, no removal of materials, and cleanly cut sections. However, a lack of methods for generating thermal stress efficiently has been the main obstacle of TCFM application. In this study, partial discharge induced by microwaves in a graphite coat of an Al₂O₃ substrate was used to cut the Al₂O₃ substrate. The experimental results indicate that partial discharge can initiate crack propagation more efficiently and precisely. The deviation of the initial cracking path was not clearly observed. Although the cut section exhibited a small discharge-affected zone, a relatively clean surface was obtained, which demonstrated superior performance compared with that of laser cutting. The simulation results revealed that the total power of the microwave discharge was 30 times greater than that of the dielectric heat process. The thermal stress induced by the microwave discharge played a dominant role in controlling the cracking process. In conclusion, this paper indicates that the partial discharge induced by microwave offers significant potential for cutting non-susceptible ceramics.