Laser Assisted Machining Process of HIPed Silicon Nitride

In this study, fiber coupled HPDL was employed for Laser-Assisted Machining (LAM) of Hot Isostatically Pressed (HIPed) silicon nitride workpieces. In LAM, the intense energy of laser was used to enhance the machinability by locally heating the workpiece and thus reducing its yield strength. In this experiment, the laser power ranged from 200 W to 800 W while the diameter of the workpiece was 16mm. While machining, the surface temperature was kept nearly constant by laser heating after a preheat phase of 58 seconds. Microscopy observations of machined surfaces and chips were performed to understand the mechnical behavior of silicon nitride with temperature. The effects of chip formation temperature on machining characteristics were assessed by measuring the cutting forces and flank wear. At a temperature of about 1153℃, a good quality machined surface on the HIPed silicon nitride workpiece was obtained with no grain pullout regions and little oxidation layer.