Experimental evaluation of the laser assisted machining of silicon nitrideceramics

To assess the feasibility of the laser assisted machining (LAM) process for the machining of difficult-to-machine materials such as structural ceramic s, experiments were performed on silicon nitride workpieces for a wide rang e of operating conditions. Data for cutting forces and surface temperatures indicate that the lower bound of the material removal temperature for avoi dance of curling tool and/or workpiece fracture corresponds to the YSiAlON glass transition temperature (920-970 degreesC). As temperatures near the c utting tool increase to values above the glass transition temperature, the glassy phase softens, facilitating visco-plastic flow and, correspondingly, the production of semi-continuous or continuous chips. The silicon nitride workpiece machined had a surface roughness of R-a = 0.39 mum at the nomina l LAM operating condition. Examination of the machined surfaces and chips r eveals no detectable sub-surface cracking or significant changes in microst ructure, respectively. Relative to grinding, the most significant advantage of LAM is its ability to achieve much larger material removal rates with h igh workpiece surface quality and reasonable levels of tool wear. [S1087-13 57(00)00704-8].