Design of operating conditions for crackfree laser-assisted machining of mullite

The present study focuses on the evaluation of the laser-assisted machining (LAM) of pressureless sintered mullite ceramics. Due to mullite's low thermal diffusivity and inferior tensile strength, a new method for applying laser power is devised to eliminate cracking and fracture of the workpiece during laser heating by controlling the development of temperature gradients. Numerical modeling of workpiece temperature along with experimental measurement by a pyrometer is performed to determine the temperature at the material removal zone during LAM and to analyze the temperature gradient information to delineate the occurrence of cracking. With a designed gradual heating method, LAM of mullite is successfully performed without inducing any surface or subsurface cracks. Under the designed heating cycle, LAM of mullite is shown to be successful with a relative long tool life of carbide tools and good surface integrity. (C) 2004 Elsevier Ltd. All rights reserved.