Welding of Alumina Using a Pulsed Dual-Beam $CO2$ Laser

Despite the many advantages of using lasers for welding ceramics (alumina in particular), cracks induced by the resulting and severe thermal stresses are often detrimental to weld quality and strength. While many factors contribute to the formation of these cracks, it is the inevitable and localized increase in temperature and the ensuing thermal stresses that usually cause the damage. To help avoid the use of a separate preheating step, while at the same time allowing for faster joining, a unique method of dual-beam laser welding was developed and qualitatively assessed. The approach outlined in this paper utilizes two beams split from a single, 500 W (1.5 kW peak) $CO2$ system to more gradually introduce the energy required to melt and bond alumina. The first or lead beam raises the local temperature just below the melting point, while the second beam introduces additional heat sufficient to melt and bond the samples. Using feed rates of 5.1 mm/s and beam separation distances ranging from 0.5 mm to 2.3 mm, clean and relatively straight weld geometries were observed at total power levels of approximately $250W+$⁠. Relatively straight and uniform welds with considerable dross occurred at smaller beam separations and higher power levels. Uneven weld lines sans discernible cracks were observed at power levels below 206 W. Based on these preliminary observations, the two-beam approach was qualitatively shown to be capable of influencing and, in some instances, improving weld characteristics in terms of overall quality, dross, and crack formation.