Alumina welding tubes with CO2 laser

The ceramic materials of high performance are being used more and more in the production of components for machines and equipments. The development and use of the ceramic techniques are braked by the joining difficulty among them and/or with metals, due the inherent fragility to the thermal shock. Nowadays, only two processes allow this union, brazing and CO2 laser beam welding. A methodology was developed in the laser welding of alumina tubes of high purity (Al2O3 > 99,5%) since is a ceramic of excellent mechanical properties, but very sensitive to thermal shock. The absence of a vitreous phase doesn't allow the stress relief imposed during the welding. To avoid the formation of cracks, an infrared furnace was built to reach a necessary pre-heating temperature of 1400 degrees C, allowing to minimize and to absorb the contractions caused by the laser treatment. The thermal cycle control is fundamental, owing the cooling to be slow and gradual after the welding. Welds with good properties were obtained.