Using fiber or rod—The influence of different filler materials during CO2 laser welding of quartz glass

Welding of quartz glass is still mainly carried out with gas torches and manually by glass specialists. The use of gas torches is highly energy inefficient as much heat energy is released around the component and into the environment. In addition, the manual process can result in inhomogeneous welds. An automated laser process would make quartz glass welding more energy-efficient and repeatable and address the growing shortage of skilled labor. In this study, quartz glass plates up to 4.5 mm in thickness are welded together at an angle of 125° to each other using a fiber or rod as the filler material. Glass thickness and angle were selected based on a project-specific application. The aim is to achieve a homogeneous weld with as few defects as possible using a lateral fiber- or rod-based deposition welding process. The main challenge is to achieve the melting of the filler material at the bottom contact point of the two glasses so that no air inclusions occur. A 400 μm fiber and a 1 mm rod are investigated as filler materials. The advantage of the fiber compared to the rod is that the contact point of the glasses is easier to reach and bond during the welding process. Due to the large gap between the glass fibers compared to the fiber diameter, a high fiber feed rate is required to fill the V-gap with the viscous glass material. The disadvantage is that the fiber is subjected to high pressure when digging into the melt, which can lead to fiber breakage. In addition, there is a high consumption of filling material. Adjustable and relevant process parameters include the ratio between substrate and fiber feed, the laser power, the spot diameter, and the process gas pressure. The fabricated samples are analyzed using optical and laser confocal microscopy.