Influence of residual oxygen during laser beam welding under vacuum

Abstract Laser beam welding under vacuum (LaVa) offers advantages regarding the achievable weld penetration depths compared to conventional laser beam welding. Thus, it is increasingly used in industry. Despite the high weld penetration depths that can be achieved and the good inner seam qualities, undesirable reworking is often necessary due to surface deposits on the welded sample. The causes of these surface deposits have not yet been investigated in depth. In this context, the influence of the residual oxygen present inside the vacuum chamber is investigated in this study. For this purpose, the oxygen content within the chamber is recorded for LaVa welds at different working pressures and different evacuation times. The welded specimens are evaluated metallographically and investigated with regard to an influence of the oxygen content within the working chamber. This study shows that the residual oxygen content considerably influences the weld formation and the surface weld appearance for all working pressures investigated. For lower oxygen contents, the weld penetration depth decreases, and the weld width, on the other hand, increases. These observations can be explained in good agreement with findings for the influence of oxygen on the weld appearance for other material joining processes, such as TIG welding.