Voluminal defects observed in laser spot welding of tantalum

Karen Girard; Jean-Marie Jouvard; Jean-Pierre Boquillon; Philippe Bouilly; Ph. Naudy

doi:10.1117/12.377048

7 February 2000 Voluminal defects observed in laser spot welding of tantalum

Karen Girard, Jean-Marie Jouvard, Jean-Pierre Boquillon, Philippe Bouilly, Ph. Naudy

Proceedings Volume 3888, High-Power Lasers in Manufacturing; (2000) https://doi.org/10.1117/12.377048
Event: Advanced High-Power Lasers and Applications, 1999, Osaka, Japan

Abstract

Significant problems in deep laser spot welding are formation of welding defects, and particularly porosities in the case of tantalum joining. In this study, we investigate and model porosities forming and trapping. Two types of porosity are observed: (1) Small porosities are round shape bubbles of less than 250 micrometer diameter. These defects may come from gas bubbles generated following hydrogen rejection during solidification or they may come from bubbles induced by both an intense evaporation inside the keyhole and a turbulent flow in the molten pool. (2) Large porosities are voids generated in the bottom of the welded zone. They arise from a lack of matter inside the weld as if the molten metal have not had enough time to fill up the keyhole completely before it solidifies. We elaborated a numerical model for the comprehension of little porosities trapping by comparing the calculated spot weld solidification time to the rising time of bubbles in the liquid phase. We also studied the melt flow back into the keyhole in order to explain the formation of the observed large voids. These two models are in good agreement with experimental observations, in particular with X-ray radiographs achieved during the solidification of tantalum spot welds.

Citation Download Citation

Karen Girard, Jean-Marie Jouvard, Jean-Pierre Boquillon, Philippe Bouilly, and Ph. Naudy "Voluminal defects observed in laser spot welding of tantalum", Proc. SPIE 3888, High-Power Lasers in Manufacturing, (7 February 2000); https://doi.org/10.1117/12.377048

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