Cracking in dissimilar laser welding of tantalum to molybdenum

• Published in: Optics and laser technology 2018-06, Vol.102, p.54-59
• Main Authors: Zhou, Xingwen, Huang, Yongde, Hao, Kun, Chen, Yuhua
• Format: Article
• Language: English
• Subjects: Crack initiation; Crack propagation; Cracking; Diffraction; Dissimilar laser welding; Dissimilar material joining; Ductility; Electron microscopy; Laser beam welding; Microhardness; Molybdenum; Scanning electron microscopy; Tantalum; Welding
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2017.12.026

•Transgranular and intergranular cracks were found in the fusion zone of dissimilar laser welded joint of Ta to Mo.•Solidification cracking tendency of Mo is a main reason for crack initiation in the Ta/Mo joint.•Low ductility feature of the fusion zone promoted the transgranular propagation of cracking. Dissimilar joining of tantalum (Ta) to molybdenum (Mo) is of great interest in high temperature structural component applications. However, few reports were found about joining of these two hard-to-weld metals. The objective of this experimental study was to assess the weldability of laser butt joining of 0.2 mm-thick Ta and Mo. In order to study cracking mechanism in Ta/Mo joint, similar Ta/Ta and Mo/Mo joints were compared under the same welding conditions. An optical microscope observation revealed presence of intergranular cracks in the Mo/Mo joint, while both transgranular and intergranular cracks were observed in Ta/Mo joint. The cracking mechanism of the Ta/Mo joint was investigated further by micro-hardness testing, micro X-ray diffraction and scanning electron microscopy. The results showed that solidification cracking tendency of Mo is a main reason for crack initiation in the Ta/Mo joint. Low ductility feature in fusion zone most certainly played a role in the transgranular propagation of cracking.