Modelling and experimental investigation on laser welding of nitinol

Laser welding of smart materials such as nitinol is a challenging task for researchers due to their temperature-dependent properties. Identifying the control parameters for laser welding of nitinol to develop flawless joints for proposing an operating window is another interesting as well as critical job of researchers. In this research work, modelling of laser-welded bead geometry, metallurgical characterisation, hardness and corrosion behaviour of laser-welded nitinol shape memory alloys are discussed. Ytterbium (Yb):yttrium aluminium garnet (Yag) laser welding equipment was used to carry out bead on plate welding trials considering various parameters such as laser power, welding speed, focal position and shielding gas flow rate. Experiments were conducted based on Taguchi L9 orthogonal array design. Comsol Multiphysics 5.1, a finite-element analysis tool, was used to predict the bead profile dimensions and the temperature variations along the weld. A comparison was made between the experimental and numerically predicted bead profile dimensions, and it was observed that the numerically predicted bead dimensions are in good agreement with the experimentally measured bead dimensions. Weld with improved hardness and corrosion resistance compared with the base metal was obtained using ytterbium:Yag laser welding.