The effect of different laser head angles and shielding gas supply systems to maximize the depth of penetration by minimizing the plasma shielding effect in fiber laser welding of 3-mm thick NiTinol sheet

Abstract

Bead-on-plate laser welding of 3 mm thick NiTinol sheet was tried with the help of 2.3 kW Yb:Fiber laser. It was found that the laser power was insufficient to get the full penetration with narrow weld-bead by varying the scan speed when shielding gas was provided from the side of the bead and the laser head was kept perpendicular to the plate. It was observed that when gas was supplied from the top of the plate and moving with the laser head, fully penetrated bead was obtained at much lesser value of heat input (P/v) because of the reduction of length of plasma plume. It was also detected that with increase in rotation of laser head angle the depth of penetration and laser bead width decreases because of the increase in laser spot area, reduction of laser intensity and increase in length of plasma plume. The increase in length of plasma plume increased the plasma shielding effect and reduced the absorptivity of the laser in the NiTinol sheet. According to the study, the maximum depth of penetration at a constant laser heat input was obtained for minimum value of plasma plume length and maximum value of laser intensity.