Process parameter optimisation and correlative metallurgical characteristics validation of fibre laser welding on nickel-based superalloy

This research aims to investigate the optimisation of wobble-assisted fibre laser welding parameters over the refurbishment of gas turbine components through a conventional design of experiments-based Taguchi L9 orthogonal array. The input variables, such as laser power, welding speed, and wobble width, were analysed systematically to find their influences over microstructural evolution, crystallite size, lattice strain, and mechanical performance of each variable. The observed optimal parameter combinations have produced a significant grain refinement up to 10.74 nm observed in the fusion zone with a microstrain of 4.235*10−³ and a dislocation density of 8.669*1015 m−². This was accompanied by minimised defects and reduced lattice distortion, which were validated by X-ray diffraction analysis and correlated through their microstructural analysis. It maintains the mechanical characterisation to a maximum yield strength of 640.87 MPa at an elongation of 13.52% and a flexural strength of 1055.79 MPa. The results exhibit that the controlled wobble-assisted fibre laser welding offers a residual stress of approximately 847 MPa. These findings, which operate at the laser power of 1400W, a welding speed of 12 mm/s, and a wobble width of about 3 mm, assure the suitability of optimised process parameters as a sustainable approach for the refurbishment of high-value turbine elements.