Weld pool shaping and microstructural control using novel computer generated holographic optic laser welding of steel and stainless steel

This work considers the use of Holographic Optical Elements (HOEs) to shape the weld beam and control the microstructure of the weld bead. The beam profiles investigated are a standard Gaussian and an Offset Rugby Post produced by a HOE. Autogenous welds have been produced on plain carbon steel with the introduction of a nickel alloy filler powder, using different energy densities. Cross sections of the welds have been analysed in terms of the weld profile, weld pool shape, HAZ and the extent of the deposit/substrate mixing. Electron BackScatter Diffraction (EBSD) coupled with Energy Dispersive X-ray Spectroscopy (EDS) has been used to study the microstructures developed. The results have shown that by utilising HOE’s the weld pool shape can be modified so that a squarer profile can be obtained. The grain structure within the weld pool can be controlled such that a finer more equiaxed grain structure can be developed when compared with the coarse columnar grains seen with a Gaussian beam with a marked difference in the microstructures in the HAZ.