Laser intensity profile as a means to steer microstructure of deposited tracks in Directed Energy Deposition

[Display omitted] •The effect of various laser intensity profiles on the Directed Energy Deposition process is studied.•Effects are analysed using both in situ melt pool monitoring and post-process microstructural analysis.•Melt pool monitoring is used to derive estimations of relative temperature gradients and cooling rates.•The laser-induced microstructure is quantified using average grain sizes, grain aspect ratios and texture indices.•Correlations are found between the laser-induced thermal gradient – growth rate ratios, grain morphology and the amount of texture. In Laser-based Directed Energy Deposition (L-DED) the laser-induced spatial and temporal thermal cycles strongly determine the microstructure of deposited layers. The effect of three different laser intensity profiles (beam shapes) on the shape of the melt pool and the resulting microstructure was studied. To this end, thermal gradients and growth rates, derived from measured melt pool emissions, are compared to characteristics of the microstructure in the deposited tracks. These characteristics are obtained using Electron Back Scatter Diffraction (EBSD). It was found that the shape of the laser beam strongly affects the melt pool morphology. Therefore it affects also the solidification characteristics and thus the resulting microstucture. Correlations are found between the thermal gradient - growth rate ratios and the grain shapes and amount of texture. Hence, the beam profile is a tool to steer the microstructure of deposited parts during L-DED.