Investigation of microstructure evolution process in circular shaped oscillating laser welding of Inconel 718 superalloy

•A macro-micro coupling model of microstructure dynamic evolution is proposed.•The evolution process and morphologies of the microstructure are obtained.•The calculated results are in good agreement with the experimental results.•The proposed model can be used to predict the microstructure of weld. A macro-micro coupling model of microstructure dynamic evolution for circular shaped oscillating laser welding of Inconel 718 superalloy is developed in this paper to investigate the evolution process of columnar crystals under the effect of oscillating laser beam. The macroscale heat transfer model is established to obtain the characteristics of temperature distribution in molten pool and the microscale phase field model is utilized to explore the microstructure evolution during the oscillating laser welding. The transient solidification conditions model based on the temperature field of the circular shaped oscillating laser welding is used for calculating the dynamic solidification conditions which consist of the temperature gradient and the solidification rate. The microstructure evolution process and morphologies in circular shaped oscillating laser welding of Inconel 718 superalloy are obtained by the macro-micro coupling model and the calculated results are in good agreement with the experimental results. The characteristics of the microstructure under the action of the circular shaped oscillating laser beam are analyzed. The proposed model can be used to predict the microstructure of weld formed in the oscillating laser welding and provide the optimal process conditions for improving the welded joint quality in practical manufacturing.