Controlling Melt Pool Dimensions Over a Wide Range of Material Deposition Rates in Electron Beam Additive Manufacturing

Electron beam-based additive manufacturing processes are being seriously considered for manufacturing and repair applications in the aerospace industry. To be successful, these processes must work over a wide range of material deposition rates to combine affordability (requiring high deposition rates) with the ability to precisely deposit fine geometries (requiring low deposition rates). Melt pool size and shape are key characteristics to control in these processes. Control of melt pool dimensions will greatly increase the ability to successfully build shapes, and may play an important role in controlling solidification microstructure. In this paper, we present an analytically-guided approach for maintaining melt pool cross sectional area and thermal finite element simulation results are presented over a wide power range (1-5kW) to evaluate the approach. Single bead finite element simulations include the effects of temperature-dependent properties, latent heat, material addition and the distribution of power by a rapidly moving beam. Experiments were carried out on electron beam deposition equipment at NASA Langley Research Center and results show the same trends as those seen in the models. Ultimately, a map of curves of constant melt pool cross sectional areas and length-to-depth ratios is presented, covering power and velocity ranges over roughly a factor of 5.