Enhanced molten-pool boundary stability for microstructure control using quasi-continuous-wave laser additive manufacturing

Abstract

The molten-pool boundary morphology and its stability play a key role in dendrite growth and solidification texture during laser additive manufacturing. In the present work, we have confirmed the advantages of quasi-continuous wave laser additive manufacturing (QCW-LAM) in enhancing the molten-pool boundary stability and promoting the continuously epitaxial growth of columnar dendrite. The influence of laser modes on the molten-pool boundary stability and solidification microstructure during laser additive manufacturing of Inconel 718 is investigated. Compared with the fluctuating molten-pool boundary of continuous-wave laser additive manufacturing (CW-LAM), the QCW-LAM is characterized by the high molten-pool boundary stability and the in-situ high-frequency remelting. These characteristics promote the continuously epitaxial growth of columnar dendrite and result in the directionally columnar structure. This work provides new insights into the control of the dendritic growth and solidification structure by improving the molten-pool boundary stability.

Keywords

• Additive manufacturing
• Nickel-base superalloy
• Molten pool
• Epitaxial growth
• Microstructure