A new coating method with potential for additive manufacturing: Premelting electron beam-assisted freeform fabrication

Abstract

Premelting electron beam-assisted freeform fabrication, as a new method to avoid the direct coupling of wire-beam-molten pool during electron beam freeform fabrication, is proposed for the first time. The three factors referring to wire, beam and molten pool, are decomposed into two factors as wire and beam. The liquid metal is formed in the diversion nozzle, as the wire is heated and melted inside it by an electron beam, and, subsequently, is transferred to the substrate with solidification process. Finally, a continuous and stable process of premelting electron beam-assisted freeform fabrication is achieved. When an aluminum alloy was deposited on a TC4 substrate by premelting electron beam-assisted freeform fabrication, the TC4 base metal did not melt because the electron beam did not directly act on the TC4 substrate. There is no stirring of the electron beam inside the liquid deposition body, and the dissolution and diffusion of elemental Ti exists, which ensures the effective connection between the deposition and the TC4 substrate. Although TiAl3 intermetallic compounds were generated in the deposition, the interface between TiAl3 and the Al matrix was coherent, as (101) TiAl3//(020) Al was clearly detected in the center of the deposition. There are no cracks or other defects in the deposition. The acicular TiAl3 intermetallic compounds are dispersed in the deposition, which improves the wear resistance of the deposition.