Laser-arc hybrid additive manufacturing of stainless steel with beam oscillation

A novel additive manufacturing approach integrating an oscillating laser beam and a cold metal transfer arc was developed to balance the surface accuracy, deposition efficiency, and mechanical properties of the deposited parts. The new method was termed as oscillating laser-arc hybrid additive manufacturing (O-LHAM). The sample properties of the wire-arc additive manufacturing (WAAM), laser-arc hybrid additive manufacturing (LHAM), and O-LHAM processes were compared. It was found that some new phenomena were induced by beam oscillation. First, both the surface roughness and minimum processing margin of the O-LHAM sample were reduced to 20 % of the WAAM sample, because the droplet transfer was stabilized by the laser-arc synergic effects. Second, the grains were refined, and the {001} <100>-cube texture content was decreased to 1.6 %, as the oscillation induced a strong stirring effect on the molten pool. The nondestructive X-ray test suggested that the visible porosity within the O-LHAM sample was suppressed by beam oscillation when the periodically oscillated laser keyhole could "capture" the bubbles, while the porosity within the LHAM sample reached 24 %. Due to the microstructure changes and the porosity suppression, the O-LHAM almost eliminated the anisotropy of tensile strength and improved the elongation by up to 34 %.