Mechanical properties improvement of nickel-based alloy 625 fabricated by powder-fed laser additive manufacturing based on linear beam oscillation

Abstract

The action mode of laser energy affects the solidification process of the molten pool, and it determines the microstructure and mechanical properties of the deposited layers in laser additive manufacturing. In this study, a continuous laser and 50 kHz pulsed laser for the linear beam oscillation (LBO) process were proposed for the preparation of alloy 625 thin-walled structure in powder-fed laser additive manufacturing (PF-LAM). Using scanning electron microscope (SEM), energy dispersive spectrometer (EDS), electron back-scattered diffraction (EBSD), and tensile test, the samples’ microstructure, Laves phase content and morphology, grain size, misorientation angle distribution, and Schmidt factor were analyzed. The results showed that the Laves phase distribution was discrete and the content was reduced to 9.38% during the LBO process. And it produces refined, equiaxed and homogenised grains. At the same time, the LBO process promotes the transformation of the thin-walled structure of LAM from low-angle grain boundaries to high-angle grain boundaries, which helps to improve the toughness. Generally, the mechanical properties of the thin-walled structure are significantly improved by the LBO process. The strength increase in the horizontal direction of the thin-walled structure is 7.40%, which is greater than that in the vertical direction, while the elongation increase in the vertical direction of the thin-walled structure is 28.88%, which is greater than that in the horizontal direction.