Effect of Gravitational Acceleration on Space Metal Laser Direct-Writing Additive Manufacturing Process

This study investigates a metal laser direct-writing additive manufacturing process for potential in-space applications. The feasibility of stable deposition under various gravitational conditions—specifically at angles of 0°, 90°, and 180° between the deposition direction and gravitational acceleration, and under zero-gravity—is demonstrated. The analysis reveals that a stable metal deposition layer can be formed under different gravity conditions by establishing a strong liquid bridge connection with the substrate; however, the direction of gravitational acceleration significantly affects the cross-sectional morphology of the deposition layer. By comparing different parameters, it is found that the best cross-sectional morphology can be obtained when the wire feeding speed is 120 mm/min and the ratio to the moving speed is 1.0. Notably, a higher wire feeding rate correlates with an increased temperature gradient within the heat-affected zone. On this basis, a thin-walled cylindrical piece printed at a 90° angle between the deposition gravity directions exhibits an outer surface cylindricity of 0.294 mm, a size deviation range of -0.168 mm to 0.126 mm, a maximum size deviation of 0.168 mm on the outer surface, and a surface roughness of less than 8.142 μm. The results indicate that this process produces printed parts with high surface quality and geometric accuracy. Tensile tests on the printed parts demonstrate that they possess excellent mechanical properties. This study provides valuable insights and a meaningful exploration of future in-orbit metal manufacturing.