# Laser Beam Welding of CubeSat 1U Structure Parts Obtained by Powder Bed Fusion
## 2 Materials and Methods  
Figure 1 shows a three-way tube connector that is to be built using SLM and EBM. The typical dimensions of a cross-sectional cut are presented in Figure 1. The computer model was designed in Solid Works version 2022 (Dassault Systemes, France), and slicing was performed in AM machines. The powders used in the SLM and EBM processes had a composition of Ti6 Al4V alloy (Ti, 5.72%Al, 4.1%V, 0.37%Fe, 0.065%C, 0.04%N, 0.15%O, 0.013%H, by weight), as given by the powder fabricant. Spherical particles of the powder were sieved to obtain a granulometric distribution between 45 and 60 \(\upmu\)m.  
SLM was performed on an EOS M280 instrument (Krailling, Germany) using a laser power of 170 W and a process speed of 1350 mm/s. Each layer was applied by rotating the previous layer by 60\({}^{\circ}\) to mitigate anisotropy, with a thickness of 30 \(\upmu\)m each and a  
Figure 1: Computer drawing of the connector (**a**) and its dimensions (**b**). distance between the lines of 0.1 mm. The process chamber was filled with argon at ambient pressure after purging to eliminate atmospheric gas. The EBM equipment was a GE ARCAM Q10 (West Chester, PA, USA) with an electron source of a current of 41 mA and a voltage of 60 keV. In the focal plane, the estimated current was 3.073 mA. After purging with pure argon, the chamber was evacuated to 3.9 kbar after a purge with pure argon. The process speed was set to 8000 mm/s, and the powder bed was preheated to 560 \({}^{\circ}\)C before the start of growth. The different processing speeds for SLM and EBM are due to the in-built recipes in the models and could not be changed, although this parameter could change the quality of the built volume. The connectors built by SLM and EBM were laser-welded to commercially pure grade 2 titanium tubes to compose a cube of 1 L volume. The tubes that made up the edges of the cube had an outer diameter of 6 mm and a wall thickness of 1 mm. The connectors and tube were designed to minimize the weight of the assembly. The maximum permissive gap tube to the connector terminal is 0.5 mm. For the LBW, IPG Photonics YLR2000 (Oxford, MA, USA) equipment with a maximum power of 2 kW and a minimum focal diameter of 0.1 mm was used. The welding strategy involves laser spot welding on one side of the connector to the tube to join the three tubes in each connector until the complete formation of the structure is reached. Each spot weld was performed 3 mm from the edge with a power of 1 kW per shot and a beam diameter of 7.4 mm. The pulse temporal length was 400 ms; therefore, each laser shot had an energy of 400 J and an energy density of 9.3 J/mm\({}^{2}\). A shielding gas nozzle blasted 10 L/min of pure argon during the spot welding. The density measurements of the connectors were obtained using the Archimedes method, according to ASTM C373-18 [13]. For the measurements, a Shimadzu analytical balance model AUX320 was used. The dry angle mass was measured after the angle was maintained in a muffle furnace at 50 \({}^{\circ}\)C for 5 h. To measure the submerged mass, the connector was first placed in a beaker with distilled water and heated at 100 \({}^{\circ}\)C for 5 h. At the end of the time that the connector was kept at 100 \({}^{\circ}\)C, the heating was turned off, and the sample was left in a beaker with water for 24 h before the mass was measured. The saturated mass was measured after the submerged mass was measured. As the connectors were removed from the beaker with water, the excess water was dried with absorbent paper, and the mass was measured. Optical microscopy (OM) was performed using a Zeiss microscope Axio Imager.A2m (Oberkochen, Germany). Microstructural analysis was performed on the samples, which were cut on a metallographic saw with a diamond disk with a constant lubrication and on Bakelite synthetic resin. The sanding process was carried out in a motorized sander at a speed of 300 rpm, with silicon carbide water sandpaper of 220, 320, 400, 600, 800, 1200, 1500, and 2000 grit.