OBRABOTKAMETALLOV TECHNOLOGY Vol. 26 No. 4 2024 The variable parameters were the wire feed and the shielding gas consumption. The gas consumption during the experiments was selected in the range of 8–12 l/min. This had to be done in order to evaluate this parameter for porosity. At the same time, other parameters, current, wire feed, surfacing speed were constant. Ultrasonic processing was carried out on the last surfacing layer for 1, 5, 10, 15 minutes using the Shmel Mg unit. Tensile tests were carried out in accordance with GOST 1497-84. A total of 3 test pieces were cut from a steel wall manufactured using standard WAAM and hybrid WAAM. Impact toughness (KCU) was carried out in accordance with GOST 9454-78 and GOST 6996. For this purpose, 3 test pieces were cut from a steel wall manufactured using standard WAAM and hybrid WAAM and prepared. After completion of the impact bending tests, the fracture surfaces of the test pieces were examined using a JEOL JIB-Z4500-SEM scanning electron microscope (SEM) to compare the main types of failure associated with diff erent forming technologies. For microstructural analysis, metallographic specimens were extracted from the wall along the growth directions, polished according to standard procedures to a surface fi nish of 1 μm, etched with 4 % aqueous nitric acid solution and examined using an optical microscope (MicroMed 2). Hardness measurements were carried out at diff erent locations and orientations of the wall, including the lower, middle and upper zones, using a Shimadzu HBR-VU-187 microhardness tester with a load of 200 g and a dwell time of 15 s. Research results Fig. 2, 3 show the results of the infl uence of the wire feed and the shielding gas consumption on the metal porosity. The numbers 1, 2, 3, 4, 5 in Fig. 2 show the number of weld beads. Fig. 3 shows the infl uence of the shielding gas consumption on the porosity. It is evident that with an increase in consumption, the porosity in the weld metal decreases to zero. Fig. 4 shows the results of the infl uence of mechanical cleaning after each layer of surfacing on the surface quality and the geometric dimensions of the surfaced bead. It is evident that the use of machining aff ects the height of the surfaced bead and the quality of the weld (Fig. 5). The microstructure of the surfaced beads material, shown in Fig. 6, consists of polygonal ferrite (PF) and intergranular lamellar pearlite (P). Tables 1 and 2 present the results of static tensile tests and impact bending tests. It is evident that machining increases the yield strength and endurance of the surfaced metal compared to the results without machining. The impact toughness values also diff er when additional machining is used. The fractography images in Fig. 7, b show that the specimens without machining contain pores, which reduces the impact toughness values. a b Fig. 1. Schematic diagram of the bead surfacing process (a) and a plate with surfaced beads (b)
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