The mechanical properties and microstructure analysis of 308LSi austenitic stainless steel produced by wire arc additive Manufacturing (WAAM) technique

Mohd Nooraimy, Muhammad Nor Saifullail (2024) The mechanical properties and microstructure analysis of 308LSi austenitic stainless steel produced by wire arc additive Manufacturing (WAAM) technique. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

Wire arc additive manufacturing (WAAM) has emerged as a promising technology for manufacturing large and complex metal parts due to its high deposition rate and material versatility. 308LSi stainless steel is austenitic stainless steel known for its excellent corrosion resistance and good weldability. Understanding of the mechanical properties of 308LSi stainless steel is limited, especially about anisotropy. Therefore, the test samples were built using the CMT-WAAM robot system, parameters 115A, 11.6V and 4.0 m/min. Based on the tests performed, for tensile testing, specimens tested at 45° showed better results than specimens tested at 0° and 90°. This is due to the upward growth of columnar dendrites. Turning to the impact test, the average absorbed energy index was 65.03 J, 68.25 J, and 62.01 J for the 0°, 45°, and 90° samples, respectively. Notably, the 45° samples exhibited higher average energy absorption, indicating better impact resistance compared to the 0° and 90° samples. During the hardness test, average hardness values of 179.814 Hv, 167.66 Hv and 164.73 Hv were recorded for the lower, middle and top zones, respectively. The hardness value in the bottom zone exceeds the value in the upper zone. Finally, microstructural analysis shows that the dendrites grow following the built direction. The microstructure at the bottom zone is also finer than other zones because heat is conducted directly to the surface, so the cooling rate is higher. The microstructure of the middle zone is coarser than that of the bottom zone because as the residue increases, heat accumulates and the cooling rate is slower. The top zone is in direct contact with air and has a short time, so it is composed of equiaxed grains. According to the results test, it shows that the 308 LSi CMT-WAAM thin-wall has anisotropic mechanical behaviour.

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