PSI - Issue 56

Sai Kumar Balla et al. / Procedia Structural Integrity 56 (2024) 41–48 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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loading on the surface (Varghese & Mujumdar, 2021). It is evident from the literature that, most of researchers have worked on implementation of shot peening as post processing technique for improving the surface quality of LPBF processed components and limited work has been conducted on other post processing methods. As stated earlier, there is a need for improving the surface quality of LPBF processed components. The present study focused on effect of different post processing techniques on surface quality of LPBF processed AlSi12 alloy and evaluated the surface roughness of the AlSi12 alloy by comparing it with as-built conditions. 2. Experimentation 2.1. LPBF process AlSi12 alloy samples are fabricated using a DMP Flex 100 LPBF (3D Systems, USA) machine which uses a 100 W optical fibre laser with a build volume of 100x100x30 mm 3 . The powder size of 5-45 µm with good flowability used to fabricate the cubes with dimensions 10x10x10 mm 3 as designed are shown in Fig. 1 (a) and manufactured using the LPBF process. The laser interaction with powder particles during the fabrication is shown in Fig. 1 (b) The AlSi12 samples are fabricated using optimal conditions and process parameters used are laser power of 90 W, layer thickness of 30 µm, scanning speed of 600 mm/s, hatch spacing of 0.06 mm with hexagonal scanning strategy. The samples are fabricated in an inert atmosphere with an oxygen content of less than 1000 ppm to prevent them from oxidation during fabrication. The manufactured samples are kept for cooling in the manufacturing chamber at room temperature and samples are cleaned using the vacuum cleaner to remove any unwanted particles from the substrate and sample surfaces.

Fig. 1. (a) Designed samples in build volume; (b) Fabrication chamber of LPBF machine

2.2. Post-processing Four post-processing operations such as sand blasting, chemical anodizing, wire electric discharge machining (Wire-EDM) and micro milling are performed on the samples to obtain different surface features as shown in Fig. 2. Sandblasting on AlSi12 alloy samples performed to remove the loosely bounded powder particles. A nozzle diameter of 6 mm and 100-120 µm stand-off distance is maintained between the samples and nozzle to ensure uniform distribution of sand particles by maintaining 6 psi pressure for sandblasting. Chemical anodizing is performed on the AlSi12 alloy surface to lay off the outer layer. 10% vol of 40% concentrated H 2 SO 4 solution with distilled water is used for chemical anodizing by supplying 5 V voltage and 2.5 A current. Wire-EDM is one of the dominant unconventional machining processes and it helps remove the surface to improve the surface quality of additively manufactured components. Wire-EDM is performed with Electronica Ezeewin ES500 for different process combinations like pulse on time (T on ) 30,60 µSec, pulse off time (T off ) 3 µSec and peak current (IP) of 3,6 mA on different surfaces of the AlSi12 alloy. Also, LPBF processed AlSi12 alloy samples are machined using micro milling (DT-100i, Mikrotools Pte. Ltd., Singapore) to reduce the surface roughness from as-built condition and high spindle micro milling with spindle speed of 14000 rpm, and 20 mm feed per minute with 100 µm depth of cut used.