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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the surface using compressed air to smooth, clean, and remove contaminants from the rough surface. It helps in removing loosely bound unwanted particles and materials from the surface. Anodizing is an electrochemical process that creates a protective oxide layer on the surface of aluminum alloys. The oxide layer can improve the surface properties of aluminum, including its durability, corrosion resistance, and aesthetic appearance. This oxide layer can reduce surface roughness by filling in small surface defects and smoothing out the surface. Wire EDM can improve the surface roughness of aluminium alloys fabricated by LPBF by removing any excess material, such as support structures or surface irregularities, that may be present on the part after the fabrication process. This process can also help create fine features and details on the part's surface that may be difficult or impossible to achieve using the LPBF process alone. Table 1 shows that the maximum surface roughness of 22.74 µm has resulted in as-built samples, which is not applicable in industrial applications. This can be reduced to 9.05 µm and 11.25 µm using post processing conditions sand blasting and chemical anodizing respectively. These two conditions help remove unwanted particles from the surface, which reduce the surface roughness but not effectively. The sand beads in sand blasting remove the unmelted and unbound particles from the surface and chances of producing pores, which doesn’t completely eliminate the surface roughness. But in Wire EDM, the outer surface is chipped off using minimal diameter wire using optimal parameters to improve the surface quality of fabricated samples. Wire EDM offers better surface finish than other non-conventional machining processes even though machining efficiency is lower. The surface integrity is mainly affected by discharge energy, which combines pulse on time and power (Abhilash & Chakradhar, 2022). The higher discharge energy forms irregular craters due to large sparks which produce rough surface. Lower discharge energy helps create surface quality due to fewer craters and a lower surface finish is obtained using a T on of 30 µSec.

Fig. 5. Comparison of microhardness and surface roughness of post processed samples with as-built AlSi12 samples And finally, micro milling is performed on LPBF fabricated AlSi12 alloy samples using different process parameters and observed the surface quality produced. We observed that, surface roughness is reduced with increasing spindle speed up to a certain limit and then starts increased. This is because higher spindle speed allows higher cutting speeds, resulting in smoother cuts and reduced tool marks on the surface. Increasing spindle speed beyond certain limits can generate more heat during cutting and causes material to soften or melt, increasing the surface roughness. By observing these different conditions in wire EDM as well as micro milling, the optimal condition results are reported and surface topography of better machined surface is represented in Fig. 4. and it is concluded that micro milling helps in producing better surface quality of additively manufactured AlSi12