Effects of Laser Powder Bed Fusion Process Parameters on Porosity, Liquid Retention, and Thermal and Surface Properties for 316L, CoCrW and Ti6Al4V Alloys

Abstract

Laser powder bed fusion (LPBF) offers several key advantages, including design flexibility, the ability to produce complex geometries and the fabrication of porous materials. These advantages have greatly expanded the range of applications for products manufactured using LPBF. Recently, there has been a significant increase in the use of LPBF products in thermal applications. In these applications, which involve intricate solid-fluid interface interactions, and thermal and surface properties of solids play a crucial role in heat flow interactions. This study focused on producing samples using the LPBF method with three different alloys: 316L, CoCrW and Ti6Al4V. The samples were subsequently analyzed for relative porosity, liquid retention, and thermal and surface properties. The influence of various laser process parameters, specifically energy density, on these properties was examined. The production processes conducted at various energy densities yielded porosity levels of approximately 7-32%, 2-20% and 3-16% for 316L, CoCrW and Ti6Al4V materials, respectively, in comparison with the theoretical density. Thermal conductivity values for 316L, CoCrW and Ti6Al4V samples ranged from 15.1 to 12.9, 7.9 to 7.1 and 6.1 to 5.8 W/m.K, respectively. Similarly, the average surface roughness was observed to vary in the range of 7.5-9.6, 8.3-10.5 and 8.9-10.3 mu m for 316L, CoCrW and Ti6Al4V samples. Based on the obtained results, the samples were evaluated in terms of their suitability for thermal applications. Among the investigated alloys, 316L alloy is determined to have potential for thermal applications (extended surface applications, transpiration cooling, etc.) due to its efficient liquid retention feature, relatively high thermal conductivity and moderate surface roughness. Moreover, the 316L stainless steel proved to be more cost-effective, as it allowed for production at low energy density and had a relatively affordable material cost. Additionally, relatively easy porosity controlling in 316L alloy LPBF productions and leveraging its ability to fabricate porous structures hold great promise for further advancements in thermal application products.