Investigation of laser powder bed fusion manufacturing and post-processing for surface quality of as-built 17-4PH stainless steel

Laser powder bed fusion (LPBF) technique enables to manufacture complex parts and difficult-to-cut materials with saving the material costs and manufacturing time. However, there still has been technical challenges and qualities issues for LPBF products to be used in engineering applications. In order to obtain the high-quality surface products including minimal defects and voids, this study systematically investigated and determined LPBF manufacturing process and post-processing using a 17-4PH stainless steel. It was experimentally found that design of LPBF process conditions could only attain the densification of as-built products, while surface qualities were not as good as commercial products. Therefore, the post-processing was indispensably explored by conducting mechanical polishing, physical vapor deposition coating, and hot isostatic pressing for the high surface quality and densification of as-built specimens. The surface qualities of the specimens, fabricated with optimum volumetric energy density of 97.66 J/mm(3), were carefully characterized for their surface roughness, gloss, surface energy and frictional behaviors. After the post-processing, the surface roughness and gloss were dramatically improved by more than 800% over the as-built parts, and the porosity was reduced by up to 57.8%. This study demonstrates that optimum LPBF process and post-processing could enhance the qualities of LPBF products up to the same or beyond level of commercial products, comparing the defects, roughness, gloss, and touch sensation. The LPBF technique coupled with post-processing, if optimized, can show the great potential for the use in a wide variety of real-world engineering applications including mobile phones, jewelry, electronic appliances, artificial teeth and bones.