Effect of contour process parameters on the surface roughness of laser powder bed fusion manufactured 304 stainless steel

Department of Industrial Engineering, Stellenbosch University, South Africa

^* Corresponding author: 27275396@sun.ac.za

Abstract

Surface roughness remains a major drawback in metal additive manufacturing (AM) processes. Even though finishing operations are applied, the surface roughness is still of interest because additive manufacturing is mainly applied in expensive materials and, in some cases, hard-to-machine materials. Additionally, conventional finishing operations are not viable for intricate components like fine porous structures or cavities, which make AM attractive. Therefore, improving the surface quality of parts created through laser powder bed fusion (LPBF) requires direct optimisation during manufacturing. In this study, the authors investigated the effect of contour process parameters on the surface roughness of vertical surfaces and sloped surfaces associated with up and down surfaces fabricated by LPBF using 304 stainless steel (304 SS) powder feedstock. The study explored the impact of varying laser power and scanning speed separately while holding other parameters constant. The obtained results showed that increasing the speed decreases the surface roughness on the vertical surfaces whereas there was no clear dependency of the roughness on the laser power. The sloped surface consistently exhibited higher roughness on the down skin than the up skin, which can be attributed to deeper laser penetration. Additionally, printed samples indicated reductions in clearance from the CAD model, attributed to unmolten powder particles adhering to the surface. Understanding and optimising surface finish and dimensional accuracy could further accelerate the adoption of LPBF technology in fabricating net- shaped direct-to-service components.