Effect of scanning strategy on the thermal behavior, dimensional accuracy, microstructure and hardness of selective laser melting thin-walled structures

Abstract

Complex thin-walled structures are widely used in engineering, which formation mainly depends on selective laser melting. Understanding the relationship between scanning strategies and forming quality of thin-walled structures is vital for process design. In this paper, the thermal behavior of thin-walled structures under short line scanning strategy (SLSS) and long line scanning strategy (LLSS) was investigated by finite element model, and the dimensional accuracy and microstructure were characterized. The simulation results showed that the SLSS led to intense local heat accumulation, which significantly affects the molten pool morphology and duration. However, the LLSS weakened the local heat accumulation by increasing the time of a single scanning track, resulting in the molten pool size and duration decreasing. Affected by local heat accumulation, the as-built size of LLSS was larger than that of SLSS. With thickness increasing, the dimension error between the two scanning strategies gradually diminished. EBSD maps and SEM figures illustrated that the grain size and cell size produced by SLSS were much larger than that of LLSS. Due the difference in microstructure, the thin walls fabricated by LLSS exhibited higher hardness of 96.62 ∼ 98.72 HV0.5. This study hopefully deepens the understanding of the relationship between scanning strategies and printability of thin-walled structures.