Effect of Hatch Spacing on Melt Pool and As-built Quality During Selective Laser Melting of Stainless Steel: Modeling and Experimental Approaches.

Zhichao Dong,Jun Liang,Weibin Wen,Yabo Liu,Jingran Ge

doi:10.3390/ma12010050

Zhichao Dong, Jun Liang + Show 3 more

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https://doi.org/10.3390/ma12010050

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Abstract

In this study, a combined simulation and experimental approach is utilized to investigate the influence of hatch spacing on the microstructure and as-built quality of 316L stainless steel (SS) samples fabricated by selective laser melting (SLM). A three-dimensional finite element model (FEM) is employed to investigate heat transfer and melt pool during the SLM of 316L SS. The phase transformation and variation of the thermo-physical properties of the materials are considered in this model. The effects of hatch spacing (H) on the temperature field, microstructure and melt pool size, overlap rate, surface quality, and relative density during the SLM of 316L SS are investigated. The simulated results indicate that, as the hatch spacing increases, the depth increases and the width of the melt pool decreases. Meanwhile, with the increase of hatch spacing, the simulated temperature of the subsequent tracks falls below the melting temperature of the first track. Moreover, the microstructures were found to coarsen with the increasing hatch spacing due to the reduced cooling rate. The optimized hatch spacing and overlap rate between adjacent tracks were obtained from numerical simulations. Simulation results illustrate that, when the optimized hatch spacing of 100 μm is adopted, fully dense parts with a smooth surface can be fabricated by SLM, thus experimentally validating the simulation results.

Highlights

Selective laser melting (SLM) is a rapidly thriving additive manufacturing (AM) process to fabricate complex geometrical metal parts [1,2]
The peak point of the temperature curve indicates that the start of each laser scan track causes the formation of a layer
3a,b, the hatch spacing of each laser scan track causes the formation of a layer

Summary

Introduction

Selective laser melting (SLM) is a rapidly thriving additive manufacturing (AM) process to fabricate complex geometrical metal parts [1,2]. A study has shown that as metal powders reach their melting and solidification temperatures by heating or cooling during SLM, phase change (i.e., melting) occurs [3,4]. Due to the particularity of SLM, it is difficult to observe the thermal behavior, phase transitions, and melt-pool behavior directly because they strongly depend on the laser process parameters, such as the hatch spacing, scanning speed, and laser power etc. Alsalla et al [13] investigated the density, surface quality, microstructure, and mechanical properties of the components of the SLM parts made at different building directions.

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