| LI Zi-shan,YANG Gao-lin,DONG Gang,YAO Jian-hua.Forming Morphology of 316L Horizontal Overhanging Structure Initial Layer by Selective Laser Melting[J],52(3):379-387, 437 |
| Forming Morphology of 316L Horizontal Overhanging Structure Initial Layer by Selective Laser Melting |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.03.036 |
| KeyWord:selective laser melting, support, horizontal overhanging structure initial layer, connection quality, morphology, radio of pore |
| Author | Institution |
| LI Zi-shan |
Institute of Laser Advanced Manufacturing,College of Mechanical Engineering,Collaborative Innovation Center of High-end Laser Manufacturing Equipment, Zhejiang University of Technology, Hangzhou, , China |
| YANG Gao-lin |
Institute of Laser Advanced Manufacturing,College of Mechanical Engineering,Collaborative Innovation Center of High-end Laser Manufacturing Equipment, Zhejiang University of Technology, Hangzhou, , China |
| DONG Gang |
Institute of Laser Advanced Manufacturing,College of Mechanical Engineering,Collaborative Innovation Center of High-end Laser Manufacturing Equipment, Zhejiang University of Technology, Hangzhou, , China |
| YAO Jian-hua |
Institute of Laser Advanced Manufacturing,College of Mechanical Engineering,Collaborative Innovation Center of High-end Laser Manufacturing Equipment, Zhejiang University of Technology, Hangzhou, , China |
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| Abstract: |
| In view of the problems such as poor forming quality of thin horizontal overhanging structure morphology and the connection quality between support structure and overhanging structure formed by selective laser melting. The horizontal overhanging structure initial layer morphology of molten metal formed by selective laser melting was studied from three factors of support spacing, support form and energy input to provide a theoretical basis for improving the quality of thin horizontal overhanging structure and the connection quality between support structure and overhanging structure. 316L parts of horizontal overhanging structure initial layer was prepared by selective laser melting technology. The influencing factors and changing process mechanism of the molten metal morphology in the initial layer before cooling and solidification were investigated by section metallographic analysis and surface topography data analysis. The spacing distances of support for the formed parts were set at 2.5, 1.67, 1.25, 1, 0.833 and 0.714 mm respectively, depending on the different amount of support structures for the uniformly divided 10 mm diameter circular model. The spacing distances of support were divided into the circular arrangement, which had fewer effects on the surface morphology, and the cross arrangement, which was more common in practice. The energy input of the initial layer increased with the decrease of the scanning speed and the increase of the laser power at constant laser power. With the decrease of the support spacing distance from 2.5 mm to 0.714 mm, the radio of pore in overhanging structure initial layer decreased continuously and the minimum pore radio can reach 6.549%. When the support spacing distance was 1 mm and with the increase of laser energy input from 0.083 W.s/mm to 0.25 W.s/mm, the pore radio can reach 13.104%. The maximun spheroidizing height of initial layer decreased from 523.454 μm to 267.951 μm, and the forming surface was more smooth. For the same spacing distances of support and support arrangement modes, the porosity of normal support was larger, and the pore shape characteristics revealed that the molten metal kept spheroidizing towards the support structure before solidification. The pore shape characteristics revealed that the molten metal converged to the support structure before solidification. The pores of the formed specimens with increasing energy input by decreasing the scanning speed were generally less than those of the formed specimens with increasing laser power by keeping the scanning speed constant at the same energy input. After the molten metal layer which is formed by laser scanning, the support spacing distance will affect the amount of molten metal, and the energy input of laser will affect the solidification time of molten metal at the same heat dissipation rate. Under the influence of surface tension, the molten metal layer which is disturbed and ruptured will converge to the joint with the support structure, and the morphology constantly deviates from the initial flat thin layer state. The line support with spacing distance less than 1mm can effectively reduce the amount of pores and improve the morphology flatness of the horizontal overhanging structure initial layer formed by SLM. |
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