Abstract
The 316 L stainless-steel samples were prepared by laser powder bed fusion (LPBF). The effects of processing parameters on the density and defects of 316 L stainless steel were studied through an orthogonal experiment. The density of the samples was measured by the Archimedes method, optical microscopy (OM) and X-ray Computed Tomography (XCT). The microstructures and defects under different LPBF parameters were studied by OM and SEM. The results show that the energy density has a significant effect on the defect and density of the structure. When the energy density is lower than 35.19 J/mm3, the density increases significantly with the increase of energy density. However, when the energy density is larger than this value, the density remains relatively stable. The process parameter with the greatest influence on energy density is the hatch distance D, followed by laser power P, scanning speed V and rotation angle θ. In this paper, the optimum parameters consist of P = 260 W, V = 1700 mm, D = 0.05 mm and θ = 67°, in which the density is as high as 98.5%. In addition, the possibility and accuracy of the XCT method in detecting the discontinuity and porosity of 316 L stainless steel were discussed. The results show that XCT can provide the whole size and variation trend of pores in the different producing direction of LPBF.
Highlights
Additive manufacturing (AM) [1,2] is a technology that allows physical components to be fabricated via the layer-by-layer addition of materials
Laser powder bed fusion (LPBF) is a complex process [20] due to some factors such as that the rapid movement of laser with high energy density leads to the rapid melting and rapid cooling of metal, and each layer of metal will be subjected to a periodic thermal cycle
The amount and morphology of porosity defects were evaluated based on the process parameters used to prepare the samples
Summary
Additive manufacturing (AM) [1,2] is a technology that allows physical components to be fabricated via the layer-by-layer addition of materials. LPBF is a complex process [20] due to some factors such as that the rapid movement of laser with high energy density leads to the rapid melting and rapid cooling of metal, and each layer of metal will be subjected to a periodic thermal cycle These characteristics of LPBF process have a significant impact on structural defects in the parts printed [21]. Mainly lack-of-fusion and keyhole, balling phenomena, and so on, are caused by the process parameters or equipment, which can be reduced or eliminated by optimizing process parameters in the oxygen content, scanning rate, fluidity and wettability of molten metal in micro-pool, etc. It is important to optimize the process parameters for LPBF
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