Investigation on Porosity and Microhardness of 316L Stainless Steel Fabricated by Selective Laser Melting

Yusuf, Shahir Mohd; Chen, Yifei; Boardman, Richard; Yang, Shoufeng; Gao, Nong

doi:10.3390/met7020064

Cited by 140 publications

(60 citation statements)

References 46 publications

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“…It should be noted that all these microhardness values obtained from the multilayered builds are higher than wrought 316L obtained in the cold rolled condition (220 HV). Looking at the literature, the micro hardness values obtained in this study are within the range found in [9,15,23,24]. Figure 10 shows the fine cellular subgrain structure that was found in almost all the builds, but that was most predominant in the ideal P f /T s range of 0.011-0.013 g/mm.…”

Section: Resultssupporting

confidence: 82%

Processing Parameter DOE for 316L Using Directed Energy Deposition

Sciammarella

Najafabadi

2018

JMMP

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Abstract:The ability to produce consistent material properties across a single or series of platforms, particularly over time, is the major objective in metal additive manufacturing (MAM) research. If this can be achieved, it will result in widespread adoption of the technology for industry and place it into mainstream manufacturing. However, before this can happen, it is critical to develop an understanding of how processing parameters influence the thermal conditions which dictate the mechanical properties of MAM builds. Research work reported in the literature of MAM is generally based on a set of parameters and/or the review of a few parameter changes, and observing the effects that these changes (i.e., microstructure, mechanical properties) have. While these articles provide results with some insight, there lacks a standard approach that can be used to allow meaningful comparisons and conclusions to be made concerning the optimization of the processing variables. This study provides a template which can be used for making comparisons across DED platforms.The tests are performed with a design of experiments (DOE) philosophy directed to evaluate the effect of selected parameters on the measured properties of the DED builds. Specifically, a laser engineering net shaping system (LENS) is used to build multilayered 316L coupons and analyze how build parameters such as laser power, travel speed, and powder feed rate influence the thermal conditions that will define both microstructure and microhardness. A fundamental conclusion of this research is that it is possible to repeatedly obtain a consistent microstructure that contains a fine cellular substructure with a low level of porosity (less than 1.1%) and with microhardness that is equal to or better than wrought 316L. This is mainly achieved by maintaining an associated powder flow to travel speed ratio at the power level, ensuring an appropriate net heat input for the build process.

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Section: Resultssupporting

confidence: 82%

Processing Parameter DOE for 316L Using Directed Energy Deposition

Sciammarella

Najafabadi

2018

JMMP

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“…Comparing with conventional manufacturing processes, such as casting or forming, this technology provides many advantages including fabrication of metallic parts with more complex shapes, less time from design stage to manufacturing, no need to post processing, and lower wastage precursors. In this technology, without the usage of specialized molds or tools, in a single step process, 3D components are fabricated through layer-wise addition of melted/sintered precursors powder on the substrate or previous layers, based on their digitally defined Computer Aided Design (CAD) data [1][2][3][4][5][6]. In recent years, various laser-based additive manufacturing methods for fabrication of metallic components have been developed, such as laser engineered net shaping (Lenz), direct metal deposition (DMD), laser solid forming (LSF), direct laser fabrication (DLF), laser metal deposition shaping (LMDS), direct metal laser sintering (DMLS), and selective laser melting (SLM) [1,5,7].…”

Section: Introductionmentioning

confidence: 99%

“…Additive manufacturing has emerged as an appropriate solution to resolve this issue. Nevertheless, the components built through these techniques have different microstructures and properties than those fabricated through conventional methods, which makes it crucial to study and research their as-printed properties [5,6,8]. In spite of existing comprehensive works on investigating various properties of SLM fabricated parts, there is very limited literature on corrosion related characteristics and electrochemical properties of AM components [9].…”

Section: Introductionmentioning

confidence: 99%

On Microstructure and Corrosion Properties of Selective Laser Melted 316L Stainless Steel

Kazemipour¹,

Mohammadi²,

Nasiri³

2018

Progress in Canadian Mechanical Engineering

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In this study, a laser additive manufacturing method, known as selective laser melting (SLM), was applied to produce cube blocks of 316L stainless steel. The microstructure and corrosion properties of the produced samples were analyzed using scanning electron microscopy, cyclic potentiodynamic polarization testing, and electrochemical impedance spectroscopy. The results were also compared with the properties of a conventional wrought 316L stainless steel sample. The microstructural studies showed that the SLM-manufactured samples have a regular network of melt pools containing austenite grains along with elongated or equiaxed cellular sub-grains. The potentiodynamic polarization results depicted that the SLM fabricated samples had higher positive pitting potential and a wider passivation range than those of the wrought sample, corresponding to their better corrosion resistance. However, the SLM fabricated samples showed a weaker re-passivation property, which possibly is attributed to the presence of preexisting porosities in the structure of the SLM sample formed during the fabrication process. The EIS data also confirmed a larger capacitive arc for the SLM fabricated samples than its wrought counterpart, indicating a higher charge transfer impedance and a better corrosion resistance.

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“…In addition, the as-built material microhardness increased simultaneously to a decreasing porosity to a maximum of 225 HV at a density of 99.62%. Other researchers presented an approach to find the optimum laser process parameters resulting in dense parts, homogeneous melt pools, and predictable microstructure [18][19][20][21][22][23]. Casati et al [24] and Kruth at al.…”

mentioning

confidence: 99%

Transferability of Process Parameters in Laser Powder Bed Fusion Processes for an Energy and Cost Efficient Manufacturing

Pannitz

Sehrt

2020

Sustainability

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In the past decade, the sales of metal additive manufacturing systems have increased intensely. In particular, PBF-LB/M systems (powder bed fusion of metals using a laser-based system) represent a technology of great industrial interest, in which metallic powders are molten and solidified layer upon layer by a focused laser beam. This leads to a simultaneous increase in demand for metallic powder materials. Due to adjusted process parameters of PBF-LB/M systems, the powder is usually procured by the system's manufacturer. The requirement and freedom to process different feedstocks in a reproducible quality and the economic and ecological factors involved are reasons to have a closer look at the differences between the quality of the provided metallic powders. Besides, different feedstock materials require different energy inputs, allowing a sustainable process control to be established. In this work, powder quality of stainless steel 1.4404 and the effects during the processing of metallic powders that are nominally the same were analyzed and the influence on the build process followed by the final part quality was investigated. Thus, a correlation between morphology, particle size distribution, absorptivity, flowability, and densification depending on process parameters was demonstrated. Optimized exposure parameters to ensure a more sustainable and energy and cost-efficient manufacturing process were determined.Sustainability 2020, 12, 1565 2 of 14 useful for medical devices, e.g., surgical devices with thin-walled structures and, alongside Ti and Co-Cr alloys, for medical implants [4,5]. The ability to create complex lattice structures has resulted in a redesign of existing stainless steel components and lightweight structures in the automotive and aerospace industry to ensure more efficient and sustainable components [5].However, in order to ensure sustainable production, the entire process chain must be taken into consideration. Starting with powder production, through transportation and processing of the powder in the PBF-LB/M system, up to the use of a durable component and recycling of the nonfused metal powder. Kellens et al. [6] emphasize that energy consumption during the PBF-LB/M process is dominated by laser exposure. This was confirmed by Liu et al. [7], who state that energy consumption depends on exposure parameters such as laser power, scanning speed, layer thickness, etc. on the process level. Thus, the correlation between powder characteristics, the PBF-LB/M-process itself, and the final part quality represent a significant area of focus for sustainable process management.Great research efforts in the scientific community concerning stainless steel 1.4404 have addressed the correlation between input parameters (e.g., particle size distribution, chemical composition, process parameters, etc.) and output parameters (e.g., mechanical properties, relative density, microstructure, etc.). Process parameters consist of a large number of variables, including laser power, scanning speed, layer thickness...

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Investigation on Porosity and Microhardness of 316L Stainless Steel Fabricated by Selective Laser Melting

Cited by 140 publications

References 46 publications

Processing Parameter DOE for 316L Using Directed Energy Deposition

Processing Parameter DOE for 316L Using Directed Energy Deposition

On Microstructure and Corrosion Properties of Selective Laser Melted 316L Stainless Steel

Transferability of Process Parameters in Laser Powder Bed Fusion Processes for an Energy and Cost Efficient Manufacturing

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