scholarly journals Strategy for Surface Post-Processing of AISI 316L Additively Manufactured by Powder Bed Fusion Using Ultrasonic Nanocrystal Surface Modification

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 843
Author(s):  
Seung-Young Cho ◽  
Min-Seob Kim ◽  
Young-Sik Pyun ◽  
Do-Sik Shim
Keyword(s):  
Surface Roughness ◽  
Surface Modification ◽  
Surface Hardness ◽  
Surface Characteristics ◽  
Scratch Resistance ◽  
Powder Bed Fusion ◽  
Optimal Conditions ◽  
Box Behnken Design ◽  
Powder Bed ◽  
Surface Method

Ultrasonic nanocrystal surface modification (UNSM) technology was applied to the surfaces of specimens additively manufactured by powder bed fusion (PBF). The changes in roughness and hardness due to the UNSM were set as objective functions, and the optimal conditions for the main parameters were derived through the response surface method (RSM) and Box–Behnken design (BBD). Regression analysis-based mathematical models for predicting the surface hardness and roughness are presented and validated. The RSM results show that the surface roughness is highly dependent on the load and ball tip diameter, and the surface roughness significantly improves as the inter-pass interval and ball tip diameter decrease. Through BBD and ANOVA, the optimal conditions for the improvement of surface characteristics were found to be a load of 40 N, inter-pass interval of 10 μm, and ball tip diameter of 2.38 m. The surface treated under these optimal conditions exhibited a hardness of 497 Hv and surface roughness of 1.32 μm, which were significantly improved compared to the values for an untreated specimen. In addition, it was confirmed that the grains are significantly refined after UNSM, and scratch resistance increases for the top layer of the surface directly affected by the UNSM horn.

Improvement in Microscratch Resistance of Graphite by Surface Modification for Molding Applications

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Auezhan Amanov ◽  
Bakhtiyor Urmanov ◽  
Ki-Chol Kim ◽  
Young-Sik Pyun
Keyword(s):  
Surface Roughness ◽  
Surface Modification ◽  
Three Dimensional ◽  
Surface Hardness ◽  
Scratch Test ◽  
Scratch Resistance ◽  
Molding Process ◽  
Cover Glass ◽  
Force Microscopy ◽  
Before And After

This paper deals with the improvement in surface properties and microscratch resistance of graphites by means of an ultrasonic nanocrystalline surface modification (UNSM) technique. The surface roughness and surface hardness of the untreated and UNSM-treated graphites were investigated using an atomic force microscopy (AFM) and a microhardness tester, respectively. The scratch resistance was assessed using a microscratch tester at a progressive load. Moreover, a Raman spectroscopy was employed to characterize the microstructure of graphites before and after UNSM treatment. The scratch test results revealed that the resistance to scratch of both UNSM-treated graphites was found to be better in comparison with the untreated graphites. The increase in scratch resistance of both UNSM-treated graphites may be mainly attributed to the reduced surface roughness and increased surface hardness by UNSM treatment. The graphite produced by Poco exhibited a higher resistance to scratch compared to that of the graphite produced by Mersen. The objective of this study is to extend the service life of three-dimensional (3D) cover glass moldings made of graphite by the application of UNSM treatment through the understanding the effects of surface roughness and surface hardness on the scratch defect generation behavior during glass molding process.

scholarly journals On the Relevance of Volumetric Energy Density in the Investigation of Inconel 718 Laser Powder Bed Fusion

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 538 ◽  
Author(s):  
Fabrizia Caiazzo ◽  
Vittorio Alfieri ◽  
Giuseppe Casalino
Keyword(s):  
Surface Roughness ◽  
Energy Density ◽  
Process Parameters ◽  
Vickers Hardness ◽  
Powder Bed Fusion ◽  
Processing Conditions ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Fractional Density ◽  
Experimental Variation

Laser powder bed fusion (LPBF) can fabricate products with tailored mechanical and surface properties. In fact, surface texture, roughness, pore size, the resulting fractional density, and microhardness highly depend on the processing conditions, which are very difficult to deal with. Therefore, this paper aims at investigating the relevance of the volumetric energy density (VED) that is a concise index of some governing factors with a potential operational use. This paper proves the fact that the observed experimental variation in the surface roughness, number and size of pores, the fractional density, and Vickers hardness can be explained in terms of VED that can help the investigator in dealing with several process parameters at once.

scholarly journals Optimizing Laser Powder Bed Fusion Parameters for IN-738LC by Response Surface Method

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4879
Author(s):  
Mireia Vilanova ◽  
Rubén Escribano-García ◽  
Teresa Guraya ◽  
Maria San Sebastian
Keyword(s):  
Response Surface ◽  
Response Surface Method ◽  
Process Parameters ◽  
Crack Density ◽  
Processing Parameters ◽  
Optimum Process ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Surface Method

A method to find the optimum process parameters for manufacturing nickel-based superalloy Inconel 738LC by laser powder bed fusion (LPBF) technology is presented. This material is known to form cracks during its processing by LPBF technology; thus, process parameters have to be optimized to get a high quality product. In this work, the objective of the optimization was to obtain samples with fewer pores and cracks. A design of experiments (DoE) technique was implemented to define the reduced set of samples. Each sample was manufactured by LPBF with a specific combination of laser power, laser scan speed, hatch distance and scan strategy parameters. Using the porosity and crack density results obtained from the DoE samples, quadratic models were fitted, which allowed identifying the optimal working point by applying the response surface method (RSM). Finally, five samples with the predicted optimal processing parameters were fabricated. The examination of these samples showed that it was possible to manufacture IN738LC samples free of cracks and with a porosity percentage below 0.1%. Therefore, it was demonstrated that RSM is suitable for obtaining optimum process parameters for IN738LC alloy manufacturing by LPBF technology.

Multi-Objective Build Orientation Optimization for Powder Bed Fusion by Laser

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Salah Eddine Brika ◽  
Yaoyao Fiona Zhao ◽  
Mathieu Brochu ◽  
Justin Mezzetta
Keyword(s):  
Mechanical Properties ◽  
Surface Roughness ◽  
Integrated Approach ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
Build Orientation ◽  
Multi Objective ◽  
Build Time ◽  
Process Factors ◽  
Experimental Data Analysis

This paper proposes an integrated approach to determine optimal build orientation for powder bed fusion by laser (PBF-L), by simultaneously optimizing mechanical properties, surface roughness, the amount of support structure (SUPP), and build time and cost. Experimental data analysis has been used to establish the objective functions for different mechanical properties and surface roughness. Geometry analysis of the part has been used to estimate the needed SUPP and thus evaluate the build time and cost. Normalized weights are assigned to different objectives depending on their relative importance allowing solving the multi-objective optimization problem using a genetic optimization algorithm. A study case is presented to demonstrate the capabilities of the developed system. The major achievements of this work are the consideration of multiple objectives and the establishment of objective function considering different load direction and heat treatments. A user-friendly graphical user interface was developed allowing to control different optimization process factors and providing different visualization and evaluation tools.

Camera signal dependencies within coaxial melt pool monitoring in laser powder bed fusion

2020 ◽  
Vol 26 (1) ◽  
pp. 100-106 ◽  
Author(s):  
Tobias Kolb ◽  
Reza Elahi ◽  
Jan Seeger ◽  
Mathews Soris ◽  
Christian Scheitler ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Layer Thickness ◽  
Powder Layer ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Content Type ◽  
Powder Bed ◽  
Sensory Signals ◽  
Melt Pool ◽  
Research Activities

Purpose The purpose of this paper is to analyse the signal dependency of the camera-based coaxial monitoring system QMMeltpool 3D (Concept Laser GmbH, Lichtenfels, Germany) for laser powder bed fusion (LPBF) under the variation of process parameters, position, direction and layer thickness to determine the capability of the system. Because such and similar monitoring systems are designed and presented for quality assurance in series production, it is important to present the dominant signal influences and limitations. Design/methodology/approach Hardware of the commercially available coaxial monitoring QMMeltpool 3D is used to investigate the thermal emission of the interaction zone during LPBF. The raw images of the camera are analysed by means of image processing to bypass the software of QMMeltpool 3D and to gain a high level of signal understanding. Laser power, scan speed, laser spot diameter and powder layer thickness were varied for single-melt tracks to determine the influence of a parameter variation on the measured sensory signals. The effects of the scan direction and position were also analysed in detail. The influence of surface roughness on the detected sensory signals was simulated by a machined substrate plate. Findings Parameter variations are confirmed to be detectable. Because of strong directional and positional dependencies of the melt-pool monitoring signal a calibration algorithm is necessary. A decreasing signal is detected for increasing layer thickness. Surface roughness is identified as a dominating factor with major influence on the melt-pool monitoring signal exceeding other process flaws. Research limitations/implications This work was performed with the hardware of a commercially available QMMeltpool 3D system of an LPBF machine M2 of the company Concept Laser GmbH. The results are relevant for all melt-pool monitoring research activities connected to LPBF, as well as for end users and serial production. Originality/value Surface roughness has not yet been revealed as being one of the most important origins for signal deviations in coaxial melt-pool monitoring. To the best of the authors’ knowledge, the direct comparison of influences because of parameters and environment has not been published to this extent. The detection, evaluation and remelting of surface roughness constitute a plausible workflow for closed-loop control in LPBF.

Realistic design of laser powder bed fusion channels

2020 ◽  
Vol 26 (10) ◽  
pp. 1827-1836
Author(s):  
Christopher Gottlieb Klingaa ◽  
Sankhya Mohanty ◽  
Jesper Henri Hattel
Keyword(s):  
Surface Roughness ◽  
Prediction Models ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Channel Design ◽  
Conformal Cooling ◽  
Content Type ◽  
Powder Bed ◽  
Cooling Channels ◽  
Conformal Cooling Channels

Purpose Conformal cooling channels in additively manufactured molds are superior over conventional channels in terms of cooling control, part warpage and lead time. The heat transfer ability of cooling channels is determined by their geometry and surface roughness. Laser powder bed fusion manufactured channels have an inherent process-induced dross formation that may significantly alter the actual shape of nominal channels. Therefore, it is crucial to be able to predict the expected surface roughness and changes in the geometry of metal additively manufactured conformal cooling channels. The purpose of this paper is to present a new methodology for predicting the realistic design of laser powder bed fusion channels. Design/methodology/approach This study proposes a methodology for making nominal channel design more realistic by the implementation of roughness prediction models. The models are used for altering the nominal shape of a channel to its predicted shape by point cloud analysis and manipulation. Findings A straight channel is investigated as a simple case study and validated against X-ray computed tomography measurements. The modified channel geometry is reconstructed and meshed, resulting in a predicted, more realistic version of the nominal geometry. The methodology is successfully tested on a torus shape and a simple conformal cooling channel design. Finally, the methodology is validated through a cooling test experiment and comparison with simulations. Practical implications Accurate prediction of channel surface roughness and geometry would lead toward more accurate modeling of cooling performance. Originality/value A robust start to finish method for realistic geometrical prediction of metal additive manufacturing cooling channels has yet to be proposed. The current study seeks to fill the gap.

scholarly journals Position-dependent mechanical characterization of the PBF-EB-manufactured Ti6Al4V alloy

2021 ◽  
Author(s):  
Daniel Kotzem ◽  
Alexandra Höffgen ◽  
Rajevan Raveendran ◽  
Felix Stern ◽  
Kerstin Möhring ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Material Properties ◽  
Mechanical Characterization ◽  
Industrial Applications ◽  
Fatigue Tests ◽  
Ti6al4v Alloy ◽  
Effective Diameter ◽  
Powder Bed Fusion ◽  
Powder Bed

AbstractBy means of additive manufacturing, the production of components with nearly unlimited geometrical design complexity is feasible. Especially, powder bed fusion techniques such as electron beam powder bed fusion (PBF-EB) are currently focused. However, equal material properties are mandatory to be able to transfer this technique to a wide scope of industrial applications. Within the scope of this work, the mechanical properties of the PBF-EB-manufactured Ti6Al4V alloy are investigated as a function of the position on the building platform. It can be stated that as-built surface roughness changes within building platform whereby highest surface roughness detected by computed tomography (Ra = 46.0 ± 5.3 µm) was found for specimens located in the front of the building platform. In contrast, no significant differences in relative density could be determined and specimens can be assumed as nearly fully dense (> 99.9%). Furthermore, all specimens are affected by an undersized effective diameter compared to the CAD data. Fatigue tests revealed that specimens in the front of the building platform show slightly lower performance at higher stress amplitudes as compared to specimens in the back of the building platform. However, process-induced notch-like defects based on the surface roughness were found to be the preferred location for early crack initiation.

scholarly journals Characterization of additively manufactured AlSilOMg cubes with different porosities

2021 ◽  
Vol 121 (4) ◽  
Author(s):  
C. Taute ◽  
H. Möller ◽  
A. du Plessis ◽  
M. Tshibalanganda ◽  
M. Leary
Keyword(s):  
Surface Roughness ◽  
Additive Manufacturing ◽  
Structural Integrity ◽  
Lead Times ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Sample Characteristics

SYNOPSIS Additive manufacturing can be used to produce complex and custom geometries, consolidating different parts into one, which in turn reduces the required number of assemblies and allows distributed manufacturing with short lead times. Defects, such as porosity and surface roughness, associated with parts manufactured by laser powder bed fusion, can severely limit industrial application. The effect these defects have on corrosion and hence long-term structural integrity must also be taken into consideration. The aim of this paper is to report on the characterization of porosity in samples produced by laser powder bed fusion, with the differences in porosity induced by changes in the process parameters. The alloy used in this investigation is AlSi10Mg, which is widely used in the aerospace and automotive industries. The sample characteristics, obtained by X-ray tomography, are reported. The design and production of additively manufactured parts can be improved when these defects are better understood. Keywords: additive manufacturing, L-PBF, AlSi10Mg, porosity, surface roughness, density.

Effect Ultrasonic Nanocrystal Surface Modification (UNSM) Treatment on Fatigue Strength of Additive Manufactured UNS S31603

2020 ◽  
Author(s):  
Young Sik Pyun ◽  
Ruslan Karimbaev ◽  
Seimi Choi ◽  
Jun Suek Ro ◽  
Choong Ho Sanseong ◽  
...  
Keyword(s):  
Surface Modification ◽  
Additive Manufacturing ◽  
Fatigue Strength ◽  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Complex Geometry ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
Wide Range

Abstract Additive Manufacturing (AM) which is also known as metal 3D printing technique is one of the promising manufacturing processes due to the capability to process a complex geometry component. This is implemented in wide range of applications in various industries such as automotive, aerospace, power plants, etc. The aging nuclear power plant components and the obsolescence of those components has become a concern in this industry, and AM has come as an alternative solution for this matter. The Board on Pressure and Technology Codes and Standards (BPTCS) and Board on Nuclear Codes and Standards (BNCS) Special Committees started to study the application of Powder Bed Fusion (PBF) technique for pressure retaining equipment made from UNS S31603. Also, later Korean International Working Group (KIWG) was also started a Task Group on Additive Manufacturing for Valves which focusing on Powder Bed Fusion (PBF) and Direct Energy Disposition (DED) process for pressure-retaining valve manufacturing especially for nuclear power plant application with the same material. However, the poor mechanical properties and performance, especially fatigue strength of AM materials become a concern due to the defects and flaws as the results of layering and multiple interfaces and welding related discontinuities. In this study, the fatigue strength of PBF and DED manufactured and Ultrasonic Nanocrystal Surface Modification (UNSM) treated UNS S31603 austenitic stainless steel was investigated.

Magnetorheological finishing of copper cylindrical roller for its improved performance in printing machine

2020 ◽  
pp. 095440892094523
Author(s):  
Manpreet Singh ◽  
Anant Kumar Singh
Keyword(s):  
Surface Roughness ◽  
Surface Hardness ◽  
Ground Surface ◽  
Surface Characteristics ◽  
Fluid Composition ◽  
Finishing Process ◽  
Finished Surface ◽  
Measuring Machine ◽  
Mr Polishing Fluid ◽  
Cylindrical Roller

The copper cylindrical roller plays an important role in the printing operation. The copper roller requires fine and uniform finishing to uniformly distribute the colours and ingot material. Fine and uniform finishing of copper cylindrical rollers get difficulty using the traditional finishing processes due to their ductility and low hardness. Therefore, to achieve this fine finishing requirement, the rotary rectangular tool core-based magnetorheological (MR) finishing process is employed. Initially, the suitable MR polishing fluid composition is selected for the effective fine finishing of the surface of the copper cylindrical rollers. Furthermore, the central composite design is used to optimize the MR finishing process parameters. The surface roughness profiles, surface texture, and reflection tests are performed on the initial ground surface and the MR finished surface of the copper roller. The surface roughness value gets reduced from 190 nm to 25 nm after 4 hrs MR finishing with the optimum parametric conditions over the copper cylindrical roller surface having a dimension of 120 mm in length and 25 mm in diameter. The present MR finishing process found effective to significantly reduce the surface roughness value and enhance the surface characteristics of the copper cylindrical rollers. The geometrical dimensions in terms of circularity and straightness are also checked on the initial ground surface and finished surface of the copper cylindrical roller using the coordinate measuring machine and waviness test. The enhancement in surface characteristics, dimensional accuracy, and surface hardness after the present MR finishing process is found to be beneficial for improving the functional performance of the copper cylindrical rollers in the printing processing machine.

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