scholarly journals Optimisation of selective laser melting parameters for the Ni-based superalloy IN-738 LC using Doehlert’s design

2017 ◽  
Vol 23 (5) ◽  
pp. 881-892 ◽  
Author(s):  
Nataliya Perevoshchikova ◽  
Jordan Rigaud ◽  
Yu Sha ◽  
Martin Heilmaier ◽  
Barrie Finnin ◽  
...  
Keyword(s):  
Image Analysis ◽  
Relative Density ◽  
Selective Laser Melting ◽  
Processing Parameters ◽  
Powder Alloy ◽  
Operating Parameters ◽  
Laser Melting ◽  
Doehlert Design ◽  
Feasible Set ◽  
Content Type

Purpose The Ni-based superalloy IN-738 LC is known to be susceptible to porosity and different types of cracking during the build-up process and, thus, challenging to manufacture using selective laser melting (SLM). Determining a feasible set of operating parameters for SLM of nickel-based superalloys involves new approach to experimental design based on the Doehlert method that assists in determining an optimal (feasible) set of operating parameters for SLM of IN-738 LC powder alloy. Design/methodology/approach The SLM parameters are evaluated in terms of their effectiveness in obtaining the microstructure with a porosity content of <0.5 per cent and without micro-cracking. The experimental approach is exemplified with the Doehlert matrix response variable, relative density, by comparing Archimedes method with microstructural assessments of pores and cracks from image analysis. The effect of heat treatment (HT) and hot isostatic pressing (HIP) on the microstructure of the SLMed IN-738 LC powder alloy has been examined and the consequential tensile response characterised. Findings By using optimised process parameters (low heat input, medium scanning speed and small hatching distance) which provides medium energy density, samples of IN-738 LC with a macroscopic porosity <0.5 per cent and free of micro-cracks can be manufactured by SLM. The results indicate that HIP of SLMed material did not lead to a noticeable effect on mechanical properties compared to HT of SLMed material suggesting that the level of both porosity and crack density might be already below the detection limit for the mere heat-treated material. Originality/value SLM processing parameters (power, scan speed, hatching distance) for IN-738 LC were successfully optimised after only 14 experiments using Doehlert design. Two independent methods, Archimedes method and image analysis, were used in this study to assess relative density of SLM-produced samples with sets of processing parameters showing coherency in prediction with predicted response by Doehlert design.

scholarly journals The Effects of Selective Laser Melting Process Parameters on Relative Density of the AlSi10Mg Parts and Suitable Procedures of the Archimedes Method

2019 ◽  
Vol 9 (3) ◽  
pp. 583 ◽  
Author(s):  
Shigang Bai ◽  
Nataliya Perevoshchikova ◽  
Yu Sha ◽  
Xinhua Wu
Keyword(s):  
Image Analysis ◽  
Relative Density ◽  
Selective Laser Melting ◽  
Laser Power ◽  
Regression Models ◽  
Processing Parameters ◽  
Response Surfaces ◽  
Laser Melting ◽  
High Relative Density ◽  
Scan Speed

In view of the importance of accurately measuring the relative density of a selective laser melted (SLMed) part for optimizing the selective laser melting (SLM) processing parameters, suitable procedures of the Archimedes method considering the surface-connected cavities were proposed by comparing the results using the Archimedes method with image analysis. The effects of the SLM processing parameters on the relative density of AlSi10Mg were investigated using the proposed procedures of the Archimedes methods and image analysis. Fourteen SLMed samples were produced by different SLM processing parameters according to Doehlert Matrix. The regression models correlating relative density and three SLM processing parameters (laser power, scan speed, and hatching distance) were built and the optimum parameter combination to get a high relative density was obtained. By plotting the response surfaces and contours of the regression models, it was found that the relative densities are both higher at the combination of the higher scan speed, higher power, and lower hatching distance and at the combination of a lower scan speed, a moderate laser power, and a optional hatching distance. It was also found that the parameter of hatching distance is the crucial parameter to get a high relative density and to get high mechanical property.

scholarly journals Collaborative Optimization on Density and Surface Roughness of 316L Stainless Steel in Selective Laser Melting

2020 ◽  
Author(s):  
Yong Deng ◽  
Zhongfa Mao ◽  
Nan Yang ◽  
Xiaodong Niu ◽  
Xiangdong Lu
Keyword(s):  
Surface Roughness ◽  
Stainless Steel ◽  
Relative Density ◽  
Selective Laser Melting ◽  
Laser Power ◽  
316L Stainless Steel ◽  
Scanning Speed ◽  
Processing Parameters ◽  
Collaborative Optimization ◽  
Laser Melting

Although the concept of additive manufacturing has been proposed for several decades, momentum of selective laser melting (SLM) is finally starting to build. In SLM, density and surface roughness, as the important quality indexes of SLMed parts, are dependent on the processing parameters. However, there are few studies on their collaborative optimization in SLM to obtain high relative density and low surface roughness simultaneously in the previous literature. In this work, the response surface method was adopted to study the influences of different processing parameters (laser power, scanning speed and hatch space) on density and surface roughness of 316L stainless steel parts fabricated by SLM. The statistical relationship model between processing parameters and manufacturing quality is established. A multi-objective collaborative optimization strategy considering both density and surface roughness is proposed. The experimental results show that the main effects of processing parameters on the density and surface roughness are similar. It is noted that the effects of the laser power and scanning speed on the above objective quality show highly significant, while hatch space behaves an insignificant impact. Based on the above optimization, 316L stainless steel parts with excellent surface roughness and relative density can be obtained by SLM with optimized processing parameters.

Effect of processing parameters on forming defects during selective laser melting of AlSi10Mg powder

2020 ◽  
Vol 26 (5) ◽  
pp. 871-879 ◽  
Author(s):  
Haihua Wu ◽  
Junfeng Li ◽  
Zhengying Wei ◽  
Pei Wei
Keyword(s):  
Selective Laser Melting ◽  
Laser Power ◽  
Scanning Speed ◽  
Processing Parameters ◽  
Argon Pressure ◽  
Powder Layer ◽  
Laser Melting ◽  
Content Type ◽  
Scan Speed ◽  
Forming Defects

Purpose To fabricate a selective laser melting (SLM)-processed AlSi10Mg part with almost full density and free of any apparent pores, this study aims to investigate the effect of ambient argon pressure and laser scanning speed on the particles splash during the AlSi10Mg powder bed laser melting. Design/methodology/approach Based on the discrete element method (DEM), a 3D model of random distribution of powder particles was established, and the 3D free surface of SLM forming process was dynamically tracked by the volume of fluid, where a Gaussian laser beam acts as the energy source melting the powder bed. Through the numerical simulation and process experimental research, the effect of the applied laser power and scanning speed on the operating laser melting temperature was studied. Findings The process stability has a fundamental role in the porosity formation, which is process-dependent. The effect of the processing conditions on the process stability and the resultant forming defects were clarified. Research limitations/implications The results shows that the pores were the main defects present in the SLM-processed AlSi10Mg sample, which decreases the densification level of the sample. Practical implications The optimal processing parameters (argon pressure of 1,000 Pa, laser power of 180 W, scan speed of 1,000 mm/s, powder layer thickness of 35 µm and hatch spacing of 50 µm ) applied during laser melting can improve the quality of selective laser melting of AlSi10Mg, Social implications It can provide a technological support for 3D printing. Originality/value Based on the analysis of the pore and balling formation mechanisms, the optimal processing parameters have been obtained, which were argon pressure of 1,000 Pa, laser power of 180 W, scan speed of 1,000 mm/s, powder layer thickness of 35 µm and hatch spacing of 50 µm. Then, a near-fully dense sample free of any apparent pores on the cross-sectional microstructure was produced by SLM, wherein the relative density of the as-built samples is larger than 97.5%.

The influence of a process interruption on tensile properties of AlSi10Mg samples produced by selective laser melting

2019 ◽  
Vol 25 (8) ◽  
pp. 1442-1452 ◽  
Author(s):  
Vincent Hammond ◽  
Michael Schuch ◽  
Matthias Bleckmann
Keyword(s):  
Tensile Properties ◽  
Selective Laser Melting ◽  
Continuous Process ◽  
Processing Parameters ◽  
Laser Melting ◽  
Content Type ◽  
Random Failure ◽  
Pressure Die Casting ◽  
Suitable Technique ◽  
Cylindrical Samples

Purpose The purpose of this paper is to investigate the influence of a process interruption on the tensile properties of AlSi10Mg samples produced by selective laser melting (SLM). Design/methodology/approach Using identical processing parameters, cylindrical samples were produced in either a continuous or interrupted SLM build operation. The tensile properties and microstructure of the samples were determined as a function of process type as well as orientation. Findings All samples produced in this paper displayed superior tensile properties to those produced in high pressure die casting. In general, the samples produced in the continuous build process had higher strengths and microhardness than those produced in the interrupted process. However, while most samples displayed random failure locations, the vertical samples produced in the interrupted build process showed a strong tendency for localized failure in the vicinity of the stoppage plane. Originality/value This paper demonstrated that samples produced in an interrupted build process tend to have poorer mechanical properties than those produced in a continuous process. Together, these observations highlight the importance of a suitable technique for restarting and completing an interrupted build process to ensure the production of high quality components.

Selective laser melting (SLM) of pure gold for manufacturing dental crowns

2014 ◽  
Vol 20 (6) ◽  
pp. 471-479 ◽  
Author(s):  
Mushtaq Khan ◽  
Phill Dickens
Keyword(s):  
Mechanical Properties ◽  
Layer Thickness ◽  
Surface Quality ◽  
Selective Laser Melting ◽  
Processing Parameters ◽  
Pure Gold ◽  
Laser Melting ◽  
Content Type ◽  
Dental Crowns ◽  
Suitable Processing

Purpose – This paper aims to present the application aspect of the work to manufacturing premolar and molar dental crowns by selective laser melting (SLM) of pure gold. Over the years different metals have been processed using laser-based Additive Manufacturing processes, but very little work has been published on the SLM of gold (Au). Previously published work presented suitable processing parameters for SLM of pure gold. Design/methodology/approach – Suitable processing parameters were used to manufacture premolar and molar dental crowns using SLM system. Different layer thickness was used to analyse the effect on surface quality of crowns. Mechanical properties are checked using nanoindentation and micro Computerized Tomography scanning. Findings – Dental crowns were successfully manufacturing using new build platform and suitable processing parameters. Parts were manufacturing using minimal supports which prevented parts from damaging during removal. A bed temperature of 100°C was found suitable for reducing warpage in the layers. Layer thickness of 50μm was found to have better surface quality and structural integrity as compared to 75μm. Porosity was found to be predominantly inter-layer. Small difference in mechanical properties of dental crowns is associated with the laser processing. Originality/value – This research is the first of its kind which presents dental crown manufacturing using SLM of pure gold.

Geometrical feature analysis of Co-Cr-Mo single tracks after selective laser melting processing

2015 ◽  
Vol 21 (3) ◽  
pp. 287-300 ◽  
Author(s):  
Karla Monroy ◽  
Jordi Delgado ◽  
Lidia Sereno ◽  
Joaquim Ciurana ◽  
Nicolas J Hendrichs
Keyword(s):  
Selective Laser Melting ◽  
Scanning Speed ◽  
Processing Parameters ◽  
Single Track ◽  
Cobalt Chromium ◽  
Laser Melting ◽  
Content Type ◽  
Dimensional Precision ◽  
Morphologic Characteristics ◽  
Definition Of

Purpose – Therefore, the purpose of this study is to understand the relationships between the processing parameters and the geometric form of the produced single tracks, in order to control dimensional quality in future experimentations. The quality of the deposited single track and layer is of prime importance in the selective laser melting (SLM) process, as it affects the product quality in terms of dimensional precision and product performance. Design/methodology/approach – In this paper, a vertical milling machining center equipped with an Ytterbium-fiber laser was used in the SLM experimentation to form single cobalt-chromium-molybdenum (CoCrMo) tracks. The different geometric features and the influence of the scanning parameters on these morphologic characteristics were studied statistically by means of ANOVA. Findings – Evidently, track height (h1) inaccuracy reduced in layer thicknesses between 100 and 200 μm. The re-melt depth (h2) was determined by the energy parameters, with laser power of 325-350 W and scanning speed (SS) of 66.6-83.3 mm/s being the most favorable parameters to obtain the required anchoring. Moreover, a contact angle of 117° was proposed as optimal, as it permitted an adequate overlapping region and a full densification, and, finally, an SS of 50 mm/s and a layer thickness of 250 were suggested for its development. Originality/value – The comprehension of the phenomena inherent to the process is related to the single track geometrical characteristics, which allow the definition of an optimal value for each factor for a further proposal of processing conditions that can finally derive a higher precision, wetting, density and mechanical properties.

scholarly journals Processing of metal-diamond-composites using selective laser melting

2015 ◽  
Vol 21 (2) ◽  
pp. 130-136 ◽  
Author(s):  
Adriaan Bernardus Spierings ◽  
Christian Leinenbach ◽  
Christoph Kenel ◽  
Konrad Wegener
Keyword(s):  
Selective Laser Melting ◽  
Feasibility Study ◽  
Matrix Material ◽  
Outer Part ◽  
Processing Parameters ◽  
Added Value ◽  
Laser Melting ◽  
Content Type ◽  
Diamond Particles ◽  
The Matrix

Purpose – The purpose of this paper is a feasibility study that was performed to investigate the basic processability of a diamond-containing metal matrix. Powder-bed-based additive manufacturing processes such as selective laser melting (SLM) offer a huge degree of freedom, both in terms of part design and material options. In that respect, mixtures of different powders can offer new ways for the manufacture of materials with tailored properties for special applications such as metal-based cutting or grinding tools with incorporated hard phases. Design/methodology/approach – A two-step approach was used to first investigate the basic SLM-processability of a Cu-Sn-Ti-Zr alloy, which is usually used for the active brazing of ceramics and superhard materials. After the identification of a suitable processing window, the processing parameters were then applied to a mixture of this matrix material with 10-20 volume per cent artificial, Ni-coated mono-crystalline diamonds. Findings – Even though the processing parameters were not yet optimized, stable specimens out of the matrix material could be produced. Also, diamond-containing mixtures with the matrix material resulted in stable specimens, where the diamonds survived the layer-wise build process with the successive heat input, as almost no graphitization was observed. The diamond particles are fully embedded in the Cu-Sn-Ti-Zr matrix material. The outer part of the diamonds partly dissolves in the matrix during the SLM process, forming small TiC particles and most likely a thin TiC layer around the diamond particles. Originality/value – The feasibility study approved the SLM processing capabilities of a metal-diamond composite. Although some cracking phenomena sill occur, this seems to be an interesting and promising way to create new abrasive tools with added value in terms of internal and local lubrication supply, tooling temperature control and improved tooling durability.

scholarly journals Collaborative Optimization of Density and Surface Roughness of 316L Stainless Steel in Selective Laser Melting

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1601 ◽  
Author(s):  
Yong Deng ◽  
Zhongfa Mao ◽  
Nan Yang ◽  
Xiaodong Niu ◽  
Xiangdong Lu
Keyword(s):  
Surface Roughness ◽  
Stainless Steel ◽  
Relative Density ◽  
Selective Laser Melting ◽  
Laser Power ◽  
316L Stainless Steel ◽  
Scanning Speed ◽  
Processing Parameters ◽  
Collaborative Optimization ◽  
Laser Melting

Although the concept of additive manufacturing has been proposed for several decades, momentum in the area of selective laser melting (SLM) is finally starting to build. In SLM, density and surface roughness, as the important quality indexes of SLMed parts, are dependent on the processing parameters. However, there are few studies on their collaborative optimization during SLM to obtain high relative density and low surface roughness simultaneously in the literature. In this work, the response surface method was adopted to study the influences of different processing parameters (laser power, scanning speed and hatch space) on density and surface roughness of 316L stainless steel parts fabricated by SLM. A statistical relationship model between processing parameters and manufacturing quality is established. A multi-objective collaborative optimization strategy considering both density and surface roughness is proposed. The experimental results show that the main effects of processing parameters on the density and surface roughness are similar. We observed that the laser power and scanning speed significantly affected the above objective quality, but the influence of the hatch spacing was comparatively low. Based on the above optimization, 316L stainless steel parts with excellent surface roughness and relative density can be obtained by SLM with optimized processing parameters.

scholarly journals High Bending Strength Hypereutectic Al-22Si-0.2Fe-0.1Cu-Re Alloy Fabricated by Selective Laser Melting

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 528
Author(s):  
Chunyue Yin ◽  
Zhehao Lu ◽  
Xianshun Wei ◽  
Biao Yan ◽  
Pengfei Yan
Keyword(s):  
Selective Laser Melting ◽  
Bending Strength ◽  
Primary Silicon ◽  
Processing Parameters ◽  
Powder Materials ◽  
Laser Melting ◽  
Maximum Value ◽  
Fine Microstructure ◽  
Average Size ◽  
Al Matrix

The objective of the study is to investigate the corresponding microstructure and mechanical properties, especially bending strength, of the hypereutectic Al-Si alloy processed by selective laser melting (SLM). Almost dense Al-22Si-0.2Fe-0.1Cu-Re alloy is fabricated from a novel type of powder materials with optimized processing parameters. Phase analysis of such Al-22Si-0.2Fe-0.1Cu-Re alloy shows that the solubility of Si in Al matrix increases significantly. The fine microstructure can be observed, divided into three zones: fine zones, coarse zones, and heat-affected zones (HAZs). Fine zones are directly generated from the liquid phase with the characteristic of petaloid structures and bulk Al-Si eutectic. Due to the fine microstructure induced by the rapid cooling rate of SLM, the primary silicon presents a minimum average size of ~0.5 μm in fine zones, significantly smaller than that in the conventional produced hypereutectic samples. Moreover, the maximum value of Vickers hardness reaches ~170 HV0.2, and bending strength increases to 687.70 MPa for the as-built Al-22Si-0.2Fe-0.1Cu-Re alloys parts, which is much higher than that of cast counterparts. The formation mechanism of this fine microstructure and the enhancement reasons of bending strength are also discussed.

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