The effect of support structures on maraging steel MS1 parts fabricated by selective laser melting at different building angles

2020 ◽  
Vol 26 (9) ◽  
pp. 1465-1476
Author(s):  
Qiqiang Cao ◽  
Jiong Zhang ◽  
Shuai Chang ◽  
Jerry Ying Hsi Fuh ◽  
Hao Wang
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Maraging Steel ◽  
Selective Laser Melting ◽  
Vickers Microhardness ◽  
Support Structures ◽  
Laser Melting ◽  
Supporting Surface ◽  
Content Type ◽  
Printing Quality

Purpose This study aims to further the understanding of support structures and the likely impacts on maraging steel MS1 parts fabricated by selective laser melting (SLM) at 45°, 60° and 75° building angles. Design/methodology/approach Two groups of samples, one group with support structures and the other group without support structures, were designed with the same specifications and printed under the same conditions by SLM at 45°, 60° and 75° building angles. Differences in dimensional accuracy, surface roughness, Vickers microhardness, residual stress and microstructure were compared between groups. Findings The results showed that with support structures, more accurate dimension and slightly higher Vickers microhardness could be obtained. Larger compressive stress dominated and was more uniformly distributed on the supporting surface. Without support structures, the dimension became more precise as the building angle increased and alternating compressive and tensile stress was unevenly distributed on the supporting surface. In addition, the surface roughness of the outer surface decreased with the increase of the built angle, regardless of the support structures. Furthermore, whether the building angle was 45°, 60° or 75°, the observed microstructures revealed that the support structures altered the orientation of the molten pool and the direction of grain growth. Originality/value This paper studies the influence of support structures on the workpieces printed at different building angles. Support structures affect the residual stress distribution, heat dissipation rate and microstructure of the parts, and thus affecting the printing quality. Therefore, it is necessary to balance the support strategy and printing quality to better apply or design the support structures in SLM.

Deformations and stresses prediction of cantilever structures fabricated by selective laser melting process

2021 ◽  
Vol 27 (3) ◽  
pp. 453-464
Author(s):  
Lan Li ◽  
Tan Pan ◽  
Xinchang Zhang ◽  
Yitao Chen ◽  
Wenyuan Cui ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Selective Laser Melting ◽  
Thermal Distortion ◽  
Cantilever Beams ◽  
Support Structures ◽  
Laser Melting ◽  
Content Type ◽  
Two Samples ◽  
Validation Experiments

Purpose During the powder bed fusion process, thermal distortion is one big problem owing to the thermal stress caused by the high cooling rate and temperature gradient. For the purpose of avoiding distortion caused by internal residual stresses, support structures are used in most selective laser melting (SLM) process especially for cantilever beams because they can assist the heat dissipation. Support structures can also help to hold the work piece in its place and reduce volume of the printing materials. The mitigation of high thermal gradients during the manufacturing process helps to reduce thermal distortion and thus alleviate cracking, curling, delamination and shrinkage. Therefore, this paper aims to study the displacement and residual stress evolution of SLMed parts. Design/methodology/approach The objective of this study was to examine and compare the distortion and residual stress properties of two cantilever structures, using both numerical and experimental methods. The part-scale finite element analysis modeling technique was applied to numerically analyze the overhang distortions, using the layer-by-layer model for predicting a part scale model. The validation experiments of these two samples were built in a SLM platform. Then average displacement of the four tip corners and residual stress on top surface of cantilever beams were tested to validate the model. Findings The validation experiments results of average displacement of the four tip corners and residual stress on top surface of cantilever beams were tested to validate the model. It was found that they matched well with each other. From displacement and residual stress standpoint, by introducing two different support structure, two samples with the same cantilever beam can be successfully printed. In terms of reducing wasted support materials, print time and high surface quality, sample with less support will need less post-processing and waste energy. Originality/value Numerical modeling in this work can be a very useful tool to parametrically study the feasibility of support structures of SLM parts in terms of residual stresses and deformations. It has the capability for fast prediction in the SLMed parts.

The effect of hatch angle rotation on parts manufactured using selective laser melting

2019 ◽  
Vol 25 (2) ◽  
pp. 289-298 ◽  
Author(s):  
Joseph Henry Robinson ◽  
Ian Robert Thomas Ashton ◽  
Eric Jones ◽  
Peter Fox ◽  
Chris Sutcliffe
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Selective Laser Melting ◽  
Pure Titanium ◽  
Commercially Pure Titanium ◽  
Laser Melting ◽  
Content Type ◽  
Axial Tensile ◽  
Effects Of Rotation ◽  
Scanning Strategies

Purpose This paper aims to present an investigation into the variation of scan vector hatch rotation strategies in selective laser melting (SLM), focussing on how it effects density, surface roughness, tensile strength and residual stress. Design/methodology/approach First the optimum angle of hatch vector rotation is proposed by analysing the effect of different increment angles on distribution of scan vectors. Sectioning methods are then used to determine the effect that the chosen strategies have on the density of the parts. The top surface roughness was analysed using optical metrology, and the tensile properties were determined using uni-axial tensile testing. Finally, a novel multi-support deflection geometry was used to quantify the effects of rotation angles on residual stress. Findings The results of this research showed that the hatch rotation angle had little effect on the density, top surface roughness and strength of the parts. The greatest residual stress deflection was measured parallel to unidirectional scan vectors. The use of hatch rotations other than alternating 90° showed little benefit in lowering the magnitude of residual stresses. However, the use of rotation angles with a good suitability measure distributes stresses in all directions more evenly for certain part geometries. Research limitations/implications All samples produced in this work were made from commercially pure titanium, therefore care must be taken when applying these results to other materials. Originality/value This paper serves to increase the understanding of SLM scanning strategies and their effect on the properties of the material.

Residual stress measurement techniques for Ti6Al4V parts fabricated using selective laser melting: state of the art review

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ruben B.O. Acevedo ◽  
Klaudia Kantarowska ◽  
Edson Costa Santos ◽  
Marcio C. Fredel
Keyword(s):  
Residual Stress ◽  
Selective Laser Melting ◽  
Stress Measurement ◽  
State Of The Art ◽  
Measurement Techniques ◽  
Residual Stress Measurement ◽  
Hole Drilling ◽  
X Ray Diffraction ◽  
Laser Melting ◽  
Content Type

Purpose This paper aims to generate a review of available techniques to measure Residual Stress (RS) in Ti6Al4V components made by Ti6Al4V. Design/methodology/approach State of the art; literature review in the field of Residual Stress measurement of Ti6Al4V parts made by selective laser melting (SLM). Findings Different Residual Stress measurement techniques were detailed, regarding its concept, advantages and limitations. Regarding all researched references, hole drilling (semi destructive) and X-ray diffraction (nondestructive) were the most cited techniques for Residual Stress measurement of Ti6Al4V parts made by SLM. Originality/value An extensive analysis of RS measurement techniques for Ti6Al4V parts made by SLM.

Design of internal branch support structures for selective laser melting

2018 ◽  
Vol 24 (4) ◽  
pp. 764-773 ◽  
Author(s):  
Zhixiong Zhang ◽  
Chunbing Wu ◽  
Tang Li ◽  
Keshan Liang ◽  
Yujun Cao
Keyword(s):  
Mechanical Properties ◽  
Selective Laser Melting ◽  
Production Efficiency ◽  
Testing Machine ◽  
Design Parameters ◽  
Support Structures ◽  
Laser Melting ◽  
Internal Branch ◽  
Content Type ◽  
Branch Support

Purpose Selective laser melting (SLM) enables the fabrication of lightweight and complex metallic structures. Support structures are required in the SLM process to successfully produce parts. Supports are typically lattice structures, which cost much time and material to manufacture. Besides, the manufacturability of these supports is undesirable, which may impact the quality of parts or even fail the process. The purpose of this paper is to investigate the efficiency and mechanical properties of advanced internal branch support structures for SLM. Design/methodology/approach The theoretic weight of a branch support and a lattice support of the same plane were calculated and compared. A group of standard candidates of branch support structures were manufactured by SLM. The weight and scanning time of specimens with different design parameters were compared. Then, these samples were tested using an MTS Insight 30 compression testing machine to study the influence of different support parameters on mechanical strength of the support structures. Findings The results show that branch type supports can save material, energy and time used needed for their construction. The yield strength of the branch increases with the branch diameter and inclined branch angle in general. Furthermore, branch supports have a higher strength than traditional lattice supports. Originality/value To the best of the authors’ knowledge, this is the first work investigating production efficiency and mechanical properties of branch support structures for SLM. The findings in this work are valuable for development of advanced optimal designs of efficient support structures for SLM process.

Investigation of selective laser melting process for Cu-5Sn alloy on surface roughness, microstructure and mechanical property

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Peng Yang ◽  
Dingyong He ◽  
Zengjie Wang ◽  
Zhen Tan ◽  
Hanguang Fu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Surface Roughness ◽  
Selective Laser Melting ◽  
High Strength ◽  
Melting Process ◽  
Scanning Speed ◽  
Laser Melting ◽  
Forming Process ◽  
Content Type

Purpose In this research, the highly dense bulk Cu-5Sn alloy specimens were fabricated using selective laser melting (SLM). This study aims to establish the relationship between laser power (LP), scanning speed (SS) and hatch space (HS) with surface roughness (Ra) and density. To obtain Cu-5Sn alloy formed parts with high strength and low surface roughness. The microstructure and mechanical properties of SLMed Cu-5Sn were investigated. Design/methodology/approach The relative density (RD) was optimized using the response surface method (RSM) and analysis of variance. First, the Ra of SLMed formed specimens was studied to optimize the forming process parameters with a good surface. Then, the dense specimens were studied by ANOVA and the RSM to obtain dense specimens for mechanical property analysis. Findings Dense specimens were obtained by RSM and ANOVA. The tensile properties were compared with the casted specimens. The yield and ultimate strengths increased from 71 and 131 MPa for the cast specimens to 334 and 489 MPa for the SLMed specimens, respectively. The ductility increased significantly from 11% to 23%, due to the refined microstructure of the SLMed specimens, as well as the formation of many twin crystals. Originality/value The Ra, RD and mechanical properties of SLM specimens Cu-5Sn were systematically studied, and the influencing factors were analyzed together. This study provides a theoretical and practical example to improve the surface quality and RD.

scholarly journals Optimising the process parameters of selective laser melting for the fabrication of Ti6Al4V alloy

2018 ◽  
Vol 24 (1) ◽  
pp. 150-159 ◽  
Author(s):  
Zhonghua Li ◽  
Ibrahim Kucukkoc ◽  
David Z. Zhang ◽  
Fei Liu
Keyword(s):  
Surface Roughness ◽  
Surface Quality ◽  
Selective Laser Melting ◽  
Process Parameters ◽  
High Surface ◽  
Optimum Process ◽  
Laser Melting ◽  
Vertical Side ◽  
Content Type

Purpose Surface roughness is an important evaluation index for industrial components, and it strongly depends on the processing parameters for selective laser molten Ti6Al4V parts. This paper aims to obtain an optimum selective laser melting (SLM) parameter set to improve the surface roughness of Ti6Al4V samples. Design/methodology/approach A response surface methodology (RSM)-based approach is proposed to improve the surface quality of selective laser molten Ti6Al4V parts and understand the relationship between the SLM process parameters and the surface roughness. The main SLM parameters (i.e. laser power, scan speed and hatch spacing) are optimized, and Ti6Al4V parts are manufactured by the SLM technology with no post processes. Findings Optimum process parameters were obtained using the RSM method to minimise the roughness of the top and vertical side surfaces. Obtained parameter sets were evaluated based on their productivity and surface quality performance. The validation tests have been performed, and the results verified the effectivity of the proposed technique. It was also shown that the top and vertical sides must be handled together to obtain better top surface quality. Practical implications The obtained optimum SLM parameter set can be used in the manufacturing of Ti6Al4V components with high surface roughness requirement. Originality/value RSM is used to analyse and determine the optimal combination of SLM parameters with the aim of improving the surface roughness quality of Ti6Al4V components, for the first time in the literature. Also, this is the first study which aims to simultaneously optimise the surface quality of top and vertical sides of titanium alloys.

Experimental and statistical analysis on process parameters and surface roughness relationship for selective laser melting of Hastelloy X

2019 ◽  
Vol 25 (7) ◽  
pp. 1309-1318 ◽  
Author(s):  
Yang Tian ◽  
Dacian Tomus ◽  
Aijun Huang ◽  
Xinhua Wu
Keyword(s):  
Surface Roughness ◽  
Statistical Analysis ◽  
Layer Thickness ◽  
Selective Laser Melting ◽  
Skin Surface ◽  
Valuable Insight ◽  
Laser Melting ◽  
Hastelloy X ◽  
Content Type ◽  
Inclined Angle

Purpose Selective laser melting (SLM) process is an additive manufacturing method that uses computer-aided design to fabricate complex components layer-by-layer. Surface roughness is one of the primary drawbacks of SLM process; hence, the purpose of this paper is to present a parametric study and optimisation of fundamental parameters, including scan power, speed, inclined angle and layer thickness on surface roughness during selective laser melting of Hastelloy X. Design/methodology/approach Parametric significance on surface finish was analysed using analysis of variance and response surface methodology. General agreement between predicted and measured values was achieved. Surface characteristics of both up-skin and down-skin with various angles were covered within the investigated range. Findings Both experimental and statistical analysis showed that surface roughness of up-skin was primarily influenced by scan power, inclined angle and layer thickness while down-skin was more affected by the former two factors. Melt pool shape and staircase size were found to determine the up-skin surface, whereas attached particles were responsible for down-skin surface roughness. Originality/value As per our understanding, this manuscript provides valuable insight into the surface quality problem of SLM, which is a very critical issue for up-grading the process for manufacturing real components. This manuscript helps promote improved knowledge and understanding of the attributes and capabilities of this rapidly evolving 3D printing technology. Moreover, it establishes usable processing window and helps obtain optimal conditions, thus offering useful information to professionals working in this field. By combining experiments with statistical analysis, both practice and theory relevant to SLM process are further developed.

Effect of the strut size and tilt angle on the geometric characteristics of selective laser melting AlSi10Mg

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Baopeng Zhang ◽  
Xuesong Han ◽  
Changpeng Chen ◽  
Wenqi Zhang ◽  
Hailong Liao ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Compressive Strength ◽  
Selective Laser Melting ◽  
Process Parameters ◽  
Tilt Angle ◽  
Lattice Structure ◽  
Dimensional Accuracy ◽  
Optimal Process ◽  
Laser Melting ◽  
Content Type

Purpose The purpose of this study is to investigate the effect of the strut size and tilt angle on the densification behavior, surface roughness and dimensional accuracy of the selective laser melting AlSi10Mg lattice structure was investigated in this study. In this study, the characteristics such as the density, up-skin and down-skin roughness and dimensional accuracy of selective laser melting forming technology manufacturing (SLMed) AlSi10Mg cellular lattice structure were carried. This work reveals the effect of the strut size and tilt angle on the geometric characteristics of SLMed AlSi10Mg and is benefit for controlling the forming performance of the SLMed cellular lattice structure. Design/methodology/approach Based on AlSi10Mg powder, the influence of the tilt angle changed from 10° to 45° with an increment of 5° were investigated, the influence of the strut size was varied from 0.4 mm to 1.2 mm with an increment of 0.2 mm were investigated. The characteristics such as the density, up-skin and down-skin roughness, dimensional accuracy and mechanical properties of SLM-ed AlSi10Mg cellular lattice structure was carried. Findings Greater than 99% relative density can be achieved for different strut size when optimal process parameters are used. In the optimized process interval, the struts with a tilt angle of 10° can still be formed well, which is higher than the design limit of the inclined angle given in the related literature. The tilt angle has a significant effect on the surface roughness of the strut. The microhardness reached to 157 ± 3 HV, and the maximum compressive strength was 58.86 MPa, with the optimal process parameters. Originality/value In this study, the characteristics such as the density, up-skin and down-skin roughness and dimensional accuracy of SLMed AlSi10Mg cellular lattice structure were carried. With the optimal geometric parameters, the authors tested microhardness and compressive strength of the cellular lattice structure. The results of this study provide theoretical and experimental basis for the realization of high-quality manufacturing and optimization design of aluminum alloy cellular lattice structure, which will meet more diversified industrial needs.

scholarly journals Effect of Process Parameters on Residual Stresses, Distortions, and Porosity in Selective Laser Melting of Maraging Steel 300

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1042 ◽  
Author(s):  
Mugwagwa ◽  
Yadroitsev ◽  
Matope
Keyword(s):  
Residual Stress ◽  
Additive Manufacturing ◽  
Residual Stresses ◽  
Maraging Steel ◽  
Selective Laser Melting ◽  
Input Parameter ◽  
Scanning Speed ◽  
Metal Powders ◽  
Laser Melting ◽  
Widespread Application

Selective laser melting (SLM) is one of the most well-known additive manufacturing methods available for the fabrication of functional parts from metal powders. Although SLM is now an established metal additive manufacturing technique, its widespread application in industry is still hindered by inherent phenomena, one of which is high residual stresses. Some of the effects of residual stresses – such as warping and thermal stress-related cracking – cannot be corrected by post processing. Therefore, establishing input process parameter combinations that result in the least residual stress magnitudes and related distortions and/or cracking is critical. This paper presents the influence of laser power, scanning speed, and layer thickness on residual stresses, distortions and achievable density for maraging steel 300 steel parts in order to establish the most optimum input parameter combinations. An analysis of the interdependence between process outcomes shows that high residual stress magnitudes lead to high dimensional distortions in the finished parts, whilst porous parts suffer relatively lower residual stresses and associated distortions.

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