Development of residual stress of parts fabricated via selective laser melting (SLM) techniques under di erent scanning strategies

The laser scanning strategy has an important influence on the surface quality, residual stress, and deformation of the molten metal (deformation behavior). A divisional scanning strategy is an effective means used to reduce the internal stress of the selective laser melting (SLM) metal part. In order to understand and optimize the divisional scanning strategy, three divisional scanning strategies and an S-shaped orthogonal scanning strategy are used to produce 316L steel parts in this study. The influence of scanning strategy on the produced parts is verified from the aspects of densification, residual stress distribution and deformation. Experiments show that the 316L steel alloy parts adopted spiral divisional scanning strategy can not only obtain the densification of 99.37%, but they also effectively improve the distribution of residual stress and control the deformation degree of the produced parts. Among them, the spiral divisional scanning sample has the smallest residual stress in plane direction, and its σx and σy stress are controlled within 204 MPa and 103 MPa. The above results show that the spiral divisional scanning is the most conducive strategy to obtain higher residual stress performance of SLM 316L steel parts.

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Determination of residual stress for Inconel 718 samples fabricated through different scanning strategies in selective laser melting

Behavior and Mechanics of Multifunctional Materials IX ◽

10.1117/12.2558342 ◽

2020 ◽

Author(s):

Vignesh Ram Kumar Rajendran ◽

Kiriti Mamidi ◽

Bharath Ravichander ◽

Behzad Farhang ◽

Amirhesam Amerinatanzi ◽

...

Keyword(s):

Residual Stress ◽

Selective Laser Melting ◽

Inconel 718 ◽

Laser Melting ◽

Scanning Strategies

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

Rapid Prototyping Journal ◽

10.1108/rpj-06-2017-0111 ◽

2019 ◽

Vol 25 (2) ◽

pp. 289-298 ◽

Cited By ~ 17

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.

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Cracking Behavior of René 104 Nickel-Based Superalloy Prepared by Selective Laser Melting Using Different Scanning Strategies

Materials ◽

10.3390/ma13092149 ◽

2020 ◽

Vol 13 (9) ◽

pp. 2149

Author(s):

Kai Peng ◽

Ranxi Duan ◽

Zuming Liu ◽

Xueqian Lv ◽

Quan Li ◽

...

Keyword(s):

Residual Stress ◽

Relative Density ◽

Selective Laser Melting ◽

Laser Melting ◽

High Quality ◽

Cracking Behavior ◽

Nickel Based Superalloy ◽

Size Number ◽

Cracking Performance ◽

Scanning Strategies

Eliminating cracks is a big challenge for the selective laser melting (SLM) process of low-weldable Nickel-based superalloy. In this work, three scanning strategies of the snake, stripe partition, and chessboard partition were utilized to prepare René 104 Ni-based superalloy, of which the cracking behavior and the residual stress were investigated. The results showed that the scanning strategies had significant effects on the cracking, residual stress, and relative density of the SLMed René 104 superalloy. The scanning strategies with more partitions boosted the emergence of cracks, as high-density cracks occurred in these samples. The overlapping zone (OZ) of the scanning partition was also susceptible to cracking, which increased the size, number, and density of the cracks. The cracking performance was relatively moderate in the snake-scanned samples, while that in the chessboard-partition-scanned samples was the most severe. It is concluded that the partition scanning strategies induced more cracks in the SLMed René 104 superalloy, of which the residual stress was apparently reduced. Therefore, it is necessary to design scanning strategies with optimized scanning partitions and overlaps to avoid cracking and acquire a high-quality, near fully dense, low-weldable Nickel-based superalloy using SLM.

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Investigating the effects of post-heat treatment on residual stress in AlSi12 parts processed with Selective Laser Melting

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/1067/1/012117 ◽

2021 ◽

Vol 1067 (1) ◽

pp. 012117

Author(s):

P Ponnusamy ◽

S H Masood ◽

D Ruan ◽

S Palanisamy ◽

R A Rashid

Keyword(s):

Heat Treatment ◽

Residual Stress ◽

Selective Laser Melting ◽

Laser Melting ◽

Post Heat Treatment

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FEM analysis of thermal and residual stress profile in selective laser melting of 316L stainless steel

Journal of Manufacturing Processes ◽

10.1016/j.jmapro.2021.03.040 ◽

2021 ◽

Vol 66 ◽

pp. 81-100

Author(s):

Saad Waqar ◽

Kai Guo ◽

Jie Sun

Keyword(s):

Residual Stress ◽

Stainless Steel ◽

Selective Laser Melting ◽

316L Stainless Steel ◽

Fem Analysis ◽

Stress Profile ◽

Laser Melting ◽

Residual Stress Profile

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Multi-scale residual stress prediction for selective laser melting of high strength steel considering solid-state phase transformation

Optics & Laser Technology ◽

10.1016/j.optlastec.2021.107578 ◽

2022 ◽

Vol 146 ◽

pp. 107578

Author(s):

Yong Chen ◽

Yan Liu ◽

Hui Chen ◽

Ying Wu ◽

JingQing Chen ◽

...

Keyword(s):

Residual Stress ◽

Phase Transformation ◽

Solid State ◽

Selective Laser Melting ◽

High Strength Steel ◽

High Strength ◽

Laser Melting ◽

Multi Scale ◽

Stress Prediction ◽

Solid State Phase Transformation

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

Rapid Prototyping Journal ◽

10.1108/rpj-10-2019-0273 ◽

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.

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Effect of Process Parameters and High-Temperature Preheating on Residual Stress and Relative Density of Ti6Al4V Processed by Selective Laser Melting

Materials ◽

10.3390/ma12060930 ◽

2019 ◽

Vol 12 (6) ◽

pp. 930 ◽

Cited By ~ 12

Author(s):

Martin Malý ◽

Christian Höller ◽

Mateusz Skalon ◽

Benjamin Meier ◽

Daniel Koutný ◽

...

Keyword(s):

Residual Stress ◽

High Temperature ◽

Residual Stresses ◽

Relative Density ◽

Selective Laser Melting ◽

Process Parameters ◽

Stress Reduction ◽

Laser Melting ◽

Preheating Temperature ◽

Laser Velocity

The aim of this study is to observe the effect of process parameters on residual stresses and relative density of Ti6Al4V samples produced by Selective Laser Melting. The investigated parameters were hatch laser power, hatch laser velocity, border laser velocity, high-temperature preheating and time delay. Residual stresses were evaluated by the bridge curvature method and relative density by the optical method. The effect of the observed process parameters was estimated by the design of experiment and surface response methods. It was found that for an effective residual stress reduction, the high preheating temperature was the most significant parameter. High preheating temperature also increased the relative density but caused changes in the chemical composition of Ti6Al4V unmelted powder. Chemical analysis proved that after one build job with high preheating temperature, oxygen and hydrogen content exceeded the ASTM B348 limits for Grade 5 titanium.

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