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

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

scholarly journals The Effect of a Scanning Strategy on the Residual Stress of 316L Steel Parts Fabricated by Selective Laser Melting (SLM)

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1821 ◽  
Author(s):  
Di Wang ◽  
Shibiao Wu ◽  
Yongqiang Yang ◽  
Wenhao Dou ◽  
Shishi Deng ◽  
...  
Keyword(s):  
Residual Stress ◽  
Selective Laser Melting ◽  
Laser Scanning ◽  
Effective Means ◽  
Laser Melting ◽  
Scanning Strategy ◽  
Deformation Degree ◽  
316L Steel ◽  
Stress And Deformation ◽  
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.

A Method to Estimate Residual Stress in Metal Parts Made by Selective Laser Melting

2015 ◽  
Author(s):  
Xiaoqing Wang ◽  
Y. Kevin Chou
Keyword(s):  
Residual Stress ◽  
Additive Manufacturing ◽  
Residual Stresses ◽  
Selective Laser Melting ◽  
Inconel 718 ◽  
Plane Surface ◽  
Texture Evolution ◽  
Large Temperature ◽  
Indentation Hardness ◽  
Laser Melting

Accurate evaluation of residual stresses in structures is very important because they play a crucial role in the mechanical performance of the components. As residual stresses can be introduced into mechanical components during various thermal or mechanical processes such as heat treatment, forming, welding and additive manufacturing. As an additive manufacturing method, selective laser melting (SLM) has become a powerful tool for the direct manufacturing of three dimensional nano-composite components with complex configurations directly from powders using 3D CAD data as a digital information source and energy in the form of a high-power laser beam. Therefore, the application of the SLM technology is necessary to manufacture Inconel 718 superalloy, which has been widely employed in industrial applications due to its remarkable properties. Hence, it is critical to measure and reduce the residual stress in the Inconel 718 parts formed by SLM due to rapid cooling and reheating. In this study, the process-induced residual stress in Inconel 718 parts produced by selective laser melting (SLM) has been investigated using the model established by Carlsson et al., which is an instrumented indentation technique based on the experimental correlation between the indentation characteristic and the residual stress. The samples were sectioned from an Inconel 718 block along its build direction, and subsequently prepared with general metallographic methods for Vickers indentation and measurements by optical microscopy. The residual stress on the scanning surface (Z-plane) and side surface (X-plane) at different build heights have been evaluated in micro-scale with the contact area, indentation hardness and the equai-biaxial residual stress and strain fields. The results show that the residual stress is unevenly distributed in the SLMed parts with some areas have an maximum absolute value around 350 MPa, about 30 percent of the yield strength of Inconel 718. The average residual stresses in the Z-plane and X-plane samples are tensile and compressive, respectively. Besides, the residual stress does not change significantly along the building direction of the part. Moreover, the Vickers hardness of the parts built with the SLM process is comparable to the literature, and the X-plane surface has a higher hardness than the Z-plane surface. The microstructures and texture evolution of the SLM processed Inconel 718 alloy are also investigated. The X-plane shows the columnar structure due to the large temperature gradient while the Z-plane presents the equiaxed structures. The random texture is shown in the SLM processed specimens.

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.

scholarly journals The effect of texture on the low cycle fatigue property of Inconel 718 by selective laser melting

2018 ◽  
Vol 165 ◽  
pp. 02007 ◽  
Author(s):  
Zhongjiao Zhou ◽  
Xu Hua ◽  
Changpeng Li ◽  
Guofeng Chen
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Selective Laser Melting ◽  
Inconel 718 ◽  
Low Cycle Fatigue ◽  
Added Value ◽  
Cycle Fatigue ◽  
Laser Melting ◽  
Safety Critical ◽  
The Impact

In recent decades, additive manufacturing (AM) technology has shown its great advantages to produce end-use products with complex design and high-added value. However, the AM-specific characters, such as inherent material anomalies (porosity, lack of fusion defects, or inclusions), anisotropy, location-specific properties and residual stresses, prevent AM from widely adoption in safety-critical parts. Therefore, the damage tolerance assessment of AM parts is desperately necessary. In this study, the impact of residual stress and the induced texture (columnar/equiax grain structure) after different heat treatment on the low cycle fatigue (LCF) behavior of Inconel 718 fabricated through selective laser melting (SLM) is investigated. The results showed that the texture of AMed parts can be controlled by suitable heat treatment, based on the residual stress during AM processing acting as the drive force to recrystallization. For SLMed Inconel 718 samples with columnar grains, anisotropic LCF properties exist, while no obvious sensitivity to orientations is shown for samples with equiaxed grains. This work is significantly meaningful to speed up the design-to-product transformation of safety-critical AM parts and optimize the orientation of components for various applications.

Understanding processing parameters affecting residual stress in selective laser melting of Inconel 718 through numerical modeling

2019 ◽  
Vol 34 (08) ◽  
pp. 1395-1404 ◽  
Author(s):  
Jia Song ◽  
Liang Zhang ◽  
Wenheng Wu ◽  
Beibei He ◽  
Xiaoqing Ni ◽  
...  
Keyword(s):  
Residual Stress ◽  
Numerical Modeling ◽  
Selective Laser Melting ◽  
Inconel 718 ◽  
Processing Parameters ◽  
Laser Melting ◽  
Image Position

Abstract

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

Materials ◽  
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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