Laser Powder Bed Fabrication of Nickel-base Superalloys: Influence of Parameters; Characterisation, Quantification and Mitigation of Cracking

Carter, L.; Attallah, M.; Reed, R.

doi:10.7449/2012/superalloys_2012_577_586

Cited by 124 publications

(65 citation statements)

References 29 publications

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“…For stainless steels and nickel-based superalloys, because of their low thermal conductivity and high thermal expansion coefficient, they are more vulnerable to generating cracks with high susceptibility to cracking in an SLM process [9,27,42,43]. To solve this problem, pre-heating the substrate and improving the ambient temperature are recommended to reduce the cracks in the SLM fabricated parts [26,27].…”

Section: Cracksmentioning

confidence: 99%

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Defect Formation Mechanisms in Selective Laser Melting: A Review

Zhang

Bai

2017

Chin. J. Mech. Eng.

698

269

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Defect formation is a common problem in selective laser melting (SLM). This paper provides a review of defect formation mechanisms in SLM. It summarizes the recent research outcomes on defect findings and classification, analyzes formation mechanisms of the common defects, such as porosities, incomplete fusion holes, and cracks. The paper discusses the effect of the process parameters on defect formation and the impact of defect formation on the mechanical properties of a fabricated part. Based on the discussion, the paper proposes strategies for defect suppression and control in SLM.

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Section: Cracksmentioning

confidence: 99%

“…The process repeats until the completion of the whole part. To date, the SLM process is able to fabricate metallic parts from different material powders, such as titanium alloys [7,8], nickel-based superalloys [9,10], aluminum alloys [11,12] and stainless steels [13,14].…”

Section: Introductionmentioning

confidence: 99%

Defect Formation Mechanisms in Selective Laser Melting: A Review

Zhang

Bai

2017

Chin. J. Mech. Eng.

698

269

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“…[28] has investigated the character and mechanisms of cracking in SLM fabricated CM247LC and established processing parameters where cracking is minimised but not eliminated. second was simply mounted to show the particle morphology.…”

Section: Weld Crackingmentioning

confidence: 99%

The influence of the laser scan strategy on grain structure and cracking behaviour in SLM powder-bed fabricated nickel superalloy

Carter

Martin

Withers

et al. 2014

Journal of Alloys and Compounds

623

200

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a b s t r a c tDuring the development of a processing route for the Selective Laser Melting (SLM) powder-bed fabrication of the nickel superalloy CM247LC it has been observed that the 'island' scan-strategy used as standard by the Concept Laser M2 SLM powder-bed system strongly influences the grain structure of the material.Optical and SEM micrographs are presented to show the observed grain structure in the SLM fabricated and Hot Isostatically Pressed (HIPped) material. The repeating pattern shown in the grain structure has been linked to the overlapping of the 'island' pattern used as standard in the Concept Laser M2 powderbed facility. It is suggested that the formation of this bi-modal grain structure can be linked to the heat transfer away from the solidifying melt pool. The concept of a 'band' heating effect across each 'island' rather than 'moving point' heating has been suggested and has been supported by Electron Back Scattered Diffraction (EBSD) evidence. For comparison an EBSD map from a sample formed using a simple 'back-and-forth' strategy has also been presented and reveals a dramatically different grain structure and crystallographic orientation.MicroCT evidence, supported by SEM microscopy, shows that in the as-fabricated material the bimodal structure caused by the 'island' scan-strategy translates directly into the macroscopic pattern for the regions of extensive weld cracking associated with the SLM fabrication of c 0 hardenable materials. Similar microCT data has shown that HIPping can effectively close the internal cracks to provide a retro-fix solution.

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“…Cracking is also a common defect generated in AM processes, which can be grouped into microscopic cracks and macroscopic ones. Among the microscopic cracks, solidification cracking often occurs in the case when the high applied energy causes the high thermal gradients, as well as the large thermal stress on the melt pool [37]. Another type of microscopic cracking called grain boundary cracking nucleates along material grain boundaries, which depends on the formation of precipitate phases and the grain boundary morphology [37].…”

Section: Additive Manufacturingmentioning

confidence: 99%

“…Among the microscopic cracks, solidification cracking often occurs in the case when the high applied energy causes the high thermal gradients, as well as the large thermal stress on the melt pool [37]. Another type of microscopic cracking called grain boundary cracking nucleates along material grain boundaries, which depends on the formation of precipitate phases and the grain boundary morphology [37]. Macroscopic cracks are different from microscopic ones, which may relate to defects like delamination caused by incomplete melting between layers [38].…”

Section: Additive Manufacturingmentioning

confidence: 99%

Integration of physically-based and data-driven approaches for thermal field prediction in additive manufacturing

Jin

2018

Materials & Design

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A quantitative understanding of thermal field evolution is vital for quality control in additive manufacturing (AM). Because of the unknown material parameters, high computational costs, and imperfect understanding of the underlying science, physically-based approaches alone are insufficient for component-scale thermal field prediction. Here, I present a new framework that integrates physically-based and data-driven approaches with quasi in situ thermal imaging to address this problem. The framework consists of (i) thermal modeling using 3D finite element analysis (FEA), (ii) surrogate modeling using functional Gaussian process, and (iii) Bayesian calibration using the thermal imaging data. Based on heat transfer laws, I first investigate the transient thermal behavior during AM using 3D FEA. A functional Gaussian process-based surrogate model is then constructed to reduce the computational costs from the high-fidelity, physically-based model. I finally employ a Bayesian calibration method, which incorporates the surrogate model and thermal measurements, to enable layer-to-layer thermal field prediction across the whole component. A case study on fused deposition modeling is conducted for components with 7 to 16 layers. The cross-validation results show that the proposed framework allows for accurate and fast thermal field prediction for components with different process settings and geometric designs. Integration of Physically-based and Data-driven Approaches for Thermal Field Prediction in Additive ManufacturingJingran Li GENERAL AUDIENCE ABSTRACT This paper aims to achieve the layer to layer temperature monitoring and consequently predict the temperature distribution for any new freeform geometry. An engineering statistical synergistic model is proposed to integrate the pure statistical methods and finite element modeling (FEM), which is physically meaningful as well as accurate for temperature prediction. Besides, this proposed synergistic model contains geometry information, which can be applied to any freeform geometry. This paper serves to enable a holistic cyber physical systems-based approach for the additive manufacturing (AM) not only restricted in fused deposition modeling (FDM) process but also can be extended to powder-based process like laser engineered net shaping (LENS) and selective laser sintering (SLS). This paper as well as the scheduled future works will make it affordable for customized AM including customized geometries and materials, which will greatly accelerate the transition from rapid prototyping to rapid manufacturing. This article demonstrates a first evaluation of engineering statistical synergistic model in AM technology, which gives a perspective on future researches about online quality monitoring and control of AM based data fusion principles. iv ACKNOWLEDGEMENTS

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Laser Powder Bed Fabrication of Nickel-base Superalloys: Influence of Parameters; Characterisation, Quantification and Mitigation of Cracking

Cited by 124 publications

References 29 publications

Defect Formation Mechanisms in Selective Laser Melting: A Review

Defect Formation Mechanisms in Selective Laser Melting: A Review

The influence of the laser scan strategy on grain structure and cracking behaviour in SLM powder-bed fabricated nickel superalloy

Integration of physically-based and data-driven approaches for thermal field prediction in additive manufacturing

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