In Operando Monitoring by Analysis of Backscattered Electrons during Electron Beam Melting

Arnold, Christopher; Bohm, J.; Körner, Carolin

doi:10.1002/adem.201901102

Cited by 17 publications

(7 citation statements)

References 22 publications

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“…Arnold et al (2019) used the same approach, but only using backscattered electrons, and installed a circular backscattered electron detector shortly above the build chamber of an Arcam S12 machine. Arnold et al (2019) demonstrated that this configuration enabled a much higher spatial resolution (60 µm/pixel). In this study, and in all previously mentioned studies, the electronic image was generated at the end of the melting phase by performing a raster scan of the entire build area with the electron beam.…”

Section: Blade Mounted Sensorsmentioning

confidence: 97%

“…In this study, and in all previously mentioned studies, the electronic image was generated at the end of the melting phase by performing a raster scan of the entire build area with the electron beam. Arnold et al (2019) demonstrated, instead, that the same image could be generated during the melting phase, leading to an 'in-operando' monitoring capability. Along the direction orthogonal to the scan tracks, the resulting image resolution was equivalent to the hatch spacing (between 50 µm/pixel and 100 µm/pixel in the published work).…”

Section: Blade Mounted Sensorsmentioning

confidence: 99%

“…Figure 11 shows some examples of electronic images in EB-PBF from Wong et al (2019a) and Arnold et al (2019).…”

Section: Blade Mounted Sensorsmentioning

confidence: 99%

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In-situ measurement and monitoring methods for metal powder bed fusion: an updated review

Grasso

Remani

Dickins

et al. 2021

Meas. Sci. Technol.

137

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The possibility of using a variety of sensor signals acquired during metal powder bed fusion processes, to support part and process qualification and for the early detection of anomalies and defects, has been continuously attracting an increasing interest. The number of research studies in this field has been characterised by significant growth in the last few years, with several advances and new solutions compared with first seminal works. Moreover, industrial powder bed fusion systems are increasingly equipped with sensors and toolkits for data collection, visualisation and, in some cases, embedded in-process analysis. Many new methods have been proposed and defect detection capabilities have been demonstrated. Nevertheless, several challenges and open issues still need to be tackled to bridge the gap between methods proposed in the literature and actual industrial implementation. This paper presents an updated review of the literature on in-situ sensing, measurement and monitoring for metal powder bed fusion processes, with a classification of methods and a comparison of enabled performances. The study summarises the types and sizes of defects that are practically detectable while the part is being produced and the research areas where additional technological advances are currently needed.

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Section: Blade Mounted Sensorsmentioning

confidence: 97%

Section: Blade Mounted Sensorsmentioning

confidence: 99%

See 1 more Smart Citation

In-situ measurement and monitoring methods for metal powder bed fusion: an updated review

Grasso

Remani

Dickins

et al. 2021

Meas. Sci. Technol.

137

View full text Add to dashboard Cite

show abstract

“…Additionally, the combined effect of high vacuum and preheating can cause sublimation of metallic elements and further condensation of metal vapors on the surrounding build area surfaces, such as the heat shields, known as metalization [20,21]. The metalization behavior of Al and its effect in TiAl was documented in an earlier study by Cormier et al [22], who showed an Al content decrease of up to 7 at% in the fabricated part compared to the original powder.…”

Section: Introductionmentioning

confidence: 96%

Characterization of Spatter and Sublimation in Alloy 718 during Electron Beam Melting

Raza¹,

Hryha²

2021

Materials

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Due to elevated temperatures and high vacuum levels in electron beam melting (EBM), spatter formation and accumulation in the feedstock powder, and sublimation of alloying elements from the base feedstock powder can affect the feedstock powder’s reusability and change the alloy composition of fabricated parts. This study focused on the experimental and thermodynamic analysis of spatter particles generated in EBM, and analyzed sublimating alloying elements from Alloy 718 during EBM. Heat shields obtained after processing Alloy 718 in an Arcam A2X plus machine were analyzed to evaluate the spatters and metal condensate. Comprehensive morphological, microstructural, and chemical analyses were performed using scanning electron microscopy (SEM), focused ion beam (FIB), and energy dispersive spectroscopy (EDS). The morphological analysis showed that the area coverage of heat shields by spatter increased from top (<1%) to bottom (>25%), indicating that the spatter particles had projectile trajectories. Similarly, the metal condensate had a higher thickness of ~50 μm toward the bottom of the heat shield, indicating more significant condensation of metal vapors at the bottom. Microstructural analysis of spatters highlighted that the surfaces of spatter particles sampled from the heat shields were also covered with condensate, and the thickness of the deposited condensate depended on the time of landing of spatter particles on the heat shield during the build. The chemical analysis showed that the spatter particles had 17-fold higher oxygen content than virgin powder used in the build. Analysis of the metalized layer indicated that it was formed by oxidized metal condensate and was significantly enriched with Cr due to its higher vapor pressure under EBM conditions.

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“…Arnold et al [27] extended and tuned the method, showing the capability to achieve a quite high spatial resolution in the measurement of the solidified layer. Arnold et al [28] demonstrated that the same approach could be generated during the melting phase, leading to an "in operando" monitoring capability. Although being potentially suitable to characterize the homogeneity of the powder bed, the electronic imaging method has so far been studied mainly for the characterization of the solidified material in the layer.…”

Section: Introductionmentioning

confidence: 99%

In Situ Monitoring of Powder Bed Fusion Homogeneity in Electron Beam Melting

Grasso

2021

Materials

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Increasing attention has been devoted in recent years to in situ sensing and monitoring of the electron beam melting process, ranging from seminal methods based on infrared imaging to novel methods based on backscattered electron detection. However, the range of available in situ monitoring capabilities and solutions is still quite limited compared to the wide number of studies and industrial toolkits in laser-based additive manufacturing processes. Some methods that are already industrially available in laser powder bed fusion systems, such as in situ detection of recoating errors, have not yet been investigated and tested in electron beam melting. Motivated by the attempt to fill this gap, we present a novel in situ monitoring methodology that can be easily implemented in industrial electron beam melting machines. The method is aimed at identifying local inhomogeneity and irregularities in the powder bed by means of layerwise image acquisition and processing, with no external illumination source apart from the light emitted by the hot material underneath the currently recoated layer. The results show that the proposed approach is suitable to detect powder bed anomalies, while also highlighting the link between the severity of in situ detected errors and the severity of resulting defects in the additively manufactured part.

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In Operando Monitoring by Analysis of Backscattered Electrons during Electron Beam Melting

Cited by 17 publications

References 22 publications

In-situ measurement and monitoring methods for metal powder bed fusion: an updated review

In-situ measurement and monitoring methods for metal powder bed fusion: an updated review

Characterization of Spatter and Sublimation in Alloy 718 during Electron Beam Melting

In Situ Monitoring of Powder Bed Fusion Homogeneity in Electron Beam Melting

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