On the effect of boron on grain boundary character in a new polycrystalline superalloy

Kontis, Paraskevas; Yusof, H.A. Mohd; Pedrazzini, S.; Danaie, Mohsen; Moore, Katie L.; Bagot, P.A.J.; Moody, Michael P.; Grovenor, C.R.M.; Reed, Roger C.

doi:10.1016/j.actamat.2015.10.006

Cited by 173 publications

(86 citation statements)

References 34 publications

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“…Mo, Cr and W segregate to the M6C phase. Similar observations of Ta and Zr enrichment in superalloy MC carbides has been reported by atom probe tomography studies [7,10]. We believe that the technique presented in this work provides a means of confirming trends in precipitate composition between alloys, as well as where elements tend to segregate upon nominal enrichment of the bulk composition.…”

Section: Chemical Analysis Of Labelled Phasessupporting

confidence: 86%

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Advancing characterisation with statistics from correlative electron diffraction and X-ray spectroscopy, in the scanning electron microscope

et al. 2020

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The routine and unique determination of minor phases in microstructures is critical to materials science. In metallurgy alone, applications include alloy and process development and the understanding of degradation in service. We develop a correlative method, exploring superalloy microstructures which are examined in the scanning electron microscope (SEM) using simultaneous energy dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD). This is performed at an appropriate length scale for characterisation of carbide phases, shape, size, location, and distribution. EDS and EBSD data are generated using two different physical processes, but each provide a signature of the material interacting with the incoming electron beam. Recent advances in post-processing, driven by 'big data' approaches, include use of principal component analysis (PCA). Components are subsequently characterised to assign labels to a mapped region. To provide physically meaningful signals, the principal components may be rotated to control the distribution of variance. In this work, we develop this method further through a weighted PCA approach. We use the EDS and EBSD signals concurrently, thereby labelling each region using both EDS (chemistry) and EBSD (crystal structure) information. This provides a new method of amplifying signal-to-noise for very small phases in mapped regions, especially where the EDS or EBSD signal is not unique enough alone for classification.

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Section: Chemical Analysis Of Labelled Phasessupporting

confidence: 86%

“…In the present work, we develop a new approach using an example in Co/Ni-base superalloys. In these alloys, there are carbide precipitates that are known to strongly influence fatigue and tertiary creep performance [5][6][7][8][9]. The precipitates are thought to increase boundary cohesivity and to mitigate sliding.…”

Section: Introductionmentioning

confidence: 99%

Advancing characterisation with statistics from correlative electron diffraction and X-ray spectroscopy, in the scanning electron microscope

et al. 2020

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“…The APT specimens were extracted from random high angle grain boundaries from both samples, following the procedures described in Ref. [26]. APT specimens were analyzed using a Cameca LEAP 5000 XR instrument operating in a laser mode with pulse rate at 125 kHz, pulse energy 0.4 pJ and temperature 60 K. The commercial package IVAS 3.8.2 was used for data reconstruction and analyses.…”

Section: Atom Probe Tomographymentioning

confidence: 99%

“…Segregation to grain boundaries may originate in AM first from solidification by sweeping of solutes during grain growth as new layers are deposited, and second by solid-state diffusion as the sample is maintained at high temperature (in S-EBM a heated powder bed is used). The intergranular films get enriched in solutes, such as Cr, Mo and B, during the building process, because of remelting and most likely solid-state diffusion, particularly of fast diffusers such as B [26]. HAGBs accommodate larger amounts of solutes than LAGBs [35], partly due to lower their relatively higher interfacial energy [36].…”

Section: Grain Boundary Segregation and Boride Formationmentioning

confidence: 99%

“…A possible alternative route would consist in adjusting the composition to achieve lower level of solutes along HAGBs that decrease the solidus for instance or to form a continuous layer of e.g. borides to strengthen the grain boundaries [26,46]. Figure 13: Quantification of grain width along the building direction for cracked and crack-free samples.…”

Section: Strategies For Additive Manufacturing Of Crack-free Superallmentioning

confidence: 99%

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Atomic-scale grain boundary engineering to overcome hot-cracking in additively-manufactured superalloys

et al. 2019

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There are still debates regarding the mechanisms that lead to hot cracking in parts build by additive manufacturing (AM) of non-weldable nickel-based superalloys. This lack of in-depth understanding of the root causes of hot cracking is an impediment to designing engineering parts for safety-critical applications. Here, we deploy a near-atomic-scale approach to investigate the details of the compositional decoration of grain boundaries in the coarse-grained, columnar microstructure in parts built from a non-weldable nickel-based superalloy by selective electron-beam melting. The progressive enrichment in Cr, Mo and B at grain boundaries over the course of the AM-typical successive solidification and remelting events, accompanied by solid-state diffusion, causes grain boundary segregation induced liquation. This observation is consistent with thermodynamic calculations. We demonstrate that by adjusting build parameters to obtain a fine-grained equiaxed or a columnar microstructure with grain width smaller than 100 μm enables to avoid cracking, despite strong grain boundary segregation. We find that the spread of critical solutes to a higher total interfacial area, combined with lower thermal stresses, helps to suppress interfacial liquation.

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Effect of Hf and B on Transverse and Longitudinal Creep of a Re‐Containing Nickel‐Base Bicrystal Superalloy

et al. 2016

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On the effect of boron on grain boundary character in a new polycrystalline superalloy

Cited by 173 publications

References 34 publications

Advancing characterisation with statistics from correlative electron diffraction and X-ray spectroscopy, in the scanning electron microscope

Advancing characterisation with statistics from correlative electron diffraction and X-ray spectroscopy, in the scanning electron microscope

Atomic-scale grain boundary engineering to overcome hot-cracking in additively-manufactured superalloys

Effect of Hf and B on Transverse and Longitudinal Creep of a Re‐Containing Nickel‐Base Bicrystal Superalloy

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