Segregation of niobium in laser cladding Inconel 718 superalloy

Long, Yi-tong; Nie, Pulin; Li, Zhuguo; Huang, Jian; Li, Xiang; Xu, Xin-mei

doi:10.1016/s1003-6326(16)64131-6

Cited by 68 publications

(21 citation statements)

References 20 publications

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“…Surprisingly, no g phase particles were reported, and their absence was attributed to the abnormal increase in niobium (Nb) concentration at the interdendritic regions thus promoting the formation of the orthorhombic d phase instead. In addition, the presence of Laves phase particles, which is induced by the micro-segregation of Nb and commonly observed in additive manufactured IN 718 [21,22] and reported in the fusion zone of welded 718Plus, [7,23] was not reported in the study. It is, however, known that some of these microconstituents, which form during the solidification stage of the process, can be extremely small in size and, thus, could be very challenging to identify through the use of conventional microscopy and spectroscopy techniques.…”

Section: Introductionmentioning

confidence: 55%

“…[4][5][6][7][8][9] The improved stability in 718Plus is achieved through changes to the composition of IN 718 in which iron (Fe) is partially replaced by cobalt (Co) and tungsten (W), while the content and ratio of aluminum (Al) and titanium (Ti) are modified. [4,[10][11][12] This allows for the replacement of metastable c¢¢ (D0 22 body-centered-tetragonal (BCT)) precipitates in IN 718 with more stable c¢ (L1 2 face-centered-cubic (FCC)) precipitates as the main strengthening phase in 718Plus which has also been found to accelerate its strengthening kinetics. [9,13] Furthermore, the increase in Al in 718Plus has been attributed to the formation of g (D0 24 hexagonal) phase particles at the grain boundaries, versus the orthorhombic d phase (D0a, Ni 3 Nb particles in IN 718.…”

Section: Introductionmentioning

confidence: 99%

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Microstructural Analyses of ATI 718Plus® Produced by Wire-ARC Additive Manufacturing Process

Asala

Khan

Andersson

et al. 2017

Metall Mater Trans A

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A detailed microstructural study of ATI 718Plus superalloy produced by the wire-arc additive manufacturing (WAAM) process was performed through the use of scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe micro-analysis (EPMA), and electron backscatter diffraction (EBSD). Extensive formation of eutectic solidification microconstituents including Laves and MC-type carbide phases, induced by micro-segregation, are observed in the build of the alloy in the as-deposited condition. Notwithstanding the significant segregation of niobium (Nb), which has been reported to promote the formation of the d-phase in ATI 718Plus, only g-phase particles are observed in the deposit. Excessive precipitation of g-phase particles is found to be linked to Laves phase particles that are partially dissolved in the deposit after post-deposition heat treatment (PDHT). The EBSD analysis shows a high textured build in the h100i directions with only a few misoriented grains at the substrate-deposit boundary and the top of the deposit. Investigation on the hardness of the build of the alloy, in the as-deposited condition, showed a softened zone about 2 mm wide at the deposited metal heat affected zone (DMHAZ), which has not been previously reported and potentially damaging to the mechanical properties. An extensive analysis with the use of both microstructural characterization tools and theoretical calculations shows that the DMHAZ has the lowest volume fraction of strengthening precipitates (c¢ and c¢¢) in terms of their number density, which therefore induces the observed softness. Delayed re-precipitation kinetics and the extent of the precipitation of c¢ and c¢¢ in the DMHAZ which is related to the diffusion of segregated solute elements from the interdendritic regions are attributed to this phenomenon. The microstructural analyses discussed in this work are vital to adequate understanding of properties of ATI 718Plus produced by the additive manufacturing process technique.

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Section: Introductionmentioning

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Microstructural Analyses of ATI 718Plus® Produced by Wire-ARC Additive Manufacturing Process

Asala

Khan

Andersson

et al. 2017

Metall Mater Trans A

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“…Figure 5d-h, this precipitate is enrichment of Nb and Mo, and depletion of Fe, Cr, and Ni. According to References [18][19][20][21], the precipitate can be confirmed as the Laves phase, which is generally accepted to be the form of (Fe,Ni,Cr) 2 (Nb,Mo,Ti). It is a eutectic with the matrix.…”

Section: First Dendrite Arm Spacementioning

confidence: 99%

Investigation on the Precipitates of IN718 Alloy Fabricated by Selective Laser Melting

Cao

Bai

Liu

et al. 2019

Metals

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The microstructure and precipitates of INCONEL 718 alloy (IN718) fabricated by selective laser melting (SLM) are investigated. The matrix is comprised of the elongated γ grains along Z direction, tilting a few degrees. The microstructure mainly consists of a cellular–columnar structure with fine first dendrite arm space of 1–1.5 µm originated from the rapid solidification rate locally. The precipitates of the SLMed IN718 are confirmed to be a significant amount of Laves in the form of irregular bulk distribution, small amount of carbonitride and spherical Al2O3 particles in nanoscale. Some of the carbonitrides grow separately and some of the carbonitrides enwrap the Al2O3 fully or partly, forming the shell structure of the Al2O3–carbonitride. The reheating effect from the following layers to the previous layers have not reached the solid-state transformation temperature of the γ′ and γ″.

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“…The large deviation in the results was sourced from the nonuniform distribution of the Nb-rich phases in different regions. Previous studies have proven that a high cooling rate is beneficial for suppressing the segregation of Nb in Alloy 718 [36,37].…”

Section: Segregation Of Nb and Variation Of Nb-rich Phasesmentioning

confidence: 99%

Effect of build location on microstructural characteristics and corrosion behavior of EB-PBF built Alloy 718

Karimi

Sadeghimeresht

Ålgårdh

et al. 2020

Int J Adv Manuf Technol

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Electron beam-powder bed fusion (EB-PBF), a high-temperature additive manufacturing (AM) technique, shows great promise in the production of high-quality metallic parts in different applications such as the aerospace industry. To achieve a higher build efficiency, it is ideal to build multiple parts together with as low spacing as possible between the respective parts. In the EB-PBF technique, there are many unknown variations in microstructural characteristics and functional performance that could be induced as a result of the location of the parts on the build plate, gaps between the parts and part geometry, etc. In the present study, the variations in the microstructure and corrosion performance as a function of the parts location on the build plate in the EB-PBF process were investigated. The microstructural features were correlated with the thermal history of the samples built in different locations on the build plate, including exterior (the outermost), middle (between the outermost and innermost), and interior (the innermost) regions. The cubic coupons located in the exterior regions showed increased level (~20 %) of defects (mainly in the form of shrinkage pores) and lower level (~30-35 %) of Nb-rich phase fraction due to their higher cooling rates compared to the interior and middle samples. Electrochemical investigations showed that the location indirectly had a substantial influence on the corrosion behavior, verified by a significant increase in polarization resistance (R p ) from the exterior (2.1 ± 0.3 kΩ.cm 2 ) to interior regions (39.2 ± 4.1 kΩ.cm 2 ).

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Segregation of niobium in laser cladding Inconel 718 superalloy

Cited by 68 publications

References 20 publications

Microstructural Analyses of ATI 718Plus® Produced by Wire-ARC Additive Manufacturing Process

Microstructural Analyses of ATI 718Plus® Produced by Wire-ARC Additive Manufacturing Process

Investigation on the Precipitates of IN718 Alloy Fabricated by Selective Laser Melting

Effect of build location on microstructural characteristics and corrosion behavior of EB-PBF built Alloy 718

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