Influence of Powder Surface Contamination in the Ni-Based Superalloy Alloy718 Fabricated by Selective Laser Melting and Hot Isostatic Pressing

Kuo, Yen-Ling; Kakehi, Koji

doi:10.3390/met7090367

Cited by 31 publications

(16 citation statements)

References 37 publications

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“…1b). Note that this is consistent with earlier made observations [1,3,4,7,8]. Large carbides with a size of 1-10 μm usually observed in the industrial Inconel 718 superalloy [20] were not revealed in the SLM superalloy.…”

Section: Microstructure Of the Superalloy Obtained By Slmsupporting

confidence: 93%

“…The grains shown in (a) consisted of subgrains (b). The γ'' phase precipitates are visible at high magnifications in the interior of subgrains [8].…”

Section: Microstructure Of the Superalloy Obtained By Slmmentioning

confidence: 98%

“…The dispersed nanoscale γ'' phase was precipitated in subgrains and was visible at high magnifications ( Fig. 1b) [8]. Variable contrast of the δ phase (changing from light to gray) indicates a variable composition of this phase, which was not diffusively equalized during rapid heating, cooling and fast solidification.…”

Section: Microstructure Of the Superalloy Obtained By Slmmentioning

confidence: 98%

“…It can be reduced through the use of additive technologies, in particular, based on selective laser melting (SLM). However, multiple cycles of heating and cooling with fast solidification during SLM lead to formation of a microheterogeneous microstructure with an increased dislocation density and precipitations of dispersed hardening phases including small carbides and oxides [1][2][3][4][5][6][7][8][9][10][11][12] that can negatively affect mechanical and service properties of the Inconel 718 superalloy. It is also known that the material obtained by SLM can have pores [13 -17].…”

Section: Introductionmentioning

confidence: 99%

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Microstructure and mechanical properties of the Inconel 718 superalloy manufactured by selective laser melting

et al. 2019

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The work is devoted to the study of the microstructure and mechanical properties of the nickel base superalloy Inconel 718 manufactured by selective laser melting (SLM). Multiple cycles of heating and cooling during SLM led to the formation of a complex microheterogeneous microstructure. The microstructure of the superalloy manufactured by SLM consisted of elongated γ grains with a transversal size of 10 -100 μm and a longitudinal size of 50 -300 μm, which in its turn consisted of columnar and equiaxed subgrains. Stable and metastable precipitates of the δ-Ni 3 Nb and γ''-Ni 3 Nb phases, carbides and probably oxides, were detected along the subboundaries. The standard heat treatment of the superalloy manufactured by SLM resulted in a partial dissolution of the δ phase and the metastable γ'' phase during solid solution treatment and precipitation of the dispersed metastable γ'' phase during ageing. The microstructure characterization performed by electron backscatter diffraction technique (EBSD analysis) revealed that the size and elongated form of the γ grains was not changed after the heat treatment, the size of the subgrains slightly increased, the fraction of low-angle boundaries (subboundaries) decreased, and the fraction of high-angle grain boundaries increased. Tensile tests were carried out at T = 20 -700°C for the superalloy samples subjected to standard heat treatment. The tensile direction was parallel to the building direction. The tensile tests showed that the superalloy manufactured by SLM exceeded the requirements of the AMS 5662 certificate for the superalloy Inconel 718 in a hot forged condition subjected to standard heat treatment.

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Section: Microstructure Of the Superalloy Obtained By Slmsupporting

confidence: 93%

“…The grains shown in (a) consisted of subgrains (b). The γ'' phase precipitates are visible at high magnifications in the interior of subgrains [8].…”

Section: Microstructure Of the Superalloy Obtained By Slmmentioning

confidence: 98%

Section: Microstructure Of the Superalloy Obtained By Slmmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Microstructure and mechanical properties of the Inconel 718 superalloy manufactured by selective laser melting

et al. 2019

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“…This excessive grain growth did not occur alongside NbC dissolution in heat-treated compacted powder specimens due to the presence of prior particle boundaries (PPB) restricting the growth of grains [35]. However, SLM-manufactured IN718 specimens are free of PPBs [37]. Without PPBs inhibiting grain growth, Ostwald ripening of NbC precipitates is expected to lead to excessive grain coarsening in heat treated SLM specimens.…”

Section: Microstructural Development Of Heat Treated Inconel 718mentioning

confidence: 99%

Microstructural and Microhardness Evolution from Homogenization and Hot Isostatic Pressing on Selective Laser Melted Inconel 718: Structure, Texture, and Phases

Seede

Mostafa

Braïlovski

et al. 2018

JMMP

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Abstract:In this work, the microstructure, texture, phases, and microhardness of 45 • printed (with respect to the build direction) homogenized, and hot isostatically pressed (HIP) cylindrical IN718 specimens are investigated. Phase morphology, grain size, microhardness, and crystallographic texture at the bottom of each specimen differ from those of the top due to changes in cooling rate. High cooling rates during the printing process generated a columnar grain structure parallel to the building direction in the as-printed condition with a texture transition from (001) orientation at the bottom of the specimen to (111) orientation towards the specimen top based on EBSD analysis. A mixed columnar and equiaxed grain structure associated with about a 15% reduction in texture is achieved after homogenization treatment. HIP treatment caused significant grain coarsening, and engendered equiaxed grains with an average diameter of 154.8 µm. These treatments promoted the growth of δ-phase (Ni 3 Nb) and MC-type brittle (Ti, Nb)C carbides at grain boundaries. Laves phase (Fe 2 Nb) was also observed in the as-printed and homogenized specimens. Ostwald ripening of (Ti, Nb)C carbides caused excessive grain growth at the bottom of the HIPed IN718 specimens, while smaller grains were observed at their top. Microhardness in the as-fabricated specimens was 236.9 HV and increased in the homogenized specimens by 19.3% to 282.6 HV due to more even distribution of secondary precipitates, and the nucleation of smaller grains. A 36.1% reduction in microhardness to 180.5 HV was found in the HIPed condition due to γ phase dissolution and differences in grain morphology.

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Influence of Post‐Heat Treatments on the Microstructure, Mechanical Responses of IN738LC Superalloy Manufactured via Laser Powder Bed Fusion

2022

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IN738LC is a precipitation-hardening Ni-Cr-Ti-Al-based superalloy that exhibits excellent mechanical properties at room and high temperatures because of the formation of γ 0 -Ni 3 (Al, Ti) precipitates. [1,2] Moreover, this superalloy offers excellent corrosion/ oxidation resistance at high temperature and in SO x and CO x atmospheres, it is used to be applied as parts exposed to high temperatures and corrosive environments such as turbine blades and vanes in aerospace and spacecraft, power plants industries. [3][4][5] Additive manufacturing (AM) has the following advantages: parts with complex shapes can be obtained, parts can be geometrically optimized, lightweight parts can be manufactured (lattice materials, foam, thin-wall structure, etc.), simplified process, low material loss, and difficultto-process/poor machinable materials can be fabricated. [6][7][8] Accordingly, manufacturing Ni-based superalloy parts using AM has attracted widespread interest, and many studies on efficient manufacturing are currently actively continuing. [9][10][11][12] However, most studies of the use of Ni-based superalloys for AM focused on the IN625 [13][14][15][16] and IN718 [17][18][19][20][21][22][23] alloys, whereas little is reported about γ 0 -Ni 3 (Al, Ti) precipitate hardening Ni-based superalloys, which exhibit excellent mechanical properties.Manufacturing of IN738LC using laser powder bed fusion (LPBF), [24][25][26][27][28][29][30] electron beam powder bed fusion (EBPBF), [31,32] or direct energy deposition (DED) [33][34][35] processes has recently been attempted. However, it is difficult to manufacture a material without defects (i.e., cracks and pores) if the Al þ Ti content added to form γ 0 -Ni 3 (Al, Ti) is over 6 wt% because the material may give rise to liquation cracking, hot cracking, and weld cracking. [36][37][38] The high Al þ Ti content of IN738LC (6.2À7.2 wt%) makes it difficult to weld, and this motivated researchers to study the crack formation mechanism and crack control of IN738LC manufactured with AM. [27,28,33,37] Furthermore, an increasing need has arisen to investigate the microstructure control and the improvement in the mechanical properties of AM IN738LC by applying different post-heat treatments.Ni-based superalloys (mainly IN625 and IN718) fabricated by AM require multi-stage post-heat treatments such as stress relieving, hot-isostatic pressing, solid-solution strengthening, and artificial aging. [26,29,[39][40][41][42][43][44][45] Likewise, IN738LC could be expected to require similar post-heat treatments. Xu et al. [30] suggested that it was possible to control the mechanical properties of a Ni-based superalloy using the variation of γ 0 fraction and size with the hot isostatic pressing (HIP) temperature change. However, previous studies were carried out at high temperatures with complex heat treatment consisting of three or more steps and thus could affect the dimensional stability of the part. In contrast, it is known to be possible to control the mechanical properties of an AM Ni-based su...

show abstract

Influence of Powder Surface Contamination in the Ni-Based Superalloy Alloy718 Fabricated by Selective Laser Melting and Hot Isostatic Pressing

Cited by 31 publications

References 37 publications

Microstructure and mechanical properties of the Inconel 718 superalloy manufactured by selective laser melting

Microstructure and mechanical properties of the Inconel 718 superalloy manufactured by selective laser melting

Microstructural and Microhardness Evolution from Homogenization and Hot Isostatic Pressing on Selective Laser Melted Inconel 718: Structure, Texture, and Phases

Influence of Post‐Heat Treatments on the Microstructure, Mechanical Responses of IN738LC Superalloy Manufactured via Laser Powder Bed Fusion

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