Unexpected δ-Phase Formation in Additive-Manufactured Ni-Based Superalloy

Idell, Yaakov; Levine, Lyle E.; Allen, Andrew J.; Zhang, F.; Campbell, Carelyn E.; Olson, Gregory B.; Gong, Jiang Hong; Snyder, David; Deutchman, H.

doi:10.1007/s11837-015-1772-2

Cited by 65 publications

(31 citation statements)

References 38 publications

(38 reference statements)

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“…After HIP treatment, however, γ precipitates were completely dissolved and 65 nm thick and~650 nm long δ-phase needles were formed. The physical dimensions of δ-phase needles are consistent with those described by Idell et al [41].…”

Section: Phase Analysis Of Heat Treated Specimenssupporting

confidence: 89%

“…The Nb-rich regions in the microdendritic spaces contain γ -phase, which was reported to undergo a phase transformation from bct-γ to orthorhombic δ-phase [42]. In the current work, the formation of δ-phase is in the same line as described by [41,42]. The Nb-rich regions in the interdendritic spaces of the powder and SLM-build specimens were observed in the EDS maps ( Figure 5), and were recognized as γ -phase using semi-quantitative EDS analysis, XRD refinement and literature data [4,17,28].…”

Section: Phase Analysis Of Heat Treated Specimenssupporting

confidence: 56%

“…The formation and changes in the δ-phase structure, as a result of several cooling and heating cycles during the AM process of ATI 718Plus nickel alloy, has been recently described by Idell et al [41]. The high concentration of Nb, microsegregated at the interdendritic spaces of the dendritic microstructure, was found the reason for the δ-phase formation during solution treatment of the rapidly solidified Ni-based components.…”

Section: Phase Analysis Of Heat Treated Specimensmentioning

confidence: 80%

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Structure, Texture and Phases in 3D Printed IN718 Alloy Subjected to Homogenization and HIP Treatments

Mostafa

Rubio

Braïlovski

et al. 2017

Metals

193

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3D printing results in anisotropy in the microstructure and mechanical properties. The focus of this study is to investigate the structure, texture and phase evolution of the as-printed and heat treated IN718 superalloy. Cylindrical specimens, printed by powder-bed additive manufacturing technique, were subjected to two post-treatments: homogenization (1100 • C, 1 h, furnace cooling) and hot isostatic pressing (HIP) (1160 • C, 100 MPa, 4 h, furnace cooling). The Selective laser melting (SLM) printed microstructure exhibited a columnar architecture, parallel to the building direction, due to the heat flow towards negative z-direction. Whereas, a unique structural morphology was observed in the x-y plane due to different cooling rates resulting from laser beam overlapping. Post-processing treatments reorganized the columnar structure of a strong {002} texture into fine columnar and/or equiaxed grains of random orientations. Equiaxed structure of about 150 µm average grain size, was achieved after homogenization and HIP treatments. Both δ-phase and MC-type brittle carbides, having rough morphologies, were formed at the grain boundaries. Delta-phase formed due to γ -phase dissolution in the γ matrix, while MC-type carbides nucleates grew by diffusion of solute atoms. The presence of (Nb 0.78 Ti 0.22 )C carbide phase, with an fcc structure having a lattice parameter a = 4.43 Å, was revealed using Energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD) analysis. The solidification behavior of IN718 alloy was described to elucidate the evolution of different phases during selective laser melting and post-processing heat treatments of IN718.

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Section: Phase Analysis Of Heat Treated Specimenssupporting

confidence: 89%

Section: Phase Analysis Of Heat Treated Specimenssupporting

confidence: 56%

Section: Phase Analysis Of Heat Treated Specimensmentioning

confidence: 80%

See 1 more Smart Citation

Structure, Texture and Phases in 3D Printed IN718 Alloy Subjected to Homogenization and HIP Treatments

Mostafa

Rubio

Braïlovski

et al. 2017

Metals

193

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“…These inter-dendritic regions contain γ identified using XRD and EDS analysis, and the Laves phase identified by EDS analysis. Idell et al [44] found that the concentration of Nb in interdendritic spaces of direct metal laser sintered (DMLS) ATI 718 Plus ® resulted in the formation of a δ phase during solution treatment. Body-centered tetragonal γ undergoes a phase transformation to orthorhombic δ during long-term exposure to high temperatures (100 h at 700 • C and 50 h at 750 • C) [45].…”

Section: Phase Analysis 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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“…The fact that the STA specimens exhibited poor ductility compared to the C&W specimen could be explained as follows. The γ phase is only metastable and will be replaced by the incoherent δ phase with the same Ni 3 Nb composition above 750 C. As the temperature increases, the coherent relationship between γ and γ could be lost with the coarsening of precipitates and the conversion reaction of γ/γ → δ would accelerate 29) . The δ phase grows into a needle-like phase (Fig.…”

Section: The Effects Of Ppb On the Mechanical Properties Ofmentioning

confidence: 99%

Effect of the Prior Particle Boundary on the Microstructure and Mechanical Properties of Hot-Isostatic-Pressed IN718 Alloy

Kuo

Kakehi

2017

Mater. Trans.

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The effects of particle surface contamination and of the prior particle boundary on the microstructure and mechanical properties of hot-isostatic-pressed IN718 alloy were investigated in this study. A thermal-plasma-droplet-re ning technique was conducted to reduce the surface contamination; i.e., oxygen and carbon contents in the gas-atomized IN718 powder. The tensile ductility of hot-isostatic-pressed materials was comparable to those of conventionally wrought materials at room temperature and at 650 C. At 650 C, the hot-isostatic-pressed and heat-treated specimens exhibited worse ductility than the conventionally wrought specimen because of the increased number of brittle precipitates, such as oxides, oxy-carbides and δ phases in the heat-treated specimens. The process of crack nucleation and propagation along the prior particle boundary will take place more easily at high temperatures.

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Unexpected δ-Phase Formation in Additive-Manufactured Ni-Based Superalloy

Cited by 65 publications

References 38 publications

Structure, Texture and Phases in 3D Printed IN718 Alloy Subjected to Homogenization and HIP Treatments

Structure, Texture and Phases in 3D Printed IN718 Alloy Subjected to Homogenization and HIP Treatments

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

Effect of the Prior Particle Boundary on the Microstructure and Mechanical Properties of Hot-Isostatic-Pressed IN718 Alloy

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