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

Kontis, Paraskevas; Chauvet, Edouard; Peng, Zirong; He, Junyang; Silva, Alisson Kwiatkowski da; Raabe, Dierk; Tassin, C.; Blandin, Jean‐Jacques; Abed, Stéphane; Dendievel, Rémy; Gault, Baptiste; Martin, Guilhem

doi:10.1016/j.actamat.2019.07.041

Cited by 203 publications

(70 citation statements)

References 45 publications

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“…In addition, recent researches [173,174] attempts to understand the liquation cracking mechanism in the EB-PBF nickel-based superalloy from the atomic-scale evidence. By advanced atom probe tomography characterization, the high-angle grain boundaries, which is the interdendritic region simultaneously, are observed to be prone to accommodate a higher amount of minor elements.…”

Section: Minor Elements Effectsmentioning

confidence: 99%

Alloy Design and Characterization of γ′ Strengthened Nickel-based Superalloys for Additive Manufacturing

2021

Linköping Studies in Science and Technology. Licentiate Thesis

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Nickel-based superalloys, an alloy system bases on nickel as the matrix element with the addition of up to 10 more alloying elements including chromium, aluminum, cobalt, tungsten, molybdenum, titanium, and so on. Through the development and improvement of nickel-based superalloys in the past century, they are well proved to show excellent performance at the elevated service temperature. Owing to the combination of extraordinary high-temperature mechanical properties, such as monotonic and cyclic deformation resistance, fatigue crack propagation resistance; and high-temperature chemical properties, such as corrosion and oxidation resistance, phase stability, nickel-based superalloys are widely used in the critical hot-section components in aerospace and energy generation industries. The success of nickel-based superalloy systems attributes to both the well-tailored microstructures with the assistance of carefully doped alloying elements, and the intently developed manufacturing processes. The microstructure of the modern nickel-based superalloys consists of a two-phase configuration: the intermetallic precipitates (Ni,Co)3(Al,Ti,Ta) known as γ′ phase dispersed into the austenite γ matrix, which is firstly introduced in the 1940s. The recently developed additive manufacturing (AM) techniques, acting as the disruptive manufacturing process, offers a new avenue for producing the nickel-based superalloy components with complicated geometries. However, γ′ strengthened nickel-based superalloys always suffer from the micro-cracking during the AM process, which is barely eliminated by the process optimization. On this basis, the new compositions of γ′ strengthened nickel-based superalloy adapted to the AM process are of great interest and significance. This study sought to design novel γ′ strengthened nickel-based superalloys readily for AM process with limited cracking susceptibility, based on the understanding of the cracking mechanisms. A two-parameter model is developed to predict the additive manufacturability for any given composition of a nickel-based superalloy. One materials index is derived from the comparison of the deformation-resistant capacity between dendritic and interdendritic regions, while another index is derived from the difference of heat resistant capacity of these two spaces. By plotting the additive manufacturability diagram, the superalloys family can be categorized into the easy-to-weld, fairly-weldable, and non-weldable regime with the good agreement of the existed knowledge. To design a novel superalloy, a Cr-Co-MoW -Al-Ti-Ta-Nb-Fe-Ni alloy family is proposed containing 921,600 composition recipes in total. Through the examination of additive manufacturability, undesired phase formation propensity, and the precipitation fraction, one composition of superalloy, MAD542, out of the 921,600 candidates is selected. Validation of additive manufacturability of MAD542 is carried out by laser powder bed fusion (LPBF). By optimizing the LPBF process parameters, the crack-free MAD542 part is achieved. I...

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Section: Minor Elements Effectsmentioning

confidence: 99%

Alloy Design and Characterization of γ′ Strengthened Nickel-based Superalloys for Additive Manufacturing

2021

Linköping Studies in Science and Technology. Licentiate Thesis

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“…The effect of solute re-distribution during solidification on the material susceptibility to cracking can be assessed by performing thermodynamic calculation using Scheil-Gulliver solidification model, as already performed elsewhere. [6]…”

Section: 28mentioning

confidence: 99%

“…This in situ heating characteristic makes EBM particularly attractive for processing high-performance alloys that are susceptible to thermal stress-induced cracking or solidification/hot cracking. For example, EBM was applied to produce precipitation-strengthened nickelbase superalloys, [2][3][4][5][6] cobalt-base alloys, [7,8] as well as titanium aluminide intermetallic alloys. [9][10][11] However, little effort has been made regarding EBM high-speed steels that are also susceptible to cracking.…”

Section: Introductionmentioning

confidence: 99%

Rapid Solidification Microstructure and Carbide Precipitation Behavior in Electron Beam Melted High-Speed Steel

Jin

Gao

Peng

et al. 2020

Metall Mater Trans A

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The solidified microstructure and carbide precipitation behavior in an S390 high-speed steel processed by electron beam melting (EBM) have been fully characterized. The as-EBM microstructure consists of discontinuous network of very fine primary carbides dispersed in auto-tempered martensite matrix together with a limited amount of retained austenite. The carbide network consists of M 2 C/M 6 C and MC carbides. Both the columnar and near-equiaxed grain structures were found in as-EBM microstructure and the presence of inter-dendritic eutectic carbides assisted in revealing the dendritic solidification nature. The top-layer microstructure observation confirmed that the columnar dendritic structured grains were located adjacent to the micro-melt pool boundary, indicating an epitaxial growth with the average growth direction parallel to the maximum thermal gradient. At the center of the micro-melt pool, the near-equiaxed grains were developed by dendritic growth parallel to the beam traveling direction. The carbide decomposition was revealed by scanning transmission electron microscopy and confirmed by transmission Kikuchi diffraction. The MC carbides (rich in V followed by W) nucleated at the interface between M 2 C (W, Fe, Mo, and Co in the order of significance) and the matrix and then grew from the outside inward, but their nucleation might occur from the M 2 C carbide itself. The thermal effect induced by the adjacent scan lines seems to trigger a solid-state phase transformation of MC fi M 2 C + c-Fe. The elemental migration was theoretically calculated and compared with the experimental results. The high hardness of~65 HRC and good transverse rupture strength of~2500 MPa in as-EBM S390 means that EBM processing can be used to fabricate highly alloyed tool steels. With the help of the post-processing heat treatment, the best Rockwell hardness of 73.1±0.2 HRC and transverse rupture strength of 3012±34 MPa can be obtained.

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“…To control material anisotropy, Haines et al performed a sensitivity analysis with a focus on adjusting alloy composition to control the columnar to equiaxed transition in Ni-base alloys 25 . Similarly, control of the columnar to equiaxed transition through AM process control has been employed by Kontis et al to successfully fabricate a non-weldable Ni-base superalloy through atomic-scale grain boundary engineering 26 . Additionally, AM allows for the mixing of alloy powders before printing, resulting in the fabrication of metal-metal composites with unique microstructures that would be difficult to fabricate by other means 27 .…”

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confidence: 99%

A defect-resistant Co–Ni superalloy for 3D printing

et al. 2020

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Additive manufacturing promises a major transformation of the production of high economic value metallic materials, enabling innovative, geometrically complex designs with minimal material waste. The overarching challenge is to design alloys that are compatible with the unique additive processing conditions while maintaining material properties sufficient for the challenging environments encountered in energy, space, and nuclear applications. Here we describe a class of high strength, defect-resistant 3D printable superalloys containing approximately equal parts of Co and Ni along with Al, Cr, Ta and W that possess strengths in excess of 1.1 GPa in as-printed and post-processed forms and tensile ductilities of greater than 13% at room temperature. These alloys are amenable to crack-free 3D printing via electron beam melting (EBM) with preheat as well as selective laser melting (SLM) with limited preheat. Alloy design principles are described along with the structure and properties of EBM and SLM CoNi-base materials.

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

Cited by 203 publications

References 45 publications

Alloy Design and Characterization of γ′ Strengthened Nickel-based Superalloys for Additive Manufacturing

Alloy Design and Characterization of γ′ Strengthened Nickel-based Superalloys for Additive Manufacturing

Rapid Solidification Microstructure and Carbide Precipitation Behavior in Electron Beam Melted High-Speed Steel

A defect-resistant Co–Ni superalloy for 3D printing

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