Influence of Al/Ti Ratio and Ta Concentration on the As-Cast Microstructure, Phase Composition, and Phase Transformation Temperatures of Lost-Wax Ni-Based Superalloy Castings

Grudzień-Rakoczy, Małgorzata; Rakoczy, Łukasz; Cygan, Rafał; Chrzan, Konrad; Milkovič, Ondrej; Pirowski, Z.

doi:10.3390/ma15093296

Cited by 3 publications

(2 citation statements)

References 56 publications

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“…Generally, the TCP precipitates are easily formed in the microstructures of Ni-based superalloys during the high-temperature, long-term aging or creep tests, which is essentially caused by the element diffusion and has a great relationship with temperature, time, and stress [ 28 , 29 ]. W, Mo, and the other refractory elements are usually enriched in the γ matrix, and the segregation of the above elements on the dendrite core cannot be completely eliminated during the solid solution treatment, thus the TCP phases precipitate in the dendrite core [ 30 , 31 ]. In contrast, the TCP phases formed at the interdendritic region in Alloy IV with 3.0 wt.% Mo content after the heat treatment in this work, which could be explained by the following reasons:…”

Section: Resultsmentioning

confidence: 99%

Effect of Mo on the Microstructures and Mechanical Properties of the Polycrystalline Superalloy with High W Content

Quan¹,

Sun

Sheng

et al. 2022

Materials

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The effect of the Mo contents of 1.0 wt.%, 1.5 wt.%, 2.0 wt.%, and 3.0 wt.% on the microstructures and mechanical properties of the polycrystalline superalloy with a high W content was studied. The typical dendrite morphology was observed in the high-W superalloy with different Mo contents, containing γ matrix, γ′ phase, eutectic, and MC carbide. After the heat treatment, the primary MC carbides were decomposed into M6C carbides, while a needle-like topologically close-packed (TCP) phase was formed in the alloy with high Mo content, in contrast to the other three alloys with low Mo content. The Mo addition increased the lattice parameter of the γ and γ′ phases and also changed the lattice misfits of the γ and γ′ phase lattice misfits towards a larger negative. The addition of Mo improved the yield strength at room temperature due to the solid solution strengthening and coherency strengthening. The improvement of the stress rupture lives at 975 °C/225 MPa was due to the combination of the suppressed propagation of the microcracks by the carbides and a more negative misfit. When the Mo content reached 3.0 wt.%, the TCP phases formed and decreased the ultimate tensile strength and the stress rupture lives as a result.

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Section: Resultsmentioning

confidence: 99%

Effect of Mo on the Microstructures and Mechanical Properties of the Polycrystalline Superalloy with High W Content

Quan¹,

Sun

Sheng

et al. 2022

Materials

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“…This leads to a yield stress anomaly, where the flow stress increases with temperature, making it advantageous for high-temperature components [ 4 ]. Due to the high costs associated with superalloy machining, investment casting is crucial for fabricating elements with complex geometries [ 5 ]. The lost-wax process is particularly effective, offering high dimensional accuracy by using monolithic ceramic molds [ 6 ].…”

Section: Introductionmentioning

confidence: 99%

The Effect of CoAl2O4 as a Nucleating Agent and Pouring Temperature on the Microstructure and Properties of Inconel 713C® Nickel-Based Superalloy Castings

Cygan

Rakoczy

2023

Materials

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In this work, three melt-pouring temperatures (1450 °C, 1480 °C, 1520 °C) and CoAl2O4 inoculant contents in the shell mold’s primary coating (0 wt%, 5 wt%, and 10 wt%) were selected to study microstructural and mechanical property changes of the Inconel 713C® nickel-based superalloy. The castings’ phase transformation temperatures, phase constitution, microstructure, and mechanical properties at room and elevated temperatures were investigated via thermodynamical simulations, differential thermal analysis, light and scanning electron microscopy, energy-dispersive X-ray spectroscopy, and tensile and stress-rupture tests. The pouring temperature and inoculant content strongly influenced the mean equiaxed grain size, which ranged between 2.36 and 6.55 mm. The primary microstructure of Inconel 713C® castings, owing to its complex chemical composition, comprised multiple phases, including γ, γ’, MC, M3B2, and Ni7Zr2. The mean size of γ’ was in the 0.446–0.613 μm range, depending on the casting variant. Grain refinement with CoAl2O4 at ambient temperature for each melt-pouring temperature led to increased yield strength (YS) and ultimate tensile strength (UTS). YS was in the range of 775–835 MPa, while UTS was in the range of 868–1010 MPa. A reverse trend was observed in samples that crept in 982 °C/152 MPa, while for each variant, the time to rupture exceeded 30 h. The maximum time to rupture was 46.1 h obtained in the unmodified casting poured at 1480 °C.

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Al- and Ta-Modified Alloy 740 Superalloy Castings Produced in Non-vacuum Conditions—Microstructure and Selected Properties

Grudzień-Rakoczy,

Rakoczy,

Lech

et al. 2024

Metall Mater Trans A

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The work focuses on characterizing the microstructure and selected properties of Al- (1.3 or 2.8 wt pct) and Ta-modified (2 or 3 or 4 wt pct) Alloy 740 Ni-based superalloy after heat treatment. The observations and analyses were conducted using thermodynamic simulations, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, steam oxidation, hardness, tensile, and stress rupture tests. The castings exhibit a typical dendritic structure, with the presence of fine γ′ precipitates, Nb-rich Laves phase precipitates, MC carbides, and MN nitrides are found in all modified castings. However, the presence of the η phase, G phase, and M23C6 is dependent on the superalloy’s chemical composition. At room temperature, the reference cast superalloy had an ultimate tensile strength and yield strength of 655 MPa and 477 MPa, respectively. In modified castings, the ultimate tensile strength and YS are higher, respectively, 713–1046 MPa and 705–903 MPa. After steam oxidation at 760 °C/1000 h, the mass gain of the modified castings was in the range of 0.339–0.429 mg/cm2. The addition of tantalum resulted in decreased oxidation resistance and the formation of the TiTaO4 oxide at the Cr2O3/superalloy interface.

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Influence of Al/Ti Ratio and Ta Concentration on the As-Cast Microstructure, Phase Composition, and Phase Transformation Temperatures of Lost-Wax Ni-Based Superalloy Castings

Cited by 3 publications

References 56 publications

Effect of Mo on the Microstructures and Mechanical Properties of the Polycrystalline Superalloy with High W Content

Effect of Mo on the Microstructures and Mechanical Properties of the Polycrystalline Superalloy with High W Content

The Effect of CoAl2O4 as a Nucleating Agent and Pouring Temperature on the Microstructure and Properties of Inconel 713C® Nickel-Based Superalloy Castings

Al- and Ta-Modified Alloy 740 Superalloy Castings Produced in Non-vacuum Conditions—Microstructure and Selected Properties

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