Investigation on the homogenization treatment and element segregation on the microstructure of a γ/γ′-cobalt-based superalloy

Sani, Saeed Aliakbari; Arabi, H.; Kheirandish, Shahram; Ebrahimi, Ghanbar

doi:10.1007/s12613-019-1727-7

Cited by 18 publications

(7 citation statements)

References 50 publications

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“…The size of the γ ' phase of the dendrite cores is slightly smaller than that of the interdendritic, about 0.687 and 0.844 μm, respectively. The distribution of alloying elements is different in the two phases, [ 30 ] and after solid solution and aging heat treatment, the segregation of the elements reduced, [ 31,32 ] then the structure is uniform, and a stable γ / γ ' two‐phase structure at high temperature is obtained, significantly improving the mechanical properties of the cobalt‐based single crystal alloy.…”

Section: Resultsmentioning

confidence: 99%

Microstructure and Tensile Behavior of a Novel Monocrystalline Co‐Based Superalloy at Different Temperatures

et al. 2022

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Microstructures and tensile properties of a novel monocrystalline Co‐based superalloy are investigated by experiments and finite element simulation. Microstructures of heat‐treated alloys are composed of γ and cubical γ' precipitates without the presence of the secondary phase, and the fraction of γ' phase is about 86%. The experimental results show that tensile properties of the novel monocrystalline Co‐based superalloy have abnormal yield behavior. In low and medium temperature ranges (R.T. 850 °C), the yield stress increases gradually with temperature increase and the tensile fracture surface is characterized by cleavage rupture. At 850 °C, fracture mechanism is composite of cleavage and microporous. While above 850 °C, the yield stress decreases rapidly, and fracture surface is constituted of mixed fracture surface of dimples and micropores. The simulation results show that the tensile stress‐–strain curves are well fitted to the experimental data at different temperatures.

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Section: Resultsmentioning

confidence: 99%

Microstructure and Tensile Behavior of a Novel Monocrystalline Co‐Based Superalloy at Different Temperatures

et al. 2022

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“…The large primary γ precipitates were characterized by SEM image analysis. They had a radius of about 150 nm formed during the recrystallization heat treatment at 1000 • C (see Figure 1a) since the γ solvus temperature was 1030 • C [6]. These precipitates were distributed heterogeneously and their volume fraction was about 3%.…”

Section: Electron Microscopymentioning

confidence: 99%

“…In recent years, different compositionally complex, γ -strengthened CoNi-base superalloys in the Co-Al-W system were developed [1][2][3][4][5][6]. Investigations revealed that, in particular, the polycrystalline CoNi-base superalloys are promising for high-temperature applications [1,7].…”

Section: Introductionmentioning

confidence: 99%

Enhancing the High-Temperature Strength of a Co-Base Superalloy by Optimizing the γ/γ′ Microstructure

Hausmann

Solís

Freund

et al. 2020

Metals

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Compositionally complex polycrystalline γ/γ′ CoNi-base superalloys, such as CoWAlloy2 (Co41-Ni32-Cr12-Al9-W5-Ti0.3-Ta0.2-Si0.4-Hf0.1-C-B-Zr) are interesting candidates for new high-temperature materials. To maximize their high-temperature strength, the γ/γ′ microstructure has to be optimized by adjusting the multi-step heat treatments. Various microstructures after different heat treatments were analyzed by scanning and transmission electron microscopy and especially in-situ small-angle neutron scattering during heat treatment experiments. The corresponding mechanical properties were determined by compression tests and hardness measurements. From this, an optimum γ′ precipitate size was determined that is adjusted mainly in the first precipitation heat treatment step. This is discussed on the basis of the theory of shearing of γ′ precipitates by weak and strong pair-couplings of dislocations. A second age hardening step leads to a further increase in the γ′ volume fraction above 70% and the formation of tertiary γ′ precipitates in the γ channels, resulting in an increased hardness and yield strength. A comparison between two different three-step heat treatments revealed an increase in strength of 75 MPa for the optimized heat treatment.

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“…The same authors published the work concerning effect of Al and W contents on the solidification and solution microstructure of new cobalt superalloys [16]. Sani et al [17] performed the research on effect of homogenization heat treatment on segregation and microstructure of γ-γ′ Co-based superalloys. The heat treatment aspects of ternary Co-Al-W alloys were investigation by Tomaszewska et al [18].…”

Section: Introductionmentioning

confidence: 99%

Crystallization behavior of ternary γ–γ′ Co–Al–W alloy

Migas

Gradoń

Mikuszewski

et al. 2020

J Therm Anal Calorim

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In the investigation, crystallization behavior of ternary γ–γ′ alloy based on Co–Al–W system was analyzed. The alloy with nominal composition Co–9Al–9W (at.%) was prepared via vacuum induction melting. Solidification characteristics of the investigated superalloy were obtained by a method of thermal analysis based on temperature measurement of metal solidifying in a mold. After casting, obtained metallic materials were investigated by differential thermal analysis in order to determine characteristic temperatures and compare results with those of obtained in the first thermal analysis. Furthermore, a description of primary microstructure was performed for ingots solidified with two different cooling rates. The analysis was made using X-ray diffraction, optical microscopy and scanning electron microscopy. The crystallization path of alloy was investigated. The solidification range of alloy was narrow. The crystallization in a sand mold resulted in the dendritic microstructure containing γ single phase. The as-cast microstructure after solidification with higher cooling rate was comparable; however, observed crystals were mostly columnar, while sand cast was characterized by equiaxed crystals structure.

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Investigation on the homogenization treatment and element segregation on the microstructure of a γ/γ′-cobalt-based superalloy

Cited by 18 publications

References 50 publications

Microstructure and Tensile Behavior of a Novel Monocrystalline Co‐Based Superalloy at Different Temperatures

Microstructure and Tensile Behavior of a Novel Monocrystalline Co‐Based Superalloy at Different Temperatures

Enhancing the High-Temperature Strength of a Co-Base Superalloy by Optimizing the γ/γ′ Microstructure

Crystallization behavior of ternary γ–γ′ Co–Al–W alloy

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