Analysis of temperature distribution in shell mould during thin-wall superalloy casting and its effect on the resultant microstructure

Rakoczy, Łukasz; Cygan, Rafał

doi:10.1016/j.acme.2018.05.008

Cited by 20 publications

(7 citation statements)

References 25 publications

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“…As a result of these changes, the Ni/Nb ratio was 1.6-2.1. The solidification of Nb-bearing austenitic superalloys like Alloy 718 begins with the formation of Nb-lean austenitic dendrites, while interdendritic eutectic-type solidification constituents involve among others NbC and Nb-rich Laves phase precipitates [46][47][48][49]. In this study, for all modified variants the segregation coefficient of Nb was lower than 1, which confirms that dendritic regions were depleted in this alloying element.…”

Section: Characterization Of the Primary Microstructure Of Castingssupporting

confidence: 60%

Fabrication and Characterization of the Newly Developed Superalloys Based on Inconel 740

et al. 2020

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The chemical composition of standard Inconel 740 superalloy was modified by changes in the Al/Ti ratio (0.7, 1.5, 3.4) and addition of Ta (2.0, 3.0, 4.0%). Remelted Inconel 740 (A0) and nine variants with various chemical compositions were fabricated by lost-wax casting. The microstructure, microsegregation, phase transformation temperatures, thermal expansion coefficients and hardness of the superalloys were investigated by scanning electron microscopy, energy dispersive X-ray spectroscopy, differential scanning calorimetry, dilatometry and Vickers measurements. Typical dendritic microstructure was revealed with microsegregation of the alloying elements. Segregation coefficient ki for Ti, Nb and Ta did not exceed unity, and so precipitates enriched mainly in these elements were found in interdendritic spaces. The Nb-rich blocky precipitates, MC carbides, MN nitrides, oxides, and fine γ’ was in all modified castings. Presence of other microstructural features, such as Ti-rich needles, eutectic γ-γ’ islands, small Al-rich and Cr-rich precipitates depended on the casting composition. The lowest solidus and liquidus temperatures were observed in superalloys with a high Al/Ti ratio. Consequently, in A7–A9 variants, the solidification range did not exceed 100 °C. In the A0 variant the difference between liquidus and solidus temperature was 138 °C. Hardness of all modified superalloys was at least 50% higher than for the remelted Inconel 740 (209 HV10).

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Section: Characterization Of the Primary Microstructure Of Castingssupporting

confidence: 60%

Fabrication and Characterization of the Newly Developed Superalloys Based on Inconel 740

et al. 2020

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“…Designed melt-pouring temperature was 1520°C and so higher than the melting point of Al (660°C), Cu (1085°C) and Ni (1455°C), whereas slightly lower than for Fe (1538°C) ( Ref 21). A previous investigation (Ref 18) showed that the maximum temperature in the second layer during investment casting process can be lower approximately 150°C than the pouring temperature. This indicates that the Fe and Ni existed as solid particles.…”

Section: Green Strength Of Moldsmentioning

confidence: 99%

The Influence of Shell Mold Composition on the As-cast Macro- and Micro-structure of Thin-Walled IN713C Superalloy Castings

Rakoczy

Grudzień-Rakoczy

Cygan

2019

J. of Materi Eng and Perform

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In the investment casting process, the building of ceramic layers around the wax pattern is the main timeconsuming stage. Increasing their number ensures sufficient mechanical properties, but also lengthens the whole process, including drying time and preheating of the mold. Four molds for casting Ni-based superalloy IN713C were strengthened by glass fibers, included in the slurry, and metal powder, of Al, Cu, Fe or Ni, in the coverage. Castings were subjected to microstructural investigations in order to find out if the new design can be promising for the manufacture of jet engine components. Bend tests revealed that the green strengths of all new molds were higher, at least 3.65 MPa, than that of the unmodified molds, 3.0 MPa. Optical microscopy revealed that the composition of a mold had a strong influence on stereological parameters of equiaxed IN713C grains. Microstructural observation and hardness measurements of castings revealed differences in the volume fraction of strengthening phases, porosity and hardness. The microstructure due to the complex chemical composition of IN713C consisted of several phases including ternary eutectics as a consequence of L fi c + Ni 7 Zr 2 + (Nb, Zr)C. Keywords aviation, glass fibers, investment casting, metal powder, shell mold This article is an invited submission to JMEP selected from presentations at the 73rd World Foundry Congress and has been expanded from the original presentation. 73WFC was held in Krakow, Poland, September 23-27, 2018, and was organized by the World Foundry Organization and Polish FoundrymenÕs Association.

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“…This alloy is also extensively used in the automotive, power and oil and gas industries due to a unique combination of strength at operating temperature and excellent hot corrosion resistance. The very good castability, low-cycle fatigue resistance (LCF) and microstructural stability determine the wide use of the Inconel 713C for low-pressure turbine (LPT) guide vanes in GP7200 engines (Ref [3][4][5][6]. Usually, superalloys are heat-treated (solution + aging); however, Inconel 713C achieves sufficiently high properties in the as-cast condition, and so increase in mechanical properties is by optimization of investment casting parameters and composition of the shell mold ( Ref 7).…”

Section: Introductionmentioning

confidence: 99%

Influence of Melt-Pouring Temperature and Composition of Primary Coating of Shell Mold on Tensile Strength and Creep Resistance of Ni-Based Superalloy

Rakoczy

Grudzień

Cygan

2019

J. of Materi Eng and Perform

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Eight investment castings of Inconel 713C superalloy were fabricated, varying in the melt-pouring temperature, from 1400 to 1520°C, and CoAl 2 O 4 inoculant content, 0 or 5 wt.%, in the primary coat. Their influence on grain size on tensile and creep properties was investigated. The best combination of yield stress (815 MPa) and elongation (A 4 = 7.65%) at ambient temperature was obtained in surface-modified castings poured from 1520°C. The longest time to rupture was for the unmodified castings (76.8 h) poured from 1520°C, while for the modified variant, the time to rupture was lower around, 7.4 h, which was still a satisfactory value. During tensile testing, microcracks were formed in large eutectic c¢, carbides and borides, due to the accumulation of stress at interfaces with the matrix. During creep, N-type rafting of c¢ precipitates and phase transformation MC + c fi c¢ + M 23 C 6 took place.

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Analysis of temperature distribution in shell mould during thin-wall superalloy casting and its effect on the resultant microstructure

Cited by 20 publications

References 25 publications

Fabrication and Characterization of the Newly Developed Superalloys Based on Inconel 740

Fabrication and Characterization of the Newly Developed Superalloys Based on Inconel 740

The Influence of Shell Mold Composition on the As-cast Macro- and Micro-structure of Thin-Walled IN713C Superalloy Castings

Influence of Melt-Pouring Temperature and Composition of Primary Coating of Shell Mold on Tensile Strength and Creep Resistance of Ni-Based Superalloy

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