subject:(Ni Based Superalloys)

1. Thébaud, Louis. Etude des relations entre microstructure et propriétés mécaniques du nouveau superalliage base nickel AD730™ : Relationships Between Microstructural Parameters and Mechanical Properties of a new Nickel Based Superalloy AD730™.

Degree: Docteur es, Mécanique des solides, des matériaux, des structures et des surfaces, 2017, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique

URL: http://www.theses.fr/2017ESMA0033

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Compte tenu de l’évolution des températures d’entrée de turbines, le principal enjeu pour les métallurgistes est d’élaborer des alliages capables de présenter d’excellentes propriétés mécaniques… (more)

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Compte tenu de l’évolution des températures d’entrée de turbines, le principal enjeu pour les métallurgistes est d’élaborer des alliages capables de présenter d’excellentes propriétés mécaniques à des températures de plus en plus élevées. Dans ce contexte, connaitre les relations entre les différents paramètres microstructuraux et les propriétés mécaniques à haute température (700°C et plus) est capital.La durabilité en fluage et en fatigue-temps de maintien ainsi que les processus d’endommagement de l’alliage AD730™, un nouveau superalliage pour disques de turbines, ont été analysés. Plusieurs paramètres ont été étudiés, qu’ils soient microstructuraux (joints de grains, taille de grains, taille et distribution des précités γ′), ou expérimentaux (température, environnement, contrainte appliquée, temps de maintien). L’utilisation de monograins de composition chimique identique à l’alliage de l’étude a permis de mettre en évidence le fait qu’une microstructure monogranulaire ne présente pas nécessairement de meilleures propriétés en fluage qu’une microstructure polycristalline. Ceci est attribué au rôle durcissant des joints de grains. Il a de plus été montré qu’à 700°C, la taille et la distribution des précipités γ′ est le paramètre microstructural pilotant les propriétés viscoplastiques à l’ordre 1.En fatigue avec temps de maintien, un comportement original a été observé pour les longs temps de maintien en fonction de la contrainte appliquée. Ce phénomène est attribué à un effet « type Bauschinger » apparaissant lors des phases de décharges.

In view of the turbine entry temperature evolution, the main challenge for metallurgists is to elaborate new alloys able to withstand higher temperatures while keeping great mechanical properties. Therefore, knowing the relationships between microstructural parameters and mechanical properties at high temperatures (700°C and more) is mandatory.The creep and dwell-fatigue durability as well as the damage mechanisms of AD730™, a new nickel base superalloy developed for turbine disks, have been analyzed. Several microstructural parameters were studied (grain boundaries, grain size, size and distribution of γ′ precipitates) as well as experimental parameters (temperature, environment, applied stress or dwell period). By using single crystalline specimens having the same chemical composition of the studied alloy, it has been shown unambiguously that single crystalline microstructures do not necessarily present better creep properties compared to polycristalline ones. This result is supposed to be caused by a grain boundary strengthening mechanism. Moreover, in creep at 700°C, it has been shown that the main viscoplasticity controlling parameters are the size and distribution of γ′ precipitates.An unexpected dwell-fatigue behavior has been observed for long hold times and in a specific applied stress window. This phenomena is attributed to a “Bauschinger type” effect, occurring during unloading phases.

Advisors/Committee Members: Villechaise, Patrick (thesis director), Cormier, Jonathan (thesis director).

Subjects/Keywords: Superalliage base nickel; Ni-based superalloys

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APA (6^th Edition):

Thébaud, L. (2017). Etude des relations entre microstructure et propriétés mécaniques du nouveau superalliage base nickel AD730™ : Relationships Between Microstructural Parameters and Mechanical Properties of a new Nickel Based Superalloy AD730™. (Doctoral Dissertation). Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique. Retrieved from http://www.theses.fr/2017ESMA0033

Chicago Manual of Style (16^th Edition):

Thébaud, Louis. “Etude des relations entre microstructure et propriétés mécaniques du nouveau superalliage base nickel AD730™ : Relationships Between Microstructural Parameters and Mechanical Properties of a new Nickel Based Superalloy AD730™.” 2017. Doctoral Dissertation, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique. Accessed January 23, 2021. http://www.theses.fr/2017ESMA0033.

MLA Handbook (7^th Edition):

Thébaud, Louis. “Etude des relations entre microstructure et propriétés mécaniques du nouveau superalliage base nickel AD730™ : Relationships Between Microstructural Parameters and Mechanical Properties of a new Nickel Based Superalloy AD730™.” 2017. Web. 23 Jan 2021.

Vancouver:

Thébaud L. Etude des relations entre microstructure et propriétés mécaniques du nouveau superalliage base nickel AD730™ : Relationships Between Microstructural Parameters and Mechanical Properties of a new Nickel Based Superalloy AD730™. [Internet] [Doctoral dissertation]. Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique; 2017. [cited 2021 Jan 23]. Available from: http://www.theses.fr/2017ESMA0033.

Council of Science Editors:

Thébaud L. Etude des relations entre microstructure et propriétés mécaniques du nouveau superalliage base nickel AD730™ : Relationships Between Microstructural Parameters and Mechanical Properties of a new Nickel Based Superalloy AD730™. [Doctoral Dissertation]. Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique; 2017. Available from: http://www.theses.fr/2017ESMA0033

Indian Institute of Science

2. Vinay, K S. Microstructural Evolution of Directionally Solidified Ni-Al-Re/Ru Alloys.

Degree: MSc Engg, Engineering, 2018, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/4056

► Nickel based superalloys are high temperature materials which find application as blade and disc components of jet engines due to their ability to retain their… (more)

▼ Nickel based superalloys are high temperature materials which find application as blade and disc components of jet engines due to their ability to retain their mechanical properties at temperatures close to 0.8 of their melting point. The modern day nickel based superalloys are multicomponent alloys, containing up to 12 alloying elements which are added in balanced proportions to achieve high temperature strength and microstructural stability, Re and Ru have been the recent additions made to superalloy compositions in the last two decades. But the roles of Re and Ru in terms of partitioning among the phases γ and γ’ and its effects on mechanical properties are still not clear. Hence an effort was made to study their effects under constrains of constant volume fractions of γ’ and misfit between γ and γ’, to isolate effects that result purely due to composition. Three model alloy systems (two ternary and one quaternary) of the type Ni-Al-xRe, Ni-Al-yRu and Ni-Al-xRe-yRu, x=2.5/4 and y=2.5/6 with minor additions of 1.4 Hf and 0.07 C for reasons of castability were synthesized by investment casting. This thesis deals with the solidification related aspects of these alloys. Chapter 1 deals with a brief overview of Ni based superalloys in terms of their physical metallurgy, processing, microstructure and the effects of Re and Ru studied in literature. These are summarized and the objective of thesis laid out. The experimental details of the techniques employed for studying the cast structure such as optical microscopy, scanning electron microscopy, electron probe microanalysis and differential scanning calorimetry are discussed in Chapter 2 In Chapter 3, the experimental results concerning microstructure, chemistries (local and global), differential scanning calorimetry and supporting Thermo-Calc based simulations are presented. The composition of the directionally solidified alloys were estimated using quantitative EPMA spot analysis after homogenizing them to the best possible extent. The cooling rates experienced by the bottom, middle and tip sections (25mm, 150mm and 295mm respectively from chill plate) of the model alloys during casting was estimated using ProCASTTM simulations. The simulations show the cooling rates to vary from 12.5 K/min to 6 K/min, corresponding to the range of thermal gradients 3000 K/m to 1500 K/m from bottom to tip sections. These estimations were performed assuming a constant withdrawal velocity of 24 cm/hr. The morphological evolution of cast structure from bottom to tip section of the alloys was studied at a coarse scale with the aid of optical microscopy. A tendency towards increased branching of dendrites to form well developed tertiary arms is observed on moving from bottom to tip sections. Quantitative measurement of primary and secondary arm spacings (PDAS and SDAS) indicate that PDAS values increase from bottom to middle section and then saturates, whereas the SDAS values show an increase from bottom to tip sections. Also, the PDAS and SDAS values of MA-3 were observed to be… Advisors/Committee Members: Banerjee, Dipankar (advisor).

Subjects/Keywords: Nickel Based Superalloys; Solidification Alloys; Alloy Composition; Ni-Based Superalloys; Ni-Al-Re/Ru Alloys; Materials Engineering

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APA (6^th Edition):

Vinay, K. S. (2018). Microstructural Evolution of Directionally Solidified Ni-Al-Re/Ru Alloys. (Masters Thesis). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/4056

Chicago Manual of Style (16^th Edition):

Vinay, K S. “Microstructural Evolution of Directionally Solidified Ni-Al-Re/Ru Alloys.” 2018. Masters Thesis, Indian Institute of Science. Accessed January 23, 2021. http://etd.iisc.ac.in/handle/2005/4056.

MLA Handbook (7^th Edition):

Vinay, K S. “Microstructural Evolution of Directionally Solidified Ni-Al-Re/Ru Alloys.” 2018. Web. 23 Jan 2021.

Vancouver:

Vinay KS. Microstructural Evolution of Directionally Solidified Ni-Al-Re/Ru Alloys. [Internet] [Masters thesis]. Indian Institute of Science; 2018. [cited 2021 Jan 23]. Available from: http://etd.iisc.ac.in/handle/2005/4056.

Council of Science Editors:

Vinay KS. Microstructural Evolution of Directionally Solidified Ni-Al-Re/Ru Alloys. [Masters Thesis]. Indian Institute of Science; 2018. Available from: http://etd.iisc.ac.in/handle/2005/4056

Penn State University

3. Ling, Yan. FIRST-PRINCIPLES CALCULATIONS AND THERMODYNAMIC MODELING OF THE HF-RE BINARY SYSTEM WITH EXTENSION TO THE HF-NI-RE TERNARY SYSTEM .

Degree: 2011, Penn State University

URL: https://submit-etda.libraries.psu.edu/catalog/12018

► This thesis describes the thermodynamic modeling of the Hf-Re binary system and prediction of the Ni-Hf-Re ternary system. Hafnium and rhenium are both alloying elements… (more)

Subjects/Keywords: thermodynamics; Ni-Hf-Re; hafnium; rhenium; Hf-Re; CALPHAD; first-principles; Ni-based superalloys; modeling

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APA (6^th Edition):

Ling, Y. (2011). FIRST-PRINCIPLES CALCULATIONS AND THERMODYNAMIC MODELING OF THE HF-RE BINARY SYSTEM WITH EXTENSION TO THE HF-NI-RE TERNARY SYSTEM . (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/12018

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Ling, Yan. “FIRST-PRINCIPLES CALCULATIONS AND THERMODYNAMIC MODELING OF THE HF-RE BINARY SYSTEM WITH EXTENSION TO THE HF-NI-RE TERNARY SYSTEM .” 2011. Thesis, Penn State University. Accessed January 23, 2021. https://submit-etda.libraries.psu.edu/catalog/12018.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Ling, Yan. “FIRST-PRINCIPLES CALCULATIONS AND THERMODYNAMIC MODELING OF THE HF-RE BINARY SYSTEM WITH EXTENSION TO THE HF-NI-RE TERNARY SYSTEM .” 2011. Web. 23 Jan 2021.

Vancouver:

Ling Y. FIRST-PRINCIPLES CALCULATIONS AND THERMODYNAMIC MODELING OF THE HF-RE BINARY SYSTEM WITH EXTENSION TO THE HF-NI-RE TERNARY SYSTEM . [Internet] [Thesis]. Penn State University; 2011. [cited 2021 Jan 23]. Available from: https://submit-etda.libraries.psu.edu/catalog/12018.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Ling Y. FIRST-PRINCIPLES CALCULATIONS AND THERMODYNAMIC MODELING OF THE HF-RE BINARY SYSTEM WITH EXTENSION TO THE HF-NI-RE TERNARY SYSTEM . [Thesis]. Penn State University; 2011. Available from: https://submit-etda.libraries.psu.edu/catalog/12018

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Loughborough University

4. Newman, Scott. Microstructural evolution in coated conventionally cast Ni-based superalloys.

Degree: PhD, 2013, Loughborough University

URL: http://hdl.handle.net/2134/12468

► The aim of this research project was to investigate the microstructural changes of MCrAlY coated Ni-based superalloys that are routinely used in industrial gas turbine… (more)

Subjects/Keywords: 620.1; Ni-based superalloys; High temperature coatings; MCrAlY; Thermal Barrier coating

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Newman, S. (2013). Microstructural evolution in coated conventionally cast Ni-based superalloys. (Doctoral Dissertation). Loughborough University. Retrieved from http://hdl.handle.net/2134/12468

Chicago Manual of Style (16^th Edition):

Newman, Scott. “Microstructural evolution in coated conventionally cast Ni-based superalloys.” 2013. Doctoral Dissertation, Loughborough University. Accessed January 23, 2021. http://hdl.handle.net/2134/12468.

MLA Handbook (7^th Edition):

Newman, Scott. “Microstructural evolution in coated conventionally cast Ni-based superalloys.” 2013. Web. 23 Jan 2021.

Vancouver:

Newman S. Microstructural evolution in coated conventionally cast Ni-based superalloys. [Internet] [Doctoral dissertation]. Loughborough University; 2013. [cited 2021 Jan 23]. Available from: http://hdl.handle.net/2134/12468.

Council of Science Editors:

Newman S. Microstructural evolution in coated conventionally cast Ni-based superalloys. [Doctoral Dissertation]. Loughborough University; 2013. Available from: http://hdl.handle.net/2134/12468

Indian Institute of Science

5. Divya, V D. Diffusion Studies On Systems Related to Nickel Based Superalloys.

Degree: PhD, Faculty of Engineering, 2013, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/1948

► Superalloys offer high temperature strength, excellent creep, corrosion and oxidation resistances, microstructural stability and good fatigue life at elevated temperatures. The composition of the superalloys… (more)

▼ Superalloys offer high temperature strength, excellent creep, corrosion and oxidation resistances, microstructural stability and good fatigue life at elevated temperatures. The composition of the superalloys has been modified continuously to improve the properties. The addition of Pt improves oxidation resistance without compromising the mechanical properties of the superalloys. To further enhance the performance of the superalloy components, various coatings are applied on them. The-(NiPt)Al intermetallic compound bond coats, which are presently utilized, have certain drawbacks. Diffusion of Al from the bond coat to superalloy during service leads to accumulation of stress near the bond coat. The refractory elements present in superalloy precipitate as topological close packed (TCP) phases in the interdiffusion zone. Consequently, a Pt enriched γ(Ni) + γ’(Ni3Al) phase mixture has been proposed as a possible alternative since TCP phases do not form in the interdiffusion zone. In this thesis, diffusion studies are performed on several binary and ternary systems with the primary purpose of understanding the effect of Pt in Ni based superalloys and also in γ + γ’ phase mixture bond coats. Further, a detailed interdiffusion study is conducted in Mo- and W- based binary and ternary systems to understand the growth of the TCP phases. By performing bulk and multifoil diffusion couple experiments, different diffusion parameters like, inter, intrinsic, tracer, impurity diffusion coefficients and activation energy that are necessary to understand the diffusion mechanism are determined. Additionally using the nanoindentation technique on diffusion couples, variation of mechanical properties such as, hardness and modulus with composition is studied. First, interdiffusion in Ni-Pt, Co-Pt, Co-Ni, Ni-Fe and Co-Fe binary systems is examined. In Ni-Pt and Co-Pt, experimental results show that Pt is the slower diffusing species at all compositions. In both the systems, driving force is found to be the reason for higher values of intrinsic diffusion coefficients observed in the range of 40-60 at. % Pt. Contribution of vacancy wind effect on diffusion parameters is found to be negligible. It is found from the multifoil diffusion couple experiments that Ni is the faster diffusing species in the Co-Ni system. Bulk diffusion couple experiments are conducted in the Co-Ni-Pt and Co-Ni-Fe systems, by coupling binary alloys with the third element. Uphill diffusion is observed for Co and Ni in Pt rich corner of the Co-Ni-Pt system. Main and cross interdiffusion coefficients are calculated at the compositions where two diffusion profiles intersect. In both the systems, the main interdiffusion coefficients are positive over the whole composition range and the cross diffusion coefficients show both positive and negative values at different regions. Hardness measured by performing the nanoindentations on diffusion couples of both the systems, shows the higher values at intermediate compositions. The effect of Pt in and’ phases of Ni-Al… Advisors/Committee Members: Paul, Aloke (advisor), Ramamurty, U (advisor).

Subjects/Keywords: Nickel Based Superalloys; Superalloys; Co-Ni System; Ni-Al-Pt Ternary System; Co-Ni-Mo System; Co-Ni-W Systems; Ni-Pt Systems; Co-Pt Systems; Ni-Mo System; Co-Mo System; Ni-Pt-Al System; Ni-Co-Pt Systems; Ni-Co-Fe Ternary Systems; Metallurgy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Divya, V. D. (2013). Diffusion Studies On Systems Related to Nickel Based Superalloys. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/1948

Chicago Manual of Style (16^th Edition):

Divya, V D. “Diffusion Studies On Systems Related to Nickel Based Superalloys.” 2013. Doctoral Dissertation, Indian Institute of Science. Accessed January 23, 2021. http://etd.iisc.ac.in/handle/2005/1948.

MLA Handbook (7^th Edition):

Divya, V D. “Diffusion Studies On Systems Related to Nickel Based Superalloys.” 2013. Web. 23 Jan 2021.

Vancouver:

Divya VD. Diffusion Studies On Systems Related to Nickel Based Superalloys. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2013. [cited 2021 Jan 23]. Available from: http://etd.iisc.ac.in/handle/2005/1948.

Council of Science Editors:

Divya VD. Diffusion Studies On Systems Related to Nickel Based Superalloys. [Doctoral Dissertation]. Indian Institute of Science; 2013. Available from: http://etd.iisc.ac.in/handle/2005/1948

6. Larrouy, Baptiste. Mécanismes de déformation et d'amorçage de fissures dans l'alliage Udimet™ 720Li en relation avec les paramètres microstructuraux : Deformation mechanisms and fatigue crack initiation in Udimet 720Li superalloy in relation with microstructure.

Degree: Docteur es, Mécanique des solides, des matériaux, des structures et des surfaces, 2014, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique

URL: http://www.theses.fr/2014ESMA0019

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Cette étude s’est focalisée sur la compréhension des mécanismes de déformation et d’endommagementd’un superalliage à base de Nickel (Udimet 720Li) utilisé pour la confection de… (more)

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Cette étude s’est focalisée sur la compréhension des mécanismes de déformation et d’endommagementd’un superalliage à base de Nickel (Udimet 720Li) utilisé pour la confection de disques de turbine hautepression soumis à des sollicitations monotones et cycliques à des températures inférieures à 500 °C.L’amorçage de fissures de fatigue à 20 °C et 465 °C a été systématiquement observé suivant des facettescristallographiques pour différents états métallurgiques. Une étude quantitative des traces de glissementplastique en surface a permis de montrer que cet endommagement est la conséquence d’une nontransmission de la déformation plastique entre grains voisins. Plus précisément, un mécanisme de rotationcristalline localisée au sein de micro-volumes à l’extrémité de bandes de glissement dans le grain voisin aété identifié à l’origine des fissures.Les configurations cristallographiques favorisant ce processus impliquent notamment les relations entresystèmes de glissement de part et d’autre du joint de grains (angle de TWIST), ou encore la présence d’uneprécipitation fine participant au confinement des bandes de glissement.

This study contributes to the understanding of the deformation and damage mechanisms in a Nickelbasedsuperalloy (the Udimet 720Li) used for the manufacturing of aeroengines high pressure turbinedisks submitted to monotonic and cyclic loadings at temperatures below 500 °C under service conditions.Fatigue crack initiation at 20 °C and 465 °C was systematically observed at large crystallographic facetswhatever the microstructure. An extensive quantitative study of the slip activity at the surface showed thatcrack initiation results from a difficult slip transmission between neighbouring grains. In more details, alocalized crystallographic rotation confined in micro-volumes detected at the tip of slip bands interactingwith the grain boundary were identified to trigger crack initiation.The crystallographic configurations favouring such a process are closely related to the TWIST anglebetween active slip systems on each side of the grain boundary and to a dense and fine precipitationconfining the plasticity.Mots-clés

Advisors/Committee Members: Villechaise, Patrick (thesis director), Cormier, Jonathan (thesis director).

Subjects/Keywords: Transmission du glissement; Superalliages à base de nickel; Slip transmission; Ni-based superalloys

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Larrouy, B. (2014). Mécanismes de déformation et d'amorçage de fissures dans l'alliage Udimet™ 720Li en relation avec les paramètres microstructuraux : Deformation mechanisms and fatigue crack initiation in Udimet 720Li superalloy in relation with microstructure. (Doctoral Dissertation). Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique. Retrieved from http://www.theses.fr/2014ESMA0019

Chicago Manual of Style (16^th Edition):

Larrouy, Baptiste. “Mécanismes de déformation et d'amorçage de fissures dans l'alliage Udimet™ 720Li en relation avec les paramètres microstructuraux : Deformation mechanisms and fatigue crack initiation in Udimet 720Li superalloy in relation with microstructure.” 2014. Doctoral Dissertation, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique. Accessed January 23, 2021. http://www.theses.fr/2014ESMA0019.

MLA Handbook (7^th Edition):

Larrouy, Baptiste. “Mécanismes de déformation et d'amorçage de fissures dans l'alliage Udimet™ 720Li en relation avec les paramètres microstructuraux : Deformation mechanisms and fatigue crack initiation in Udimet 720Li superalloy in relation with microstructure.” 2014. Web. 23 Jan 2021.

Vancouver:

Larrouy B. Mécanismes de déformation et d'amorçage de fissures dans l'alliage Udimet™ 720Li en relation avec les paramètres microstructuraux : Deformation mechanisms and fatigue crack initiation in Udimet 720Li superalloy in relation with microstructure. [Internet] [Doctoral dissertation]. Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique; 2014. [cited 2021 Jan 23]. Available from: http://www.theses.fr/2014ESMA0019.

Council of Science Editors:

Larrouy B. Mécanismes de déformation et d'amorçage de fissures dans l'alliage Udimet™ 720Li en relation avec les paramètres microstructuraux : Deformation mechanisms and fatigue crack initiation in Udimet 720Li superalloy in relation with microstructure. [Doctoral Dissertation]. Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique; 2014. Available from: http://www.theses.fr/2014ESMA0019

The Ohio State University

7. Smith, Timothy M, Jr. Orientation and Alloying Effects on Creep Strength in Ni-Based Superalloys.

Degree: PhD, Materials Science and Engineering, 2016, The Ohio State University

URL: http://rave.ohiolink.edu/etdc/view?acc_num=osu1480599553519057

► The creep deformation mechanisms present during creep at intermediate stress and temperatures in ME3 were further investigated using diffraction contrast imaging. Both conventional transmission electron… (more)

▼ The creep deformation mechanisms present during creep at intermediate stress and temperatures in ME3 were further investigated using diffraction contrast imaging. Both conventional transmission electron microscopy and scanning transmission electron microscopy were utilized. Distinctly different deformation mechanisms become operative during creep at temperatures between 677-815ºC, and at stresses ranging from 274-724MPa. Both polycrystalline and single crystal creep tests were conducted. The single crystal tests provide new insight into grain orientation effects on creep response and deformation mechanisms. Creep at lower temperatures (760C) resulted in the thermally activated shearing modes such as microtwinning, stacking fault ribbons and isolated superlattice extrinsic stacking faults (SESFs). In contrast, these faulting modes occurred much less frequently during creep at 815ºC under lower applied stresses. Instead, the principal deformation mode was dislocation climb bypass. In addition to the difference in creep behavior and creep deformation mechanisms as a function of stress and temperature, it was also observed that microstructural evolution occurs during creep at 760C and above, where the secondary coarsened and the tertiary precipitates dissolved. Based on this work, a creep deformation mechanism map is proposed, emphasizing the influence of stress and temperature on the underlying creep mechanisms.Next, the effects of varying crystal orientation and composition on active deformation modes are explored for two different, commercially used Ni-base disk alloys, ME3 and ME501. Understanding these effects will allow for improved predictive deformation modeling and consequently faster advancements in Ni-base alloy development. In order to investigate these effects, compression creep tests were conducted on [001] and [110] oriented single crystal specimens of the disk alloys ME3 and ME501, at different stress/temperature regimes. At 760 C and below, a prominent creep anisotropy exists between the two orientations, with the [110] oriented samples exhibiting superior creep strength. At 815 C, the creep anisotropy disappeared between the two orientations. Through bright field scanning transmission electron microscopy, it was determined that the existence of creep anisotropy is a result of differences in deformation modes between the different orientations and alloy compositions. Results of phase field modeling in which the interaction of dislocations with realistic precipitate structures is also conducted to further advance predictive creep deformation models.Furthermore, the local compositional and structural changes occurring in association with stacking faults in ME501 are characterized and related to the possible rate-controlling processes during creep deformation at intermediate temperatures. These rate-controlling processes are not presently understood. In order to promote stacking fault shearing, compression creep tests on specially prepared single crystals of ME501 were conducted at 760°C in the [001]… Advisors/Committee Members: Mills, Michael (Advisor).

Subjects/Keywords: Materials Science; Ni-based Superalloys, Creep, Phase Transformation, Modeling, Deformation, Scanning Transmission Electron Microscopy, Characterization

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APA (6^th Edition):

Smith, Timothy M, J. (2016). Orientation and Alloying Effects on Creep Strength in Ni-Based Superalloys. (Doctoral Dissertation). The Ohio State University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=osu1480599553519057

Chicago Manual of Style (16^th Edition):

Smith, Timothy M, Jr. “Orientation and Alloying Effects on Creep Strength in Ni-Based Superalloys.” 2016. Doctoral Dissertation, The Ohio State University. Accessed January 23, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480599553519057.

MLA Handbook (7^th Edition):

Smith, Timothy M, Jr. “Orientation and Alloying Effects on Creep Strength in Ni-Based Superalloys.” 2016. Web. 23 Jan 2021.

Vancouver:

Smith, Timothy M J. Orientation and Alloying Effects on Creep Strength in Ni-Based Superalloys. [Internet] [Doctoral dissertation]. The Ohio State University; 2016. [cited 2021 Jan 23]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1480599553519057.

Council of Science Editors:

Smith, Timothy M J. Orientation and Alloying Effects on Creep Strength in Ni-Based Superalloys. [Doctoral Dissertation]. The Ohio State University; 2016. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1480599553519057

8. Tézenas du Montcel, Henri. Ingénierie des joints de grains dans les superalliages à base de nickel : Grain boundary engineering in Ni-based superalloys.

Degree: Docteur es, Sciences et génie des matériaux, 2012, Paris, ENMP

URL: http://www.theses.fr/2012ENMP0006

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Ce travail est consacré à l'étude de l'ingénierie des joints de grains dans les superalliages à base de Nickel pour disques de turbines aéronautiques. L'ingénierie… (more)

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Ce travail est consacré à l'étude de l'ingénierie des joints de grains dans les superalliages à base de Nickel pour disques de turbines aéronautiques. L'ingénierie des joints de grains a montré son efficacité dans l'amélioration des propriétés en fatigue et en fluage dans certains alliages de cuivre et de nickel. Cette amélioration est obtenue en réalisant une succession de déformations à température ambiante séparées par des traitement thermiques. Ce traitement a pour objectif de modifier la distribution du réseau de joints de grains. L'objectif de l'étude est d'adapter ces traitements au procédé du forgeage à haute température des superalliages. Une étude expérimentale est menée pour mettre en évidence l'influence des paramètres de forgeage sur les caractéristiques du réseau de joints de grains. La caractérisation de ce réseau est faite grâce à la réalisation de cartographies d'orientations cristallographiques par EBSD. Une méthode de caractérisation innovante basée sur la discrétisation des cartographies en réseaux de points triples est proposée. Cette méthode permet d'analyser la connectivité du réseau de joints de grains en vue d'une corrélation avec les propriétés mécaniques.

This work is dedicated to the study of Grain Boundary Engineering in Ni-based superalloys for aircraft turbine disk. The grain boundary engineering has proven its efficiency for the improvement of the fatigue and creep properties of copper and nickel alloys. This improvement is achieved by performing a succession of room temperature deformations interspaced by heat treatments to modify the distribution of the grain boundary network. The aim of the study is to adapt these processes to high temperature forging of superalloys. An experimental study is achieved to highlight the influence of forging parameters on the grain boundary network. The characterization of the grain boundary network is made through the completion of crystallographic orientation mapping by EBSD. An innovative characterization method based on the discretization of orientation maps in a triple junction network is proposed. This method allows to analyze the connectivity in the grain boundary network with the objective of a correlation with mechanical properties.

Advisors/Committee Members: Rémy, Luc (thesis director).

Subjects/Keywords: Ingénierie des joints de grains; Superalliage base Ni; EBSD; Grain Boundary Engineering; Ni Based Superalloys; EBSD

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APA (6^th Edition):

Tézenas du Montcel, H. (2012). Ingénierie des joints de grains dans les superalliages à base de nickel : Grain boundary engineering in Ni-based superalloys. (Doctoral Dissertation). Paris, ENMP. Retrieved from http://www.theses.fr/2012ENMP0006

Chicago Manual of Style (16^th Edition):

Tézenas du Montcel, Henri. “Ingénierie des joints de grains dans les superalliages à base de nickel : Grain boundary engineering in Ni-based superalloys.” 2012. Doctoral Dissertation, Paris, ENMP. Accessed January 23, 2021. http://www.theses.fr/2012ENMP0006.

MLA Handbook (7^th Edition):

Tézenas du Montcel, Henri. “Ingénierie des joints de grains dans les superalliages à base de nickel : Grain boundary engineering in Ni-based superalloys.” 2012. Web. 23 Jan 2021.

Vancouver:

Tézenas du Montcel H. Ingénierie des joints de grains dans les superalliages à base de nickel : Grain boundary engineering in Ni-based superalloys. [Internet] [Doctoral dissertation]. Paris, ENMP; 2012. [cited 2021 Jan 23]. Available from: http://www.theses.fr/2012ENMP0006.

Council of Science Editors:

Tézenas du Montcel H. Ingénierie des joints de grains dans les superalliages à base de nickel : Grain boundary engineering in Ni-based superalloys. [Doctoral Dissertation]. Paris, ENMP; 2012. Available from: http://www.theses.fr/2012ENMP0006

9. Laurence, Aude. Impact du sur-vieillissement métallurgique sur le comportement et la durabilité du nouveau superalliage pour disque de turbine René 65 : Microstructure Long-Term Stability and Impact on Mechanical Properties of the Ni-Based Superalloy for Turbine Disk Applications René 65.

Degree: Docteur es, Mécanique des solides, des matériaux, des structures et des surfaces, 2016, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique

URL: http://www.theses.fr/2016ESMA0006

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Cette étude traite de l'impact du vieillissement thermomécanique sur la microstructure et sur les propriétés mécaniques du nouveau superalliage base Nickel pour disque de turbine… (more)

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Cette étude traite de l'impact du vieillissement thermomécanique sur la microstructure et sur les propriétés mécaniques du nouveau superalliage base Nickel pour disque de turbine René 65.Le vieillissement thermique conduit à trois évolutions microstructurales majeures, à savoir la croissance des précipités y' intragranulaires et à la nucléation de particules TCP aux joints de grains accompagnés d'une ségrégation de molybdène. Une méthode innovante basée sur des traitements thermiques adaptés a permis de dissocier les effets de ces deux évolutions microstructurales sur les propriétés en fluage et fatigue-temps de maintien à 700° Cdu René 65. La croissance des précipités y' intragranulaires est majoritairement responsable de l'abattement des propriétés mécaniques. Il s'avère néanmoins que la présence des particules TCP aux joints de grains ainsi que la ségrégation de molybdène affectent également le comportement viscoplastique et la durabilité de l'alliage, contribuant à un abattement supplémentaire des propriétés mécaniques. Ce phénomène est attribué à l'adoucissement localisé de la matrice au voisinage des particules TCP et des joints de grains par la perte d'éléments durcissants de la solution solide y.

This study focused on the impact of thermo-mechanical aging on the microstructure and on the mechanical properties of the new nickel-based superalloy René 65 for turbine disk applications.Thermal aging causes three main microstructural evolutions, namely the intragranular y'-growth, the nucleation of TCP particles at grain boundaries along with a segregation of molybdenurn. An innovative method based on appropriated thermal treatments enabled to dissociate these microstructural evolutions' impacts on the René 65 creep and dwell-fatigue properties at 700°C.The y'-growth is mainly responsible of the overall mechanical proprerties degradation. However, it turns out TCP particles and the molybdenum segregation at grain boundaries also affect negatively the alloy viscoplastic behavior and its durability, contributing to an additional decrease in its mechanical properties. This phenomenon is attributed to the softening of the matrix locally at grain boundaries by solid solution elements depletion in favor of TCP precipitation.

Advisors/Committee Members: Villechaise, Patrick (thesis director), Billot, Thomas (thesis director), Cormier, Jonathan (thesis director).

Subjects/Keywords: Superalliages à base nickel; Croissance des précipités γ’; Phase TCP; Fatigue-temps de maintien; Ni-based superalloys; Γ’-growth; TCP phases; Dwell-fatigue

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APA (6^th Edition):

Laurence, A. (2016). Impact du sur-vieillissement métallurgique sur le comportement et la durabilité du nouveau superalliage pour disque de turbine René 65 : Microstructure Long-Term Stability and Impact on Mechanical Properties of the Ni-Based Superalloy for Turbine Disk Applications René 65. (Doctoral Dissertation). Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique. Retrieved from http://www.theses.fr/2016ESMA0006

Chicago Manual of Style (16^th Edition):

Laurence, Aude. “Impact du sur-vieillissement métallurgique sur le comportement et la durabilité du nouveau superalliage pour disque de turbine René 65 : Microstructure Long-Term Stability and Impact on Mechanical Properties of the Ni-Based Superalloy for Turbine Disk Applications René 65.” 2016. Doctoral Dissertation, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique. Accessed January 23, 2021. http://www.theses.fr/2016ESMA0006.

MLA Handbook (7^th Edition):

Laurence, Aude. “Impact du sur-vieillissement métallurgique sur le comportement et la durabilité du nouveau superalliage pour disque de turbine René 65 : Microstructure Long-Term Stability and Impact on Mechanical Properties of the Ni-Based Superalloy for Turbine Disk Applications René 65.” 2016. Web. 23 Jan 2021.

Vancouver:

Laurence A. Impact du sur-vieillissement métallurgique sur le comportement et la durabilité du nouveau superalliage pour disque de turbine René 65 : Microstructure Long-Term Stability and Impact on Mechanical Properties of the Ni-Based Superalloy for Turbine Disk Applications René 65. [Internet] [Doctoral dissertation]. Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique; 2016. [cited 2021 Jan 23]. Available from: http://www.theses.fr/2016ESMA0006.

Council of Science Editors:

Laurence A. Impact du sur-vieillissement métallurgique sur le comportement et la durabilité du nouveau superalliage pour disque de turbine René 65 : Microstructure Long-Term Stability and Impact on Mechanical Properties of the Ni-Based Superalloy for Turbine Disk Applications René 65. [Doctoral Dissertation]. Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique; 2016. Available from: http://www.theses.fr/2016ESMA0006

10. Penso, Graciela Carolina. Welding of X65 Internally Clad with Precipitation Strengthened Ni-Based SUperalloy Filler Metal: Application in Pre-Salt Oil Extraction.

Degree: MS, Welding Engineering, 2016, The Ohio State University

URL: http://rave.ohiolink.edu/etdc/view?acc_num=osu1480600980467914

► Giant oil reservoirs were found off the coast of Brazil in the Santos Basin Bay. They are located under a geological salt layer; thus they… (more)

▼ Giant oil reservoirs were found off the coast of Brazil in the Santos Basin Bay. They are located under a geological salt layer; thus they are called pre-salt. The fact that these reservoirs are located far from shore, has presented some technological challenges. Currently, X65 pipes internally clad with Alloy 625 are used for traditional subsea oil extraction. Such pipes are joined using Alloy 625 filler material. Since the depth and the amount of risers and pipelines to be installed in the pre-salt oil reserves are very large, pipe reeling is considered the most efficient technology for pipeline installation. For pipe reeling, it is necessary for the welds joining the pipes to overmatch the X65 base metal yield strength by 100 MPa, without any post wed heat treatment, thus Alloy 625 does not meet those requirements. The objective of this project was to explore the applicability of precipitation strengthened nickel-based filler metals for welding of internally clad X65 pipes for application in pipelines and risers for oil extraction from pre-salt subsea oil fields. Ni-base super alloys 718 and 282 were considered as potential welding consumables for this application. The solidification behavior in the weld metal of these alloys diluted with the Alloy 625 pipe cladding was evaluated using thermodynamic simulations with Scheil-Gulliver module of Thermo-Calc™. The Alloy 718 / Alloy 625 system exhibited almost constant solidification temperature range of about 250 °C with formation of Laves phase at the end of solidification throughout the whole dilution range. The Alloy 282 / Alloy 625 system exhibited potential for lower susceptibility to solidification cracking with the solidification temperature range gradually degreasing to 150 °C and no formation of Laves at dilutions lover than 70%.The compatibility of Alloy 718 and Alloy 625 filler metals with alloy the 625 cladding and X65 steel base metal was evaluated by performing bead-on-plate welding and producing multilayer buildups using cold metal transfer (CMT) and gas metal arc welding pulsed (GMAWp) processes. No solidification and liquation cracking or lack of fusion defects were experienced in large range of welding parameters with both filler metals.The precipitation behavior during multipass welding in both alloys was evaluated as a potential strengthening mechanism to meet the weld metal overmatching strength requirement. Hardness mapping on multipass weld buildups has shown that at least two reheats by high heat input subsequent weld passes with GMAWp are needed to cause precipitation hardening in Alloy 718. Significant precipitation hardening in Alloy 282 occurred by three reheat weld passes with CMT. Tensile testing in all-weld metal multipass buildups showed that multipass welding with GMAWp cannot generate sufficient precipitation strengthening in Alloy 718 filler metal to meet the X65 yield strength overmatch requirement of 550 MPa. With yield strength of 620 MPa, Alloy 282 multipass weld buildup produced with CMT met this requirement.Successful test… Advisors/Committee Members: Alexandrow, Boian (Advisor).

Subjects/Keywords: Engineering; Welding, precipitation strengthened superalloys, ni-based, GMAW, CMT

…7 2.1 Introduction to Ni-based Alloys… …Table 8: Etchants for Ni-based Alloy and Steel base Alloys. .............................. 54… …Welding configuration schematic. 6 CHAPTER 2: LITERATURE REVIEW 2.1 Introduction to Ni-based… …strengthened Ni-based alloys, these can be strengthened by alloying additions by a variety of… …welding. During welding, it is common for nickel-based superalloys to experience 16 cracking…

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APA (6^th Edition):

Penso, G. C. (2016). Welding of X65 Internally Clad with Precipitation Strengthened Ni-Based SUperalloy Filler Metal: Application in Pre-Salt Oil Extraction. (Masters Thesis). The Ohio State University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=osu1480600980467914

Chicago Manual of Style (16^th Edition):

Penso, Graciela Carolina. “Welding of X65 Internally Clad with Precipitation Strengthened Ni-Based SUperalloy Filler Metal: Application in Pre-Salt Oil Extraction.” 2016. Masters Thesis, The Ohio State University. Accessed January 23, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480600980467914.

MLA Handbook (7^th Edition):

Penso, Graciela Carolina. “Welding of X65 Internally Clad with Precipitation Strengthened Ni-Based SUperalloy Filler Metal: Application in Pre-Salt Oil Extraction.” 2016. Web. 23 Jan 2021.

Vancouver:

Penso GC. Welding of X65 Internally Clad with Precipitation Strengthened Ni-Based SUperalloy Filler Metal: Application in Pre-Salt Oil Extraction. [Internet] [Masters thesis]. The Ohio State University; 2016. [cited 2021 Jan 23]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1480600980467914.

Council of Science Editors:

Penso GC. Welding of X65 Internally Clad with Precipitation Strengthened Ni-Based SUperalloy Filler Metal: Application in Pre-Salt Oil Extraction. [Masters Thesis]. The Ohio State University; 2016. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1480600980467914

11. Phillips, Patrick J. Advanced defect characterization via electron microscopy and its application to cyclically deformed Ni-based superalloy R104.

Degree: PhD, Materials Science and Engineering, 2012, The Ohio State University

URL: http://rave.ohiolink.edu/etdc/view?acc_num=osu1330915484

► Ni-based superalloys continue to be used in the hot sections of turbine engines due to their superior high temperature properties and retained strength. The… (more)

▼ Ni-based superalloys continue to be used in the hot sections of turbine engines due to their superior high temperature properties and retained strength. The present document will focus specifically on the polycrystalline alloy R104, and the deformation substructure observed during and following cyclic mechanical testing. Both low cycle fatigue (LCF) and sustained peak low cycle fatigue (SPLCF) tests are considered. Two chapters on electron microscopy technique development follow a brief introduction on general properties of Nickel superalloys. Almost exclusively, scanning transmission electron microscopy (STEM) was performed for defect characterization. Furthermore, through a systematic study of STEM-based diffraction contrast methods, including experimental and computational results, STEM is presented as a valid means of defect analysis. The second chapter in this set also uses STEM, but in a non-traditional setting: the microscope is configured for high resolution imaging, i.e., the sample is aligned along a low index zone axis and a large convergence angle is used. In this low angle annular dark field (LAADF) mode, an annular detector accepts low-angle scattering, which allows one to obtain atomic resolution images while retaining defect contrast. Both techniques described in these two chapters were used extensively throughout this research. The remaining chapters discuss the application of the microscopy techniques developed in the proceeding chapters to cyclically deformed specimens of R104. Both interrupted and failed samples were deformed in LCF at 427C and 704C, and interrupted SPLCF samples were tested at 704 and 760C. The deformation mechanisms observed will be discussed at length in this document. In general, dislocation activity dominates under LCF conditions while stacking faults and stacking fault ribbons are most prominent under SPLCF conditions. Time and temperature components will be discussed in regards to the operative mechanisms. A point of emphasis will remain the importance of understanding the deformation substructure in order to better understand the macroscopic behavior, such as cyclic stress-strain data. Advisors/Committee Members: Mills, Michael (Advisor).

Subjects/Keywords: Materials Science; STEM; Ni-based superalloys; deformation substructure; ADF; fatigue

…Prime phase in Ni-based superalloys via high-resolution backscatter imaging, Materials Science… …Introduction and physical metallurgy of Ni-based superalloys . . . . . . . . 1.1 1 1 1.1.1 𝛾… …in Ni-based superalloys . . . . . . . . . . . . 4 1.1.3 𝛾 ′ morphology and distribution… …7 1.1.4 1.2 Microstructure of Ni-based superalloys… …in Ni-based superalloys . . . . . . . . . . . . . . 16 Mechanical Behavior…

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APA (6^th Edition):

Phillips, P. J. (2012). Advanced defect characterization via electron microscopy and its application to cyclically deformed Ni-based superalloy R104. (Doctoral Dissertation). The Ohio State University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=osu1330915484

Chicago Manual of Style (16^th Edition):

Phillips, Patrick J. “Advanced defect characterization via electron microscopy and its application to cyclically deformed Ni-based superalloy R104.” 2012. Doctoral Dissertation, The Ohio State University. Accessed January 23, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1330915484.

MLA Handbook (7^th Edition):

Phillips, Patrick J. “Advanced defect characterization via electron microscopy and its application to cyclically deformed Ni-based superalloy R104.” 2012. Web. 23 Jan 2021.

Vancouver:

Phillips PJ. Advanced defect characterization via electron microscopy and its application to cyclically deformed Ni-based superalloy R104. [Internet] [Doctoral dissertation]. The Ohio State University; 2012. [cited 2021 Jan 23]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1330915484.

Council of Science Editors:

Phillips PJ. Advanced defect characterization via electron microscopy and its application to cyclically deformed Ni-based superalloy R104. [Doctoral Dissertation]. The Ohio State University; 2012. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1330915484

12. Lee, Seungjun. Instabilities on High Temperature Isothermal Creep Performance in Ni-Based Single Crystal Superalloys.

Degree: MS, Aerospace Engineering, 2019, Texas A&M University

URL: http://hdl.handle.net/1969.1/186940

► Nickel-based singe crystal superalloys are a class of metallic materials with a combination of high-temperature strength, toughness, and resistance to degradation in oxidizing environments, which… (more)

▼ Nickel-based singe crystal superalloys are a class of metallic materials with a combination of high-temperature strength, toughness, and resistance to degradation in oxidizing environments, which makes them great candidates for aircraft engine turbine blades that operate at temperatures beyond 1000 degrees C. The lifetime of such materials is directly connected to the integrity of the strengthening phase, or the so-called the y’ precipitates. Uniaxial thermo-mechanical environments have already been shown to lead to the phase transformations, microstructure gradients, and lattice rotation, which all contribute to the change in mechanical properties. Stress field in turbine blades are, however, multiaxial, and the load bearing section of the turbine blades decreases due to depletion of the y’ precipitates during oxidation. In order to accurately predict the lifetime of the turbine blades, it is critical to understand how multiaxiality and oxidation kinetics affect the damage evolution during creep. Samples of the second-generation Ni-based single crystal superalloy, Rene N5, were prepared with specified triaxialities using notches according to Bridgman’s equation for creep tests. Through SEM analysis, it was found that the material had too much y/y’ eutectics that were not properly eliminated during the heat treatment, which resulted in earlier fractures. Kachanov-Rabotnov creep-damage model with Hayhurst stress criterion was modified to account for the depletion of the strengthening phase due to oxidation. Among many factors that affect the kinetics of oxidation, the effects of surface roughness and the initial plastic strain were studied. According to a number of studies, it was found that the kinetics of oxidation tends to increase with decrease in the surface roughness and increase in initial plastic strain. A dimensionless variable eox was introduced to represent the depleted zone thickness and its evolution was simulated varying the two aforementioned factors. Simulation results of creep curves both in vacuum and in air were analyzed, and the results showed conceptually matching trends found in the literatures. Advisors/Committee Members: le Graverend, Jean-Briac (advisor), Benzerga, Amine (committee member), Karaman, Ibrahim (committee member).

Subjects/Keywords: Ni-based single crystal superalloys; creep; oxidation; damage; superalloys; model; Rene-N5; eutectics; depletion; multiaxial; FE simulation

…1 1.1. Microstructure of Ni-based Single Crystal Superalloys… …32 xii 1. INTRODUCTION 1.1. Microstructure of Ni-based Single Crystal Superalloys The… …precipitates and γ matrix. In <001>-oriented Ni-based single crystal superalloys, the γ’ precipitates… …typically Ni3Al in case of Ni-based single crystal superalloys. The γ’ phase directionally… …previously conducted on Ni-based single crystal superalloys, the creep behavior of such materials…

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APA (6^th Edition):

Lee, S. (2019). Instabilities on High Temperature Isothermal Creep Performance in Ni-Based Single Crystal Superalloys. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/186940

Chicago Manual of Style (16^th Edition):

Lee, Seungjun. “Instabilities on High Temperature Isothermal Creep Performance in Ni-Based Single Crystal Superalloys.” 2019. Masters Thesis, Texas A&M University. Accessed January 23, 2021. http://hdl.handle.net/1969.1/186940.

MLA Handbook (7^th Edition):

Lee, Seungjun. “Instabilities on High Temperature Isothermal Creep Performance in Ni-Based Single Crystal Superalloys.” 2019. Web. 23 Jan 2021.

Vancouver:

Lee S. Instabilities on High Temperature Isothermal Creep Performance in Ni-Based Single Crystal Superalloys. [Internet] [Masters thesis]. Texas A&M University; 2019. [cited 2021 Jan 23]. Available from: http://hdl.handle.net/1969.1/186940.

Council of Science Editors:

Lee S. Instabilities on High Temperature Isothermal Creep Performance in Ni-Based Single Crystal Superalloys. [Masters Thesis]. Texas A&M University; 2019. Available from: http://hdl.handle.net/1969.1/186940

The Ohio State University

13. Yablinsky, Clarissa A. Characterization of Fatigue Mechanisms in Ni-based Superalloys.

Degree: PhD, Materials Science and Engineering, 2010, The Ohio State University

URL: http://rave.ohiolink.edu/etdc/view?acc_num=osu1285006918

► Ni-based superalloys are important for turbine engine airfoil applications. Historically, creep has been the main failure mode and thus creep mechanisms have been the… (more)

▼ Ni-based superalloys are important for turbine engine airfoil applications. Historically, creep has been the main failure mode and thus creep mechanisms have been the subject of numerous studies. However, modern airfoil designs maintain cooler temperatures, and consequently creep is no longer the primary failure mode. Rather, in the cooled components, experience and experimental studies have shown that fatigue is the life-limiting factor. The changing cause of failure highlighted the need for a comprehensive study of fatigue deformation mechanisms. Information about crack propagation and the associated deformation mechanisms has allowed appropriate design changes based on fatigue as a life-limiting factor. The focus of the study will be on a monocrystalline Ni-based superalloy, René N5, which is currently used for airfoils. Compact tension specimens were tested under cyclic loading conditions to determine the influence of microstructure and material properties on crack propagation and fatigue failure. The crack growth rate as a function of temperature, environment, frequency, and crystallographic orientation was determined. High resolution scanning electron microscopy was used to examine the fracture surface on length scales from nano to macro. Deformation mechanisms in the plastic zone ahead of the crack tip and within the plastic wake of the crack were studied using TEM and FIB techniques. Environment and frequency seem to have a larger effect on fatigue crack growth rates and threshold stress intensity factor ranges, while temperature and orientation effects are present, but not as dramatic. In the normal blade orientation, (001)[100], mode I crack propagation was prevalent, with mode II crack propagation found at higher ΔK values. Interdendritic particles appear to be slowing crack growth rates in the threshold region of specimens tested in air. Microstructural analysis showed no change in γ’ precipitate size or morphology with temperature or stress. From TEM investigations, it is theorized that a combination of mechanisms is occurring during testing, which is the reason there is no universal trend with temperature for the threshold stress intensity factor ranges. The mechanisms discussed include Kear-Wilsdorf locking, oxide-induced crack closure, and crack tip softening due to γ’ depletion. Advisors/Committee Members: Flores, Katharine (Advisor), Williams, James (Advisor).

Subjects/Keywords: Aerospace Materials; Engineering; Materials Science; Metallurgy; Ni-based Superalloys; Fatigue Crack Growth; Rene N5; Fatigue; Temperature; Environment; Frequency; Orientation; Characterization; TEM

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Yablinsky, C. A. (2010). Characterization of Fatigue Mechanisms in Ni-based Superalloys. (Doctoral Dissertation). The Ohio State University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=osu1285006918

Chicago Manual of Style (16^th Edition):

Yablinsky, Clarissa A. “Characterization of Fatigue Mechanisms in Ni-based Superalloys.” 2010. Doctoral Dissertation, The Ohio State University. Accessed January 23, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1285006918.

MLA Handbook (7^th Edition):

Yablinsky, Clarissa A. “Characterization of Fatigue Mechanisms in Ni-based Superalloys.” 2010. Web. 23 Jan 2021.

Vancouver:

Yablinsky CA. Characterization of Fatigue Mechanisms in Ni-based Superalloys. [Internet] [Doctoral dissertation]. The Ohio State University; 2010. [cited 2021 Jan 23]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1285006918.

Council of Science Editors:

Yablinsky CA. Characterization of Fatigue Mechanisms in Ni-based Superalloys. [Doctoral Dissertation]. The Ohio State University; 2010. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1285006918

Kyoto University

14. Ahmad, Afandi. Development of Fe-based Superalloys Strengthened by the γ'Phase .

Degree: 2020, Kyoto University

URL: http://hdl.handle.net/2433/259045

Subjects/Keywords: Fe based Superalloys; Ternary Fe-Ni-Ge Phase Diagram; γ΄ Precipitation strengthening mechanism; Yield Strength Anomaly (YSA); Phase Equilibria

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Ahmad, A. (2020). Development of Fe-based Superalloys Strengthened by the γ'Phase . (Thesis). Kyoto University. Retrieved from http://hdl.handle.net/2433/259045

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Ahmad, Afandi. “Development of Fe-based Superalloys Strengthened by the γ'Phase .” 2020. Thesis, Kyoto University. Accessed January 23, 2021. http://hdl.handle.net/2433/259045.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Ahmad, Afandi. “Development of Fe-based Superalloys Strengthened by the γ'Phase .” 2020. Web. 23 Jan 2021.

Vancouver:

Ahmad A. Development of Fe-based Superalloys Strengthened by the γ'Phase . [Internet] [Thesis]. Kyoto University; 2020. [cited 2021 Jan 23]. Available from: http://hdl.handle.net/2433/259045.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Ahmad A. Development of Fe-based Superalloys Strengthened by the γ'Phase . [Thesis]. Kyoto University; 2020. Available from: http://hdl.handle.net/2433/259045

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

15. Heggadadevanapura Thammaiah, Mallikarjuna. Effect of composition and microstructure on the oxidation and corrosion performance of Ni-based superalloys.

Degree: Mechanical Engineering, 2019, University of Manitoba

URL: http://hdl.handle.net/1993/34147

► The cyclic oxidation behaviour of three Ni-based superalloys IN738LC, Rene 80 and N5 was performed at 900°C for 1000 cycles including 1 h holding at… (more)

▼ The cyclic oxidation behaviour of three Ni-based superalloys IN738LC, Rene 80 and N5 was performed at 900°C for 1000 cycles including 1 h holding at oxidation temperature and cooling to room temperature by ambient air. Oxidation kinetics were determined by mass change measurement in each cycle. The cyclic oxidation resistance of N5 was found to be better than that of IN738LC and Rene 80; also, scale spallation for N5 was minimal compared to the other two alloys. Although both IN738LC and Rene 80 showed scale spallation, the rate was more severe in Rene 80 due to the combined effects of high Ti and formation of volatile Mo-rich oxides. The spallation in N5 was due to the formation of Ta-Hf-oxy carbides, which generate a high shear strain at the matrix-oxide and oxy-carbide interface. To assess the effect of γ' intermetallic size on the oxidation resistance of IN738LC, coupons (four sizes γ'; monomodal distribution) were subjected to isothermal and cyclic oxidation between 750-950ºC for 150 h/cycles respectively. Parabolic oxidation was found in all cases; based on rate constants, samples with the largest starting γ' were the most oxidation-resistant. Activation energies calculated from precipitate free zone (PFZ) thickness measurements were higher for samples with larger γ' (324 kJ/mole vs 279 kJ/mole). Decreasing the γ' precipitate size increases the oxidation rate of IN738LC. Sub-surface γ' precipitate dissolution was found to be γ' precipitate-size dependent. The interdiffusion coefficient for Al across the PFZ was found to decrease with increasing γ' size. The influence of γ' size and composition on the corrosion behaviour of IN738LC was also investigated while maintaining a monomodal microstructure. Experimental results showed a negative influence on the corrosion resistance of IN738LC with an increasing rate of cooling, which is attributable to an increase in the volume fraction of γ', i.e., reduction in chromium-containing matrix phase expose to the environment. Corrosion current density was found to be higher for a specimen with smaller γ' precipitates compared to specimens with larger precipitates. These results serve to further support the concept that oxidation resistance is indeed dependant on γ' intermetallic size whereby smaller precipitates exhibit a higher oxidation rate. Advisors/Committee Members: Caley, William F. (Mechanical Engineering), Ojo, Olanrewaju (Mechanical Engineering).

Subjects/Keywords: Cyclic oxidation; Ni-based superalloys; Oxidation behaviour; Scale spallation; Modelling; Cooling rate; Inter-diffusion; Dissolution; Microstructure; Precipitates

…77 Figure 4-1. Initial SEM microstructures of all three Ni-based superalloys a)… …85 Figure 4-3. Parabolic mass change plots for the three Ni-based superalloys as a… …167 List of Tables Table 2-1. Effects of major alloying elements in Ni-based superalloys… …substrate material is very important. The Ni-based superalloys are one of a family of materials… …in Ni-based superalloys to increase their strength and resistance to oxidation [1]…

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APA (6^th Edition):

Heggadadevanapura Thammaiah, M. (2019). Effect of composition and microstructure on the oxidation and corrosion performance of Ni-based superalloys. (Thesis). University of Manitoba. Retrieved from http://hdl.handle.net/1993/34147

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Heggadadevanapura Thammaiah, Mallikarjuna. “Effect of composition and microstructure on the oxidation and corrosion performance of Ni-based superalloys.” 2019. Thesis, University of Manitoba. Accessed January 23, 2021. http://hdl.handle.net/1993/34147.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Heggadadevanapura Thammaiah, Mallikarjuna. “Effect of composition and microstructure on the oxidation and corrosion performance of Ni-based superalloys.” 2019. Web. 23 Jan 2021.

Vancouver:

Heggadadevanapura Thammaiah M. Effect of composition and microstructure on the oxidation and corrosion performance of Ni-based superalloys. [Internet] [Thesis]. University of Manitoba; 2019. [cited 2021 Jan 23]. Available from: http://hdl.handle.net/1993/34147.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Heggadadevanapura Thammaiah M. Effect of composition and microstructure on the oxidation and corrosion performance of Ni-based superalloys. [Thesis]. University of Manitoba; 2019. Available from: http://hdl.handle.net/1993/34147

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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