Creep behaviour and microstructure of Ni-Cr base alloys

Gibbons, T. B.; Hopkins, B. E.

doi:10.1179/030634584790420104

Cited by 33 publications

(12 citation statements)

References 14 publications

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“…In addition, the creep resistance could be improved by increasing the γ′ phase volume, e.g. the life to creep rupture increased almost one order of magnitude by increasing 3.1% γ′ to 24% γ′ via different heat treatment of the same superalloy [208]. In the advanced single-crystal nickel-based superalloys (widely used for the turbine blade applications), the relatively high γ′ volume fraction could go up to 60-80% [209].…”

Section: Mad542: a Novel Nickel-based Superalloy For Am Processmentioning

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: Mad542: a Novel Nickel-based Superalloy For Am Processmentioning

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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“…Some of these authors [7][8][9][10][11] attribute this difference to environmental factors such as high temperature oxidation. It has been shown in several publications [11][12][13][14][15][16][17][18][19], that oxidation has a strong influence on the microstructure of nickel-based superalloys. This leads, for example, to the formation of a γ′-free layer just below the oxide film [11,16].…”

Section: Introductionmentioning

confidence: 99%

“…The longer-range diffusion of alloying components from the interior towards the oxidized surface alters the alloy composition [18] and changes the γ′-fraction over a much wider section. As γ′ precipitates are essential for improved creep behavior and the γ′-fraction strongly influences creep behaviour [12][13][14][15], thin-walled specimens are likely to be affected not only by a γ′-free layer, but also by a much wider layer where the γ′ is reduced [16]. The present work concentrates on the effect of the oxidation-modified γ′-volume fraction on secondary creep.…”

Section: Introductionmentioning

confidence: 99%

Secondary Creep of Thin‐Walled Specimens Affected by Oxidation

et al. 2012

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The creep behavior of thin-walled specimens cannot be assumed to be as uniform as for thick-walled specimens. The difference is attributed to the influence of oxidation. Oxidation tests have been carried out on single crystal nickel-based superalloy M247LC SX specimens with different thicknesses down to 0.1 mm. The results show that the γ′-volume fraction is strongly affected by oxidation in near surface regions. Depletion of the aluminium reservoir required to establish a protective alumina scale causes the change. Based on these results five single crystal nickel-based superalloys with different compositions have been cast. These alloys represent different near surface regions within an oxidation affected specimen. Creep tests on single crystals of these alloys have been performed to quantify the influence of different γ′-volume fractions on secondary creep. The stress dependence was fit to the Norton creep law and the exponent n, exhibited sigmoidal behavior as a function of the γ′-fraction, almost doubling at 50% volume fraction. This behavior suggests a change in the dominant creep mechanism. These results are essential for modeling and predicting the creep properties of thin-walled specimens in turbine blade applications.

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“…10) This relationship has been demonstrated to hold for heat resistant structural materials such as ferritic steels, 11,12) nickel base alloys, 13) etc. Die-casting is a dominant processing route to produce magnesium components due to its high productivity of complex near net shape parts.…”

Section: Introductionmentioning

confidence: 99%

Relationship between Minimum Creep Rate and Rupture Life for a Die-Cast Mg-Al-Mn Alloy

Terada

Sato

2008

Mater. Trans.

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Creep rupture tests were performed for a die-cast Mg-Al-Mn alloy, AM50, at 34 kinds of creep conditions in the temperature range between 423 and 498 K. The creep curve is characterized by a minimum in the creep rate followed by an extended accelerating stage. The minimum creep rate ( _ " " m ) and the creep rupture life (t rup ) follow the phenomenological Monkman-Grant relationship; t rup ¼ C 0 = _ " " m m . It is found for the die-cast AM50 alloy that the exponent m is unity and the constant C 0 is 0.13, independent of creep testing temperature. The values of m and C 0 are compared with those for other die-cast magnesium alloys.

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Creep behaviour and microstructure of Ni-Cr base alloys

Cited by 33 publications

References 14 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

Secondary Creep of Thin‐Walled Specimens Affected by Oxidation

Relationship between Minimum Creep Rate and Rupture Life for a Die-Cast Mg-Al-Mn Alloy

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