Topologically close-packed phase precipitation in a nickel-base superalloy during thermal exposure

Yang, Jia; Zheng, Qiwen; Sun, Xiaofeng; Guan, H.R.; Hu, Z.Q.

doi:10.1016/j.msea.2007.01.152

Cited by 111 publications

(57 citation statements)

References 10 publications

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“…Some of these belong to the family of TCP phases that are detrimental for high temperature and creep properties of the superalloys [43] and are known to form during long exposures at elevated temperatures [44]. The formation and the effect of TCP phases on properties in Nibased super alloys have been extensively studied [45][46][47][48]. The presence of these phases in the microstructure reduces the solute content in the matrix and hence reduces the solid solution strengthening contribution to the overall strength of an alloy.…”

Section: Phase Stability and Decomposition Behavior Of Co-30ni-10al-5mentioning

confidence: 99%

Phase evolution and crystallography of precipitates during decomposition of new “tungsten-free” Co(Ni)–Mo–Al–Nb γ–γ′ superalloys at elevated temperatures

et al. 2016

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This article reports the microstructural stability and consequent phase decomposition including the appearance of topologically close-packed (TCP) phases at high temperature of recently discovered tungsten-free c-c 0 alloys of base composition Co-10Al-5Mo-2Nb with or without the addition of Ni and Ti. On prolonged aging at 800°C of the Co-10Al-5Mo-2Nb alloy, needle-shaped DO 19 -ordered precipitates with stoichiometry of Co 3 (Mo, Nb) start appearing in the microstructure. In addition, growth of cellular domains from the grain boundaries featuring a three-phase composite lamellar structure could be observed. These phases are fcc c-Co with composition different from the original matrix, CoAl with B2 ordering and Co 3 (Mo, Nb) with DO 19 ordering. All the phases exhibit well-defined crystallographic orientation relationships. The decomposition of the alloys depends on the solvus temperature of the c 0 phase. The Nicontaining alloy exhibits no phase decomposition until 100 h of aging at 800°C without any significant effect on c 0 volume fraction (76 %). However, at 950°C, the alloy decomposes leading to the appearance of four different phases including TCP phases: a Cr 3 Si-type cubic phase, a hexagonal Laves phase, rhombohedral l phase, and solid solution of Co phase. The c-c 0 microstructure in the Co-10Al-5Mo-2Nb and Co-30Ni-10Al-5Mo-2Ta alloys is not stable at 800 and 950°C, respectively, on long-term aging. This shows that the measured solvus temperatures (i.e., 866 and 990°C) are metastable solvus temperatures. We also report that the Ti-containing alloy exhibits superior stability with no evidence of either TCP phase formation or any other decomposition of c 0 precipitates, even after aging at 950°C for 100 h.

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Section: Phase Stability and Decomposition Behavior Of Co-30ni-10al-5mentioning

confidence: 99%

Phase evolution and crystallography of precipitates during decomposition of new “tungsten-free” Co(Ni)–Mo–Al–Nb γ–γ′ superalloys at elevated temperatures

et al. 2016

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“…Because of controlled silicon contents and higher temperatures used for homogenization, this phase is no longer detected in conventional alloy 718. [27][28][29][30] Besides these intermetallic phases, nitride and carbide precipitation also occurs in alloy 718. The nitrogen content of alloy 718 is not part of the intentional composition, but comes from the impurity levels of the raw material and contamination during melting and casting.…”

Section: Introductionmentioning

confidence: 99%

Identification of Mo-Rich M23C6 Carbides in Alloy 718

Aghajani¹,

Tewes²,

Parsa

et al. 2016

Metall Mater Trans A

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In the present study, we systematically identify and characterize a (Nb, Mo)-rich M 23 C 6 type of M 23 C 6 carbide with a lattice parameter of 1.094 nm in alloy 718 for the first time using a combination of selected area electron diffraction pattern and powder X-ray diffraction analysis. The time-temperature-precipitation diagrams of the precipitates in both annealed and strained conditions are obtained by particle analysis using an automated scanning electron microscopy method. (Nb, Mo)-rich M 23 C 6 carbides first precipitate after 24 hours at 1223 K (950°C) annealing, while they form after 10 minutes at 1273 K (1000°C) in the strained condition. This correlates with the excess dislocations produce during deformation.

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“…These needle-like particles can also be the sigma phase if there is no carbon present and an abundance of Ni and Cr. Given that the C content in the powder mixtures used here was much lower than that reported by Yang et al 8 for superalloy K465 and that the particles were completely removed by the chemical reagent used to reveal the microstructure, it is plausible to assume that they were the sigma phase.…”

Section: Variation In Microstructure With Exposure To Temperaturementioning

confidence: 67%

“…After 1 hour at 1000 °C, H-shaped precipitates were identified (Figure 3b). Yang et al 8 studied the microstructural features of a polycrystalline nickel-base superalloy K465 after exposure to temperature and suggested that some of the needle-like particles were M 6 C carbides because of their higher carbon, W and Mo content. These needle-like particles can also be the sigma phase if there is no carbon present and an abundance of Ni and Cr.…”

Section: Variation In Microstructure With Exposure To Temperaturementioning

confidence: 99%

Characterization of NiCrAlC PTA coatings

Benegra¹,

Pintaúde

D'Oliveira

et al. 2012

Mat. Res.

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Surface tailoring with plasma transferred arc (PTA) hardfacing involves the deposition of powder mixtures to produce coatings with an almost unlimited chemical composition. PTA hardfacing is particularly important for processing low weldability alloys, such as those for high-temperature applications, of which NiCrAlC is an example. This study analyzed NiCrAlC coatings processed by PTA using a mixture of elemental powders. Deposition on AISI316L plates was carried out with currents of 100 A and 130 A to induce variations in the chemical composition of the coatings, which were also subjected to isothermal exposure at temperatures of up to 1000 °C for up to 72 hours in an air furnace. The results show that the aluminide compounds were stable, the coatings that solidified more slowly having the highest hardness after temperature exposure and potentially being suitable for use in high-temperature abrasion environments.

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Topologically close-packed phase precipitation in a nickel-base superalloy during thermal exposure

Cited by 111 publications

References 10 publications

Phase evolution and crystallography of precipitates during decomposition of new “tungsten-free” Co(Ni)–Mo–Al–Nb γ–γ′ superalloys at elevated temperatures

Phase evolution and crystallography of precipitates during decomposition of new “tungsten-free” Co(Ni)–Mo–Al–Nb γ–γ′ superalloys at elevated temperatures

Identification of Mo-Rich M23C6 Carbides in Alloy 718

Characterization of NiCrAlC PTA coatings

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