Effect of � Phase on the Mechanical Properties of a Nickel-Base Single Crystal Superalloy

Pessah, M.; Caron, Pierre; Khan, T.

doi:10.7449/1992/superalloys_1992_567_576

Cited by 35 publications

(38 citation statements)

References 11 publications

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“…Four morphologically distinct phases can be distinguished. 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].…”

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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“…Micro-structural instability, especially the precipitation of topologically close packed (TCP) phases, should be avoided during alloy development [1]. Many studies indicate that TCP phases, such as σ , µ, P and R phases, are detrimental to mechanical properties, since their hard and brittle nature causes damage accumulation or cracking and their formation depletes the strengthening elements of the γ matrix [2,3].…”

Section: Introductionmentioning

confidence: 99%

Compositional effect on TCP phase formation in Ru-containing Ni-based single crystal superalloys

Shi

Huo

Cao

et al. 2014

MATEC Web of Conferences

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Abstract. Microstructural instability involving the formation of topologically close-packed (TCP) phases is restricted during the alloy development of Ni-based single crystal superalloys. In this study, the effects of alloying elements including Co, Cr, Mo and Ru on the formation of different TCP phases were investigated in a series of single crystal superalloys. Experimental results showed that more additions of Cr and Mo promoted the TCP phase formation, while Co and Ru played a positive role in improving microstructural stability. It is indicated that σ , P and R phases existed with various morphology and compositions in different experimental alloys during thermal exposure at 1100• C. The content of Co, Cr and Mo in those alloys affected the types of TCP phases significantly, while Ru additions showed a negligible effect. R phase was prone to form in alloys containing high level of Co addition. Meanwhile, the ratio of Cr and Mo content had strong influence on the formation of σ and P phases in alloys containing low level of Co addition. The effects of alloying additions on the elemental partitioning ratios between γ and γ phases contributed to their corresponding influence on TCP phase formation.

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“…Their precipitation during the service depletes the matrix from refractory elements and reduces the solid solution effect. Moreover the TCP phases are often associated with the formation of voids at high temperatures, which may act as an initiation sites for fracture [44]. However, there is conflicting data whether they are responsible for failure and fracture of single crystal alloys [45,46].…”

Section: Microstructure Stability At High Temperaturementioning

confidence: 99%

Classification and microstructural stability of high generation single crystal Nickel-based superalloys

Sowa¹,

Arabasz²,

Parlińska-Wojtan³

2016

Zas Mat

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Effect of � Phase on the Mechanical Properties of a Nickel-Base Single Crystal Superalloy

Cited by 35 publications

References 11 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

Compositional effect on TCP phase formation in Ru-containing Ni-based single crystal superalloys

Classification and microstructural stability of high generation single crystal Nickel-based superalloys

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