Phase stability and yield stress of Ni-base superalloys containing high Co and Ti

Cui, Chuanyong; Sato, Akihiro; Gu, Yuefeng; Ping, Dehai; Harada, Hiroshi

doi:10.1007/bf02586152

Cited by 54 publications

(32 citation statements)

References 11 publications

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“…[7][8][9][10] However, co-additions of Co and Ti to conventional Ni-based superalloys have been found to confer significant strength benefits to the material. [11][12][13][14][15] In one such study, increasing the concentration of Co and Ti in RR1000 resulted in yield and tensile strengths that were~20 pct greater than that of conventional RR1000. Although the creep life of the modified alloys was found to deteriorate when tested at 750°C and 460 MPa as a result of the precipitation of the TCP r phase along the grain boundaries.…”

Section: Alloy Design Methodologymentioning

confidence: 99%

On the Effect of Nb on the Microstructure and Properties of Next Generation Polycrystalline Powder Metallurgy Ni-Based Superalloys

Christofidou

Hardy

et al. 2018

Metall Mater Trans A

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The effect of Nb on the properties and microstructure of two novel powder metallurgy (P/M) Ni-based superalloys was evaluated, and the results critically compared with the Rolls-Royce alloy RR1000. The Nb-containing alloy was found to exhibit improved tensile and creep properties as well as superior oxidation resistance compared with both RR1000 and the Nb-free variant tested. The beneficial effect of Nb on the tensile and creep properties was due to the microstructures obtained following the post-solution heat treatments, which led to a higher γ′ volume fraction and a finer tertiary γ′ distribution. In addition, an increase in the anti-phase-boundary energy of the γ′ phase is also expected with the addition of Nb, further contributing to the strength of the material. However, these modifications in the γ′ distribution detrimentally affect the dwell fatigue crack-growth behavior of the material, although this behavior can be improved through modified heat treatments. The oxidation resistance of the Nb-containing alloy was also enhanced as Nb is believed to accelerate the formation of a defect-free Cr2O3 scale. Overall, both developmental alloys, with and without the addition of Nb, were found to exhibit superior properties than RR1000.

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Section: Alloy Design Methodologymentioning

confidence: 99%

On the Effect of Nb on the Microstructure and Properties of Next Generation Polycrystalline Powder Metallurgy Ni-Based Superalloys

Christofidou

Hardy

et al. 2018

Metall Mater Trans A

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“…However it can be considered that 718Plus and TMW4 do not improve the combination between cost and mechanical properties currently offered by U720Li. TMW4 shows higher properties than U720Li [6][7][8] but is significantly more expensive due to its high cobalt content. Inversely, 718Plus [9][10] presents a lower cost (presence of iron and reasonable cobalt content) but restricted creep properties at 700°C compared to the current U720Li disk alloy.…”

Section: Tmmentioning

confidence: 99%

AD730TM - A New Nickel-based Superalloy for High Temperature Engine Rotative Parts

Devaux¹,

Picque²,

Gervais³

et al. 2012

Superalloys 2012 (Twelfth International Symposium)

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The enhancement of efficiency in gas turbine engines requires the development of new superalloys capable of withstanding higher temperatures. The development of new industrial cast and wrought (C&W) disk alloys with required combination of strength, creep and fatigue properties at 700°C is highly desired due to the expensive cost of powder metallurgy. AD730 TM , which is the newly nickel base superalloys developed by Aubert & Duval, was therefore designed to offer a better combination between high temperature properties at 700°C and cost compared to other C&W superalloys. This paper describes the alloy design based upon the chemistries of the previous experimental alloys Ni30 and Ni33 [1][2]. The control of expensive elements contents and the presence of iron in AD730 TM alloy confer to this alloy an attractive cost compared to other C&W superalloys for disk applications. Gamma prime solvus was decreased compared to Ni33 in order to improve hot workability and (Ti+Nb)/Al ratio was decreased compared to Ni30 and Ni33 in order to avoid any risk of Eta-phase precipitation. It was actually observed that the precipitation of the needle-shape Eta-phase predicted by the thermodynamic databases was not in agreement with experimental results obtained on various alloys of the AD730 TM chemical system. Industrial ingots with a diameter equal to 500mm were produced (Vacuum melting and remelting) and converted to evaluate the mechanical properties and the ability for the conventional C&W route. A special attention is made in this paper to the AD730 TM workability which was highly evaluated with various industrial forging process routes (close-die forging, ring-rolling...etc). Heat treatment optimization was then performed on this alloy in regard to tensile and creep properties. The effect of solution heat-treatment temperature and cooling rate after solution heat treatment were investigated on AD730 TM . Solution heat treatment temperature has a slight effect on the tensile strength if the temperature is lower than the gamma prime solvus. Yield strength remains stable and close to 1100MPa at 700°C. Solution heat-treatment was therefore optimized in regard of grain size in order to increase creep properties. As most of superalloys strengthened by gamma prime phase, cooling rate after solution heat-treatment has to be as fast as possible to get the highest tensile and creep properties.Oil quenching can be easily performed on AD730TM without any issues due to the moderate gamma prime content in the alloy (35-40%) and the fine grain size. Tensile, creep, long-term aging performed on a forged disk heat-treated in optimized conditions, are presented and discussed in this paper. A comparison with Udimet720 TM properties and 718Plus TM ones show that AD730 TM alloy presents a higher combination between cost and mechanical properties at 700°C than current C&W superalloys.

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“…In addition, these alloys also include a range of other elemental additions to further improve their properties. Recently, elevated levels of Co and Ti have been shown to be beneficial, providing improved high temperature strength and creep resistance [1,2]. However, in addition to their mechanical performance, the environmental resistance of these alloys is also critical, as surface degradation can accelerate fatigue crack initiation during high temperature exposure, leading to premature failure [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

The Oxidation Behaviour of Alloys Based on the Ni–Co–Al–Ti–Cr System

et al. 2015

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The isothermal oxidation behaviour of a series of quinary Ni-Co-AlTi-Cr alloys were studied at 800°C. Alloys with higher Cr concentrations exhibited lower mass gain after 100-h exposure, as did the alloys richest in Ni and Al for a given Cr concentration. Extensive internal oxidation and nitridation was also observed in all alloys, except those containing the highest concentrations of Ni and Al. All alloys studied generated continuous chromium oxide layers, beneath which alumina particles were observed. Compositional analysis of the subscales identified shallower Cr concentration gradients in alloys containing equiatomic levels of Ni and Co, suggesting increased availability of Cr in the alloy. Thermodynamic calculations confirmed that these alloys contained higher concentrations of Cr in their c matrices as a result of a combination of both the elemental partitioning behaviour and the increased mole fraction of c 0 precipitates forming in the alloy.

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Phase stability and yield stress of Ni-base superalloys containing high Co and Ti

Cited by 54 publications

References 11 publications

On the Effect of Nb on the Microstructure and Properties of Next Generation Polycrystalline Powder Metallurgy Ni-Based Superalloys

On the Effect of Nb on the Microstructure and Properties of Next Generation Polycrystalline Powder Metallurgy Ni-Based Superalloys

AD730TM - A New Nickel-based Superalloy for High Temperature Engine Rotative Parts

The Oxidation Behaviour of Alloys Based on the Ni–Co–Al–Ti–Cr System

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