The oxidation properties of fourth generation single-crystal nickel-based superalloys

Kawagishi, Kyoko; Harada, Hiroshi; Sato, Akihiro; Sato, Atsushi; Kobayashi, Toshiharu

doi:10.1007/s11837-006-0067-z

Cited by 70 publications

(46 citation statements)

References 15 publications

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“…It was shown that the volume change ratio / Al 2 O 3 associated with this reaction and defined as: 3 . This fractional volumetric expansion of 0.336 corresponds to a lateral expansion of each c 0 particle of *10%.…”

Section: (A) (B) (D) (C)mentioning

confidence: 99%

“…They have been optimised for high creep strength and microstructural stability and, with *6 wt% Al and *3 wt% Cr, would be expected to have only a borderline capacity to form and maintain a protective alumina layer [1]. Reported work on the oxidation of these types of alloys tends to be focussed on behaviour at high temperatures, C1,000°C [2][3][4][5][6][7]. At these temperatures, under thermal cycling conditions, non-protective oxides form together with sub-surface oxidation.…”

Section: Introductionmentioning

confidence: 99%

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The Role of the γ′ Precipitate Dispersion in Forming a Protective Scale on Ni-Based Superalloys at 750 °C

2009

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Fourth generation Ni-based superalloys are being developed for use as single crystal turbine blades in aero-engines. They contain between, approximately, 2-5 wt% Ru together with *6 wt% Re and differing amounts of other refractory elements such as W, Ta and Mo. These alloys experience sub-surface pitting attack when oxidised in air at intermediate temperatures (*750°C). The pits consist of c 0 particles (nominally, Ni 3 Al) which are oxidised in situ and separated by unoxidised c channels. Earlier generations of alloys do not show this form of attack and, in contrast, form a protective surface layer of NiAl 2 O 4 . The reasons for this difference are explored in this paper. It is shown that the dispersion of the strengthening c 0 particles is much more ordered in the fourth generation, Ru-bearing alloy than in a third generation (CMSX10-K, also known as RR3000), Ru-free variant. It is considered that this is the principal reason why pit formation is observed in the later alloy. Pits arise because the long c channels between the arrays of c 0 particles have insufficient aluminium content to form the protective oxide and remain open to inward diffusion of oxygen over extended periods of time. The third generation alloy, on the other hand, has a more random arrangement of c 0 particles which is conducive to the early formation of a protective oxide layer.

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Section: (A) (B) (D) (C)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Role of the γ′ Precipitate Dispersion in Forming a Protective Scale on Ni-Based Superalloys at 750 °C

2009

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“…800 C [8]), improved phase stability by Ru can all attribute its superiority in creep resistance over previous generations [1,8]. However, higher Ru and Re content in both low Cr bearing TMS-162 and TMS-173 have resulted in poorer oxidation resistance at elevated temperatures due to vaporization of Ru and Re oxides [12], so a much improved oxidation resistance would be required for their practical applications. During oxidation at temperatures above 700 C, scales of Al 2 O 3 , Cr 2 O 3 , NiO, spinel Ni(Cr, Al) 2 O 4 can form on advanced superalloys.…”

Section: Introductionmentioning

confidence: 99%

A 5th Generation SC Superalloy with Balanced High Temperature Properties and Processability

Sato¹,

Harada²,

Yeh³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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A 5th generation single crystal (SC) superalloy TMS-196 with improved microstructural stability and environmental properties was designed with using NIMS Alloy Design Program and evaluated experimentally. It was found that TMS-196 has a very stable microstructure even after 1000h creep at 1100 C and also very well balanced creep, TMF and environmental properties. TMS-196 also had excellent SC castability; sound cooling blades of up to 300mm long were successfully cast.

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“…Given the rising turbine entry temperatures sought by engine manufacturers for efficiency gains, oxidation is becoming a more and more prevalent failure mechanism. However, generally fourth generation alloys are significantly poorer in oxidation than second generation alloys such as CMSX-4 [2,3]. It is desirable for intermediate pressure (IP) turbine blades to be uncoated but since the oxidation performance of fourth generation alloys may not be acceptable it is necessary to evaluate simple economically viable coatings, such as aluminides.…”

Section: Introductionmentioning

confidence: 99%

Oxidation and Coating Evolution in Aluminized Fourth Generation Blade Alloys

Edmonds¹,

Evans²,

Jones³

2008

Superalloys 2008 (Eleventh International Symposium)

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Oxidation tests have been undertaken in air on two aluminized experimental fourth-generation Ni-based superalloys containing, respectively, 3 and 5 wt.% Ru, in order to detail the effect of Ru on oxidation characteristics and coating evolution. A Ru-free, aluminide coated third generation alloy (CMSX-10K) was also included in the test programme which used temperatures covering the range 750-1100 o C.Aluminization has been shown to effectively minimize the effect of alloy chemistry on oxidation rate constants over the timescales studied, when compared to the uncoated substrates. Aluminization also prevents the formation of internal oxidation pits in the coated Ru-bearing alloys after oxidation at 750°C. Increasing Ru marginally decreased the mass-gain due to oxidation of the three aluminized alloys at all temperatures. At 750°C the rate of oxidation of aluminized specimens was controlled not by the formation of aluminas but by that of the spinel phase Ni(Al,Cr) 2 O 4 . Interestingly, each of the three aluminized alloys produced a different coating -substrate microstructural interaction after exposure at 1100°C, with Ru increasing the propensity for secondary reaction zone (SRZ) formation. SRZs are characterized by a weak high angle boundary which can lead to localized coating loss (and hence increased section loss). Ru also underwent long range diffusion, concentrating in the β-NiAl phase in solution, and where SRZ was present resulted in the precipitation of β2-RuAl within the γ' SRZ matrix in addition to the topologically close-packed precipitates (TCPs).

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The oxidation properties of fourth generation single-crystal nickel-based superalloys

Cited by 70 publications

References 15 publications

The Role of the γ′ Precipitate Dispersion in Forming a Protective Scale on Ni-Based Superalloys at 750 °C

The Role of the γ′ Precipitate Dispersion in Forming a Protective Scale on Ni-Based Superalloys at 750 °C

A 5th Generation SC Superalloy with Balanced High Temperature Properties and Processability

Oxidation and Coating Evolution in Aluminized Fourth Generation Blade Alloys

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