Cooling precipitation and strengthening study in powder metallurgy superalloy Rene88DT

Abstract. Microstructures of the new PM superalloy N19 have been investigated for various heat treatments in order to reach the best compromise between static strength and cyclic resistance. One subsolvus and several supersolvus heat treatments were applied to produce fine (7 µm) and medium (25 µm) grain sizes, respectively. The alloy is shown to be quite sensitive to the cooling conditions after solutioning as the γ hardening precipitates, both secondary and tertiary, have a direct influence on mechanical properties. Two cooling conditions after solutioning produce a high crack propagation resistance at 650• C with dwell time cycles, which is one of the basic requirements. The low cycle fatigue behaviour appears to be correlated to the grain size, which determines the origin of crack initiation (from ceramic inclusions or not). The other mechanical properties (tensile, creep) remain above target levels. Despite the medium size grain microstructure in the supersolvus condition, a high level of mechanical strength is observed in N19 at elevated temperature. It is understood that further improvement in properties can be achieved by developing coarse grain microstructures.

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“…As usually observed, the size of these precipitates increases as the cooling rate decreases [3][4][5].…”

Section: Effects Of Cooling Path On Secondary γ Sizementioning

confidence: 78%

Metallurgical optimisation of PM superalloy N19

Locq

Nazé

Franchet³

et al. 2014

MATEC Web of Conferences

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“…Multimodal microstructures are usually achieved by special multistage heat treatments, which are generally complex and costly. Some authors have already shown that such bimodal size distributions of c 0 precipitates can also be achieved by two c 0 nucleation bursts during continuous cooling from the solution-annealed state [17][18][19][20][21][22][23][24]. Thereby, the individual particle populations precipitate at different temperatures and from different chemical compositions of the c matrix.…”

Section: Introductionmentioning

confidence: 96%

Multimodal size distributions of γ′ precipitates during continuous cooling of UDIMET 720 Li

et al. 2009

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“…Based on the classic strengthening theory, if a particle size is smaller than a critical size, then the strength increases with particle size, and vice versa. [18,19] For U720Li, as suggested by Jackson and Reed, [2] this critical size is approximately 40 nm, of which may be applicable to TMW-4M3 because of their similar chemical compositions and processing received. As presented in Table III, 4M3-2 had larger grain size and secondary c¢ size.…”

Section: B Tensile Propertiesmentioning

confidence: 97%

Effect of Solution Temperature on the Microstructure and Mechanical Properties of a Newly Developed Superalloy TMW-4M3

Zhong

Yuan

Osada

et al. 2011

Metall Mater Trans A

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The influence of solution temperature on the microstructure and mechanical properties of TMW-4M3 superalloy has been investigated. Comparisons of mechanical properties have also been made between the heat-treated TMW-4M3 variants and the commercial U720Li. The key microstructural variables examined were grain size and the volume fraction and size of the strengthening c¢ precipitates that control the mechanical properties of these alloys. By increasing the solution temperature from 1373 K to 1393 K (1100°C to 1120°C), the volume fraction of primary gamma prime dropped from 16.9 pct to 14.5 pct, whereas the average grain size increased from 8.7 lm to 10.6 lm. Compared with an alloy with a smaller grain size, the alloy with a larger grain size exhibited superior resistances to creep and fatigue crack growth without the expense of reduced tensile strength and low-cycle fatigue resistance. This suggested that a higher solution temperature may benefit TMW-4M3 in terms of superior overall properties. The greater overall properties of TMW-4M3 variants than that of commercial U720Li were also demonstrated experimentally. The possible explanations for the improvement of mechanical properties were discussed.

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Cooling precipitation and strengthening study in powder metallurgy superalloy Rene88DT

Cited by 80 publications

References 8 publications

Metallurgical optimisation of PM superalloy N19

Metallurgical optimisation of PM superalloy N19

Multimodal size distributions of γ′ precipitates during continuous cooling of UDIMET 720 Li

Effect of Solution Temperature on the Microstructure and Mechanical Properties of a Newly Developed Superalloy TMW-4M3

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