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Journal ArticleDOI

Production of net-shape static parts by direct HIPing of nickel base superalloy prealloyed powders

Gérard Raisson, Jean Yves Guedou1, Didier Guichard1, Jean Marc Rongvaux1 
01 Jul 2011-Advanced Materials Research (Trans Tech Publications, Ltd.)-Vol. 278, pp 277-282

AbstractIn order to reduce costs and increase the operating temperatures in aero-turboengines and space propulsion systems, net-shape or near net-shape production processes have been developed for static parts through HIPing (Hot Isostatic Pressing) of nickel base superalloys prealloyed powders. The presented results hereafter are related to the manufacturing processes and the mechanical properties (tensile, creep and LCF) characterisation. The effects of net shape surfaces and of surface conditioning have been investigated too. Examples of actual parts (CFM56 turbine casing and Vulcain rocket engine gas generator) illustrate the presentation. This study has confirmed the interest of this production route and future potential for development.

Topics: Hot isostatic pressing (56%), Superalloy (51%), Powder metallurgy (51%)

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Citations
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Journal ArticleDOI
Abstract: A high strength high γ ′ fraction nickel-based superalloy powder RR 1000 has been hot isotatically pressed (HIPed) at different temperatures. Microstructural analysis and assessment of the tensile properties were performed on these samples. It was found that HIP led to the formation of (Hf,Zr)O 2 particles on prior particle boundaries (PPBs) which were not present in the as-received powder. It is suggested that the oxides are formed by the diffusion of Hf and Zr from the interior of powder particles to the particle surfaces where oxygen level is usually high. When different HIP temperatures were used, no obvious effect on oxide size and distribution was observed but there was an effect on the microstructure and tensile properties. Thus, HIPing at super-solvus temperatures reduced the density of PPBs over the density observed in samples HIPed at sub-solvus temperatures by making grains within the original powder particles grow beyond the precipitates on PPBs, resulting in larger grains with serrated boundaries. Slow cooling from HIPing temperatures also led to the formation of irregular-shaped γ ′. The 0.2% yield strengths at room temperature and at 700 °C were found to decrease with increase of HIP temperature but the high temperature ultimate tensile strengths and elongation increased considerably. Increasing HIPing temperature from sub-solvus to super-solvus temperatures also led to the transition of fracture mode from interparticle debonding to transgranular fracture mode.

68 citations


Journal ArticleDOI
Abstract: A nickel-based superalloy powder RR1000 has been hot isostatically pressed (HIPed) and heat treated to produce different microstructures. Microstructures were investigated using a scanning electron microscope (SEM). Tensile testing was performed at room temperature and 700 °C and the deformed samples were examined using SEM and transmission electron microscope (TEM). It was found that in the as-HIPed condition the microstructure consisted of coarse and irregular-shaped primary and secondary γ′ together with a low volume fraction of fine γ′ (

51 citations


Cites background from "Production of net-shape static part..."

  • ...Net-shape HIPing [1-5] offers a possible solution to this high cost of producing components from powder since this would lead to the reduction in forging and machining operations and thus to considerable cost reduction....

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  • ...It is suggested that the optimum treatment of the powder superalloy is to solution-treat and age after HIPing; this results in properties which are comparable with those of thermomechanically processed samples....

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  • ...However, the mechanical properties (especially tensile strengths) of as-HIPed RR1000 samples could not meet actual requirements due to the development of irregular and coarse γ´ during slow cooling from HIPing temperature [15]....

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  • ...Previously, a HIPing condition which minimized the harmful PPBs has been developed for RR1000 alloy powder [15]....

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  • ...Therefore, it is very important to find out proper processing conditions for net-shape HIPing of nickel-based superalloy powder....

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Journal ArticleDOI
Abstract: Inconel 718 powders have been hot-isostatic-pressed (HIPed) at representative temperatures to investigate the variations in microstructure, tensile properties and tensile fracture mode of the powder compact. Microstructure of the powder compacts were characterized by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and so on. The results showed that the interdendritic precipitates inherited from the powders were partially retained in the powder compacts when the powders were HIPed at or below 1210 °C but were eliminated when HIPed at and above 1260 °C. The grain size uniformity of the powder compacts first increases and then decreases with increasing HIPing temperature. Prior particle boundaries (PPBs) were observed in the powder compacts HIPed at and below 1260 °C but was eliminated when HIPed at 1275 °C. The PPBs were decorated with carbide particles, the amount of the carbide particles at the PPBs decreases with increasing HIPing temperature. Most of the PPBs were pinned by the carbide particles in the compacts HIPed at 1140 °C. When the HIPing temperature was increased to 1210 °C and 1260 °C, a large number of PPBs de-pinned and moved beyond the pinning carbide particles, leading to grain growth and leaving carbide particles at the site of the original PPBs within the new grains. With increasing HIPing temperature, the 0.2% yield strength of the powder compacts at 650 °C decreases, the tensile elongation increases, and the tensile fracture mode changed from inter-particle dominant fracture to fully dimple ductile fracture.

51 citations


Journal ArticleDOI
Abstract: In the current study, the effect of strain distribution in a simple forging geometry on the propensity for recrystallization, and its impact on mechanical properties has been investigated in a newly developed experimental nickel-based superalloy. The new alloy was produced via a Powder Metallurgy (PM) route and was subsequently Hot Isostatic Processed (HIP), isothermally forged, and heat treated to produce a coarse grain microstructure with average grain size of 23–32 μm. The alloy was examined by means of Electron Back-Scatter Diffraction (EBSD) to characterise the microstructural features such as grain orientation and morphology, grain boundary characteristics and the identification of potential Prior Particle Boundaries (PPBs) throughout each stage of the processing route. Results at the central region of the cross-section plane parallel to the loading direction showed significant microstructural differences across the forging depth. This microstructural variation was found to be highly dependent on the value of local strain imparted during forging such that areas of low effective strain showed partial recrystallisation and a necklace grain structure was observed following heat treatment. Meanwhile, a fully recrystallised microstructure with no PPBs was observed in the areas of high strain values, in the central region of the forging.

44 citations


Journal ArticleDOI
Abstract: Powder metallurgy (PM) processing of nickel-based superalloys has been used for a wide range of near net-shape fine grained products. In this paper a novel forming process, i.e. direct forging of unconsolidated powder superalloys is proposed. In this process, encapsulated and vacuumed powder particles are heated up to a forming temperature and forged directly at high speed to the final shape, by using a high forming load. Experiments of direct powder forging have been conducted on an upsetting tool-set. Microstructure, relative density and hardness of the formed specimen have been investigated. A finite element model of the direct powder forging process has been established in DEFORM and validated by the comparisons of experimental with simulation results of load variation with stroke as well as relative density distribution. The stress state and the relative density variation have been obtained from FE simulation. The correlation between the stress and consolidation condition has been rationalised. The developed FE model can provide a guide to design the geometry and thickness of preform for direct powder forging.

26 citations


References
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Journal ArticleDOI
R Baccino, F. Moret, F Pellerin1, D. Guichard2, G. Raisson 
Abstract: ISOPREC® is a powder metallurgy process in which a highly sophisticated mould is filled with powder and further densified through a HIP cycle. After compaction, the mould is mechanically or chemically removed, and a net shape part is obtained. Examples of applications of this technology to Inconel 625, Ti-6-4 and A316LN are presented. High dimensional accuracy and mechanical performance are obtained for complex parts, therefore minimizing cost and production cycle time for such high level components.

65 citations


Journal ArticleDOI
Abstract: Industrial production of critical parts in aero engine by PM is now more than 30 years old. During this period, evolution of design principles and better evaluation of the impact of cleanliness has led to an evolution of metallurgy (grades and microstructure) and processes. The basis of this evolution will be presented and illustrated by examples taken from companies worldwide.

33 citations


"Production of net-shape static part..." refers background in this paper

  • ...Mechanical properties can be similar to those of extruded + forged products [1,2]....

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  • ...In as-HIPed conditions, mechanical properties of superalloys are very similar to those obtained on extruded + forged products [1, 2]....

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Journal ArticleDOI
Abstract: ISOPREC® est un procede de metallurgie des poudres dans lequel un moule particulierement elabore est rempli de poudre puis densifie en Compression Isostatique a Chaud (C.I.C.). Apres compaction, le moule est elimine mecaniquement ou chimiquement, et une piece aux cotes finales est obtenue. Les deformations importantes et complexes qui interviennent au cours de la densification ne peuvent etre predites manuellement et un outil de modelisation numerique est developpe, de facon a minimiser les cycles et les couts de developpement des pieces. Des exemples d'application de cette technologie dans les domaines aeronautiques et spatiaux sont presentes. Les proprietes mecaniques elevees obtenues sur les pieces associees a la grande precision dimensionnelle du procede font d'ISOPREC® une reponse au difficile challenge de la recherche de l'amelioration des performances au moindre cout.

1 citations


"Production of net-shape static part..." refers methods in this paper

  • ...• Vulcain gas generator for Ariane rocket engine Isoprec@ process has been first used for titanium alloy components in rocket engine parts (impellers in pumps) [4] and later for hotter parts....

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