Production of net-shape static parts by direct HIPing of nickel base superalloy prealloyed powders
TL;DR: In this article, the effects of net shape surfaces and surface conditioning have been investigated for static parts of aero-turboengines and space propulsion systems using HIPing of nickel base superalloys prealloyed powders.
Abstract: In 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.
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TL;DR: In this paper, the influence of gas atomised powder particle size and characteristics on the microstructure and mechanical properties of hot isostatically pressed (HIPped) CM247LC nickel-base superalloy powders was investigated.
37 citations
05 Jan 2015-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a direct forging of unconsolidated powder superalloys is proposed, where 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.
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.
31 citations
TL;DR: It was found that relatively high temperature and pressure of HIPping were preferred to obtain an as-HIPped superalloy FGH96 with diminished PPB precipitation and homogeneously refined grains.
Abstract: The microstructure with homogeneously distributed grains and less prior particle boundary (PPB) precipitates is always desired for powder metallurgy superalloys after hot isostatic pressing (HIPping). In this work, we studied the effects of HIPping parameters, temperature and pressure on the grain structure in PM superalloy FGH96, by means of scanning electron microscope (SEM), electron backscatter diffraction (EBSD), transmission electron microscope (TEM) and Time-of-flight secondary ion spectrometry (ToF-SIMS). It was found that temperature and pressure played different roles in controlling PPB precipitation and grain structure during HIPping, the tendency of grain coarsening under high temperature could be inhibited by increasing HIPping pressure which facilitates the recrystallization. In general, relatively high temperature and pressure of HIPping were preferred to obtain an as-HIPped superalloy FGH96 with diminished PPB precipitation and homogeneously refined grains.
29 citations
02 Jan 2019-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the microstructure evolution, tensile properties and fracture mechanism of the FGH4097 superalloy were systematically studied by optical microscopy, scanning electron microscopy and TEM, while the mechanical properties were assessed by hardness measurements and tensile tests at room temperature (RT) and 650
Abstract: A newly-developed γ′-hardenable powder metallurgy (P/M) nickel based surperalloy FGH4097 developed by China was fabricated by hot isostatic pressing (HIP) with different processing temperatures. The microstructure evolution, tensile properties and fracture mechanism of the FGH4097 superalloy were systematically studied. Grains size, strengthening γ′ phase, prior particle boundaries and carbide precipitations, were characterized by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), meanwhile the mechanical properties were assessed by hardness measurements and tensile tests at room temperature (RT) and 650 °C. A dendrite structure inherited from the pre-alloy powder was partially reserved in the as-sintered alloy processed at 1100 °C. It transformed into a cellular structure when the HIP temperature was increased to 1200 °C. With increasing the HIP temperature, the contents of γ′ phase forming element decreased, accompanied by the decrease of γ′ lattice parameters and volume fraction. Due to a promoted atomic diffusion at higher temperatures, MC carbide and two types of HfO2 precipitations formed in the γ matrix that were not present in the pre-alloy powder. Besides, the grain size increased with increasing HIP temperatures, and the average grain sizes of the sintered samples were 5.8 µm (1100 °C), 17.8 µm (1200 °C) and 74.7 µm (1300 °C), respectively. Compared with two other processing temperatures, samples fabricated with at 1200 °C had the highest ultimate tensile strengths (1410 MPa at room temperature and 1236 MPa at 650 °C), along with a superior elongation (33.0 at room temperature and 31.4 at 650 °C), which was attributed to an appropriate microstructure and mediate volume fraction of γ′ phase. Owing to the incomplete recrystallization and prior particle boundaries, the yield strength and ultimate tensile strength at 1100 °C exhibited a bit less than that of at 1200 °C, but showed obvious difference in elongation. However, the tensile strengths decreased significantly at 1300 °C as a result of coarse grains. With increasing the HIP temperature, the fracture appearances indicated that the fracture changed from dimple ductile mode to brittle mode, because of the formation of coarsening MC carbide at grain boundaries.
27 citations
TL;DR: In this article, a comprehensive review of powder prior boundary (PPB) formation in the powder metallurgy of super alloys is presented and methods to reduce PPB effects on the mechanical properties of nickel-based super alloy, including heat treatment, changing the proportions of composition elements, and plastic deformation to break up the PPB networks.
Abstract: Powder metallurgy of nickel-based super alloys have been developed and used for a wide range of products, owing to their excellent high temperature rupture life, creep strength and fatigue crack growth resistance. Typical processes for high performance PM super alloys include hot isostatic pressing (HIPing), hot extrusion and hot isothermal forging. Hot isostatic pressing is normally conducted at a high temperature by using metal forming standards at low pressure for a long time. However an intrinsic problem, i. e. powder prior boundary (PPB) precipitate networks, can occur in the HIPing process. In this paper, a comprehensive review of PPB formation in the powder metallurgy of super alloys is presented. Research on PPB formation process from room temperature to high temperature and during HIPing, has been reviewed and PPB formation mechanisms are discussed. Methods to reduce PPB effects on the mechanical properties of nickel-based super alloys, including heat treatment, changing the proportions of composition elements, and plastic deformation to break up the PPB networks, are reviewed.
26 citations
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TL;DR: The ISOPREC process as discussed by the authors is a powder metallurgy process in which a highly sophisticated mold is filled with powder and further densified through a HIP cycle, and a net shape part is obtained.
72 citations
TL;DR: In this paper, the evolution of design principles and better evaluation of the impact of cleanliness has led to an evolution of metallurgy (grades and microstructure) and processes.
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.
37 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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TL;DR: ISOPREC® as discussed by the authors is a 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.).
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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