High Temperature Materials Research Institution

Beijing, China

High Temperature Materials Research Institution

Beijing, China
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Wu K.,University of Science and Technology Beijing | Liu G.,University of Science and Technology Beijing | Hu B.,University of Science and Technology Beijing | Li F.,University of Science and Technology Beijing | And 4 more authors.
Materials Characterization | Year: 2010

The hot deformation behavior of a new Ni-Cr-Co based P/M superalloy was studied in the temperature range of 950-1150 °C and strain rate range of 0.0003-1 s- 1 using hot compression tests. It was characterized by true stress-true strain curves, constitutive equation, strain rate sensitivity m contour maps, power dissipation η maps and hot processing maps. The microstructural validation of processing maps was also done. The results show that the flow stress decreases with increasing temperature and decreasing strain rate. The hot deformation apparent activation energy of the Ni-Cr-Co based P/M superalloy at peak stress is 805 kJ/mol. The m and η contour maps are similar, and the values of m and η in the peak zones increase with increasing strain. When the strain is 0.5, a domain with its peak η of 40% and peak m of 25% occurs at 1050 °C and 0.0003 s- 1, which corresponds to dynamic recrystallization and can be as an optimum condition for good workability. Crown Copyright © 2009.


Wu K.,University of Science and Technology Beijing | Liu G.-Q.,University of Science and Technology Beijing | Hu B.-F.,University of Science and Technology Beijing | Li F.,University of Science and Technology Beijing | And 4 more authors.
Hangkong Cailiao Xuebao/Journal of Aeronautical Materials | Year: 2010

The high temperature deformation behavior of a new type 3rd generation nickel-based powder metallurgy(P/M) superalloy FGH98 I was studied in the different deformation temperatures (950~1150°C) and different strain rates (0.0003~1 s-1) using Gleeble-1500 thermal simulator. It developed the dynamic RTT curve and established the constitutive relationship of hot deformation. The results show the flow stress decreases with increasing deformation temperature and decreasing strain rate. The flow stress represents as the characteristic of dynamic crystallization with the increasing of strain at the deformation temperature lower than 1100°C and strain rates higher than 0.0003 s-1. The beginning time of dynamic crystallization has no linear relationship with deformation temperatures in the condition of the strain rates lower than 0.01 s-1. Besides, the experiments verify that the sinh model including the variable of strain reflects the changing law of flow stress during the hot deformation process.


Wu K.,University of Science and Technology Beijing | Liu G.Q.,University of Science and Technology Beijing | Hu B.F.,University of Science and Technology Beijing | Li F.,University of Cambridge | And 4 more authors.
Journal of Materials Science | Year: 2012

The formation mechanism and coarsening behavior of fan-type structures in a new Ni-Cr-Co-based powder metallurgy superalloy were investigated by means of field scanning electron microscope, transmission electron microscope, electron backscattered diffraction, and differential scanning calorimetry. The results show that he fan-type structures consist of finger-shaped λ dendrites and c matrix between them. They nucleate in the chemical segregation regions on grain boundaries and grow by diffusion. There are three types of solute atoms flow: (a) rapid diffusion along grain boundary; (b) the diffusion from supersaturated c matrix to fan-type c0 phases; and (c) shortdistance diffusion from the previous formed λ0 phases at high temperature to c0 phases formed at low temperature within the branches of fan-type structures. These λ dendrites are perpendicular to grain boundaries and grow asymmetrically, resulting in grain boundary serration. In addition, the fan-type structures coarsen within the c0 depletion zone after the standard aging treatment. © 2012 Springer Science+Business Media, LLC.


Wu K.,University of Science and Technology Beijing | Liu G.,University of Science and Technology Beijing | Hu B.,University of Science and Technology Beijing | Ma W.,University of Science and Technology Beijing | And 4 more authors.
Procedia Engineering | Year: 2012

The effects of alloy elements on the precipitation behaviours of TCP and γ′phases in new type powder metallurgy (P/M) turbine disk superalloy René104 at the aging temperature of 815 °C were studied systematically by a thermodynamic calculation method. The chemical compositions of new type nickel-based P/M superalloy were designed combining with d-electron theory. The results show that the contents of Cr, Co, Mo and W mainly influence the precipitation temperature and amount of TCP and γ′phases in René104. The suggested contents of Cr and Co are 13% and 20.6% respectively, and the suggested content of Mo is higher than W. The results also show that the content ratios of Al/Ti and Nb/Ta affect the precipitation behaviours of TCP and γ ′phases. The balance values of Al/Ti and Nb/Ta are suggested in order to make the alloy having desired microstructural stability and strengthening effect. In addition, Hf also influenced the precipitation behaviours of TCP and γ'phases and the suggested content of Hf is 0.2%. The main precipitates of the new type P/M turbine disk superalloy FGH98I are γ ′, MC, M23C6 and M 3B2, and no any TCP phases precipitate. After the exposure at 750 °C, 815 °C and 850 °C for 1000 h, the new alloy still shows good microstructural stability. © 2011 Published by Elsevier Ltd.


Wu K.,University of Science and Technology Beijing | Liu G.,University of Science and Technology Beijing | Hu B.,University of Science and Technology Beijing | Ma W.,University of Science and Technology Beijing | And 4 more authors.
Procedia Engineering | Year: 2012

The hot forging deformation experiments of a new type high performance powder metallurgy (P/M) turbine disk superalloy FGH98 I has been performed under the conditions of the deformation temperatures of 1050-1100 °C and strain rates of 0.0003∼0.01 s-1, and then with subsequent subsolvus and supersolvus heat treatments for 0.25-1 h. The results show that FGH98 I alloy exhibits the desired thermoplastic response under the testing conditions. The forging flow stress increases with increasing strain rate and decreasing temperature. The mean grain size of as-forged FGH98 I varies between 6.0 μm and 8.0 μm, and only slightly coarsens with the increasing temperature and decreasing strain rate. The mean grain size of the subsolvus heat treated specimens varies between 8.6 μm and 24 μm, slowly coarsens with increasing solution time, and moderately coarsens with increasing temperature and decreasing strain rate. The mean grain size under supersolvus heat treated varies between 10 μm and 46 μm, obviously coarsens with increasing temperature and solution time, and coarsens with decreasing strain rate. The above results can be used for optimizing the practical forging process of FGH98 I disk alloy. © 2011 Published by Elsevier Ltd.


Wu K.,University of Science and Technology Beijing | Liu G.,University of Science and Technology Beijing | Hu B.,University of Science and Technology Beijing | Zhang Y.,University of Science and Technology Beijing | And 3 more authors.
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering | Year: 2012

The effect of solution cooling rate on the microstructure and microhardness of a novel type nickel-based P/M superalloy FGH98Iin subslovus plus superslovus and superslovus heat treatment condition was studied by means of optical microscope (OM), field emission scanning electron microscope (FESEM) and microhardness tester. The results show that subslovus pre-heat treatment makes the large grain boundary γ′ phase of as-forged alloy partial dissolution, and the grains grow a little, while the influence on the cooling γ′ precipitates of superslovus heat treatment is not obvious. The average sizes of secondary and tertiary γ′ precipitates decrease with the cooling rate increasing. Meanwhile, the shape of secondary γ′ precipitates changes from the butterfly-like to the spherical, the γ′ phase particle density increases and the area fraction decreases. It is also found that γ′ phases nucleate and precipitate in two stages if the cooling rate is not faster than 1.4°C/s. The higher the cooling rate, the higher the microhardness, and the microhardness increases more after aging. In addition, the average sizes of γ′ precipitates and the microhardness as a function of cooling rate are established. The above results can be used as a theoretical reference for the selection of actual superslovus processing of FGH98Idual-property disk. © 2012, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved.


Wu K.,University of Science and Technology Beijing | Liu G.,University of Science and Technology Beijing | Hu B.,University of Science and Technology Beijing | Li F.,University of Cambridge | And 4 more authors.
Materials Characterization | Year: 2012

The solidification characterization of a new rapidly solidified Ni-Cr-Co based superalloy prepared by plasma rotating electrode process was investigated by means of optical microscope, scanning electron microscope, and transmission electron microscope. The results show that the solidification microstructure changes from dendrites to cellular and microcrystal structures with decreasing powder size. The elements of Co, Cr, W and Ni are enriched in the dendrites, while Mo, Nb and Ti are higher in the interdendritic regions. The relationships between powder size with the average solid-liquid interface moving rate, the average interface temperature gradient and the average cooling rate are established. Microsegregation is increased with larger powder size. The geometric integrity of MC′ type carbides in the powders changes from regular to diverse with decreasing powder size. The morphology and quantity of carbides depend on the thermal parameters and non-equilibrium solute partition coefficients during rapid solidification. © 2012 Elsevier Inc.


Wu K.,University of Science and Technology Beijing | Liu G.Q.,University of Science and Technology Beijing | Hu B.F.,University of Science and Technology Beijing | Wang C.Y.,University of Science and Technology Beijing | And 4 more authors.
Materials Science and Engineering A | Year: 2011

The hot compressive deformation behavior of a new Ni-Cr-Co based P/M superalloy was studied in the temperature range of 950-1150°C and strain rate range of 0.0003-1s-1 using hot compression tests. The effect of processing parameters on flow stress, activation energy, power dissipation η maps and instability maps were investigated. The results show that the flow stress decreases with increasing temperature and decreasing strain rate. The apparent activation energy of deformation decreases while the values of η in the peak zones increase with increasing strain, due to the occurrence of dynamic recrystallization. When the strain is 0.5, a domain with its peak η of 40% occurs at 1050°C and 0.0003s-1, which corresponds to dynamic recrystallization with grain size of ASTM 10-11 and can be as the optimum processing parameters for good workability. © 2011.


Wu K.,University of Science and Technology Beijing | Liu G.,University of Science and Technology Beijing | Hu B.,University of Science and Technology Beijing | Li F.,University of Cambridge | And 4 more authors.
Materials and Design | Year: 2011

The hot compressive deformation behavior of a new hot isostatically pressed Ni-Cr-Co based powder metallurgy (P/M) superalloy was studied in the temperature range of 950-1150°C and strain rate range of 0.0003-1s-1 using Gleeble-1500 thermal simulator. The dynamic recrystallization-time-temperature (RTT) curve was developed and the constitutive equation of flow stress during hot deformation was established. The results show that the flow stress decreases with increasing deformation temperature and decreasing strain rate. The flow stress represents as the characteristic of dynamic crystallization with the increasing of strain at the deformation temperatures lower than 1100°C and strain rates higher than 0.0003s-1. The beginning time of dynamic crystallization has no linear relationship with deformation temperature in the condition of strain rate lower than 0.01s-1. Besides, the experiments verify that the hyperbolic sine model including the variable of strain reflects the changing law of flow stress during the hot deformation process. © 2010.

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