Jianping NIU
,
Kenu YANG
,
Tao JIN
,
Xiaofeng SUN
,
Hengrong GUAN
,
Zhuangqi HU
材料科学技术（英文）
The variation of S content during VIM refining Ni-base superalloy using CaO crucible was studied. It was found that the desulphurization process could not be carried out by only using CaO crucible. The role of Al addition to desulphurization was also studied. Combining with the results of XRD and composition analysis of the CaO crucible, the mechanism of desulphurization was proposed. Thermodynamical calculation about the reaction between the interface of CaO crucible and liquid metal has been discussed. This work indicated that under proper refining technology the S content in the liquid Ni-base alloy could be reduced from 3×10-5 to 2×10-6-4×10-6.
关键词:
Ni-base superalloy
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null
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null
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Wen LI
,
Tao JIN
,
Xiaofeng SUN
,
Yi GUO
,
Hengrong GUAN
,
Zhuangqi HU
材料科学技术（英文）
The Ni-base single crystal superalloy was bonded by the transient liquid phase (TLP) bonding, using a Ni-base flexible metal cloth as an insert alloy. TLP bonding of superalloy was carried out at 1473~1523 K for 0.5~24 h in vacuum. The [001] orientation of each test specimen was aligned perpendicular to the joint interface. The bonded region was observed by optical microscopy, and the microstructural and compositional analyses across the bonded interlayer were performed by using a scanning electron microscopy (SEM). The electron back scattering diffraction (EBSD) method was applied to determine the crystallographic orientation. The results indicated that the chemical homogeneity across the bonded region can be achieved, and γ′ phase both in the bonded interlayer and in the superalloy substrate is almost identical, while the bonded interlayer had almost matched the crystallographic orientation of the bonded substrates.
关键词:
Single crystal superalloy
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null
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null
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Hua WEI
,
Xiaofeng SUN
,
Qi ZHENG
,
Guichen HOU
,
Hengrong GUAN
,
Zhuangqi HU
材料科学技术（英文）
A numerical method has been developed to extract the composition-dependent interdiffusivity from the concentration profiles in the aluminide coating prepared by pack cementation. The procedure is based on the classic finite difference method (FDM). In order to simplify the model, effect of some alloying elements on interdiffusivity can be negligible. Calculated results indicate the interdiffusivity in aluminide coating strongly depends on the composition and give the formulas used to calculate interdiffusivity at 850, 950 and 1050ºC. The effect on interdiffusivity is briefly discussed.
关键词:
Interdiffusivity
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null
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Mengjin LI
,
Xiaofeng SUN
,
Hengrong GUAN
,
Xiaoxia JIANG
,
Zhuangqi HU
材料科学技术（英文）
(Ni,Pd)Al coating, prepared by low pressure pack cementation on the Ni-base superalloy M38 where Pd-20 wt pct Ni alloy was predeposited, consists of a single β-(Ni,Pd)Al phase. The initial isothermal oxidation behavior of (Ni,Pd)Al coating was investigated by TGA, XRD, SEM/EDS at 800-1100℃. Results show that oxidation kinetics accord preferably with parabolic law at 800, 900 and 1100℃, but not at 1000℃. β-Al2O3 was observed at 800-1100℃. It is found that Pd plays an important role in accelerating the diffusion of Ti from the substrate to the coating surface in the aluminide coating.
关键词:
(Ni
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null
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null
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null
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Wenhui JIANG
,
Xiangdong YAO
,
Hengrong GUAN
,
Zhuangqi HU
材料科学技术（英文）
The carbide behavior of a directionally solidified Co-base superalloy DZ40M has been investigated after creep at 700 and 900℃. During the high temperature creep, a great amount of secondary carbide, M23C6 precipitated in alloy matrix. At 700℃, the M23C6 precipitation occurred in slip bands, indicating that it was stress-induced, while at 900℃, M23C6 formed surrounding the primary carbides, which is a characteristic of thermally aged alloy. The M23C6 particles pinned up dislocations and subgrain boundaries, strengthening the alloy matrix effectively. The creep crack initiation of DZ40M alloy was exclusively related to the primary carbides. The fracture of the primary carbide and the crack at the interface between them and matrix resulted in the crack formation. Furthermore, it was found that at 900℃, the surface of specimens was oxidized severely and the preferentially oxidized primary carbides acted as crack initiation sites.
关键词:
Chao YUAN
,
Fengshi YIN
,
Xiaofeng SUN
,
Hengrong GUAN
,
Zhuangqi HU
材料科学技术（英文）
Effect of phosphorus on the microstructure and high temperature properties of a cast Ni-base superalloy M963 has been investigated. SEM observation and EDS analysis showed that P was mostly enriched in the interdendritic region, and the P-rich phase was formed in the front position of finally solidified eutectics in high P doped alloys. It was found that the P-rich phase, as preferred initiation and propagation site of cracks, could aggravate the fracture process at high temperature in high P doped alloys.Consequently, high P addition would reduce remarkably the ductility and creep life of M963 superalloy at high temperature.
关键词:
Phosphorus
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