Hunan Research Institute of Metallurgy and Materials

Changsha, China

Hunan Research Institute of Metallurgy and Materials

Changsha, China
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Wang Y.M.,Central South University | Xiong X.,Central South University | Min X.B.,Hunan Research Institute of Metallurgy and Materials | Xie L.,Central South University | Zheng F.,Central South University
Materials Science and Engineering A | Year: 2010

Tungsten heavy alloy 95W-3.5Ni-1.5Fe (in wt.%) refractory metallic thin-walled products (diameter ≤100mm, length ≤150mm and wall thickness ≤5mm) were produced using plasma spray forming (PSF) covered in argon atmosphere at a pressure of 1.01×105Pa followed by vacuum liquid phase sintering at 1465, 1485 and 1500°C for 90min, respectively.A lamellar structure consisting of vertical columnar grains and some fine particles was found in PSF deposits. Relative density of the deposits was about 87.70% with poor mechanical property. Upon vacuum liquid phase sintering, their density and property have been improved significantly. The microstructures of PSF deposits before and after vacuum sintering were found to consist with tungsten and (Ni, Fe)-rich phase. Volume fraction of (Ni, Fe)-rich phase was decreased due to vaporization that occurred in plasma spraying and vacuum liquid phase sintering. Their fracture surfaces were dominated by intergranular rupture. The lamellar structure remained in the deposits during early stages of sintering (solid state sintering and initial of liquid phase sintering). Particle rearrangement and rapid densification of the deposits did not occur until the surface of tungsten particles being modified and changed into spheroids by solution and precipitation. In the end, the PSF deposits have been transformed from lamellar structure into two phase composites with dispersed spheroidal tungsten grains embedded in a continuous network of (Ni, Fe)-rich phase. © 2010 Elsevier B.V.


Chu Z.-Q.,Central South University | Chu Z.-Q.,Hunan Research Institute of Metallurgy and Materials | Guo X.-Y.,Central South University | Zhang L.,The State Key Laboratory of Powder Metallurgy | Liu D.-H.,Hunan Research Institute of Metallurgy and Materials
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2015

The prealloy powders used in diamond matrix were produced by super high pressure water atomization technology. The diameter and micrograph of prealloy powders were measured by laser scattering particle analyzer and scanning electron microscope. The effects of atomizing pressure, alloy melt superheat and diameter of delivery on the average diameter and micrograph of prealloy powders were studied. The results show that, with increasing atomization pressure, alloy melt superheat and decreasing diameter of delivery, the average diameter of the powder decreases, and the micrograph of prealloy powders changes from spherical to similar spherical and then to irregular shape. When the atomization water pressure is over 60 MPa and the alloy melt superheat is above 250 ℃, increasing water pressure and alloy melt superheat has no obvious effect on the powders diameter. The delivery will be frequently stopped when the diameter of delivery is less than 2.0 mm. © 2015, Central South University. All right reserved.


Li H.,Central South University | Duan J.,Central South University | Min X.,HuNan Research Institute of Metallurgy and Materials
Journal of Alloys and Compounds | Year: 2014

A comparative study of the electric arc-sprayed (AS) and zinc-rich powder (ZRP) coatings, was performed in sulfur-rich environment involving atmospheric corrosion test and cyclic wet-dry test. The surface morphologies and characterization of corrosion products were investigated using SEM/EDS, XRD and EPMA techniques. The anti-corrosion properties of both coatings were compared by taking electrochemical measurements. The results revealed that the corrosion resistance of the ZRP coating was higher than that of AS one in the experimental test. A general sequence for the evolution of corrosion products on zinc coatings in sulfur-rich environment was proposed: Zn → ZnO/Zn(OH) 2/ZnSO4 → Zn5(CO3) 2(OH)6 → Zn4SO4(OH) 6/ZnSO4·7H2O. © 2014 Elsevier B.V. All rights reserved.


Li F.,Central South University | Liu Y.,Central South University | Liu Q.-N.,Central South University | Wu H.,Central South University | And 2 more authors.
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2012

Iron-based amorphous alloy coatings were deposited on Q235 stainless steel substrates by high velocity oxy-fuel (HVOF) thermal spraying and detonation gun thermal spraying. The dry friction and wear characteristics of the amorphous alloy coatings at room temperature were studied, the friction and wear mechanism was also discussed. Experiment results show that the iron-based amorphous alloy coatings prepared by detonation gun spraying process present more compact structure with lower porosity of 2.1%, higher micro-hardness with the average hardness of 1095.6 HV and more excellent wear resistance than that of the iron-based amorphous alloy coatings prepared by HVOF. The iron-based amorphous alloy coating prepared by detonation gun spraying process takes shorter time to achieve stable friction coefficient, and it has a more stable friction and wear behavior. The wear mechanism of the iron-based amorphous alloy coatings deposited by HVOF is mostly fatigue wear. However, the wear mechanism of detonation gun thermal sprayed coatings is the combination of adhesive wear and abrasive wear, and the main wear mechanism is adhesive wear.


Chu Z.-Q.,Central South University | Chu Z.-Q.,Hunan Research Institute of Metallurgy and Materials | Guo X.-Y.,Central South University | Tian Q.-H.,Central South University | Zhang L.,Central South University
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2015

Vanadium nitride was prepared by carbon thermal reduction method using V2O5 as raw material. The morphology and composition of the reduction products were observed and analyzed by SEM and XRD. The contents of carbon, nitrogen and oxygen of the product were tested, and the effects of raw materials parameters, such as carbon content, temperature and time on the reduction of the product were also studied. The results show that the reduction product is a solid solution of carbon and nitride. The carbon content of raw material is the key factor to affect the content of nitrogen in the reaction products, and nitrogen content in the product has the highest value of 14.76% when the mass fraction of carbon in raw materials is about 21%; the nitriding temperature should be controlled in the range of 1400~1420 ℃, and the nitriding time can be reached by 4 h. © 2015, Central South University. All right reserved.


Wang Y.-M.,Central South University | Hao A.-L.,Anyang Institute of Technology | Xiong X.,Central South University | Xu X.,Central South University | And 2 more authors.
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2012

95W-3.5Ni-1.5Fe composite feedstock fabricated by spray drying was instantaneously sintered at 1600°C. Tungsten alloy with high density and wall thickness less than 5 mm were produced using plasma spray forming (PSF) followed by vacuum sintering at 1200, 1300, 1400 and 1465°C for 90 min, respectively. After instantaneous sintering at 1600°C, the ball milled fine particles of spray dried agglomerated powders transform from the mechanical bonding into the metallurgical bonding with deposition rate increasing from 45% to 70%. A typically lamellar structure is found in PSF deposits with the relative density of 88.90%. After sintering at 1200 and 1300°C for 90 min, the initial lamellar structure is remained in the tested samples with increasing the relative density and ultimate tensile strength (UTS). The intergranular rupture can be found in fracture surfaces of deposits with no measurable elongation. The initial lamellar structure with dominated intergranular rupture is presented in the samples after sintering at 1400°C for 90 min. While sintering at 1465°C, PSF deposits transform from lamellar structure into granular structure. The fracture surface of deposits is dominated by the mixture of intergranular rupture and transgranular rupture with UTS and elongation increase up to 567.10 MPa and 8.65%, respectively.


Min X.,Hunan Research Institute of Metallurgy and Materials | Wang Y.,Central South University | Xia G.,Hunan Research Institute of Metallurgy and Materials | Yan S.,Hunan Research Institute of Metallurgy and Materials | Lu J.,Hunan Research Institute of Metallurgy and Materials
Fenmo Yejin Jishu/Powder Metallurgy Technology | Year: 2010

The high energy spray forming technology and its applications to heat-resistant materials were introduced. Vacuum hot pressing and high-pressure hot isostatic pressing were used to improve densification. The results show that the relative density of pure tungsten throat liner fabricated by plasma spray forming is 85.6%, that by vacuum hot pressing is increased to 91.7%, and that by high-pressure hot isostatic pressing is to 96.7%, which indicates that high-pressure hot isostatic pressing can raise density. High energy spray forming technology can also fabricate heat-resistant materials with complicated shape, such as special-shaped parts like W/Mo composite nozzle tube, tungsten crucible, tungsten heating unit, heterotypical component of highexplosive antitank HEAT and MoSi2 gyroroter etc.


Wang Y.M.,Central South University | Xiong X.,Central South University | Min X.B.,Hunan Research Institute of Metallurgy and Materials
Proceedings of the World Powder Metallurgy Congress and Exhibition, World PM 2010 | Year: 2010

Complex and thin-walled refractory metallic products such as molybdenum heating elements and tungsten crucible were fabricated using plasma spray forming (PSF) followed by hot isostatic pressing (HIPing). A lamellar structure consisting of vertical columnar grains, micron-sized pores, unmolten particles and rough interlamellar contacts with gaps of sub-micron sizes between lamellas were found in PSF molybdenum and tungsten deposits with relative density of 89.5% and 85.6%, respectively. During low-pressure HIPing, densification only took place in surface layers with gaps disappearing, while a large numbers of gaps and micro-pores retained in the inner layers. After two-step HIPing, lamellar structure of molybdenum products was not shown so distinctly, but it was still retained in tungsten ones. In addition, relative density, micro-hardness and ultimate tensile strength (UTS) of the products were increased with HIPing pressure and time.


Wang Y.,Central South University | Xiong X.,Central South University | Xie L.,Central South University | Xu X.,Central South University | And 2 more authors.
Materials Transactions | Year: 2011

Refractory metallic thin-walled products of 95W-3.5Ni-l.5Fe (in mass%) were fabricated by plasma spray forming (PSF) in argon atmosphere at 1.01 × 105 Pa followed by high temperature sintering (1200, 1300, 1400 and 1465°C). Scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), Archimedes method, differential scanning calorimetry (DSC) and X-ray diffractometer (XRD) have been employed to study microstructure, solubilities, density, solidus and liquidus temperatures and phases of the parts. Lamellar structure consisting of vertical columnar grains and fine particles was found in PSF deposits. Supersaturated solid solutions were formed in the deposits with the relative density of 88 ± 2%. Solidus and liquidus temperatures of γ phase were measured to be 1392 and 1412 ± 5°C, respectively. Initial lamellar structure was remained in the tested samples after sintering at lower temperatures ( 1200°C/90 min, 1300°C/90 min and 1400°C/ 15,90 min) and turned into granular structure at 1465°C/5,15,30,90 min. In addition, the relative densities of deposits, after sintering at 1200, 1300,1400 and 1465°C for 90 min, were increased from 88 to 90,92,94 and 98 ± 2%, respectively. A five-stage sintering mechanism proposed by us previously has been re-validated and double checked by experimental results. ©2011 The Japan Institute of Metals.


Wang Y.,Central South University | Xiong X.,Central South University | Xie L.,Central South University | Xu X.,Central South University | And 2 more authors.
Materials Transactions | Year: 2011

Complex and thin-walled refractory metallic parts including molybdenum (Mo) rocket nozzle and crucible were fabricated using plasma spray forming (PSF) followed by hot isostatic pressing (HIPing). Optical microscope (OM), scanning electron microscope (SEM), Archimedes method, Vickers hardness and tensile tests have been employed to study microstructure, density, micro-hardness and mechanical properties of the parts. A lamellar structure consisting of vertical columnar grains, micron-sized pores, partially melted particles and rough interlamellar contacts with gaps of sub-micron sizes between lamellae were found in PSF Mo deposits. Relative density, micro-hardness and ultimate tensile strength (UTS) of the deposits were about 89%, 150 HV0 025 and 44 MPa, respectively. After low-pressure and two-step HIPing, those changed up to about 92%, 250∼400 HV0 025 (interior ∼ exterior layers), 93 MPa, and 97%, 325 HV0 025 and 170 MPa, respectively. Moreover, a fourstage mechanism of HIPing for PSF parts including heating up, recrystallization, lamellae movement, plastic yielding and creep has been proposed and discussed in detail. © 2011 The Japan Institute of Metals.

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