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Peng W.,State Key Laboratory of Cemented Carbide | Peng W.,Zhuzhou Cemented Carbide Group Corporation Ltd. | Kong D.,State Key Laboratory of Cemented Carbide | Kong D.,Zhuzhou Cemented Carbide Group Corporation Ltd.
Jingangshi yu Moliao Moju Gongcheng/Diamond and Abrasives Engineering | Year: 2016

The basic principle of synthesizing of gem-grade diamond using pressless "split sphere" high-pressure apparatus (BARS) was introduced. The property of cemented carbide anvils placed in BARS was presented, as well as the industrializing process of Chinese cemented carbide for BARS. Research showed that using WC-Co ultrafine composite powder after stirring ball milling, cold isostatic pressing and low pressure sintering would increase the uniformity of organizational structure, together with compressive strength and elastic modulus of hard alloy. The optimum project to machine self-localization anvil was to mutually act as reference and control product concentricity. Using M22/36 finishing wheel with a reasonable amount of feed in the grinding was the key to ensure the machining accuracy. © 2016, Zhengzhou Institute of Abrasives Grinding. All right reserved.


Peng Y.,Central South University | Peng Y.,Hunan University of Technology | Buchegger C.,Vienna University of Technology | Lengauer W.,Vienna University of Technology | And 4 more authors.
International Journal of Refractory Metals and Hard Materials | Year: 2016

Cr3C2, VC, TaC, NbC, ZrC and their certain combinations are commonly added to WC-Co-based cemented carbides as grain-growth inhibitors. The solubility of these grain-growth inhibitors in the binder phase is an important knowledge in the development of cemented carbides. Thermodynamic calculations have been carried out to design the alloy compositions of WC-Co-based model alloys with high Co contents. The calculations are compared to the data obtained on model alloys, which were characterised by means of X-ray diffraction (XRD), light-optical microscopy (LOM) and wavelength-dispersive electron-probe microanalysis (WDS-EPMA). Extensive thermodynamic calculations were performed and compared with the experimental data from our work and those reported in the literature. A good agreement between calculation and experiment thereby validates the accuracy of our established thermodynamic database of the cemented carbides. © 2016 Elsevier Ltd


Long J.-Z.,State Key Laboratory of Cemented Carbide | Long J.-Z.,Zhuzhou Cemented Carbide Group Corporation Ltd. | Zhang Z.-J.,State Key Laboratory of Cemented Carbide | Zhang Z.-J.,Zhuzhou Cemented Carbide Group Corporation Ltd. | And 10 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2012

In order to develop the liquid phase sintering process of WC-Ni 3Al-B composites, the preparation process of WC+Ni 3Al prealloyed powder by reaction synthesis of carbonyl Ni, analytical purity Al and coarse WC powders was investigated. DSC and XRD were adopted to study the procedure of phase transformation for the 3Ni+Al and 70WC+(3Ni+Al) mixed powders in temperature ranges of 550-1200 °C and 25-1400 °C, respectively. The results demonstrate that the formation mechanism of Ni 3Al depends on the reaction temperature. Besides WC phase, there exist Ni 2Al 3, NiAl and Ni 3Al intermetallics in the powder mixture after heat treatment at 200-660 °C, while only NiAl and Ni 3Al exist at 660-1100 °C. Homogeneous WC+Ni 3Al powder mixture can be obtained in the temperature range of 1100-1200 °C. The WC-30(Ni 3Al-B) composites prepared from the mixed powders by conventional powder metallurgy technology show nearly full density and the shape of WC is round. WC-30(Ni 3Al-B) composites exhibit higher hardness of 9.7 GPa, inferior bending strength of 1800 MPa and similar fracture toughness of 18 MPa·m 1/2 compared with commercial cemented carbides YGR45 (WC-30(Co-Ni-Cr)). © 2012 The Nonferrous Metals Society of China.


Wang H.,State key laboratory of cemented carbide | Chen D.,Hunan University
Fenmo Yejin Jishu/Powder Metallurgy Technology | Year: 2016

This paper systematically elaborate the research progress of fatigue crack initiation and propagation for powder metallurgy high speed steels in the past 30 years. Powder metallurgy high speed steels has fine grain, homogeneous distributed carbide, high dispersity, which drastically improve its bending strength and impact toughness. However, because of the mean distance between microstructure much smaller than fused cast high speed steels, powder metallurgy high speed steels have high rate of crack propagation, which makes it has higher risk of early fracture than fused cast high speed steels. Moreover, the decrease of critical size and porosity for inclusions in powder metallurgy high speed steels is an effective means to improve its fatigue property. © 2016, University of Science and Technology Beijing. All right reserved.


Zhang W.,Central South University | Peng Y.,Central South University | Du Y.,Central South University | Chen L.,Central South University | And 4 more authors.
International Journal of Refractory Metals and Hard Materials | Year: 2015

The C-Ti-V system was assessed by means of the CALPHAD (CALculation of PHAse Diagram) method. All of the experimental phase diagram data available from the literature were critically reviewed and assessed using thermodynamic models for the Gibbs energies of individual phases. The solution phases including the liquid, fcc, hcp and bcc were described by a substitutional solution model. There was no ternary compound in this system. A set of self-consistent thermodynamic parameters for the C-Ti-V system was obtained. Comparisons between the calculated and measured phase diagrams show that the experimental information is satisfactorily accounted for by the present thermodynamic description. The liquidus projection, three-dimensional isometric view and reaction scheme were generated by using the present thermodynamic parameters. © 2014 Elsevier Ltd. All rights reserved.


Wang Y.,Central South University | Chen C.,Central South University | Zhang Z.,State Key Laboratory of Cemented Carbide | Long J.,State Key Laboratory of Cemented Carbide | And 6 more authors.
International Journal of Refractory Metals and Hard Materials | Year: 2014

Based on a critical literature review, the Al-C-Ni and C-Ni-W ternary systems are thermodynamically reassessed using the CALPHAD (CALculation of PHAse Diagrams) method. The calculated phase equilibria and thermodynamic properties can well reproduce the experimental data. The Al-C-Ni-W thermodynamic database is then established using descriptions of the accepted ternary systems. The calculated solubility of WC in AlNi3 is in good agreement with the experimental result. The computed solubility is used to describe the hardness-solubility dependence along the WC-AlNi3 section according to the solid solution strengthening mechanism. The effect of substitution of Co by Ni and AlNi3 as the binder phase on the phase relations in the WC-based cemented carbides is also investigated using the present thermodynamic parameters. Good agreement between calculated and experimental results indicates that the current thermodynamic database could provide an efficient guidance for designing and developing innovative WC-AlNi3 cemented carbides. © 2014 Elsevier Ltd.


Long J.-Z.,State Key Laboratory of Cemented Carbide | Long J.-Z.,Zhuzhou Cemented Carbide Group Corporation Ltd. | Xu T.,State Key Laboratory of Cemented Carbide | Xu T.,Zhuzhou Cemented Carbide Group Corporation Ltd. | And 4 more authors.
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2012

The WC-Ni 3Al composites were fabricated by powder metallurgy via reaction synthesis to form Ni3Al by the direct addition of Ni and Al during liquid sintering process. The microstructure and properties were observed and measured, respectively. The influences of Al content on densification and phase types of nickel aluminides were analysed. High temperature oxidation resistance was determined. The results show that WC grain of WC-Ni 3 Al composites has smooth topography. Besides main Ni 3 Al phase, there exists a small amount of NiAl and Ni phases in the binding phase. The densification affected by Al content relates to the amount of high-melting-point NiAl phase. WC-15Ni 3 Al composite has inferior bending strength of 1170 MPa and high hardness of 86.5 HRA at room temperature compared with WC-15Ni cemented carbide. As the content of binding phase Ni 3 Al increases to 30% (mass fraction), the WC-30Ni 3 Al composite has bending strength of 1660 MPa and hardness of 81.7 HRA at room temperature and its high temperature oxidation resistance is about an order of magnitude higher than that of WC-30(Co-Ni-Cr) cemented carbide.


Zhang K.,Central South University | Zhang Z.,State Key Laboratory of Cemented Carbide | Lu X.,Central South University | Li K.,Central South University | And 7 more authors.
International Journal of Refractory Metals and Hard Materials | Year: 2014

The microstructure and composition of WC/Ni3Al interface were studied. An orientation relationship of [100]WC//[110] Ni3Al and (001)WC//(001)Ni3Al with a good coherence, besides many random orientation relationships between WC and Ni 3Al, has been repetitively found by selected area electron diffraction and high resolution TEM observations. The XRD pattern of WC-Ni 3Al composites indicated that the major binder phase was Ni 3Al and showed possibility of coherence between WC and Ni 3Al as common interplanar spacings existed. Electron probe microanalysis results revealed that the atomic ratio of Al:Ni is close to 1:3 in binder phase and WC/Ni3Al interface in the WC-Ni3Al composites has a sharper compositional gradient and a smaller width of transition region than the WC/Co interface in WC-Co composites. © 2014 Published by Elsevier Ltd.


Gu L.,Central South University | Huang J.,Central South University | Huang J.,Key Laboratory of Nonferrous Materials Science and Engineering | Tang Y.,Central South University | And 2 more authors.
Journal of Alloys and Compounds | Year: 2015

Effects of different post treatments on microstructure and properties of WC-11 wt.% Co cemented carbides were investigated in this paper. The different post treatments that are carried out to the cemented carbides are (a) heating and quenching in oil bath, (b) controlled cryogenic treatment. Various mechanical and microstructural characterization of these alloys including density, coercive force, hardness, transverse rupture strength, phase composition, W solubility of the cobalt phase, martensitic phase transformation of the cobalt phase and WC grain shape were analyzed before and after post treatments. The experimental results show that post treatments have a significant influence on WC-Co cemented carbides and the details of the experimental study are presented in this paper. © 2014 Elsevier B.V. All rights reserved.


Long J.,State Key Laboratory of Cemented Carbide | Zhang Z.,Zhuzhou Cemented Carbide Group Corporation Ltd. | Xu T.,Zhuzhou Cemented Carbide Group Corporation Ltd. | Lu B.,Zhuzhou Cemented Carbide Group Corporation Ltd.
International Journal of Refractory Metals and Hard Materials | Year: 2013

In this paper, the effect of the carbon contents on the microstructure, mechanical properties and fracture behavior of WC-40 vol.% Ni3Al composites prepared by conventional powder metallurgy was studied. Microstructure examinations of WC-40 vol.% Ni3Al specimens indicated that the WC grain is round and fine compared with faceted and large WC grain of WC-Co composites. With increasing carbon contents, the WC morphology of WC-40 vol.% Ni3Al composites is similar and the size of WC grain is approximate and the distribution of binder phase becomes relatively uniform. Furthermore, composition analysis of binder phase showed that, with the increase of carbon content, the solubility of W in Ni3Al reduced slightly. The ~ 9 wt.% solubility of W in Ni3Al is much lower compared with ~ 22.4 wt.% of WC-40 vol.% Co composites. The hardness and transverse rupture strength of WC-40 vol.% Ni3Al composites decrease with increasing carbon contents slightly. WC-40 vol.% Ni3Al composites present higher hardness and lower transverse rupture strength than that of WC-40 vol.% Co composites. With increasing carbon contents, the fracture behavior of the WC-40 vol.% Ni3Al composites is affected greatly and the fracture mode changes from transgranular fracture towards intergranular fracture. © 2013 Elsevier Ltd.

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