State Key Laboratory of Cemented Carbides

Zhuzhou, China

State Key Laboratory of Cemented Carbides

Zhuzhou, China
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Wang Y.,Central South University | Zhou P.,Central South University | Zhou P.,Hunan University of Science and Technology | Peng Y.,Central South University | And 6 more authors.
Journal of Alloys and Compounds | Year: 2016

Phase equilibria of the Al–Co–Ni system is extremely useful for understanding phase behavior of AlNi3-based L12 phases, regarding its attractive properties, such as high-temperature oxidation resistance and corrosion resistance, high hardness and strength. In the present work, all the experimental data about the phase equilibria and thermodynamic properties of the Al–Co–Ni system were critically evaluated, and a thermodynamic description for this system over the whole composition and temperature ranges was obtained. Most importantly, the ordered/disordered transition between fcc_A1 and L12 phases was described using a four-sublattice (4SL) model. Based on the crystallographic and experimental data, three stable ternary intermetallic phases were described using sublattice model. Two of them were treated as semi-stoichiometric compounds with homogeneity ranges for Co and Ni, and the other one was treated as a stoichiometric compound. The other phases were described by using substitutional solution model. The present work provides a more complete and accurate thermodynamic description compared with previous ones. A reasonable agreement was obtained between calculations and experimental data in the ternary system. The occupancy behavior of Co in AlNi3 is thermodynamically predicted, and the computed occupancy shows a much better fit to the experimental data than previous first-principles calculations. In addition, the composition range of the Co + AlNi3 two-phase region, concerning a new type of composite binder for cemented carbides, was found to shift to the Co-rich side with the decrease of the temperature. © 2016 Elsevier B.V.

Zhang W.,Central South University | Du Y.,Central South University | Peng Y.,Central South University | Peng Y.,Hunan University of Technology | And 15 more authors.
Cailiao Kexue yu Gongyi/Material Science and Technology | Year: 2016

The ICME (Integrated Computational Materials Engineering) for cemented carbides aims to combine key experiments with multi-scale numerical simulations from nano (10-10~10-8 m) to micro (10-8~10-4 m) to meso (10-4~10-2 m) and to macro (10-2~10 m) during the whole R&D (research and development) process of cemented carbides. Using integrated analysis of the composition-processing-structure-properties, the methodology for developing cemented carbides is promoted from trial and error to scientific design, which will significantly speed up the R&D of cemented carbides and reduce the costs. In this paper, multi-scale simulation approaches including Ab-initio, CALPHAD (CALculation of PHAse Diagram), phase field, and finite element method together with experimental methods characterizing structure and properties are elaborated. The function of each method in the R&D of cemented carbides is carefully discussed. Based on ICME, the framework for R&D of cemented carbides, involving end-user demand, product design and industrial design, is established. Several application examples are presented to describe the important role of ICME during the development stage of cemented carbides, which provides an innovative pattern for R&D of advanced cemented carbides. © 2016, Harbin Institute of Technology. All right reserved.

Chen W.-M.,State Key Laboratory of Cemented Carbides | Chen W.-M.,Central South University | Xu T.,State Key Laboratory of Cemented Carbides | Zhang W.-B.,Central South University | And 8 more authors.
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2012

The gradient zone formation in Co-W-Ti-C-N, Co-W-Ti-Nb-C-N and Co-W-Ti-Ta-C-N cemented carbides was simulated by using the DICTRA software package in conjunction with thermodynamic calculations. Simulated elemental concentration profiles for Co were compared with the experimental results. Taking into account the volume fractions of different phases and elemental concentration profiles, the effects of sintering time, sintering temperature, as well as the contents of Co and Ti on gradient zone formation, were investigated. The results show that the simulated results agree reasonably with the experimental data. The long sintering time, high sintering temperature and large content of Co increase the thickness of the gradient zone, but the high content of Ti restrains the thickness of gradient zone increasing.

Li P.,Central South University | Li P.,Zhuzhou Cemented Carbide Cutting Tools Co. | Chen L.,Central South University | Chen L.,Zhuzhou Cemented Carbide Cutting Tools Co. | And 8 more authors.
International Journal of Refractory Metals and Hard Materials | Year: 2013

The wide application range of multilayer Ti-Al-N and Cr-Al-N coatings for wear protection leads to sustaining development in their performance. Here, we prepare TiAlN/CrAlN nano-multilayer coatings with different bilayer periods in order to improve the properties of Ti-Al-N and Cr-Al-N single layer coatings. Multilayer structure results in an increased hardness with a maximum value of ~ 38.2 GPa for TiAlN/CrAlN coating (TiAlN/CrAlN-2) with bilayer period of ~ 18 nm, and also an increase in adhesive strength to a maximum value of 98 N for TiAlN/CrAlN coating (TiAlN/CrAlN-1) with bilayer period of ~ 18 nm. Additionally, TiAlN/CrAlN nano-multilayer coatings combine the thermal stability of Ti-Al-N and oxidation resistance of Cr-Al-N, and thus their application temperature range is broadened. Consequently, an improved machining performance regardless of continuous cutting or milling is obtained by TiAlN/CrAlN nano-multilayer coated inserts. © 2013 Elsevier Ltd.

Chen C.,Central South University | Zhang L.,Central South University | Xin J.,Central South University | Wang Y.,Central South University | And 5 more authors.
Journal of Alloys and Compounds | Year: 2015

Based on various experimentally measured diffusivities available in the literature together with the reported thermodynamic parameters, the atomic mobilities for disordered fcc and ordered L12 Ni-Al-W alloys were assessed on the basis of a recently developed phenomenological model incorporated in the DICTRA software. In order to provide the missing impurity diffusion coefficients of W in fcc-Al, first-principles calculations were utilized in the present work. Comprehensive comparisons between the calculated and experimental diffusion coefficients show that all the experimental data can be well reproduced by the atomic mobilities obtained in the present work. In order to further verify the reliability of the presently obtained atomic mobilities, two fcc/L12-type diffusion couples (i.e., Ni-5 at.% Al-5 at.% W/Ni-20 at.% Al-4 at.% W and Ni/Ni-22 at.% Al-2 at.% W) were prepared and the concentration-distance profiles after annealing at 1323 K for 86.4 ks were measured. The excellent agreement between the model-predicted concentration-distance profiles and the experimental data indicates that the presently obtained atomic mobilities in fcc/L12 Ni-Al-W alloys are reliable. © 2015 Elsevier B.V. All rights reserved.

Wang A.,Central South University | Shang S.,Pennsylvania State University | Zhao D.,Central South University | Wang J.,Central South University | And 6 more authors.
Calphad: Computer Coupling of Phase Diagrams and Thermochemistry | Year: 2012

Structural, phonon, and thermodynamic properties of fcc-based metal nitrides MN (M=Ti,Al,Zr,Hf) have been investigated by first-principles calculations within the local density approximation (LDA) and the generalized gradient approximation (GGA). The supercell method for lattice dynamics is utilized to calculate the phonon density of states, and the thermodynamic properties (heat capacity, enthalpy, entropy, and Gibbs energy) of these nitrides at elevated temperatures are predicted via the quasiharmonic approximation. We find that the lattice parameters predicted by GGA agree well with experiments compared to those from LDA. The GGA predicts a larger bond length and a smaller bulk modulus than those from LDA. It is found that the vibrational contribution to Gibbs energy is larger for HfN in comparison with other metal nitrides due to its higher population of phonon density of state in the low frequency region. Calculated structural, phonon, and thermodynamic properties are in good agreement with the available experiments and CALPHAD-type evaluations.© 2012 Elsevier Ltd. All rights reserved.

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