Xiamen Tungsten Co. Technology Center

Xiamen, China

Xiamen Tungsten Co. Technology Center

Xiamen, China
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Sun X.-Y.,Xiamen Golden Egret Special Alloy Co. | Sun X.-Y.,Xiamen Tungsten Co. Technology Center
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2010

It is important to control carbon content during cemented carbide production. The conventional method for controlling carbon content is adjusting magnetic saturation intensity. Because of the limitation of the detecting system, the big manufactures can't be detected in magnetic saturation intensity equipment. In the view of cobalt as the binder phase of cemented carbide is magnetic, ferrite detecting method is proposed in this paper to replace the tradition method of detecting the carbon content of cemented carbide manufactures in large size. The WC-Co samples with different carbon content sintered in low pressure sintering furnace using WC and Co mixed powders as raw materials were used to detect the magnetic saturation intensity and the ferrite content. Besides, the relationships of carbon content, magnetic saturation intensity and ferrite content value were investigated. The results indicate that the relationship of carbon content and ferrite content value is linear, thus, ferrite content can be considered to be used to represent carbon content. Since detecting method of test ferrite content is simple, it's a good way to give benefit to the improvement of the cemented carbide quality.


Xiao M.-D.,Xiamen Tungsten Co. Technology Center | Xiao M.-D.,Xiamen Golden Egret Special Alloy Co.
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2010

Raw material oxidation is the most strict problem in submicron grain (≤ 0.8 μm) cemented carbides production. By means of adding oxide, the morphology of pores induced by the oxide in samples prepared at different sintering temperature was investigated using SEM. The results show that pores induced by oxide have obvious characterization of coarse grain structure. In addition, the mechanism of the coarse grain structure formation is discussed and it is recognized that the coarse grain structure is resulted from gas participated reaction. TG-DSC result shows the temperatures of carbon reducing Co3O4 and WO3 are around 732°C and 1050°C, respectively.


Wu C.-H.,Xiamen Tungsten Co. Technology Center | Wu C.-H.,Xiamen Golden Egret Special Alloy Co.
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2010

A novel method to inhibit Mo codeposition from ammonium tungstate solution during ammonium paratungstate (APT) crystallization process by control the concentration of Cl- in the solution. Based on the plentiful APT production practices, the wonderful effect of Cl- on inhibition Mo co-deposition with APT during APT crystallization process has been found out. For a special ammonium tungstate solution with given Mo concentration, there is a corresponding threshold concentration of Cl- in order to achieve high crystallization rate and low Mo content for APT production. Using this high effective method, the primary crystallization rate of the APT increases from 80% to 96% and the resultant APT is zero-grade with very low Mo concentration (≤ 2 × 10-5). The APT products have perfect crystal morphology and homogenous particle size (40~50 μm). A possible mechanism of Cl- inhibiting molybdenum deposition is proposed.


Du W.,Xiamen Golden Egret Special Alloy Co. | Nie H.-B.,Xiamen Golden Egret Special Alloy Co. | Nie H.-B.,Xiamen Tungsten Co. Technology Center | Wu C.-H.,Xiamen Golden Egret Special Alloy Co. | Wu C.-H.,Xiamen Tungsten Co. Technology Center
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2010

Low Cobalt ultrafine cemented carbide has higher hardness, higher red hardness and better wear resistance than conventional ultrafine cemented carbide, therefore it is widely used as precision parts, cutting tools, special wear resistant material and components as well as drawing dies, etc. In the present study, 2.5% Co ultrafine cemented carbide was fabricated by low pressure sintering using ultrafine WC powders and spherical Co powders as raw materials. The samples density, porosity, coercive force, transverse rupture strength and hardness were measured by using scanning electron microscope, metallograph, vickers hardometer, mechanical test system, etc. The effects of sintering technology on properties of low cobalt ultrafine cemented carbide were studied. The micro-morphology of raw material powders and the microstructure of cemented carbides were studied by SEM. The results show that, the hardness, transverse rupture stress and coercive force are 2110 HV30, 2250 MPa and 55.7 kA/m, respectively, increasing sintering temperature or using low pressure sintering can reduce pores in cemented carbides and then improve their strength; the WC average particle size of cemented carbide sintered in low pressure sintering furnace is larger than those sintered in vacuum furnace and there is the phenomenon of abnormal growth of WC in the alloys sintered in vacuum furnace.


Ma L.-L.,Xiamen Tungsten Co. Technology Center | Ma L.-L.,Xiamen Golden Egret Special Alloy Co.
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2010

The WC-10%Co rods are adopted to study the corrosion behavior of cemented carbide in water. The finished grinding rods were stored at room temperature in the presence of water for a certain time. It can be found that there are many yellow "rusted spots" on the finished grinding rods. The SEM and EDS analysis results show that the formed "rusted spots" are yellow compact oxide films which indicate the corrosive effect of water on cemented carbide. Moreover there are cobalt-free defects on the corroded rods after the oxide films removed by finished grinding. The existence of cobalt-free defects on the rods also demonstrates that water has the effect of cobalt leaching from cemented carbide rods. In addition, the electrochemical mechanism of the cobalt corrosion and leaching is also discussed in this paper.


Liu C.,Xiamen Tungsten Co. Technology Center | Liu C.,Xiamen Golden Egret Special Alloy Co.
Materials China | Year: 2016

Binderless carbide has higher hardness, higher Young's modulus, while the corrosion resistance and wear resistance are improved greatly compared to conventional WC-Co alloy. Because there is no metal binder phase in the carbide, binderless carbide is very difficult to sinter. But with the advanced sintering technology's invention, such as hot isostatic pressing (HIP), spark plasma sintering (SPS), and the development of submicro, nano powder manufacturing technology, pure WC, WC-TiC-TaC, WC-SiC, WC-MoC-SiC and other binderless carbides have emerged. These materials are gradually used in some fields requiring high precision, high hardness, high Young's modulus and high corrosion resistance, such as precision optical mould, blast nozzle, nuclear industry seal, etc. In this paper, we introduced several binderless carbides and their applications, and has made a simple prospect for future development. © 2016, The Editorial Board of Materials China. All right reserved.


Nie H.-B.,Xiamen Tungsten Co. Technology Center | Nie H.-B.,Xiamen Golden Egret Special Alloy Co.
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2010

By settling the scope of loads and amending system error caused by the elastic deformation of the instrument, the elastic modulus of cemented carbides were determined by means of three-point bend tests on electronic universal testing machine in the present paper. The results showed that the quantitative relationship between the measured elastic modulus (y) and Co content of cemented carbides (x) can be expressed as y=0.13x2-14.24x+708.41, which shows the elastic modulus decreases with Co content increasing. The measured values of the three-point bend method are reliable and accurate, and are consistent with the measured values of an impulse excitation/acoustic resonance technique. The above mentioned measure method of the elastic modulus of cemented carbides is simple, and can be generally used in mechanical property measurement for cemented carbide materials.


Zhang T.-Q.,Xiamen Tungsten Co. Technology Center
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2010

Cobalt powder used in cemented carbides is mainly fabricated by hydrogen decomposition-reduction technology using cobalt compounds of cobalt oxalate (CoC2O4 · 2H2O), cobalt carbonate (CoCO3 · xH2O), or cobalt oxide (Co3O4) as raw materials. The decomposition-reduction mechanisms of the above three cobalt compounds have been analyzed and discussed in detail in the present paper. According to the decomposition-reduction mechanisms, the effects of the character of raw materials powders and the technology parameters on the quality of cobalt powders were also discussed based on nucleation and growth theories. The results indicate that the ultra-fine spherical raw materials powders are necessary to obtain ultra-fine spherical cobalt powders. It is very important to improve the nucleation rate of the cobalt particles and restrain their growth rate during decomposition-reduction, and the order of the raw materials from difficult to easy for controlling technology is CoC2O4 · 2H2O > CoCO3 · xH2O > Co3O4.


Zhang Q.,Central South University | He Y.,Central South University | Wang W.,Central South University | Lin N.,Central South University | And 2 more authors.
Corrosion Science | Year: 2015

Many microbial issues have been widely proposed in the omnipresent metalworking fluids (MWFs). In this work, a particular sulfate reducing Citrobacter sp. strain was isolated from engaged oil-in-water emulsion, named as CK2. The occurrence of microbially influenced corrosion of WC-30Co hardmetals caused by CK2 in O/W emulsion and nutrient media was proved by electrochemical and micro-morphological analyses. Preferential cobalt loss determined the corrosion failure in biodegraded emulsions. CK2 made the emulsion more corrosive to hardmetals. Microbially influenced corrosion inhibition was observed in CK2-containing emulsion. In nutrient media, the corrosion rates of WC-30Co multiplied about 10 times due to microbial activities. © 2015 Elsevier Ltd.


Lin N.,Central South University | He Y.,Central South University | Wu C.,Xiamen Tungsten Co. Technology Center | Zhang Q.,Central South University | And 2 more authors.
Scripta Materialia | Year: 2012

An innovative way to synthesize tungsten carbide-vanadium carbide core-shell structure powders, which are predicted to act as inhibitors for cemented carbides, has been explored. The core-shell structures were synthesized by chemically induced precipitation and carbonization reactions. The cemented carbides with a homogeneous microstructure were prepared at 1400 °C. The existence of tungsten carbide-vanadium carbide core-shell structure can significantly refine tungsten carbide grains, inhibit the abnormal growth of finer grains in the liquid sintering and improve the mechanical properties of the hard metals. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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