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Liu Y.,Sichuan University | Liu Y.,Southwest Jiaotong University | Wang X.-M.,Southwest Jiaotong University | Cen S.-B.,Southwest Jiaotong University | And 5 more authors.
Rare Metals | Year: 2014

A series of the electrochemical and long-term corrosion tests was carried out in a 3.5 wt% Na2SO4 solution on thermal-sprayed WC-17Co and WC-10Co-4Cr cermet coatings in order to examine the effect of composition of binder materials on the corrosion behavior. The results reveal that the overall corrosion resistance of the WC-17Co coating is inferior to that of the WC-Co-Cr coatings due to the corrosion of binder materials which induce WC particles to fall off. CoO and WO3 oxide films form on the surface of WC-17Co coating in Na2SO4 solution electrochemical corrosion process, which will protect the coating in the process of corrosion. Cr2O3 oxide film formed on the WC-10Co-4Cr coating surface has a strong hindered role to corrosion. The corrosion mechanism of WC-17Co coating in Na2SO4 solution is entire corrosion of Co matrix, while it is film-hole corrosion mechanism for WC-10Co-4Cr coating. © 2014 The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg.


Wang L.-J.,Southwest Jiaotong University | Qiu P.-X.,Southwest Jiaotong University | Liu Y.,Southwest Jiaotong University | Zhou W.-X.,Zigong Tungsten Carbide Co. | And 2 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2013

A series of electrochemical and long-term corrosion tests were carried out in a neutral saline (5% NaCl) vapor of 35 °C on thermal sprayed WC cermet coatings containing different kinds of metallic binders in order to examine the effect of composition of binder materials on the corrosion behavior. The experimental results revealed that the overall corrosion resistance of WC-Co coating was inferior to that of WC-Co-Cr coating. For the coatings without Cr, WC-Co, general corrosion occurred in binder materials in addition to galvanic corrosion between WC particles and metallic binders in the neutral environment. By contrast, the formation of passive film in the form of surface oxide in the coatings containing Cr, WC-Co-Cr, suppressed the binder and metallic binders to be eroded. It is found that the chemical composition of metallic binder materials is one of the important factors influencing the corrosion resistance of HVOF sprayed WC cermet coatings in the neutral vapor.


Liu X.,Beijing University of Technology | Wang H.,Beijing University of Technology | Song X.,Beijing University of Technology | Wang X.,Beijing University of Technology | Li Y.,Zigong Tungsten Carbide Co.
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering | Year: 2016

WC-Co composite powder was synthesized with carbon black and W, Co oxides as raw materials and VC as additive by the in-situ reduction and carbonization process. The nanocrystalline WC-Co alloys were fabricated by the spark plasma sintering technique using the prepared WC-Co composite powder. The phase composition, microstructure characteristics and mechanical properties of the sintered cemented carbides were analyzed. The results show that VC addition plays a significant role in phase composition, grain size and properties of the prepared WC-Co alloy. When the VC addition is 2.0%, the average grain size is 101 nm, the phases are WC and Co, and the cemented carbides possess high hardness and good fracture toughness. © 2016, Science Press. All right reserved.


Zhou W.-X.,Zigong Tungsten Carbide Co. | Li Y.-X.,Zigong Tungsten Carbide Co. | Li S.-L.,Central South University | Yi C.-B.,Zigong Tungsten Carbide Co. | Yan W.,Zigong Tungsten Carbide Co.
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2013

Three WC10Co4Cr coatings were prepared by high velocity oxygen fuel (HVOF) spray with various spraying distance (380, 340 and 300 mm) using agglomerated and sintered WC10Co4Cr powder with particle size range of -45~+15μm. The coatings properties were characterized by means of optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness measurements and so on. The results indicate that with the spray distance decrease, WC10Co4Cr coating's porosity decreases, microhardness increases, abrasive wear resistance enhances; spray distance from 300 mm to 380 mm has slightly effect on phase nature of the coatings, WC, W2C and small amount of amorphous phase are detected in the three sprayed coatings; spray distance from 300 mm to 340 mm has slightly effect on coatings microhardness and abrasive wear resistance. Abrasive wear mechanism and effect of different spray distance on the abrasive wear resistance properties of the WC10Co4Cr coating were also discussed, combining with the microstructure of the central site of wear area, the physical property of the spray and the changement of the surface roughness.


Yang Z.-J.,Zigong Tungsten Carbide Co. | Li Y.-X.,Zigong Tungsten Carbide Co. | Yan W.,Zigong Tungsten Carbide Co. | Zhou W.-X.,Zigong Tungsten Carbide Co. | Yu W.,Zigong Tungsten Carbide Co.
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2015

Cast WC, Cr3C2 (mass fraction varies from 10% to 40%) powders with a particle size distribution between 53 and 150 microns reinforced NiCrBSi matrix was deposited by Kennametal Stellite Plasma Transferred Arc (PTA) welding system on 45# steel substrate. Optical microscope (OP), X-Ray diffraction (XRD), Scanning electron microscope (SEM, EDS) as well as Sclerometer were used to characterize micro structure and wear performance. The results show that the coating of NiCrBSi is composed of γ-(Ni, Fe) and inside randomly distributing small hard phases, such as CrB and (Cr, Fe, Ni)7C3. The addition of Cr3C2 results in the appearance of Cr3C2 phase. With increasing of Cr3C2 content, the macro hardness, porosity rate and wear resistance increase gradually. When Cr3C2 content is 30%, the peak values of macro hardness and wear resistance are obtained. With the addition of cast WC, there are two strong diffraction peaks, WC and W2C, as well as some weak diffraction peaks of (Cr, Fe, Ni) 7C3 and (Ni, Cr, W)3C. Compared with Ni50A and WC/Ni coating, the wear resistance value of 40% Cr3C2/Ni coating increases by 197.6% and 97.6%, respectively. The wear mechanisms of Cr3C2/Ni and WC/Ni coating are different, in which the former is even wear, while the latter is uneven. © 2015, Central South University. All right reserved.


He Y.-L.,Central South University | Long A.-P.,Central South University | Zhou W.-X.,Central South University | Zhou W.-X.,Zigong Tungsten Carbide Co. | And 3 more authors.
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2014

4.5%Y2O3-ZrO2, 0.6%Sc2O3-YSZ composite ceramic nanopowders were prepared by chemical co-precipitation method in ethanol/water (the volume ratio of alcohol to aqueous is 5:1) using ZrOCl2 .8H2O, Y(NO3)3·6H2O, Sc2O3 as raw materials and polyethyleneglycol (PEG) as dispersant. The synthesized powders were characterized by means of TEM and XRD analysis. High temperature stability of composite ceramic nanopowders was also studied. The results show that, after calcined at 600°C for 2 h, the presynthesized powders show the pure noneequilibrium tetragonal structure, the size of 0.6%Sc2O3-YSZ particles prepared by reverse titration method is ~20 nm compared with~30 nm prepared by the straight titration method. After sintered at 1 200°C for 100 h, YSZ shows equilibrium tetragonal structure together with cubic phase; after sintered at 1 300°C for 100 h, the equilibrium tetragonal structure partly transforms to cubic phase and a small amount of monoclinic phase; after sintered at 1 400°C for 100 h, the tetragonal structure transforms to cubic and monoclinic phase entirely. Whereas, 0.6%Sc2O3-YSZ keeps the pure noneequilibrium tetragonal structure after sintered at 1 200, 1 300 or 1 400°C for 100 h. Therefore, the high temperature phase stability of YSZ can be modified by addition small fraction of Sc2O3.


Zhou W.-X.,Central South University | Zhou W.-X.,Zigong Tungsten Carbide Co. | Li Y.-X.,Zigong Tungsten Carbide Co. | Yan W.,Zigong Tungsten Carbide Co. | And 2 more authors.
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2014

WC12Co, WC17Co, WC10Co4Cr coatings were prepared by super high velocity oxygen fuel spray with the same sprayed parameters using agglomerated and sintered WC12Co, WC17Co, WC10Co4Cr powders with particle size range of -45~+15 μm. The properties of powders and coatings were characterized by means of optical microscopy, X-ray diffraction analysis, microhardness meter and so on. The results indicate that all powders exhibit good flow-ability (~13 s/50 g) and spherical morphologies and nearly the same apparent density (4.8~5.0 g/cm3); WC and Co phases are detected in all the powders; the microstructure and physical properties of all the powders are suitable for the spraying. High deposition efficiency (52%~55%) and Vickers microhardness (1 200~1 300 HV300 g), low porosity (< 1.1%), are obtained for coatings; WC, W2C phase and amorphous or nanocrystalline phase were detected in all coatings; the results of abrasive wear rate show that WC10Co4Cr coating has the best abrasive wear resistance than other two coatings under the same spray parameter; WC10Co4Cr coating also has the best corrosion resistance in salt fog exposure.

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