Papers by Keyword: WC

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Authors: Zakiah Kamdi, P.H. Shipway, K.T. Voisey
Abstract: Various research programmes have been conducted examining cermet coatings in relation to wear, corrosion and the combination of both (erosion-corrosion and abrasion-corrosion). Several methods have been employed to deposit cermet coatings, the most common being thermal spraying or hard facing (weld overlaying).The cermet coatings are carbide-sized ranging from 50 150 μm which is larger than abrasive particles which range between 2 to 10 μm. This allows the abrasive particles to interact with the carbide and matrix separately. Understanding the mechanism of this situation is necessary as abrasion maybe caused by a small abrasive. However, carbide sinking caused by this large carbide leads to diverse local carbide distributions and wear rates with a larger standard deviation. Modified micro-scale abrasion tests were performed with a silica abrasive of 2-10 μm particle size distribution and suspended in water. Due to the sinking of carbide particles during the coating process, the ground samples with more carbide on the surface displayed better wear resistance than those with a lower local carbide content. By using a modified micro-scale abrasion wear test, the correlation between local carbide content and wear rate may be determined with a smaller standard deviation. Rolling wear mode was observed due to the lower degree of hardness of the abrasive compared to the hard phase. The wear behaviour is related to the microstructure.
Authors: Seok Woo Lee, Hon Jong Choi, Hyun Woo Lee, Jae Young Choi, Hae Do Jeong
Authors: Guo Jian Cao, Er Jun Guo, Yi Cheng Feng, Li Ping Wang
Abstract: In this paper, WC particles and NH4HCO3 powders were mixed evenly, and then pressed under 150MPa. The WC porous preforms were obtained after the compacts being heat treated to eliminate NH4HCO3. The volume ratios of WC in the preforms were 30%, 40% and 50% respectively. WC/Fe composites were fabricated by infiltrating liquid cast iron into the WC porous preforms. Optic microscope and scanning electron microscope were employed to observe the microstructure of the matrix alloy and the composites. The results showed that matrix alloy without WC addition had pores in the surface. The microstructure of the composites with WC volume fractions of 30%, and 40% were denser than that of 50%. Hardness and wet sliding wear behaviors of the composites were investigated at room temperature. The addition of WC particles could effectively improve the hardness and the wear resistance of the composites. The influence of volume fractions on hardness of the composites was similar to that on wear resistance. The hardness and the wear resistance of the 40vol.%WC/Fe composite was better than those of the 30vol.%WC/Fe composite. And the properties of the 50vol.%WC/Fe composite were the worst.
Authors: G.D. Semchenko, E.S. Gevorkyan
Abstract: Application of modern ways of ceramic materials’ consolidation and association of synthesis methods of organic and inorganic chemistry, sol-gel method and mechanochemistry, allowing to control processes of synthesis of the defined phases at molecular level, gives the chance to create highly effective composite materials. It is known that properties of composites on the basis of refractory compounds become dimensionally dependent at reduction of the particles’ size to several interatomic distances in one, two or three dimensions . Obtaining of durable nanostructural ceramics on the basis of ZrO2 with substantial increase of mechanical properties can be realized by creation of material with fine homogeneous structure, on the basis of powders of nonoxygen compounds when strength properties and crack resistance increase at creation of –intra and –inter nanostructures. In work results of creation of the consolidated nanomaterials and composite ceramics with usage of the peculiarities set forth above for synthesis of precursors of powders and the defined phases that self-reinforce ceramic matrixes have been presented.
Authors: Sun Hui Yao, Yan Liang Su, Hung Yu Shu, Zong Ling You, Yu Chen Lai
Abstract: This study aimed to understand the effect of a different binder on fundamental properties and corrosion behavior of WC based HVOF coatings. Three kinds of coatings, each with a different binder, were prepared using commercial feedstock powders, i.e. WC-12Co, WC-10Co4Cr and WC-12Ni. Micro Vickers hardness tester, XRD and SEM were used. The corrosion performance was evaluated using a salt spray tester. It was found that the WC-10Co4Cr coating showed the highest corrosion resistance and superior hardness comparable to the WC-12Co coating.
Authors: Yong Xu, Z.N. Guo, Guan Wang, Y.J. Zhang
Abstract: Resistance Spot Welding (RSW) is a widely used technology. And the rapid wear is the main reason for the short life of RSW electrodes. To improve electrode life during RSW, a novel ultrasonic-aided electro-spark deposition technology (UESD) and device are proposed in this paper. The WC metallurgical bond coating was fabricated on the surface of CuCr1 electrodes by UESD, and some experimental results were also analyzed. Moreover, the surface morphology of WC coating was studied by SEM and the quality of coating wear resistance was analyzed through experimental method. This study provides a novel way to extend the life of common moulds and RSW electrodes.
Authors: Quan Shan, Zu Lai Li, Ye Hua Jiang, Rong Zhou, Yu Dong Sui
Abstract: The interface between matrix and casting tungsten carbide particle is produced by the the particles’ decomposition. Casting tungsten carbide particle is a kind of eutectic product,which is composed of two phases: WC and W2C. The two phases have differing chemical and physical properties, and thus follow different paths to achieve their decomposition process. By observing the decomposition of the particle, a hypothesis was put forward about how the casting tungsten carbide particle decomposes in steel/iron composites. An experiment was then designed to prove this hypothesis. The experimental result shows that heat gain plays a significant role in the decomposition process of casting tungsten carbide particles.
Authors: Chen Xin Ouyang, Shi Gen Zhu
Abstract: The master sintering curve (MSC) of nanocomposite WC-MgO was constructed based on the combined-stage sintering model. Nano-sized WC-4.3wt%MgO powder with average particle size of 35nm was synthesized by high-energy ball milling, and then uniaxially pressed at the pressure of 500MPa to fabricate green compacts. The shrinkage response of the compacts, used to construct the master sintering curve, were studied by dilatometric runs at two constant heating rates of 5°C/min and 10°C/min up to 1900°C. Using the estimated activation energy, the master sintering curves were established and compared to acquire an optimum value (Q=361.8 kJ/mol). The obtained MSC was validated by non-isothermal sintering with the identical green compacts. The results demonstrate that the MSC can be applied successfully to predict and control shrinkage level and final density during heating up regardless of heating rates.
Authors: Yong Cheng
Abstract: Using high-pressure sealed microwave heating method, the WC-Co based cemented carbide samples were digested completely by nitric acid and phosphoric acid (VHNO3: VH3PO4 = 5:1). Then the digestion solution was diluted with water to a constant volume, and directly using inductively coupled plasma atomic emission spectrometry (ICP-OES) determination of the content of 0.005 to 10% Co and 0.005 ~ 1% of Fe, Nb, Ta, V, Cr, Mo and Ni. This paper examine the best digestion conditions, including reagent composition, ratio, and microwave control parameters, etc., then establish a set of microwave digestion and by complex reactions with inorganic reagents to stabilize the high tungsten matrix digestion method, in order to quickly and completely digest the tungsten-cobalt-based samples and avoid the generation of tungsten acid precipitation resulting in the loss of some of the analyte and impact of organic complex agents on the spectral determination. The results showed that: the control parameters of using 5 min to heat the sample to 130 °C and keep for 5 min, then heated to 190 °C in 5 min and keep for 15 min is better to maintain the digestion. By optimizing elemental analysis line, ICP measurement parameters and matrix matching and synchronization of background correction method, the high tungsten matrix effects and spectral interference are eliminated; ensure the detection performance of the method. Background equivalent concentration of 5μg/L (Nb) ~ 18μg/L (Fe), elements of the detection limit of 4μg/L (Nb) ~ 13μg/L (Fe), which used for the determination of impurities in the alloy or elements with the results is RSD <3%, recovery 97.0% ~ 103.5% corresponding with the national standard examination method.
Authors: Luis Antonio C. Ybarra, Afonso Chimanski, Sergio Gama, Ricardo A.G. da Silva, Izabel Fernanda Machado, Humberto Naoyuki Yoshimura
Abstract: Tungsten carbide (WC) based composites are usually produced with cobalt, but this binder has the inconvenience of shortage, unstable price and potential carcinogenicity. The objective of this study was to develop WC composite with intermetallic Fe3Al matrix. Powders of WC, iron and aluminum, with composition WC-10 wt% Fe3Al, and 0.5 wt% zinc stearate were milled in a vibration mill for 6 h and sintered in a SPS (spark plasma sintering) furnace at 1150 °C for 8 min under pressure of 30 MPa. Measured density and microstructure analysis showed that the composite had significant densification during the (low-temperature, short time) sintering, and X-ray diffraction analysis showed the formation of intermetallic Fe3Al. Analysis by Vickers indentation resulted in hardness of 11.2 GPa and fracture toughness of 24.6 MPa.m1/2, showing the feasibility of producing dense WC-Fe3Al composite with high mechanical properties using the SPS technique.
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