Papers by Keyword: Tungsten Carbide

Abstract: Process parameters play a crucial role in the final characteristics and properties of every product. The current work focuses mainly on improving the vacuum furnace brazing process for tungsten carbide reinforced Ni-based alloy (NiCrBSi) metallic composite coatings, by establishing the best set of parameters adapted to this specific chemical composition. In order to determine the optimum parameters, a fine adjustment of a typical vacuum brazing process was performed. The melting interval of the filler metal was identified by means of Differential Thermal Analysis. Morphology, microstructure and metallurgical bond of the cladding to the substrate material were investigated by Scanning Electron Microscopy and Light Microscopy combined with a Porosity Analysis Software. The process optimization resolved the initial problem of fractures and crack initiation, making possible to achieve high quality hardfacing coatings with a low degree of porosity (approximately 1 %).

Abstract: With the aim of enhancing the precision and quality of turning processes, this study investigated cutting stress and thermal deformation induced by friction between the tool and chip of a Wolfram carbide (WC) tool cutting AISI-1045 carbon steel. Analysis of cutting stress and thermal deformation using COMSOL Multiphysics software is useful for evaluating the compensation for machining errors and reducing tool wear. Three cutting loads were adopted for the simulation of the thermal conduction, and changes in temperature and the stress field. Simulation results show that thermal deformation in the tool tip is proportional to cutting speed and time. As long as the temperature of the tool remains below the quasi-steady-state temperature, the amount of deformation does not change significantly. An understanding of the thermo-mechanical coupling effect during turning can help to improve the accuracy of compensation for thermal deformation in turning tools.

Abstract: The prediction of tool wear can help understand the influence of tool wear on the machining process and result, and change or grind the worn tool in time. The two-dimensional ultrasonic vibration turning method can reduce the crack of tool and decrease the negative effect on processing thus extends the tool life. In this paper, two-dimensional ultrasonic cutting theory was applied to the precision machining of tungsten carbide. With self-developed two-dimensional ultrasonic cutting device, series of cutting experiments were carried out. During cutting process, the flank wear under different cutting length was observed; flank wear situations were compared with those in traditional cutting. In order to predict the tool wear and thus heighten the machining precision, a tool wear prediction model based on time series analysis method was built in the paper. The research results show the built AR (9) time series model can predict the flank wear condition with high precision.

Abstract: The use of hard and brittle materials for manufacturing optical parts, such as dies and molds are required in order to extend mold life. Although, cobalt-free tungsten carbide is one of the hardest materials, micro-cutting is very difficult due to its hardness and its brittleness. This paper investigates face turning of cobalt-free tungsten carbide using a nanopolycrystalline diamond [NPD] tool and Zinc dialkyldithiophosphate (ZnDTP) fluid. Surface roughness of the cobalt-free tungsten carbide achieved was 22nmRz, which is far larger than the theoretical value. That is, traditional cutting theory does not directly apply for face turning of cobalt-free tungsten carbide using NPD tool and ZnDTP fluid.

Abstract: Tungsten carbide is the choice of predilection for producing parts requiring good wear resistance. In this context it is produced in large quantities by the carburization of tungsten trioxide under a stream of hydrogen at elevated temperature followed by grinding to achieve the required fineness. This work aims to study the conditions in which tungsten carbide can be produced by mechanical alloying method. Using this method would facilitate obtaining carbide through a simple and easy to use technology without prohibitive costs, directly by an end user. For this purpose the thermodynamic study is conducted to establish the conditions under which the carburizing reaction can take place. The condition for the reaction to occur spontaneously is reaching a temperature of 621°C. Carrying out this reaction in a system without external energy input seems impossible. Mechanical alloying experiments were carried out in a Fritch Pulverisette 7 premium line planetary mill, equipped with two bowls of 80ml capacity lined with sintered tungsten carbide. Each bowl contained 200 g of tungsten carbide balls with dimensions of 10 mm and 12 mm. The balls/load ratio was 10:1. Grinding was performed in steps of 3 hours, with breaks for sampling, with rotation speeds of 600 and 800 rpm. Tests conducted showed complete conversion of raw materials into tungsten carbide after different durations of time.

Abstract: The paper reports experimental results from tests carried out at room temperature on servo-hydraulic system dedicated for examination of the exploitation properties of rocker arms. The ball joint of this element was modified by an application of composite coating such as the tungsten carbide (WC). To apply cyclic loading to rocker arms the griping system was designed and elaborated. Results from tests performed on the composite coated ball joints were compared with data obtained for typical elements. Variations of the following parameters versus time i.e. force, temperature and surface topography of balls were analysed with respect to exploitation properties of the modified ball joints. An increase of the wear coefficient was achieved for sliding joints of the steel ball-steel cups coated by the WC.

Abstract: Tungsten carbide is an anorganic compound with very interesting tribology features such as: the highest melting point and hardness values among the known compounds, high elasticity (Young) modulus, high thermal stability on a large temperature range, low chemical reactivity, etc. Magnetron sputtering is the most convenient deposition method for obtaining tribological coatings with binary/ternary/quaternary composition starting from WC commercially magnetron sputtering targets. Roughness and grain size of such coatings were investigated by Atomic Force Microscopy and electrical sheet resistance was investigated by using the Four Point Probe Method with ALESSI head and W electrodes.

Abstract: WC–20 mol% SiC ceramics with added Cr₃C₂ were sintered at 1600°C with a resistance-heated hot-pressing machine. Dense WC–SiC ceramics containing 0.1–0.9 mol% Cr₃C₂ were obtained. Above 1.2 mol% Cr₃C₂, the relative density decreased with increasing Cr₃C₂ content. A small amount of a Nowotny-phase type (Mo₅Si₃C-type) product was formed by the addition of Cr₃C₂, and no Cr₃C₂-based solid solution was found. The WC–20 mol% SiC–Cr₃C₂ ceramics had very fine equiaxed granular WC grains because of inhibited grain growth of WC. The Young’s modulus of the WC–20 mol% SiC–Cr₃C₂ ceramics decreased with increasing Cr₃C₂ content because Cr₃C₂ has a much lower Young’s modulus than WC. Cr₃C₂ addition below 0.9 mol% increased the Vickers hardness from 20.9 to 23.0 GPa, but a larger added amount reduced the Vickers hardness. The hardness of the WC–20 mol% SiC–Cr₃C₂ ceramics and the WC grain size obeyed a Hall–Petch-like relationship, suggesting that the hardness was strongly controlled by the WC grain size. A higher fracture toughness, 6.4 MPa m^1/2, was obtained for the ceramics containing a small amount of Cr₃C₂ than for the binder-free WC. The addition of 0.1–0.3 mol% Cr₃C₂ improved the fracture toughness without reducing the hardness.

Abstract: This paper presents the applications of advanced CVD Tungsten Carbide coating to extend the life of tooling used for forming abrasive and corrosive materials.Hardide nanostructured Tungsten Carbide coating combines high hardness (70-77Rc) with excellent toughness. Unlike other hard coatings Hardide can produce a conformal coating layer on complex-shaped tools, including internal surfaces of extrusion die cavities and moulds. In ASTM G65 test the Hardide coating abrasion resistance exceeded WC/Co (9%) cemented carbide by a factor of 4X, and D2 tool steel by 10X. Thus the coating can significantly increase the life of D2 steel tooling used for forming abrasive materials and by maintaining better dimensional tolerances and surface finish of the tool it will manufacture better quality products.The Hardide coating has enhanced resistance to corrosion and aggressive media, including acids; this makes the coating especially suitable for the tooling used in forming uPVC, PTFE and other corrosive materials.The Hardide coating has been tested on extrusion and pelletizing dies processing abrasive and corrosive slurries and typically showed a 3X increase in the life of the tooling. Similar results were achieved by the coating of powder compaction punch/die sets for pharmaceuticals tableting.

Abstract: A flame combustion method enables the synthesis of diamond using acetylene-oxygen in ambient atmosphere. It has various advantages over other methods, such as in terms of speed, safety and cost. Tungsten carbide (WC) is used as cutting tools in the machining industry. In this study, to obtain nanocrystalline diamond films and to achieve good adhesion on the WC substrate, diamond films were synthesized by flame combustion using a mixture of high-purity acetylene and oxygen gas with the addition of nitrogen gas. Nitrogen gas added as the nanocrystalline diamond promotion agent; nitrogen flow rate was varied. The results indicated that, at the mixture of high-purity acetylene and oxygen gas, the diamond nanocrystallites was not synthesized on the diamond microcrystallites at nitrogen flow rate 0.000 cm³/s. As nitrogen flow rate was increased, the diamond nanocrystallites was synthesized on the microcrystallites. The diamond nanocrystallites was synthesized with high density all over the diamond microcrystallites.