Papers by Keyword: Cemented Carbide

Abstract: In this study, the characteristics of the production process of cemented carbide-alumina composite material made using the wet-shaping process were investigated. The production process in this study produced a green compact of composite material by repeating the wet-shaping process for the molding of each material, and it made possible the sintering of plural materials with varying sintering conditions at the same time, a process that was difficult until now. By using wet-shaping and ultra-fine powder, which have superior sintering characteristics, sintering conditions were found in which it was possible to sinter cemented carbide and alumina at the same time, with a sintering temperature of 1723 K and a sintering time of 5.4 ks. With these sintering conditions, the relative densities of the sintered compact of cemented carbide and alumina were 99.0 % and 98.9 %, respectively. It is clear that the characteristics of sintered compact made with these sintering conditions are superior. When the cemented carbide slurry and the alumina slurry were layered by repeating the wet-shaping process, a composite material was able to be produced by inserting an active brazing filler metal in the interface to improve the bondability of the cemented carbide and the alumina during the sintering. However, it was observed that the active brazing filler metal and the cobalt in the cemented carbide flowed out from the interface between the cemented carbide and the alumina in the sintered compact of the composite material.

Abstract: Conventional WC-Co hardmetals are widely used in various applications due to their excellent properties. High hardness can be achieved using compositions with little to no content of cobalt or nickel. These binder metals are hazardous to health, making a substitution not only desirable because of availability and cost reasons. A new possibility to manufacture such hard materials is the combination of tungsten carbide with oxides such as Al₂O₃ and ZrO₂. In this way the binder metal content can be replaced. Furthermore the content of the also expensive WC can be reduced. Such metal carbide – oxide composites with oxide contents between 16 vol% and 40 vol% were manufactured. The completely dense composites feature high hardness values of 2000 HV10 to 2400 HV10 while also having an acceptable fracture toughness of up to 7 MPa⋅m^1/2. The improved mechanical properties make the replacement of WC-Co hardmetals and binder free WC ceramics in special areas possible.

Abstract: This paper deals with hobbing and finish-hobbing that considers the machine environment when using various hard hob materials. Experiments were conducted by simulating hobbing by fly tool cutting on a milling machine. The results are summarized as follows. (1) Under the condition of hobbing with TiN-coated tools in dry cutting and with a minimal quantity of lubricant (MQL) system, P20 and P30 hob materials as the substrate show stable cutting and do not cause tool failure. The flank wear obtained with P30 is less than that obtained with P10 and P20 in the case of the coated TiAlN film tool. The MQL system shows flank wear reduction compared with dry cutting. (2) Under the condition of finish-hobbing, when using the TiN-coated tool, the flank wear obtained with dry cutting is smaller than that obtained with the MQL system. The flank wear increases in the order of P10, P20 and P30 hob materials, and the P10 hob material is effective. The TiAlN-coated P30 tool decreases flank wear and is suitable for finish-hobbing in dry cutting and with the MQL system. (3) Under the condition of hobbing, the finished surface roughness obtained with the MQL system when using TiN-and TiAlN-coated tools is smaller than that obtained by dry cutting. (4) Under the condition of finish-hobbing, the finished surface roughness obtained with TiN-and TiAlN-coated P30 is small in dry cutting and with the MQL system.

Abstract: Using a fiber laser welding head, crack-free WC-Co/Steel weld depositions are obtained with optimized welding parameters. The microstructure, composition, phase, structure, and bend strength are analyzed using optical metallography, scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and bend test. The influence of the microstructure and WC/matrix interfaces in the vicinity of joint failure at the cemented carbide side is discussed. It is evident that the deposit consists of austenite dendrites and interdendritic eutectic carbides. The austenite further transforms to martensite on-cooling. The flexural bend strength and yield strength of the joints attained 970 MPa and 876 MPa, respectively. Bend fracture occurs at the HAZ in the cemented carbide side of the joint, characterized with cleavage fracture and quasi-cleavage fracture. TEM and HRTEM image of WC/Co interfaces verified the W₂C and eta phase formation in the HAZ that contributed to the embrittlement.

Abstract: Iron-based sintered materials are fabricated via the process of compacting iron powder by using die, sintering in 1100 to 1300°C, and quenching or sizing. These materials are used as variable valve system and oil pump system in automobiles. Recently, the severe requirement for complication and high precision shape of them has increased the products machined by turning and drilling. In general, it is more difficult to machine the sintered materials than the steel. However, the quantitative evaluations and the mechanisms of those are ambiguous, then there is a few suggestion for improvement of the machining. In this study, we will report the machinability of sintered materials by compare with that of steel materials, and the improvement of machinability of sintered materials.

Abstract: The wetting and spreading of molten Cu, Ag and Ag-28Cu (wt.%) on the WC-Co cemented carbide were investigated by the sessile drop technique at different temperatures, and the interfacial behaviors of the metal/WC-Co couples were analyzed by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The experimental results showed that the testing temperature and the composition of drop can play a key role in the wetting and spreading, and the good wettability with contact angle of less than 40^o can be obtained. Moreover, the strongest interactions can be produced between the molten Cu and the WC-Co substrate at the higher temperature of 1100 ^oC due to the strong interdiffusion and solid solution between Cu and Co, resulting in the lowest equilibrium contact angle of ~0^o. In addition, smooth and clean interfaces, without formation of visible interfacial reaction layer, were observed in all the three wetting systems. This work may also provide guidance to brazing of the cemented carbide.

Abstract: The diamond coating can improve the performance and durability of cutting tool. To obtain the structure of nano/micro CVD diamond coating, the finite element analysis of nano/micro composite CVD diamond coating on boronized cemented carbide was carried on using ANSYS. The relationship between nanoand micron diamond layer thickness and coating fall off stress was simulated. The thickness of nanodiamond and the micron diamond layer was suggested for the nano/micro CVD diamond coating on boronized cemented carbide cutting tool.

Abstract: The chemical compositions and microstructures of several different cemented carbides were checked by XRD, XRF, SEM, metallographic microscope and stereomicroscope. The influences of phase compositions and microstructures on mechanical properties were investigated. The results show that improving the Co content and refining WC grain properly are effective means to acquire the excellent mechanical properties of cemented carbide. A series of friction and wear tests were carried out in a high-speed tribometer to explore the tribological behavior of three cemented carbides with different Co content and WC grain size against aluminum alloy 7050-T7451. It was found that the tribological behaviors of cemented carbides are largely dependent on their microstructures and mechanical properties. The enhancement of flexural strength and fracture toughness can be ascribed to deformation buffering effects of Co binder, but the improved hardness depends on the rigid skeleton of WC-WC grains.

Abstract: Aiming at the problem of bonding breakage of cemented carbide insert in the process of heavy-duty cutting large cylinder, the experimental study of element diffusion between workpiece and insert material is done. Firstly, the conditions of insert bonding breakage are analyzed according to the heavy-duty cutting conditions of large cylinder and the material characteristics of workpiece and insert. And then, the experimental scheme of element diffusion is proposed. The element diffusion experiment is done, and the diffusion elements in the diffusion section of specimens are analyzed. At last, the species, distance and concentration of diffusion elements are analyzed. This provides a basis for further research of tool bonding breakage.

Abstract: In our previous research, precise groove machining could be achieved on a cemented carbide workpiece by utilizing a combined method of EDM and grinding using only a single tool, i.e. a rotary PCD disc tool acting as an electrode for EDM and as a wheel for grinding. In this study, the authors applied this method to forming a 3D shape on a cemented carbide workpiece. Firstly, an EC-PCD disc-shaped tool of φ33.4mm was mounted on a spindle of the EDM machine vertically to the workpiece. And the tool was rotated to make a spherical concave on the workpiece by EDM. The surface roughness of the workpiece was Rz=6.4μm and no electrode wear resulted at all. Secondly, the EDMed surface was ground with the same PCD tool. As a result, the improved surface roughness of Rz=1.7μm was obtained on the workpiece maintaining the precise tool profile and dimension.