Papers by Keyword: WC

Abstract: Ti (C,N)-based cermets with varying WC additions (Ti (C_0.6N_0.4)-36Ni-12Mo-1C-xWC, x = 0, 3, 6 and 9 wt%) were prepared by conventional powder metallurgy techniques. The microstructure and mechanical properties of all four Ti (C,N)-based cermets were investigated. Isothermal oxidation of all four cermets were also investigated in air at 800°C up to 100 h using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction analysis (XRD). The grains of Ti (C,N)-based cermets became more homogeneous with the increase of WC content. The TRS and fracture toughness increased with the increase of WC content and then decreased when WC content exceeded 6wt%, but hardness decreased continuously with the increase of WC content. The oxide scales formed on the surface of all four samples during the oxidation process were porous and multi-layered, consisting of NiO outerlayer and TiO₂ based innerlayer, respectively. The thickness of the oxide scales and oxidation rates increased with the increase of WC content, especially when the content of WC addition reached 9wt%. The cermet with 6wt% WC addition showed excellent mechanical properties and acceptable high temperature oxidation resistance.

Abstract: In this paper, the microstructural evolution of the composite formed by fibre laser deposition of Ti-6Al-4V wire and WC-W₂C powder was investigated and reported. Nine single tracks were deposited using combinations of four laser processing parameters (laser power, traverse speed, wire feed rate and powder feed rate) with each having three levels based on Taguchi design of experiments. The samples of the deposited composites were subjected to microstructural examinations using scanning electron microscopy with energy dispersive spectroscopy and X-ray Diffractometry, and microhardness tests. The resultant microstructure is characterised by uniform distribution of the reinforcement particles (WC-W₂C) and dispersion of in-situ synthesised TiC and W solid solution precipitates in a β-stabilised Ti matrix. The TiC precipitates have blocky and fine eutectic morphologies, while the W solid solution precipitates have blocky and leaf-like equiaxed morphologies. The retained W composition in the β-Ti was found to range from 7.5-9 at%, and it helped to β-stabilise the matrix which was considered beneficial for the composite matrix to retain its ductility. Increasing laser power was found to decrease the amount of W retained in the Ti matrix which resulted in a lower cooling rate, favourable for the nucleation of W solid solution. The uniform dispersion of the TiC and W solid solutions in the β-Ti matrix phase has significantly enhanced its hardness which ranged from 455-543 HV_0.3. It is anticipated that the composite formed will possess excellent wear resistance and contact deformation characteristics.

Abstract: Cobalt is widely used to produce WC-Co hard metals, but this binder has problems of shortage and unstable price. In this work, cobalt was replaced by an iron aluminide intermetallic binder. WC-10%(Fe₃Al-3%B) composite was prepared by vibration milling of WC, Fe, Fe-B, and Al powders and sintered by spark plasma sintering (SPS) at 1150 °C for 8 min under 30 MPa. The milling time was 0.17, 12, 25 and 50 h. The SPS was efficient to consolidate the composite resulting in relative density of ~98% or higher. With increasing milling time, Vickers hardness (HV₃₀) of composite increased from 12 to 14 GPa due to the enhanced homogeneity of microstructure, while the fracture toughness, K_Ic, determined by an indention fracture method using Shetty equation, remained constant at around 9.1 MPa.m^1/2.

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.

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.m^1/2, showing the feasibility of producing dense WC-Fe₃Al composite with high mechanical properties using the SPS technique.

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.

Abstract: The microstructure of 40CrNi2Mo steel matrix strengthened with wear resistance alloy is observed by the optical scope, SEM with EDS and FESEM. Analysis emphasis is lied on the distribution regulation of nanosized WC particulates in the microstructure of the steel matrix. Experimental results show that the method of adding wear resistance alloy in steel matrix can avoid gravity segregation phenomenon effectively and guarantee a uniform distribution of WC in steel matrix. nanosized WC particulates distributing evenly in steel matrix improve the wear resistance, and make microstructure of the steel matrix more uniform, finer and denser proved by its high-expansion micrograph.

Abstract: Micro EDM milling process is accruing a lot of importance in micro fabrication of difficult to machine materials. Any complex shape can be generated with the help of the controlled cylindrical tool in the pre determined path. Due to the complex material removal mechanism on the tool and the work piece, a detailed parametric study is required. In this study, the influence of various process parameters on material removal mechanism is investigated. Experiments were planned as per Response Surface Methodology (RSM) – Box Behnken design and performed under different cutting conditions of gap voltage, capacitance, electrode rotation speed and feed rate. Analysis of variance (ANOVA) was employed to identify the level of importance of machining parameters on the material removal rate. Maximum material removal rate was obtained at Voltage (115V), Capacitance (0.4μF), Electrode rotational Speed (1000rpm), and Feed rate (18mm/min). In addition, a mathematical model is created to predict the material removal

Abstract: A metal matrix composite 40CrNi2Mo strengthened with nanoscale WC particulate was fabricated through conventional casting in this work. The microstructure, hardness and wear resistance of this material were studied. The diffusion annealing processing was conducted at 900°C for 6.5h, and the quenching process with oil at 880°C for 2h. The temper process was conducted at 180°C, 220°C, 260°C and 500°C for 2h. It was found that the WC particulates surrounding the Fe3C phase were distributed evenly within the matrix. The segregation was discovered in the cast and was eliminated through annealing at the cost of hardness. The quenching, annealing at 180°C for 2hrs plus air cooling induced the tempered martensite, some ferrite and few retained austenite. The microstructure changed into the tempered sorbite after tempering at higher temperatures. The amount of precipitated carbides increased with the tempering temperature, but the hardness decreased gradually. Diffusion tempering, treated at 880°C for 2h followed by oil quenching, annealing at 180°C for 2h plus air cooling can give rise to the best wear resistance, which equals to 124.5% of the material currently employed.

Abstract: This study aimed to understand the effect of a binder on the wear performance of HVOF WC-based coatings. Three kinds of commercial feedstock powders were studied, i.e. WC-12Co, WC-10Co4Cr and WC-10Ni. Characterization was conducted using SEM, micro Vickers hardness test and XRD. It was found the WC-10Co4Cr coating showed the highest hardness, while the WC-10Ni coating the lowest. The WC-10Co4Cr coating showed very good wear resistance as compared with the widely used WC-12Co coating.