# I. Introduction emented carbides are used as oxygen-free ceramics in high temperature engineering applications due to its properties like, high melting temperature, hardness, elastic moduli, wear resistance, electric conductivity and high-temperature strength. Cemented carbides are also widely applied as a base of hard metals. Applications of cemented carbides include structural, heating and reflecting functions as well as tool materials in composition with other refractory compounds [1]. The compacted products of these compounds are made by powder metallurgy technology where sintering methods are of decisive importance. In General; cemented carbides are composite materials, which consist of hard refractory carbides containing metals of the transition groups IV, V and VI (such as WC, TiC, TaC, NbC) embedded in a tough metal binder phase like nickel or cobalt which are by far the dominating binder metals employed due to its excellent wetting to WC and its good thermo-mechanical properties [2][3][4]. (W,Ti)C has a high melting point and high hardness than the commercial WC. In this regard, the transition metal carbide is primarily used in cutting tools and as an abrasive material as a single phase or in composite structures. In the case of cemented (W,Ti)C, Co or Ni is added as a binder for the formation of composite structures [5][6][7][8][9]. There are two basic ways of obtaining cemented carbide: through melt-solidification processing at about 2000-2500 o C or by powder metallurgy processing at a temperature range of 1350-1500 o C. Fabrications of WC as well as TiC in metalbase alloys have been studied from both theoretical and practical points of view. However, the production of (W:Ti)C in metal matrices has received little attention. The comparatively light TiC particles may float during the preparation by conventional melting and casting route. A large difference in density between TiC and the metal matrix melt-results segregation in metal ingot. The (W:Ti)C as reinforcements innickel, cobalt and iron alloy melts may be more appropriate because its density(6.66 g/cm 3 for (Ti 0.75 :W 0.25 )C [10] and 9.1 g/cm 3 for (Ti 0.5 :W 0.5 )C [11]) is higher than that of TiC (4.25 g/cm 3 ) and close to that of iron melt(7.8 g/cm 3 ). The hardness of (Ti 1 -x :W x )C (19-21 GPa) [12] is more or less the same as that of TiC (18-23 GPa) [13]. However, the fracture toughness of (Ti 1 -x :W x )C (6.4-7.7 MPa m 1/2 ) [14] is higher than that of TiC (3.5-4.3 MPa m 1/2 ) [15,16] and this may result better mechanical properties of the (Ti 1? x : W x )C-reinforced composite compared to those of the TiC-reinforced composite. The sintering step in the powder metallurgy process is the main determine step among the forming processes. It can be evaluated by measuring the mechanical properties like hardness and physical properties like density and magnetic properties of the sintered product. Magnetic data shows some interesting relations between the physical properties, such as C relations between the physical properties, such as density, and the mechanical properties such as hardness. There is interdependence between the mass saturation magnetization, M s , and the coercive force, H c , both of which frequently occur in an inverse relation. M s is mostly related to the amount of magnetic material present, whereas H c appears to be strongly influenced by the interaction between the particles and the density or between the porosity and the grain size of the carbide phase [17,18]. In this work, cold compaction and vacuum sintering of (W:Ti)C cemented carbides samples with different binder content of a homemade water atomized Ni powder were occurred. The densification and properties of the prepared cemented carbide samples were characterized by microstructure investigations based on measurements of magnetic and mechanical properties. # II. Experimental Elemental powder of Ni was prepared by atomization technique. Nickel powder was prepared by induction melting in graphite crucibles in air by superheated up to 1700°C and bottom pouring through a ceramic melt delivery nozzle of 6 mm diameter into a confined water atomizer operating at a pressure of 20 MPa. The high-pressure water jets were directed against the molten stream. The melt flow rate, estimated from the operating time and weight of the atomized melt, was about 4 kg/min. The water flow rate, calculated from the water consumption rate, was about 200 l/min. Table 1list the atomization conditions adapted for Ni powder fabrication process. The size distribution of the Ni powder particles was measured by conventional mechanical sieving, and sieved powders with a specific size range of 20 µm and 1 µm were chosen for this investigation. The produced atomized Ni and (W:Ti)C powders were used to prepare six samples with compositions of 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, and 30 wt.% of a Ni binder mixed with (W:Ti)C by means of Agate mortar for 30 min. After the different compositions were prepared, they under went cold compaction at 600 MPa in a uniaxial hydraulic pressing machine, where they were compressed into a cylindrical shape. The cold compacts were sintered in a vacuum furnace at 10 -3 torr with graphite heating elements and at a heating rate of 5 o C/min in accordance with the sintering cycle shown in Fig1. The samples were heated at 120 o C for 2 h to dry any moister content, and the temperature was then raised to 750 o C for one hour to expel any gases embedded in the pores. The temperature was raised again to 1450 o C for one hour to start the sintering process. Finally, the furnace was turned off and the sintered compacts were cooled for 8 h by means of a water cooling system. The dimensions of the cold compacts were measured before and after sintering to calculate the green, the sintered and the relative densities. The sintered samples were mounted and ground with 800, 1000, and 1200 grit SiC paper, respectively, and then polished with 3 ?m diamond paste. To investigate the microstructure of each phase as well as the compositional analysis of the carbide and liquid phase binder, scanning electron microscope (SEM, model: JEOL, JSM-5410) is used to take SEM micrographs and EDAX-SEM were used. The phases in the specimens were analyzed by means of X-ray diffraction (XRD), for which purpose we used a Cu Ka source and a x-ray diffract meter of the model x , pert PRO PAN analytical with Cu k ? radiation (?=0.15406nm) diffract meter. The magnetic properties of samples were measured using vibrating sample magnetometer (model DEAS/FDD-2) in which the samples were vibrated at a constant frequency between a set of sense coils. As the magnetic field is varied through a specified range up to 2 Tesla, the magnetic moment of the sample is measured by the sense coils with a lock-in amplifier. The dependency between the magnetization and magnetic field (hysteresis loop) for the prepared samples was measured. Because the saturation magnetization changes with weight of the sample, the results were Global Journal of Researches in Engineering ( ) Volume XVIII Issue I Version I divided by sample's weight. The magnetization values were expressed using the magnetic moment per gram (emu/g). The measured properties included saturation magnetization (Ms), coercivity (H c ) and remnant magnetization (M r ).The hardness was measured with a Vickers hardness tester of the modelIndentec 5030 SKG. The load was selected at 30 kgf. The test was repeated five times at different points in each sample, the average being reported. The maximum attainable densification of the obtained (W:Ti)C-Ni cemented carbides are due to the particles rearrangement is influenced by different parameters, such as the amount of liquid present, the particle size, the contact angle, and the solubility of the solid in the liquid.Fig. 5 shows the results of the micro structural investigation with respect to the different metal binder content for (W:Ti)C-Ni. We can see, firstly, that the porosity of the materials decreases as the Ni content increases. However, when the Ni content is high, the Ni metal binder prevents the coalescence of the carbide particles, producing a more uniform and finer grain structure. In other words, all the carbidegrains are separated by a layer of the nickel metal binder and consequently producea normal grain growth [20][21][22][23]. # III. Results and Discussion The results of the high resolution SEM and the composition alanalysis (EDAX), as shown in Fig. 6, clearly reveal that the (W:Ti)C particles have a rounded morphology with a carbide core/rim structure. This morphology is formed when the carbide particles are dissolved in the Ni liquid and re-precipitated on the large carbide grains, where they cause grain coarsening, called Ostwald ripening [24,25]. # Intensity (a.u.) Fig. 8 shows the results of the measured hardness of the obtained (W:Ti)C-Ni cemented carbides indicated that the exact character of the microstructure has a critical influence on the resultant hardness. The insitu hardness of nickel, namely 440, is much higher than the typical valuesof240 for bulk nickel. This difference is explained by the solid solution of W, Ti and C in the liquid phase binder and by the complex stress state resulting from the different thermal expansion coefficients of nickel and W, Ti and. The compositional analysis confirms that the hardening effect of nickel is due to the solid solution of Ti in the Ni binder. Moreover, due to the solubility of WC in the TiC forming (W:Ti)C phase, the hardness value of the (W:Ti) Cphase is 2530, which is higher than the micro-hardness value of the WC (1300) and lower than that of the TiC (3200).Fig. 9also shows increasing in the hardness by increase the metal binder content. This result can be discussed due to the densification effect. By increasing the metal binder content the porosity was decreased, the densification was increased and as a result the hardness increased and by increasing the Ni binder content which has lower hardness than the carbide phase [26]. that are separated or combined in a solution; and, third, the presence of carbide grains, which act as magnetic voids where opposing magnetic fields can occur and in turn reduce the saturation magnetization values [28:29].Fig. 12 illustrates the influence of the Ni binder on the coercively (H c ). First, the coercively decreases with increasing the metal binder content. Second, the sinter ability increases and the porosity decreases, thereby decreases the particle-particle interactions and decreasing the coercivity of the materials because of the porosity values of the (W:Ti)C-Ni, and by decreasing the porosity the particle-particle interaction was decreased and the coercively decreased [30][31][32][33]. # 2? (degree) (W, Ti) C Ni # IV. Conclusion The microstructure, hardness and magnetic properties of (W,Ti)C-Ni cemented carbides were investigated. The (W:Ti)C cemented carbides were consolidated with a water atomized Ni as the liquid phase binder by using the vacuum liquid phase sintering at 1450 o C. The major results are summarized as follows: 2![Figure 2: SEM Images for the investigated powders; where a) as received (W:Ti)C, b) the prepared atomized Ni](image-2.png "Figure 2 :") 3![Figure 3: XRD pattern for the investigated powders, where: (a) as received (W,Ti)C, (b) atomized Ni and (c) admixed (W:Ti)C-30wt%Ni.](image-3.png "Figure 3 :") 2![Fig.2(a) shows the typical SEM morphology of the as received (W:Ti)C powder. The particle shape of the as received powders was mostly irregular and had a rough surface morphology. Fig.2(b) shows the typical optical morphology of the as atomized Ni powder. The particle shape of the as-solidified powders was mostly cubic to irregular and had a rough surface morphology. Fig.2(c, d) shows the typical optical morphology of the admixed powder.](image-4.png "Fig. 2 (") 4![Figure 4: XRD pattern for the produced (W:Ti)C-20wt%Ni cemented carbide by vacuum sintering at 1450 o C for 1h.](image-5.png "Figure 4 :") 5![Figure 5: SEM micrographs of the cross-sectional (W:Ti)C-Ni cemented carbides samples sintered at 1450 o C, where; for (a) (W:Ti)C-10 wt%Ni, (b) (W:Ti)C-20 wt%Ni, and (c) (W:Ti)C-30 wt%Ni. According to the EDAX analysis, the estimated chemical composition of the (W:Ti)C-Ni cemented carbides, which is shown in Fig.6c which is the carbide rim, (W:Ti)C-Ni has an estimated chemical composition of (W 25.67 :Ti 40.6 )C 1.73 Ni 31.00 with a Ti/W ratio of 1.6. As a result of the significant difference in the way the two phases form cemented carbides. One can show from the data of the measured density as shown in Fig.7that by increasing the Ni binder content the density of the obtained (W:Ti)C-Ni cemented carbides were increased up to 95% in case of the (W:Ti)C-30wt%Ni.](image-6.png "Figure 5 :") 6![Figure 6: SEM micrographs with different magnifications and a typical compositional EDAX analysis for the crosssectional area of the produced (W:Ti)C-30 wt. % Ni cemented carbides.](image-7.png "Figure 6 :") 7![Figure 7: Effect of the Ni metal binder composition on the relative density of the produced (W:Ti)C-Ni cemented carbides by vacuum sintering at 1450 o C for 1h.](image-8.png "Figure 7 :") 8![Figure 8: Effect of the Ni metal binder composition on the hardness of the produced (W,Ti)C-Ni cemented carbides by vacuum sintering at 1450 o C for 1h. The measured M-H hysteresis loops are shown in Fig. 10. The value for the mass saturation magnetization (Ms) of the obtained (W:Ti)C-Ni series at 2 Tesla as shown in Fig. 11is lower than the absolute saturation of 54.8 emu/g for the nickel [27]. The volume fraction of liquid phase of nickel binder affects the magnetic properties. The magnetic saturation values reveal the presence of the ferromagnetic Ni phase, which intensifies as the Ni content rises, 9 emu/g for (W:Ti)C-30wt%Ni.Three factors can contribute to the lower readings in the M s of the obtained (W:Ti)C-Ni cemented carbides: first, the ratio of the fcc phases to the hcp phases; second, the lower saturation magnetization caused by any residual tungsten, Tior C](image-9.png "Figure 8 :") 9![Figure 9: M-H hysteresis loops of the (W:Ti)C-Ni cemented carbides measured at 2 T for (a) (W:Ti)C-5 wt%Ni, (b) (W:Ti)C-10 wt%Ni, (c) (W:Ti)C-15 wt%Ni, (d) (W:Ti)C-20 wt%Ni, (e) (W:Ti)C-25 wt%Ni and (f) (W:Ti)C-30 wt%Ni.](image-10.png "Figure 9 :") 10![Figure 10: Effect of the Ni binder composition on the saturation induction (M s ) of (W:Ti)C-Ni cemented carbides.](image-11.png "Figure 10 :") 1ParameterConditionPouring temperature, o C1700Nozzle angle35 oNozzle diameter, mm6Number of water jets4Molten stream flow rate, kg/min.4Water pressure, MPa20Water flow rate, l/min.200Water velocity, m/s90 © 2018 Global Journals( ) G Fabrication, Microstructure, Hardness and Magnetic Properties of (W: Ti) C-Ni Cemented Carbides using Atomized Ni Powder Fabrication, Microstructure, Hardness and Magnetic Properties of (W: Ti) C-Ni Cemented Carbides using Atomized Ni Powder ## Acknowledgment The authors wish to thank the researchers and the technicians of the Central Metallurgical R&D Institute (CMRDI) in Cairo, Egypt for their cooperation. * High-temperature characteristics YKumachiro Kumashiro Y 2000 Marcel Dekker, Inc New York-Basel Electric refractory materials * Physical and chemical nature of cemented carbides HEExner Int. Met. Rev 243 1979 * Hardmetals and Cermets PEttmayer Annu. Rev. Mater. Sci 19 1989 * The erosion-corrosion resistance of tungsten-carbide hard metals EJWentzel CAllen Int. J. Refract. Met. Hard Mater 15 1997 * Properties of ultra-fine grain binder less cemented carbide RCCFN SImasato KTokumoto TKitada SSakaguchi Int. J. Refract. Met. Hard Mater 13 5 1995 * Identification of optimum binder phase compositions for improved WC hard metals EAAlmond BRoebuck Mater. Sci. Eng. A 105 1988 * Advanced and new grades of WC and binder powder-their properties and application GGille JBredthauer BGries BMende Int. J. Refract. Met. Hard Mater 18 3 2000 * Boron as sintering assitive in cemented WC-Co(or Ni) alloys PGoeuriot FThereunto Ceram. Int 13 2 1987 * Criteria for the formation of protective Al 2 O 3 scale on Fe-Al and Fe-Cr-Al alloys ZGZhang FGesmundo PYHou YNiu Corros. Sci 48 2006 * Development and characterization of ZrC-reinforced steel-based of composite AAnal TKBandyopadhyay KDas J Mat Process Tech 127 2006 * In situ synthesis of (TiW)C/Fe composites WHJiang JFei XLHan Mater Lett 46 2000 * Development of an iron-based hardfacing material reinforced with Fe-(TiW)C composite powder EOCorrea NGAlcantara DGTecco RVKumar Met and Mat Trans. 38A 2007 * Microstructure and abrasive wear study of (Ti,W)C-reinforced high-manganese austenitic steel matrix composite AKSrivastava KDas Materials Lett 62 2008 * Reaction synthesis of Fe-(W,Ti)C composites, J Mat Process Tech ASaidi 1999 * JJung SKang Sintered Scr Mater 56 2007 * The influence of (Ti,W)C and NbC on the mechanical behavior of Alumina WAcchar CACairo Mater Res 9 2006 * Microstructures of cemented carbides HOAndren Mater 22 2001 * Production of (W,Ti)C reinforced Ni-Ti matrix composites ASaidi MBarati JMater Prod Technol 124 2002 * HEngqvist SJacobson Axénn Wear 252 384 2002 * Constitution of binary alloys MHansen KAnderko 1958 MCGraw-Hill * The growth of crystals and the equilibrium structure of their surfaces WKBurton NCabrera FCFrank Philos Trans Roy Soc 243 1951 * Condensation and evaporation JPHirth GMPound 1963 Pergamon Press 77 Oxford * Computer simulation of recrystallization in nonuniformly deformed metals ADRollett DJSrolovitz RDDoherty PAnderson Acta Metall 37 1989 * Growth kinetics of solid-liquid Ga interfaces SDPeteves RAbbaschian MetallTrans 22 1991 * Shape dependence of the coarsening behavior ofniobium carbide grains dispersed in a liquid iron matrix KSOh JYJun DYKim J Am Ceram Soc 83 12 2000 * Phase composition in cemented carbides and cermets HOAndrén URolander PLindahl Int J Refract Met Hard Mater 12 1993 * Effect of liquid phase composition on the microstructure and properties of (W,Ti)C cemented carbide cutting tools WMDaoush KHLee HSPark Int J Refract Metal Hard Mater 27 2009 * Bozorth American institute of physics handbook5 206 1957 * Ni-coated powder approach for advanced materials. PhD this is, Faculty of science WDaoush Ein Shams University 2004 * Processing of metallic filters by powder metallurgy technique WDaoush SMoustafa SKayetbay Powder MetallProg 6 2006 * Processing of FeCo nanosized softmagnetic material by powder metallurgy technique WDaoush Mater Sci 558 2007 * Synthesis of nanosized Fe-Ni powder by chemical process for magnetic applications SFMoustafa WMDaoush Mater Prog Technol 181 2007 * Coating points a way for synthesis of toughintermetallics WDaoush SFMoustafa Met Powder Rep 1 2007