The Effect of Microwave Sintering on the Properties of Electroless Ni Plated WC-Fe-Ni Composites (original) (raw)
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Microwave Sintering of Electroless Ni Plated WC Powders
Gazi University Journal of Science, 2009
Nickel matrix reinforced with WC has been manufactured by microwave sintering at various temperatures. A uniform nickel layer on WC powders was deposited prior to sintering using electroless plating technique, allowing close surface contact than can be achieved using conventional methods such as mechanical alloying. The reactivity between WC powders to form compounds is controlled through Ni layer existing on the starting powders. A composite consisting of quaternary additions, a ceramic phase, WC, within a matrix of Ni WC and etc., has been prepared at the temperature range 500°C-900°C under Ar shroud. XRD (X-Ray diffraction, SEM (Scanning Electron Microscope), compressive testing and hardness measurements were employed to characterize the properties of the specimens. Experimental results carried out for 900°C suggest that the best properties as σmax and Vikers Hardness (HV) were obtained at 900°C and the microwave sintering of electroless Ni plated WC powders can be used to produce ceramic reinforced Nickel composites.
Development of Ni-WC composite clad using microwave energy
Materials Today: Proceedings, 2017
Cladding of suitably designed materials on functional surface which are subjected to sever tribological loading can lead to increase in components life. Development of clad includes several techniques such as thermal spraying, High velocity oxy fuel and laser cladding. However cladding done through the above listed process pertain certain defects like cracks, distortion, poor adhesion strength etc.In the present work a new process method has been developed to clad Ni (matrix)-80 wt.%WC (reinforcement)-20 wt.% powder on poor wear resisting material through microwave irradiation of frequency 2.45GHz. The characterization of developed clad is done using X-ray diffraction (XRD), Field emission electron microscope (FE-SEM), Back scattered electron image and Vickers micro hardness. XRD pattern of developed composite clad showed presence of compounds like NiSi, NiW, and W 2 C phase. The wear resistant complex carbide phase have been seen in the structure of the clad transverse section showed good metallurgical bonding between the substrate and the developed clad.
Production and characterization of Ni-Co (WC) composites materials
Agronomy research, 2016
Ceramic-Metal Composite such as NiWC, CoWC are among advanced technology materials that have outstanding mechanical and physical properties for high temperature applications. Especially low density and high hardness properties stand out in such ceramic-metal composite. The microstructure, mechanical properties of %60Ni, %20Co and %20WC powders have been sintered by using tube furnace at 1,000–1,100–1,200–1,300–1,400 °C temperature. Mecahnical proporties and metalograhphic analysis were investigated after sintering. NiCo phases observed after metallographic analaysis. XRD, SEM (Scanning Electron Microscope)results showed us best microhardness of composites 174.16 HV, 8,563 g cm density were obtained at 1,400 °C sintering tempareture.
Materials Research Innovations, 2010
Tungsten based composites such as W-Cu have been widely used as electrical contacts, especially in heavy duty applications and as spark erosion electrodes. The lack of solubility between tungsten and copper makes it very difficult to achieve full densification through liquid phase sintering. Higher sintering temperatures or longer holding times always help to improve the densification but Cu may leach out from the skeleton which leads to Cu segregation and results in non-homogeneous microstructure and poor product performance. Microwave heating has been increasingly gaining popularity in the field of sintering of particulate materials. As compared to conventional heating, microwave heating is more rapid resulting in substantial reduction in the overall sintering time. In addition to the energy efficiency, the faster heating rate achieved in microwave furnaces minimises microstructural coarsening and improves homogeneity. This study examines the effect of heating mode (conventional and microwave) and temperature on the consolidation of specially prepared commercial W-Cu powder. Near theoretical density has been achieved under optimum conditions in microwave sintering. The bulk hardness and electrical conductivity of the samples sintered by two methods have been determined and the data compared.
Mechanical characterization of composites prepared from WC powders coated with Ni rich binders
International Journal of Refractory Metals and Hard Materials, 2008
In this study composite powders of WC and Ni/Fe/Cr were prepared in an innovative way, which consists of the sputter-deposition of the metallic binder onto the tungsten carbide particles. Compacts of coated powders were sintered by conventional vacuum sintering followed by hot isostatic pressing (HIP) to reach almost full densities. In order to evaluate the mechanical properties of reduced specimens size (microcomponents), depth-sensing indentation equipment was used. This method enabled the evaluation of the hardness, H, Young's modulus, E, and the yield stress, r y , in a non-destructive way, using only one sample. For the composites of sputter-coated WC-Ni/Fe/Cr the results showed an effective reduction of H and E due to the properties of Ni and the binder characteristics of the coated powders, such as uniform distribution and nanometer structure.
The stainless steel SS-304 is used to produce turbine blades in some of the hydraulic power plants. It has excellent corrosion resistance and forming characteristics. In the present investigation, the nickel based clads were developed through microwave energy using domestic microwave oven equipped with 900 W power at 2.45 GHz frequency. The developed clads were characterized through optical metallography, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and porosity. Microstructure study revealed that microwave clads are free from visible interfacial cracks and porosity is significantly less at approximately 0.87%. The various complex metal car-bides and intermetallics were found through XRD analysis. The distribution of metal carbides and intermetallics are the clearest indication for the improvement of hardness. The average microhardness of the developed clad surface is 364 ± 70 HV.
Journal of Alloys and Compounds, 2010
The effect of mechanical alloying and the sintering regime on the microstructural and the physical properties of W-SiC composites were investigated. Powder mixtures of W-20 vol.% SiC were mechanically alloyed (MA'd) using a Spex mill for 3 h, 6 h and 24 h. MA'd powders were characterized by Laser Diffraction Particle Size Analyzer, SEM and XRD investigations. MA'd W-20 vol.% SiC powder composites were sintered under inert Ar and reducing H 2 gas conditions at 1680 • C and 1770 • C for 1 h. The microstructural and mechanical characterizations of the sintered samples were carried out by scanning electron microscope (SEM) and X-ray diffraction (XRD) and Vickers Hardness analyses. The addition of SiC remarkably increases the hardness of the composites. Hardness is also increased with decreasing grain size and increasing amount of MA.
Microwave Sintering of Refractory Metals/alloys: W, Mo, Re, W-Cu, W-Ni-Cu and W-Ni-Fe Alloys
"Refractory metals and alloys are well known for their high mechanical properties which make them useful for wide range of high temperature applications. However, owing to the refractoriness of these metals and alloys, it is very difficult to consolidate them under moderate conditions. Conventional P/M processing is a viable sintering technique for these refractory metals. One of the constraints in conventional sintering is long residence time which results in undesirable microstructural coarsening. This problem gets further aggravated when using smaller (submicron and nano) precursor powder sizes. Furthermore, conventional heating is mostly radiative, which leads to non-uniform heating in large components. This review article describes recent research findings about how these refractory metals and alloys (W, Mo, Re, W-Cu, W-Ni-Cu and W-Ni-Fe) have been successfully consolidated using microwave sintering. A comparative study with conventional data has been made. In most cases, microwave sintering resulted in an overall reduction of sintering time of up to 80%. This sintering time reduction prevents grain growth substantially providing finer microstructure and as a result better mechanical properties have been observed. "
Comparative studies of WC-Co and WC-Co-Ni composites obtained by conventional powder metallurgy
Materials Research, 2011
The present work reports a comparative study of cemented carbides of compositions WC-6Co, WC-10Co, WC-20Co, WC-6Co-6Ni and WC-12Ni-6Co. The purpose was to study the powder metallurgical production process of these compositions starting from a commercial WC-6Co powder, obtaining the desired compositions by mass balance with pure Co and pure Ni powders. During the process steps mixing, milling, compacting and sintering the powders were described by its apparent density, green density, shrinkage and sintered density. Lower densities were observed in composites with higher binder content. The process was monitored by scanning electron microscopy and EDS analysis to evaluate the homogeneity of the powders, to detect contaminations by the process and to characterize the microstructure of the sintered materials. A finer microstructure was found when the binder contained Ni. Potentiodynamic polarization tests in sulfuric acid revealed pseudo-passive behavior for all the tested hard metals.