Volume Fraction Of WC Particles Research Articles

Predicting the CTE & hardness for directed energy deposition of functionally graded WC-SS316L Coatings

One of the key components in the design of wear resistant coatings for directed energy deposition is the analysis of the thermo-mechanical properties within the substrate-coating interface. The coefficient of thermal expansion (CTE) and the mismatch are crucial due to their significant influence on the structural integrity and operational performance of the coating. In this study, a four-layered functionally graded tungsten carbide (WC)-316L stainless steel composite coating was designed using a rule-of-mixtures approach for manufacture by directed energy deposition. Two theoretical models were employed to predict the CTE and micro-hardness as a function of increasing volume fraction of WC particles. According to the graded concentrations predicted from the linear models, the four-layer coating exhibits a good hardness with minimal CTE mismatch.

Corrosion mechanism of HVOF thermal sprayed WC-CoCr coatings in acidic chloride media

HVOF thermal sprayed WC cermet coatings exhibit excellent abrasive and erosive wear resistance due to the presence of high volume fraction of WC particles bounded by a tough cobalt or cobalt-chromium alloy binder. However, less information is at present available on the corrosion response of these coatings in strong acidic environment. In this study, the corrosion behaviour of the HVOF WC-CoCr coatings was investigated by electrochemical polarization technique in 0.1 N hydrochloric (HCl) acid solution at 25 °C. The coating morphology was studied by scanning electron microscopy (SEM) and the relationships between the microstructure and corrosion mechanism were investigated using small-angle X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy measurements. The analysis of the corroded coating surface showed that during anodic polarization, the corrosion attack of the WC-CoCr coating began with active oxidation of the binder phase followed by the formation of a pseudo-passive layer composed by anhydrous Cr-oxides (CrO), Co-oxides (CoO/Co3O4) and W-oxides (WO3). At higher potentials the corrosion was governed by the hydration of tungsten oxide (WO3·xH2O) and the extension of the oxidation to the WC particles.

Evaluation of the microstructure and mechanical properties of WC particle reinforced aluminum matrix composites fabricated by friction stir processing

Tungsten carbide (WC) is an attractive reinforcing material for aluminum and its alloys. However, it is technically challenging to fabricate WC particle reinforced aluminum matrix composites (AMCs) with homogeneous distribution of WC particles by liquid state processing techniques because of large density gradient. The present work aim to produce WC particle reinforced aluminum matrix composites (AMCs) through friction stir processing (FSP) and analyze the effect of its volume fraction on the microstructural features and the mechanical behavior of the developed AMCs. Microstructural evaluation was conducted on the cross-sections of the samples by optical microscopy (OM), scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). Microhardness testing was conducted across the cross-sections of FSPed samples to obtain hardness profiles and tensile test was conducted on as-received Al and FSPed samples. The fabricated AMCs exhibited the homogeneous distribution of WC particle with no obvious particle clustering in the stir zone, irrespective of position and WC particle volume fraction. Excellent WC/Al interfacial bonding was obtained in all FSPed AMCs with obviously refined grains. The average size of WC particles after FSP was slightly reduced with the increased volume fraction. It was also found that increasing the volume fraction of WC particles favored the grain refinement, improved the hardness and strength, but decreased the ductility. This improvement in the hardness and strength was attributed to the grain refinement strengthening and homogeneous distribution of WC particles. The decreased ductility resulted from the introduction of more WC particles. Increasing the volume fraction of WC particles caused the nature of fracture to move towards brittle nature.

The effect of volume fraction of WC particles on wear behavior of in-situ WC/Fe composites by spark plasma sintering

Tungsten carbide (WC) particles have been in-situ synthesized through the reaction between tungsten particles and carbide particles by spark plasma sintering (SPS). The composites with different WC content were comparatively observed by the techniques of scanning electron microscopy (SEM), high-resolution transmission electron microscope (HRTEM), X-ray diffraction, hardness and pin-to-disc abrasive wear test. The results showed that the formed WC particles were homogenously distributed in the iron matrix with the size of smaller than 25μm. Additionally, with the increasing of the WC content, the hardness of composites, the microhardness of matrix and the wear resistance increased, but there was no change significantly between 32vol% WC/Fe composites and 42vol% WC/Fe composites. The composites possessed excellent wear resistance comparing the specific wear rate determined in the present work to the martensitic wear-resistant steel under the load of 80N after a sliding distance of ~950m. The specific wear rate of the martensitic wear-resistant steel was a factor of 24 and 48 times higher than WC/Fe composites, when the content of WC was 32vol% and 42vol% in WC/Fe composites, respectively. The main wear mechanism was synthetic of abrasion wear and oxidation wear. The wear performance of 32vol% WC/Fe composites didn't appear to be much different from 42vol% WC/Fe composites, due to the WC particles in the 42vol% composites produced stress concentration easily, which could ultimately induce the creak initiation around WC particles in the subsurface (near wear surface) and propagation to wear surface promoting the breakup of surface film.

Metal-matrix composite fabricated with gas tungsten arc melt injection and precoated with NiCrBSi alloy to increase the volume fraction of WC particles

AbstractThe volume fraction, dissolution, and segregation of WC particles in metal-matrix composites (MMCs) are critical to their wear resistance. Low carbon steel substrates were precoated with NiCrBSi coatings and processed with gas tungsten arc melt injection method to fabricate MMCs with high volume fraction of WC particles. The microstructures and wear resistance of the composites were investigated. The results showed that the volume fraction of WC particles increased with decreasing hopper height and was as high as 44% when hopper height was 100 mm. The dissolution of WC particles was minimal. The content of the alloying elements decreased from the top to the bottom of the matrix. More WC particles dissolved in the overlapping area, where Fe3W3C carbide blocks could be found. The wear loss of the MMCs after 40 min was 6.9 mg, which is 76 times less than that of the substrate after the 4 min test.

Friction performance of WC-Co coating with lithium grease and water lubrication

WC-Co coatings were sprayed by high-velocity oxygen fuel (HVOF) on bearing steels. The coating consisted of a high volume fraction of WC particles in cobalt matrix. The hardness of WC-Co coating was 60% higher than that of the bearing steel. The friction coefficients of WC-Co coating and bearing steel sliding against mild steel were tested with lithium grease and water lubrication. The friction results indicated that the friction coefficient increased with increasing loads. The friction coefficient of WC-Co coating was lower than that of bearing steels no matter with grease lubrication or with water lubrication.

Strain Rate Dependency of Bronze Metal Matrix Composite Mechanical Properties as a Function of Casting Technique

Strain rate dependency of mechanical properties of tungsten carbide (WC)-filled bronze castings fabricated by centrifugal and sedimentation-casting techniques are examined, in this study. Both casting techniques are an attempt to produce a functionally graded material with high wear resistance at a chosen surface. Potential applications of such materials include shaft bushings, electrical contact surfaces, and brake rotors. Knowledge of strain rate-dependent mechanical properties is recommended for predicting component response due to dynamic loading or impact events. A brief overview of the casting techniques for the materials considered in this study is followed by an explanation of the test matrix and testing techniques. Hardness testing, density measurement, and determination of the volume fraction of WC particles are performed throughout the castings using both image analysis and optical microscopy. The effects of particle filling on mechanical properties are first evaluated through a microhardness survey of the castings. The volume fraction of WC particles is validated using a thorough density survey and a rule-of-mixtures model. Split Hopkinson Pressure Bar (SHPB) testing of various volume fraction specimens is conducted to determine strain dependence of mechanical properties and to compare the process-property relationships between the two casting techniques. The baseline performances of C95400 bronze are provided for comparison. The results show that the addition of WC particles improves microhardness significantly for the centrifugally cast specimens, and, to a lesser extent, in the sedimentation-cast specimens, largely because the WC particles are more concentrated as a result of the centrifugal-casting process. Both metal matrix composites (MMCs) demonstrate strain rate dependency, with sedimentation casting having a greater, but variable, effects on material response. This difference is attributed to legacy effects from the casting process, namely, porosity and localized WC particle grouping.

Wear resistance of WC p/Duplex Stainless Steel metal matrix composite layers prepared by laser melt injection

Laser Melt Injection (LMI) was used to prepare metal matrix composite layers with a thickness of about 0.7 mm and approximately 10% volume fraction of WC particles in three kinds of Cast Duplex Stainless Steels (CDSSs). WC particles were injected into the molten surface layer using Nd:YAG high power laser beam. As a result the microstructure characterized by hard ceramic particles distributed in a metal matrix with the strong bonding to substrate is formed in the surface layer of the treated metal. Dry sliding wear properties of these metal matrix composites layers were measured and compared with the wear properties of the substrate and with surfaces simply remelted by the laser beam. The observed wear mechanisms are summarized and related to detailed microstructural observations. The layers have been found to show excellent interfacial bonding, coupled with substantially improved tribological properties expressed through the wear resistance increase of 8 times. The amount of WC particles was sufficient to reinforce the matrix and the particles have shown a good bonding to the matrix to support the contact stress in the layer.

Dry three-body abrasive wear behavior of WC reinforced iron matrix surface composites produced by V-EPC infiltration casting process

This paper fabricated tungsten carbide (WC) particles reinforced iron matrix surface composites on gray cast iron substrate using vacuum evaporative pattern casting (V-EPC) infiltration process, investigated dry three-body abrasive wear resistance of the composites containing different volume fractions of WC particles, comparing with a high chromium cast iron. The fabricated composites contained WC particles of 5, 10, 19, 27, 36, and 52 vol.%, respectively. The results in abrasive wear tests showed that, with the increase in the volume fraction of WC particles, the wear resistance of the composites first increased until reached the maximum when the volume fraction of WC was 27%, then decreased, and was 1.5–5.2 times higher than that of the high chromium cast iron. The changes of the wear resistance of the composites with the volume fraction of WC particles and the mode of material removal in dry three-body abrasive wear condition were analyzed.

The effect of volume fraction of WC particles on erosion resistance of WC reinforced iron matrix surface composites

This paper fabricated tungsten carbide (WC) particles reinforced iron matrix surface composites on gray cast iron substrate using the vacuum infiltration casting technique, investigated the relationship between the erosion resistance and the volume fraction of WC particles, comparing with a high chromium cast iron. The composites were fabricated through iron melt penetrating into thin performs, which consist of WC particles, chromium–iron (Cr–Fe) alloy particles and a small amount of bind, and were paved in advance on some surfaces of a casting mould, with the assistance of wetting of WC particle by the iron melt and sucking of a vacuum degree. The fabricated composites contained WC particles of 10, 15, 19, 27, 36, 45, and 52 vol.%, respectively. In the erosion tests, the erosion velocity was chosen as 9.1 ms −1, the erosion angle as 70° and the test period for each test as 20 h. The results showed that, with increase in volume fraction of WC particles, the wear rates of the composites first decreased until reached the minimum, then increased, and were as a whole 1.38–2.93 times lower than that of the high chromium cast iron. The changes of the wear rates of the composites with the volume fraction of WC particles, and the comparison of the wear performances between the composites and the comparative material were analyzed.

Deposition of WC/Ni clad layers with a pulsed Nd:YAG laser

A series of experiments was performed to investigate the production of WC/Ni clad layers on H13 tool steel using a pulsed Nd:YAG laser and optical fibers. The effects of laser parameters, such as laser pulse energy and pulse frequency as well as material parameters such as powder composition and shape on the clad layer geometry and microstructure, were investigated. The microstructure of the clad layers was assessed by optical and scanning electron microscopy in conjunction with x-ray diffraction. The results indicate that up to 1 mm thick, fully dense clad layers can be formed in a single pass from WC/Ni powder containing up to 70% by weight pure WC with an average laser power of 440 W delivered through a 600 μm diam, step-index glass fiber. The results further show that the WC powder composition and shape can affect the structure and composition of the coating. The coatings produced with pure, angular, monocarbide exhibited the highest retained volume fraction of WC particles.

Pre-placed WC/Ni clad layers produced with a pulsed Nd:YAG laser via optical fibres

Laser clad WC/Ni layers were produced on H13 tool steel substrates with a pulsed Nd:YAG laser and optical fibres using the pre-placed powder technique. The effects of parameter variation, such as laser pulse energy, beam profile, traverse speed and volume fraction of the reinforced WC particles, on clad layer formation and its properties were investigated. The microhardness of the clad layers was measured and the microstructure was characterised by optical and scanning electron microscopy and X-ray diffraction. The results show that relatively thick (>0.5 mm), fully dense and crack-free clad layers of WC/Ni can be formed on H13 substrates without any pre-heating. The results further show that the volume fraction of the reinforced WC particles is the dominant factor affecting most clad layer properties such as its porosity, microhardness and wear resistance. The greater the volume fraction of WC particles, the lower the porosity, the higher the microhardness and the higher the wear resistance of the clad layer. Average microhardness values of the matrix were as high as 800 HV and the pin-on-plate (reciprocating) wear tests showed the weight loss of the clad layers is substantially lower than that for the unclad substrate.

Transmission Electron Microscope Specimen Preparation of Metal Matrix Composites Using the Focused Ion Beam Miller

The focused ion beam (FIB) miller has been widely accepted as a powerful tool in the semiconductor industry. However, it is now finding applications in more general materials science applications. The high resolution, energetic gallium ion beam can rapidly and precisely section materials to reveal their internal structure; one particularly valuable application being the preparation of thin foils for TEM examination, especially from heterogenous materials.To date, TEM sample preparation using FIBs has concentrated on semiconductor cross-sections [1], powders [2], and surface treated materials, e.g. galvanized steels [3]. However, thin foils of grossly heterogeneous materials, such as metal-matrix composites, are also difficult to prepare using conventional methods and are therefore well suited to sectioning using the FIB. In this study, thin foils were prepared from two composite materials: a 7075 aluminium alloy containing a 20% volume fraction of SiC particles and a FeAl alloy containing a 60% volume fraction of WC particles.

Crystallization characteristics and viscous flow behavior of WC/amorphous Ni 73Si 10B 17 metal matrix composites

The crystallization and viscous flow behavior of WC/amorphous Ni 73Si 10B 17 metal matrix composites was examined by using X-ray diffraction, differential scanning calorimetry and thermochemical analysis. The progress of crystallization is faster in the tungsten carbide (WC)-dispersed composites than in the single-phase amorphous Ni 73Si 10B 17, and the enthalpy of crystallization decreases with increasing volume fraction of the WC particles. It was observed that the activation energy of crystallization of WC-containing samples increased rapidly at almost the same peak temperature relative to the amorphous Ni 73Si 10B 17 alloy. For every composition studied, the viscosity decreased with increasing volume fraction of WC particles; hence the yield stress was raised by increasing the volume fraction of WC particles. T gi can be controlled by changing the volume fraction of WC particles.