Mechanical Properties Of WC Research Articles

Effect of SPS frequency on the transformation of diamond to graphite in WC-Co composite

(WC–6wt%Co)/5Vol% diamond composites were successfully fabricated at 1150–1300 °C and 40 MPa for 5 minutes under the thermodynamically unstable conditions of the Spark Plasma Sintering method. The influence of on-off time, and frequency of the DC pulse of SPS on diamond stability, microstructure, and mechanical properties of WC–Co/diamond composites were investigated. The diamond particles are strongly bounded with the cemented carbide matrix by a transition layer composed of a solid solution of tungsten and carbon in cobalt. The amount of graphitization was low in the sintered composites at 1300 °C due to the low temperature and short sintering time. Reduction of SPS frequency effectively inhibited graphite preformation, and no graphite was detected in the sintered composites at 1150 °C. Diamond morphology was not affected during SPS as examined by SEM, and Raman scattering spectra. The uniform dispersion of the super-hard diamond phase in matrix which good bonded, caused the high hardness, fracture toughness and flexural strength of this composite. The reduction of pulse frequency of SPS leads to a significant enhancement in the hardness, fracture toughness, and flexural strength of the composites, overcoming the graphitization of diamond typically observed in SPS. The sample sintered with 4 Hz showed simultaneously the highest hardness (23.6 GPa), the highest fracture toughness (24.6 MPa.m½), and the highest flexural strength (2050 MPa).

Effect of diamond volume fraction on the microstructure and mechanical properties of SPS WC–Co/diamond composites

AbstractIn this research, the effect of the volume percentage of diamond additive on the sintering behavior, microstructure, and mechanical properties of WC–Co was investigated. WC–Co/diamond composites with different percentages of 0%, 2.5%, 5%, 7.5%, and 10% by volume of diamond were made by spark plasma sintering at 1300°C and 40 MPa for 5 min. A small amount of phase transformation from the diamond phase to the graphite phase was observed. The amount of graphitization was low due to low temperature and short sintering time. The addition of diamond leads to a significant enhancement in both the hardness and fracture toughness of the composites, overcoming the trade‐off between hardness and toughness typically observed in WC‐based materials. The sample reinforced with 5% by volume of diamond showed simultaneously the highest hardness (22.9 GPa), the highest fracture toughness (22.7 MPa m1/2), and the highest flexural strength (1896 MPa). The uniform dispersion, good bonding of the superhard diamond phase with the matrix, and the fine microstructure caused the high hardness and toughness of composite. The main effective mechanisms in increasing the fracture toughness of the composite were crack deflection, bridging, and blocking of crack propagation by diamond particles.

Effects of carbothermal prereduction temperature and Co content on mechanical properties of WC–Co cemented carbides

AbstractWC–Co cemented carbides were prepared via an in situ synthesis method, including the carbothermal prereduction of WO3 and Co2O3 to remove all oxygen and a subsequent carbonization‐vacuum sintering process. The experimental results revealed that as the prereduction temperature increased from 1000 to 1200°C, the grain sizes of WC in WC–6Co and WC–12Co cemented carbides increased from .91 to 1.09 and .97 to 1.19 μm, respectively. Further, the fracture toughness of the sintered WC–6Co and WC–12Co cemented carbides increased from 9.97 to 10.83 and 11.11 to 18.30 MPa m1/2, respectively. In contrast, the hardness of the WC–6Co and WC–12Co cemented carbides decreased from 1477 to 1368 and 1351 to 1184 HV30, respectively. For a given prereduction temperature, an increase in Co content can improve the fracture toughness while lowering the hardness. In addition, an increase in the prereduction temperature or Co content led to an increase in the grain size of WC, which resulted in a transgranular fracture as the dominant mode.

Interfacial microstructure and mechanical properties of WC–Co/40Cr joints brazed at low–temperature with Ag–Cu–Ti + Sn novel filler

It is crucial to design a novel active filler metal for brazing WC–Co cemented carbide–steel joints at low temperatures. In this study, we designed a low-melting-point multi-component active filler metal (Ag–Cu–Sn–Ti) based on Ag–Cu–Ti filler metal to achieve perfect combination of WC–Co/40Cr steel joints. The interfacial microstructure of the WC–Co/40Cr steel joint was comprehensively characterized, and the joint-bonding mechanism, mechanical properties, and fracture behavior after brazing at 700–780 °C were systematically analyzed. On both sides of the filler metal, WC and α-Fe combined with the TiC layer, enhancing the bonding of the filler metal to base materials. The typical structure of the joint is WC–Co/TiC layer/Co2SnTi + Cu–doped Cu81Sn22 + Ag [s, s] + Ti–Cu granules/TiC layer/40Cr. The maximum shear strength of 241 MPa was obtained when the joint was brazed at 740 °C for 10 min, which is approximately 50% higher than those of previous low-temperature vacuum-brazed WC–Co/steel joints. The main factors leading to premature failure of joint include the distribution of phases in filler metal layer and defects of WC–Co caused by Co diffusion.

Effect of Repetitively Pulsed Laser Radiation on the Morphology, Microstructure and Mechanical Properties of WC – NiCrBSi Coatings Obtained by Laser Surface Cladding

Effect of Repetitively Pulsed Laser Radiation on the Morphology, Microstructure and Mechanical Properties of WC – NiCrBSi Coatings Obtained by Laser Surface Cladding

The Structure and Mechanical Properties of WC–8 wt.% Co Hardmetal Produced by Cold and Hot Isostatic Pressing

The Structure and Mechanical Properties of WC–8 wt.% Co Hardmetal Produced by Cold and Hot Isostatic Pressing

Influence of Cr3C2 and VC Content on WC Grain Size, WC Shape and Mechanical Properties of WC-6.0 wt. % Co Cemented Carbides.

In this paper, the influences of Cr3C2/VC content on WC grain size, WC grain shape and mechanical properties of WC–6 wt. % Co cemented carbides were investigated. The results showed that the grain size first rapidly decreased and then slightly decreased with the increasing Cr3C2/VC content, and VC led to finer grain size and narrower size distribution. HRTEM/EDS analysis of the WC/Co interface indicates that the segregation concentration of V is much larger than that of Cr, which may be a strong response to the higher inhibition efficiency of VC. The addition of Cr3C2 induced triangular prism shape WC grains while VC generated stepped triangular prism grains. Despite the grain growth inhibitor (GGI) mechanisms of Cr3C2/VC have been extensively studied in the literature, the doping amount, especially the doping limit, has not been systematically investigated. In this work, the saturated solubilities of Cr and V in cobalt binder phase along with carbon content hare been predicted based on thermodynamic calculations. Based on the theoretical calculations, the doping amount of Cr3C2/VC is designed to be gradually increasing until more or less over their maximum solubilities in the binder phase, thereby investigating the subsequent microstructure and mechanical properties. When the doping of Cr3C2/VC exceeds the maximum solubility in Co phase, Co-rich Cr-carbides and Co-deficient V-carbides would form respectively, which were detrimental to the transverse rupture strength (TRS) and impact toughness. The hardness increased with the increasing Cr3C2/VC content, while the fracture toughness decreased with the increasing Cr3C2/VC content. The TRS initially enhanced and then declined, but the stepped triangular prism shape grains and low fraction of WC/Co interface in WC–6Co–VC cemented carbide led to a more pronounced decline in the TRS. The sample with 0.6 wt. % Cr3C2 addition had good comprehensive mechanical properties, its hardness, fracture toughness and TRS were 1880 kg/mm2, 9.32 MPa·m1/2 and 3450 MPa, respectively.

Microstructure and mechanical properties of WC-(Ti,W)C-Co hardmetals fabricated by in-situ carbothermal reduction of oxides and subsequent liquid phase sintering

WC-(Ti,W)C-Co hardmetal was fabricated using carbon black, WC, Co, WO3, TiO2 as raw materials, through an energy-efficient and cost-efficient method that the process of carbothermal reduction of oxides and the liquid phase sintering of hardmetal were combined in one heating cycle. Phase transformation and microstructure characteristics of the hardmetals were examined by XRD, SEM, EDX, and TEM. Moreover, mechanical properties were tested with related mechanical property testing instruments. Results demonstrated that the in-situ carbothermal reactions and outgassing processes had finished below 1200 ℃. Microstructures of hardmetal consisted of WC grains, (Ti,W)C solid solution, and Co binder phase. Moreover, the mean size of WC and (Ti,W)C grains were both smaller than those of hardmetal prepared with TiC powders. A coherent relationship between Co and (Ti,W)C grain was noticed. Moreover, a coherent relationship between two (Ti,W)C grains was observed. Compared with hardmetal prepared with TiC powders, TRS and KIC were improved. The increase of TRS was chiefly due to the smaller grain size and the coherent interface structure. Moreover, the increase of KIC was ascribed to the (Ti,W)C solid solution and the coherent interface structure. Hardmetals prepared through this method showed good mechanical properties with a hardness of 90.7 ± 0.2 HRA, a TRS of 3007 ± 87 MPa, a KIC of 13.1 ± 0.2 MPa·m1/2.

Effects of Powder Microscopic Defects on Densification and Mechanical Properties of WC via Spark Plasma Sintering

The WC composite powder was synthesized by a new specific chemical activation technique. A large number of lattice defects such as surface humps, dislocations and stacking fault exist in the surface of the WC powder after chemical activation technique. By using such activated WC powder, the binderless WC cemented carbide with high density (15.54 g/cm3), super hardness (average 26.29 GPa) and excellent fracture toughness (8.9 MPa.m1/2) can be fabricated by SPS at 1700 °C and 50 MPa pressure. The improvement in density, hardness and fracture toughness are respectively 4.5%, 15.3% and 17.1% compared to when using the original WC powder. This improvement is because microscopic defects on the surface of the WC powder can greatly improve surface free energy of the powder, which improves the sintering activity and reduces the sintering temperature of the WC powder.

Microstructure and mechanical properties of WC or Mo2C modified NbC-Ni cermets

In this study, the influence of up to 15 vol% WC or Mo2C addition to Ni bonded NbC matrix cermets, prepared by pressureless liquid phase sintering in vacuum for 90 min at 1390 °C was assessed. The constituent phases and W/Mo dissolution in the Ni binder and NbC phases were simulated by thermodynamic modelling. Microstructure and phase analysis using XRD and SEM indicated that the WC or Mo2C modified NbC based cermets were composed of a (Nb,W)C or (Nb,Mo)C solid solution cubic phase dispersed in a cubic Ni alloy binder. Residual WC was present in the cermets with ≥10 vol% WC addition, whereas up to 15 vol% Mo2C addition completely dissolved into the NbC cermets. The phase evolution and influence of the WC/Mo2C content on the solid solution formation is discussed and the fracture toughness, Vickers hardness and transverse rupture strength was assessed.

Effects of carbide substrate properties and diamond coating morphology on drilling performance of CFRP composite

Abstract The properties of a cemented carbide tool substrate and diamond coating were studied for the precision drilling of carbon fiber-reinforced plastic (CFRP). The microstructures and mechanical properties of WC–6 wt.% Co substrates using different WC particle sizes were examined to determine correlations between the mechanical properties and the drilling performance. The results demonstrated that WC powders with an average particle size of 2.3 μm were suitable drill substrates. Coatings of either microcrystalline diamond (MCD) or gradient nanocrystalline diamond (NCD) were deposited using hot-filament chemical vapor deposition. A drilling test using T700-grade CFRP was conducted to evaluate the drilling performance, tool wear resistance, and CFRP hole quality achieved based on the diamond coating morphology. In the CFRP drilling tests, the diamond-coated drills showed superior tool lifetimes four times longer than that of the uncoated drill. The MCD-coated drill exhibited good wear resistance compared to the gradient NCD-coated drill; however, the gradient NCD-coated drill demonstrated better machining quality in terms of the delamination factor, surface roughness inside the machined hole, and accuracy of the machining dimensions. In this study, we aimed to develop the optimal tool substrate for the drilling of general-purpose CFRP and proposed directions for the development of diamond coatings to maximize drilling performance.

Microstructure and mechanical properties of WC and Ti(C0.7N0.3) modified NbC solid solution cermets

Eight NbC solution matrix cermets were prepared by liquid phase sintering of mixtures containing NbC, WC, Ti(C0.7N0.3), Mo2C, Co and Ni powders. The influence of the WC and Ti(C0.7N0.3) content on the microstructure and mechanical properties of the cermets was investigated. Microstructural investigation was supported by thermodynamic equilibrium calculations to predict the composition of the constituent phases as a function of WC content at 1420 °C. The results indicated the variation in WC and Ti(C0.7N0.3) content had a significant influence on the phase content, the in-situ formed (Nb,W,Ti,Mo) (C,N) solution grain growth and concomitant mechanical properties. The NbC solution cermets with 12–32 wt% WC were composed of a core-rim (Nb,W,Ti,Mo) (C,N) phase, Co–Ni alloy binder, and rimless Ti(C0.57N0.43) phase. XRD phase analysis and simulations revealed that the composition of the cubic structure (Nb,W,Ti,Mo) (C,N) and Ti(C,N) solid solutions depend on the WC content. The NbC matrix cermets with 12–32 wt% WC exhibited a Vickers hardness (HV30) of ∼1500 kg/mm2 and indentation toughness of ∼9 MPa m1/2.

Исследование фазового состава и его влияние на механические свойства карбидосталей WC-(Fe-Mn-C)

Исследование фазового состава и его влияние на механические свойства карбидосталей WC-(Fe-Mn-C)

EFFECT OF WC REINFORCED ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF CUALMN ALLOYS PRODUCED BY HOT PRESSING METHOD

In this study, the effect of WC reinforcing particles on the microstructure and mechanical properties of CuAlMn and CuAlMn-WC alloy produced by powder metallurgy method was investigated by adding 5 %, 10 % and 15 % by volume WC to CuAlMn alloy. Cu, Al, Mn and WC powders of approximately 99.9 % purity with a grain size of 325 mesh were used in the production of the alloys. The samples were produced by hot pressing method at 900 ℃ temperatures under 35 MPa pressure for 6 minutes. Microstructure, phase formation, hardness and corrosion properties of the samples were investigated in detail. Scanning electron microscopy (SEM) was used for microstructure analysis and X-ray diffractogram (XRD) was used for phase formation detection. The hardness measurements of the samples were measured by microhardness measuring device. The corrosion tests were performed potentiodynamic polarization curves of the composite materials in 3.5% NaCl solution. As a result, it has been determined that the mechanical properties of WC reinforcing particles added to CuAlMn matrix increase with increasing volume ratio.

Preparation and Properties of WC-Based Alloy Coatings with Controlled Co and Cr via High Velocity Oxy-Fuel Spray Technique.

WC based alloy coatings included different mass percent of Co and Cr have been synthesized on high carbon steel by using a facile high velocity oxy-fuel spray method. The mechanical nature of the coating films has been investigated by micro vickers hardness and fracture toughness. X-ray diffraction (XRD) and EDX analyses indicate that the three different samples (WC-10Co-4Cr, WC-17Co, and WC-12Co) consist of pure WC, W, Cr, and Co constituents as well as W2C and Co6W6C phases. The SEM and image analysis results show that WC-10Co-4Cr condition has higher porosity than those of WC-17Co, and WC-12Co coatings. WC-17Co coating showed the highest value in the hardness and fracture toughness test among three different samples. The obtained results revealed that the mechanical properties of WC based alloy coatings synthesized by a facile high velocity oxy-fuel spray method is very sensitive to Co content.

Effect of Annealing Temperature on the Microhardness of Tungsten Carbide Coatings

Tungsten carbides (WC) coatings have been deposited by RF magnetron sputtering onto steel substrate (XC70) temperature in the range of 500-1000 °C under vacuum for 25 minutes. The mechanical properties of WC were investigated by the measurements of microhardness by Vickers tests. We carried out microhardness tests with loads varying between 10 g and 1000 g, and the variations of the microhardness of our samples were followed as a function of the annealing temperature, the applied load and the penetration depth of the indenter.

Effect of diamond additions on the microstructure, physical and mechanical properties of WC- TiC- Co/Ni Nano-composite

WC- TiC- Co- Ni/diamond composites have been prepared by powder metallurgy technique. 2.5%, 5%, 7.5% and 10wt% diamond were added. WC- TiC- Co/diamond was coated with 12wt% nickel by the electro-less deposition process. All the samples were compressed at 700MPa then sintered at 1450 for 1h. XRD, EDAX, and microstructure were investigated. Density, electrical resistivity, thermal conductivity, magnetic properties, the coefficient of thermal expansion, fracture toughness and hardness were studied. The results of XRD and EDAX analysis show that new phases were formed. It also revealed that the diamond content has a positive effect on the thermal properties of composites. Presence of Ni content improves the Fracture toughness of the composites but decreases the hardness.

Effect of Bonding Temperature on Microstructure and Mechanical Properties of WC–Co/Steel Diffusion Brazed Joint

In this work, the diffusion brazing of AISI 4145 steel to WC–Co cemented carbide using RBCuZn-D interlayer with bonding temperature values of 930, 960, 990 and 1020 °C was studied. The microstructure of the joint zone was evaluated by scanning electron microscope (SEM) and X-ray diffraction (XRD). Vickers microhardness and shear strength tests were performed to investigate mechanical behaviors of the brazed joints. The XRD and SEM results indicated that with increase of bonding temperature, the elements readily diffused along the interface and formed various compounds such as γ, α and β and Co3W3C. The results also showed that with the increase of bonding temperature from 930 to 960 °C, a sound metallurgical bond was produced, however in higher bonding temperatures (990 and 1020 °C) a decrease in mechanical properties of the joints was observed which could be due to the excessive zinc evaporation, interface heterogeneity and voids formation. The maximum shear strength of 425 MPa was obtained for the bond made at 960 °C.

Microstructure and mechanical properties of WC–Co, WC–Co–Cr3C2 and WC–Co–TaC cermets fabricated by spark plasma sintering

Spark plasma sintering was successfully used to produce WC–Co cermets with the addition of Cr3C2 and TaC grain growth inhibitors. The spark plasma sintered compacts were investigated by scanning electron microscopy, X-ray diffraction analysis, density measurements, hardness tests, fracture toughness tests and elastic modulus tests. The results were compared with an inhibitor-free WC–Co cermet consolidated under the same process parameters. By using Cr3C2 and TaC additives, it is possible to improve the hardness and fracture toughness of WC–Co cermets, but Cr3C2 has better grain growth inhibition property than that of TaC. The best combination of hardness (HV30 (2105±38)) and fracture toughness ((8.3±0.2) MPa·m1/2) was obtained by the WC–5Co–2Cr3C2 cermet.

Microstructural evolution and mechanical properties of hot pressed WC–α-Al2O3 with Y2O3 and CeO2

WC–α-Al2O3 composites, with the rare earth oxides (Y2O3 or CeO2) as sintering additives, were fabricated by mechanical alloying and hot pressing sintering. The microstructure and mechanical properties of WC–Al2O3 with and without oxides were investigated. The appearance of rare oxides increased the density of sintered bulk materials and suppressed the decarburisation due to the decrease of surface activation energy in sintering process. The hardness and fracture toughness of the samples first increased and then decreased, indicating that an appropriate addition of Y2O3 or CeO2 could strengthen the properties of samples. Microstructure observation results revealed that the grain growth of WC was significantly retarded, and the homogeneity of Al2O3 particulate dispersion was improved with the addition of Y2O3 and CeO2.