WC Grain Size Research Articles

Insight into Grain Refinement Mechanisms of WC Cemented Carbide with Al0.5CoCrFeNiTi0.5 Binder.

High-entropy alloys (HEA) as a kind of new binder for cemented carbide have garnered significant attention. In this work, WC/(17~25 wt.%)Al0.5CoCrFeNiTi0.5 cemented carbides were prepared by hot pressing sintering (HPS), and the reactions between WC powder and Al0.5CoCrFeNiTi0.5 powder during hot pressing sintering were elucidated. It found that different from traditional Co binder, the Al0.5CoCrFeNiTi0.5 binder effectively inhibited WC grain growth. During HPS, the decomposed W and C atoms from WC diffused into the Al0.5CoCrFeNiTi0.5 binder, reacted with the elements in the binder, and then formed the M(Co, Fe, Ni)3W3C phase. The back-diffusion of W and C atoms to WC grains was restricted by the Al0.5CoCrFeNiTi0.5 alloy and inhibited them from re-precipitating onto the large undissolved WC grains. As a result, the average size of WC grains in the cemented carbides was less than 200 nm. This work bright new insight into the grain refinement mechanisms of WC cemented carbide with HEA binder and provide a guidance for designing performance-stable WC/HEA cemented carbide and promoting their application.

Effects of sintering method and Al2O3 content on microstructure and mechanical properties of WC-10Co cemented carbide

Ultra-high toughness and ultra-high hardness WC-10Co-xAl2O3 cemented carbides were successfully prepared by vacuum liquid phase sintering (VS) and spark plasma sintering (SPS) using ultrafine WC and commercial Co powders as raw materials, respectively. The effects of nano-Al2O3 content and sintering process on the relative density, average grain size, microstructure and mechanical properties of WC-10Co alloys were investigated. The results showed that the densification degree of the samples decreased with the increase of Al2O3 content. In addition, the relative densities of the samples prepared by SPS were lower than those of the samples prepared by VS. For the samples prepared by VS, the average grain size increased first and then decreased as the Al2O3 content increased from 3 wt% to 9 wt%, and the percentage of coarse grain showed the same trend. When the addition of Al2O3 was 6 wt%, the average grain size reached the maximum value of 1.39 ± 1.03 μm. Meanwhile, the sample with 6 wt% Al2O3 had a typical inhomogeneous dual-grain structure, and the percentages of fine grain (< 1 μm) and coarse grain (> 1 μm) were about 50%, which displayed the highest fracture toughness of 18.59 MPa·m1/2. The dual-grain structure not only improved the toughness, but also compensated the loss of hardness. However, for the samples prepared by SPS, with the increase of Al2O3 content, the average grain size of WC decreased, while both hardness and toughness were continuously improved. When the Al2O3 content increased to 9 wt%, the grain size reached the minimum value of 0.25 ± 0.08 μm, and meanwhile, the hardness and toughness reached the maximum value of 19.69 GPa and 12.29 MPa·m1/2, respectively. Moreover, as the Al2O3 content increased, the transverse rupture strength (TRS) of the samples prepared by VS increased first and then decreased, and the TRS of sample with 3 wt% Al2O3 reached the maximum value of 1410 MPa. However, the TRS of the sample prepared by SPS showed a decreasing trend.

Processing of ZrO2 strengthened and toughened WC matrix composites based on ML

Binderless WC matrix cemented carbide was considered a novel material with the potential to replace WC-Co cemented carbide. However, current research was insufficient to address the trade-off between strength, toughness, and strength in binderless WC matrix cemented carbide. In this work, the machine learning was employed to estimate mechanical property and optimize the composition of WC matrix cemented carbide. WC-MgO-ZrO2 composites were successfully developed with uniform microstructure and excellent mechanical properties. The experimental results showed that the grain size of WC reached 1.05μm where the mass fraction of ZrO2 was 2%. The WC-MgO-2 wt%ZrO2 composite exhibited superior Vickers hardness, fracture toughness, and flexural fracture strength, which were 1851HV, 11.2 MPa·m1/2 and 1368 MPa, respectively. The fracture mode of WC-MgO-ZrO2 composites was mainly a mixture of transgranular fracture and intergranular fracture. The main toughening mechanisms were crack deflection, crack bridging, grain pull out and phase transformation. The comprehensive mechanical properties of WC-MgO-2 wt%ZrO2 composites rank at a superior level compared to similar binderless WC matrix composites reported in the current literature. Meanwhile, the wear behaviors of WC-MgO-ZrO2 composites were examined under three different loads. And the wear behavior and mechanism of WC MgO-2 wt% ZrO2 composite were revealed.

Microstructure, Mechanical Properties and Wear Behaviors of Ultrafine-Grain WC-Based Cermets with Different Binder Phases Fabricated by Spark Plasma Sintering.

In this work, to explore potential substitutions for the Co binder phase, ultrafine-grain WC-based cermets with various binder phases of Co, Ni and AlCoCrNiFeCu HEA were prepared using the SPS method. Based on SPS, WC-based cermets were fabricated at higher speed, showing fine carbide particles less than 410 μm. The microstructure, mechanical properties and wear properties were systematically evaluated. By comparison, the grain size of WC was the lowest for WC-10Co, while WC-10 HEA cermet held the coarsest WC particles. The hardness and fracture toughness of WC-10 HEA were the best among all three samples, with values of 93.2 HRA and 11.3 MP·m1/2. However, the bending strength of WC-10HEA was about 56.1% lower than that of WC-10Co, with a value of 1349.6 MPa. The reduction in bending strength is attributed to the lower density, formation of a newly Cr-Al rich phase and coarser WC grains. In dry sliding wear conditions, WC-10 HEA showed the lowest wear rate (0.98 × 10-6 mm3/(N·m)) and coefficient of friction (0.19), indicating the best wear resistance performance. This reveals that WC-based cermet with a HEA binder phase has superior wear performance due to the higher hardness and good self-lubricating effect of the wear products.

Corrosion resistance of WC-Co-GO cemented carbides in NaCl solution

WC-Co cemented carbide with deferent content (0, 0.1 wt% and 0.3 wt%) of graphene oxide (GO) were prepared by hot-pressing sintering. The effect of added GO on the corrosion resistance of WC-Co cemented carbide in sodium chloride solution was investigated by electrochemical method. With the increase of GO content, the grain size of WC shows a decreasing trend. The research findings suggested that the added GO increased remarkably the corrosion potential and decreased the corrosion current density in sodium chloride solution. As the GO content increased from 0 to 0.1 wt% and 0.3 wt%, the charge-change resistance (Rct) first increased from 6393 to 9201 Ω·cm2 and then decreased to 7842 Ω·cm2, correspondingly. The characterization of corrosion surface by SEM, EDS and XPS indicated that GO acted as the physical barrier and enabled WC-Co cemented carbide to have a larger ratio of the surface area of the anode phase to the cathode phase, which improved the corrosion resistance.

Ultrafine grained WC-10FeCoCu cemented carbides doped with La2O3 prepared by spark plasma sintering

La2O3/WC-10FeCoCu cemented carbides were fabricated using FeCoCu medium-entropy alloy (MEA) as a novel binder and La2O3 as a grain growth inhibitor via spark plasma sintering (SPS). Effects of sintering temperature and the amount of La2O3 on the microstructure and properties were investigated. WC-10FeCoCu with good mechanical properties was obtained. To further refine the grain size of WC, La2O3 was introduced as grain growth inhibitor. It was found that grain size of the WC-10FeCoCu samples added with 0.6 wt% of La2O3 is finer than 400 nm (388 nm). Its Vickers hardness and fracture toughness reach 1944.2 HV30 and 16.16 MPa∙mm1/2, respectively. The experimental findings highlight the successful preparation of La2O3/WC-10FeCoCu with ultrafine grains and favorable properties by using FeCoCu MEA as a binder and La2O3 as a grain growth inhibitor.

Formation of core-rim structure and interface toughening mechanism in cast WC- FeCoNiCrMo (HEA) based composite materials

The aim of the work is to improve the toughness of cast WC-based composite material by introducing FeCoNiCrMo high-entropy alloy (HEA) into the system. The results indicated that a circular ‘diffusion layer’ formed on the surface of cast WC after HEA addition, resulting in a ‘core-rim’ structure. During the pressureless infiltration process, decomposition of cast WC occurs and the carbon element reacts with Mo in HEA forming Mo2C, and the other elements such as Co, Fe and Ni react with Mo and W forming (Fe, Co, Ni)3Mo3C type carbon-deficient phase. The composition of the ‘diffusion layer’ is mainly HEA content, but the binder is enriched in Ni and rare in Mo regardless of HEA addition level. With the increase of HEA addition, formation of irregular island-shaped structure can be seen in the Cu binder phase. Due to the core-rim structure, the grain size of cast WC can be reduced and the hardness of the composite is improved. The bonding energy of WC (0001) -Mo2C (0001) and WC (101¯0) -Mo2C (0001) interfaces is evaluated using DFT calculation, which 7.975 eV and 6.480 eV and higher than that of WC-Cu interface in composite without HEA addition. FEM analysis reveals that the interfacial residual stress is alleviated due to the existence of the diffusion layer. In composite without HEA addition, the cracks initiated in the cast WC phase mainly propagates along the ceramics-metal interface, resulting in debonding and early fracture. The crack propagation mode shows much difference after the formation of core-rim structure, which indicate the toughening by HEA addition. When the crack propagates towards the interface, the crack does not propagate along the interface, but passes through the interface area and quickly stops propagating. Therefore, the interface toughness is improved after HEA addition.

Effects of nanocomposite grain growth inhibitors and multi-walled carbon nanotubes on the microstructure and mechanical properties of ultrafine cemented carbides

Obtaining cemented carbides with smaller WC grain size and better properties is key to their wider application. Ultrafine cemented carbides were prepared by using spark plasma sintering (SPS) with nano VC-Cr3C2 as nanocomposite grain growth inhibitors (NGGIs) and multi-walled carbon nanotubes (MWCNTs) as reinforcing materials. The effects of NGGIs and MWCNTs on the microstructure and mechanical properties of alloys were evaluated. The results indicated that the specimens (0.5 wt % NGGIs and 0.4 wt % MWCNTs) prepared at 1350 °C for 8 min under a pressure of 50 MPa have enhanced mechanical properties (HV 2520.85 kgf/mm2, KIC 13.26 MPa m1/2) and a homogeneous microstructure. The grain size of WC is suppressed (the average grain size is 200–400 nm). NGGIs can prevent the dissolution of W and C in liquid Co, thereby inhibiting the growth of WC grains. The uniform dispersion of MWCNTs in WC matrix mobilizes their fiber-reinforcement effect. The combination of NGGIs, MWCNTs, and SPS can improve the mechanical properties and optimize the microstructure of the alloy.

Microstructure and Properties of Fine-Grained WC-10Co-0.5Cr3C2-1TaC-0.5Ru Prepared by Rolling Ball Milling and Low-Pressure Sintering

This study focuses on the preparation of fine-grained WC/Co composite powder using rolling ball milling and spray drying techniques. The cemented carbide composition achieved through low-pressure sintering technology was WC-10Co-0.5Cr3C2-1TaC-0.5Ru (wt.%). To study the effect of sintering temperature on the microstructure and mechanical properties of WC-10 wt.% cemented carbide, the microstructure and phase constituents of the material were analyzed using X-ray diffractometry and scanning electron microscopy. Additionally, the physical and mechanical properties of the material were examined. The results indicate that as the sintering temperature increased from 1390 °C to 1450 °C, the grain size of WC in the alloy increased, resulting in a slight decrease in hardness, an increase in fracture toughness, and the transverse fracture strength increasing first and then decreasing. The sintered hard alloy prepared at 1410 °C exhibited fewer pores and a uniform and fine grain size, reaching a density of 99.98%, a hardness of 91.8 HRA, a fracture strength of 3962 MPa, and a fracture toughness of 14.7 MPa⋅m1/2

Investigations on Thermal Conductivity of Two-Phase WC-Co-Ni Cemented Carbides through a Novel Model and Key Experiments

Excellent thermal conductivity is beneficial for the fast heat release during service of cemented carbides. Thus, thermal conductivity is a significant property of cemented carbides, considerably affecting their service life. Still, there is a lack of systematic investigation into the thermal conductivity of two-phase WC-Co-Ni cemented carbides. To remedy this situation, we integrated experiments and models to study its thermal conductivity varying the phase composition, temperature and WC grain size. To conduct the experiments, WC-Co-Ni samples with two-phase structure were designed via the CALPHAD (Calculation of Phase Diagrams) approach and then prepared via the liquid-phase sintering process. Key thermal conductivity measurements of these prepared samples were then taken via LFA (Laser Flash Analysis). As for modeling, the thermal conductivities of (Co, Ni) binder phase and WC hard phase were firstly evaluated through our previously developed models for single-phase solid solutions. Integrating the present key measurements and models, the values of ITR (Interface Thermal Resistance) between WC hard phase and (Co, Ni) binder phase were evaluated and thus the model to calculate thermal conductivity of two-phase WC-Co-Ni was established. Meanwhile, this model was verified to be reliable through comparing the model-evaluated thermal conductivities with the experimental data. Furthermore, using this developed model, the thermal conductivity of two-phase WC-Co-Ni varying with phase-fraction, temperature and grain size of WC was predicted, which can contribute to its design for obtaining desired thermal conductivities.

Friction and wear behavior of cemented carbide self-matching pairs under different water lubrication conditions

The friction and wear behavior of WC based cemented carbides ring-ring samples in different water environments were systematically tested. The average grain size of WC is 1.2 μm and the mass fraction of binder Co is 8%. The water environments include distilled fresh water, artificial seawater with NaCl mass content of 4%, and sediment water with SiO2 mass content of 0.6% and average particle size of 88 μm. The friction torque was measured for each friction pairs at different speeds and specific pressure loads. The surface morphology of the friction pairs before and after the test were observed by a scanning electron microscope, and the weight losses were also measured by a balance. The test results suggest that the friction coefficient of all the sample pairs decreases exponentially with the increase of load at proper revolution speed. In the range of 4–10 MPa specific pressure, the friction coefficient of the bearing during stable operation is between 0.01–0.02. The wear rate of the stationary ring is about 3 times that of the matching rotary ring, no matter in the environment of artificial seawater, distilled fresh water or sediment water lubrication medium. However, the wear rates of the samples in artificial seawater are higher than those of the two rings friction under the same speed and load conditions in the other two water environments. SiO2 particles in the sediment water has no effect on the bearings wear rate. The wear of cemented carbide self-matching pair bearings is mainly the peeling of WC particles caused by the alternating contact and friction force or plowing of WC abrasive particles. The corrosivity of artificial seawater can aggravate the peeling of WC particles. The results and conclusions of this study can provide a meaningful reference for the design of cemented carbide bearings utilized in water lubrication environment.

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.

Improved comprehensive mechanical properties of oscillatory pressure sintered WC–ZrO2–Al2O3 ceramics with VC/Cr3C2 addition

To optimize the microstructure and comprehensive mechanical properties of WC-based ceramics, the addition of grain growth inhibitors was an important and effective approach. The effect of VC/Cr3C2 addition on the densification behavior, microstructural evolution, comprehensive mechanical properties of WC-based ceramics fabricated by oscillatory pressure sintering was investigated in this work. The introduction of VC/Cr3C2 significantly controlled the size of WC grains and regulated the distributed uniformity of ZrO2 and Al2O3 grains in the WC matrix. When the added contents of VC and Cr3C2 were 0.2 wt% and 0.8 wt% respectively, WC-based ceramics with the best comprehensive mechanical properties were achieved, in which their Vickers hardness, fracture toughness and bending strength were up to 29.15 GPa, 8.37 MPa m1/2 and 1513 MPa, respectively. Furthermore, the enhancement of mechanical properties was mainly attributed to the grain refining strengthening, the transformation of fracture modes and dislocation toughening.

Effects of TiC0.4 on microstructure and properties of WC composites

WC composites with 5 wt% TiC0.4 were fabricated by spark plasma sintering (SPS) at sintering temperature of 1400–1700 °C for 10 min under an external pressure of 50 MPa. It can be observed that the WC-5 wt% TiC0.4 composites mainly consisted of WC phase and non-stoichiometric (W1−x, Tix)Cn solid solution phase and the amount of WC dissolving in TiC0.4 increased with sintering temperature. The (W1−x, Tix)Cn solid solutions uniformly distributed around WC grains and formed a semi-coherency interface with WC, which restricted the growth of WC grains and enhanced mechanical properties of the WC-5 wt% TiC0.4 composites. The average grain size of WC (251.5 ± 201.6 nm) in WC-5 wt% TiC0.4 composite sintered at 1600 ℃ was considerably smaller compared to most of previously reported WC-based composites. The existence of high content of C vacancies in non-stoichiometric TiC0.4 raised remarkably the diffusion rate of W and Ti atoms in the sintering process of WC-5 wt% TiC0.4 composites in contrast with stoichiometric TiC. The WC-5 wt% TiC0.4 composite sintered at 1600 ℃ possessed the optimum properties, with the hardness of 21.9 GPa, fracture toughness of 7.6 MPa·m1/2, flexural strength of 612 MPa and compressive strength of 2.7 GPa. Moreover, it can be confirmed that the oxidation resistance of WC-5 wt% TiC0.4 composite at higher temperature outperformed that below 1218 ℃. In addition, the WC-5 wt% TiC0.4 composite sintered at 1600 ℃ showed higher high-temperature hardness, lower thermal conductivity and better resistance to oxidation than those of conventional WC-Co composites.

Laser powder bed fusion of cemented carbides by developing a new type of Co coated WC composite powder

The study addresses the issue of the absence of high-quality WC-Co composite powder for laser powder bed fusion and assessing the printability of the new powder in terms of densification, microstructure and mechanical properties. The fluidized bed chemical vapor deposition (FBCVD) combined with electroless plating process was adopted to make core-shell structured WC-Co composite powder. The excellent uniformity of Co and good powder flowability were achieved by tuning the size and distribution of Co catalyst during FBCVD and regulating their relationship to the subsequent electroless plating behavior. The newly developed composite powder exhibited excellent printability. The densification mechanism was largely dependent on the laser energy density. The liquid formed by the melting of Co was responsible for the densification at low laser energy density, while the Co-W-C ternary liquid resulted from the dissolution of WC into Co melt dominated the densification at high laser energy density. Microstructurally, the morphology and size of WC grains were insignificantly changed because of its non-participation with liquid formation at low laser energy density. The rectangular/triangular WC grain morphology similar to the traditional sintered was formed at high laser energy density because of the precipitation of WC from the Co-W-C ternary liquid. Affected by the different liquid formation processes, increasing laser energy density increased the relative density, promoted the W 2 C phase formation and decreased WC grain size, which remarkably improved the hardness and tribological properties of the printed cemented carbide.

Effects of Processing Parameters on the Microstructure and Mechanical Properties of Nanoscaled WC-10Co Cemented Carbide

This work was mainly focused on the processing-parameter-related microstructure and properties of ultrafine WC-10Co-0.4VC-0.5Cr3C2 cemented carbide. The samples were prepared via a spark plasma sintering (SPS) technique using nano WC and Co powders and the corresponding inhibitor VC and Cr3C2 powders. The influence of the processing process on the microstructure and mechanical properties of ultrafine-grained cemented carbide was investigated under different ball-milling times and sintering temperatures. The results showed that the grain size of WC decreased with increasing ball-milling time and decreasing sintering temperature and that the specific gravity of ε-Co increased with increasing ball-milling time. The hardness of cemented carbide increased with increasing ball-milling time and decreased with increasing sintering temperature due to the corresponding variation in grain size and the relative density of samples. The transverse fracture strength (TRS) was mainly affected by ball-milling time. The increase in ball-milling time led to decreased TRS values, mainly ascribed to the formation of WC particle agglomeration and the decreased WC-Co eutectic temperature. In addition, temperature changes were found to have little effect on TRS. The samples sintered at 1250 °C with a ball-milling time of 60 h had comprehensive mechanical properties. Their average grain size, relative density, hardness, and TRS were 355.5 nm, 95.79%, 2035.5 kg/mm2, and 2155.99 MPa, respectively.

Preparation and properties of Ni-coated WC powder and highly impact resistant and corrosion resistant WC-Ni cemented carbides

WC powders were uniformly coated by Ni nanoparticles through a combined chemical co-precipitation and subsequent high temperature hydrogen reduction strategy (abbreviated as CM-WCN), and then were consolidated by vacuum sintering at 1450 °C for 1 h to obtain WC-Ni cemented carbides. The microstructure and properties of the as-consolidated CM-WCN were investigated. The average grain size of WC in the consolidated CM-WCN was calculated to be in the range of 3.0–3.8 μm and only few pores were observed. A relative density of 99.6%, hardness of HRA 86.5 and bending strength of 1860 MPa were obtained for the CM-WCN-10wt.%Ni, and the highest impact toughness of 6.17 J/cm2 was obtained for the CM-WCN-12wt.%Ni, surpassing those of the hand mixed WC-Ni (HM-WCN) cemented carbides examined in this study and the other similar materials in the literature. CM-WCN cemented carbides possess excellent mechanical properties, due to their highly uniform structure and low porosity that could be ascribed to the intergranular-dominated fracture mode accompanied by a large number of plastic deformation tears of the bonding phase. In addition, the corrosion resistance of CM-WCN was superior to that of HM-WCN at the Ni content of 6-12 wt.%.

Effect of MWCNTs on microstructure and properties of WC-9Co gradient cemented carbides

WC-9Co-xMWCNTs (Multiwalled carbon nanotubes) gradient cemented carbides with cubic carbides free layer (CCFL) were prepared by powder metallurgy method. The effect of different MWCNTs content on the microstructure and mechanical properties of WC-9Co gradient cemented carbides have been studied. The microstructure and phase composition of WC-9Co-xMWCNTs composites were characterized by means of optical microscope, scanning electron microscopy (SEM) and X-ray diffraction (XRD). In addition, the hardness, fracture toughness, bending strength and friction coefficients were tested by Vickers indenter, universal testing machine and tribometer. The results showed that the MWCNTs could promote the growth of CCFL. The minimum grain size of WC was obtained in the WC-9Co-0.08 wt% MWCNTs composites and the sample possessed the highest hardness and bending strength, the lowest friction coefficient and the best wear resistance at the same time. The fracture toughness and relative density increased steadily together with the addition of MWCNTs. Besides, the mechanism of MWCNTs enhancing the alloys include bridge connection, crack deflection, pull-out and strengthening effect of the network structure.

Strengthening mechanism of cemented carbide containing Re

In the present study, the microstructural changes of WC hard phase, phase transition of Cobalt (Co) in the binder and grain boundary characteristics were investigated to interpret the strengthening mechanism of the cemented carbides containing Rhenium (Re). As the content of Re increased, the mean grain size of WC decreased from 0.95 μm to 0.43 μm. Re promoted the martensite transition of Co phase from face-centred cubic structure (fcc) to close-packed hexagonal structure (hcp) by lowering the stack fault energies, which stabilized the hcp-Co. Meanwhile, the addition of Re weakened the concentration of textures {0001}, which indicated the preferred textures {0001} disappeared and promoted the isotropy of WC grains. The number of special grain boundaries (especially the big angle grain boundaries and coincidence site lattice (Σ = 2)) increased obviously after Re addition. With the increase of Re content, hardness and transverse rupture strength (TRS) rose rapidly. Cemented carbide with 6 wt% Re displayed the topmost hardness of 1648.4 HV30 and TRS of 3690 MPa. The wear rate of cemented carbide with 6 wt% Re was approximately one-fifth of cemented carbide without Re addition. The excellent hardness, TRS and wear resistance of the cemented carbides were attributed to the Re induced synergistic strengthening effect of grain refinement, phase transition and formation of special grain boundaries.

Effects of Nb and NbC additives on microstructure and properties of WC-Co-Ni cemented carbides

Cemented carbides (WC-Co-Ni) with the addition of Nb and NbC respectively were prepared by the conventional powder metallurgy method. The microstructure and mechanical properties of the sintered samples were analyzed. The results indicated that the addition of Nb or NbC reduced the grain size of WC and Nb had a greater inhibition effect on WC grain growth than NbC. The transverse fracture strength of the samples first increased and then decreased with the increase of the amount of Nb and NbC, and reached 3120 MPa and 2850 MPa respectively when adding 1.0 wt% Nb and NbC. The hardness of cemented carbides showed an upward trend as the content of additives increased. The fracture toughness decreased with the increases of NbC and Nb contents respectively and the fracture toughness of NbC-added samples was lower than that of Nb-added samples. The impact toughness decreased in a mass with the increase of additives.