WC Grain Growth Research Articles

Co첨가에 의한 WC의 비정상입성장

Co첨가에 의한 WC의 비정상입성장

Mechanical properties of WC–WB–W2B composites prepared by reaction sintering of B4C–W–WC powders

Abstract Composites of WC–WB–W 2 B with no metallic binder were prepared by the reaction sintering of a B 4 C–W–WC (mole ratio 1:5:80) powder mixture at sintering temperatures between 1500 and 1900 °C using resistance-heated hot pressing. WB, W 2 B and a part of WC in the composites were formed by the solid-state reaction between B 4 C and W. Dense sintered bodies were obtained at and above 1650 °C, in which small aggregates composed of WB and W 2 B were scattered in WC matrices. The rapid grain growth of WC occurred over a temperature range between 1650 and 1700 °C, and correspondingly resulted in decreases of both the hardness and fracture toughness. The sintering temperature 1650 °C was the most suitable for preparing dense sintered bodies with combined high values of Young's modulus, hardness and fracture toughness.

Microstructures of binderless tungsten carbides sintered by spark plasma sintering process

Pure WC was sintered by spark plasma sintering (SPS) process for a binderless cemented carbide application. The relative density of spark plasma sintered WC was over 98% when the SPS temperature was 1700 °C under 50 MPa pressure. Grain growth of WC could be suppressed with full densification by shortening sintering time. When the initial WC powder size was varied from 0.57 to 4.06 μm, the sintered density decreased with decreasing WC powder size. However, WC with an initial powder size of 0.57 μm could be sintered to densification by addition of free carbon. The higher amount of surface oxide in the finer WC powder is considered to have caused decarbonization during the sintering process. For WC powders of 4.06 μm, abnormal grain growth occurred when the sintering time was over 1 min if the sintering temperature was over 1700 °C. Also, with the sintering temperature and sintering time where no abnormal grain growth occurred, abnormal grain growth occurred by addition of carbon. This result shows that the abnormal grain growth in WC sintered by SPS process can be controlled by carbon addition. The abnormal grain growth in sintered WC somewhat increased fracture toughness by crack deflection.

Preparation and Mechanical Properties of Nanostructured Tungsten Carbide Alloys Strengthened by Carbon Nanotubes

ABSTRACTA novel approach for the synthesis of carbon nanotubes strengthened nanostructured tungsten carbide was investigated, in which nanophase tungsten powders are carburized by C2H2 instead of CO and a fraction of decomposed carbons were in situ converted to nanotubes. In this way, the composite powders of nanocrystal WC-Co and carbon nanotubes have been in situ prepared. The composite WC-Co powders were then hot pressed into bulk alloy which shows a exceptionally high microhardness up to 3307 kg/mm2. It is proposed that carbon nanotubes with extra high Young's modulus (1.8 Tpa) play both roles on strengthening the composite matrix and prohibiting growth of WC grains, which results in the great improvement of the mechanical properties of the samples. The average grain size of the prepared WC-Co hard alloys was estimated to be less than 100 nm. The effect of hot press temperature on the mechanical properties of the prepared alloys was also studied in detail.

Production of gradient tungsten carbide-cobalt materials by electrophoretic deposition

Cemented tungsten carbides have received much attention because of their superior characteristics. Traditional cemented tungsten carbides usually contain 3–30 wt% binder phase. In this paper, WC with low Co concentration less than 3 wt% is studied using traditional powder metallurgy. The binder phase has tremendous effect on sinterability of WC. High sinterability and high hardness can be achieved for the WC (0.7 μm) with 0.5 wt% Co. Abnormal grain growth (AGG) is often observed in sintering WC with small amount of Co. It seems that AGG is affected by the concentration of Co and a range of Co concentrations may exist for the large amount of AGG. To control the grain size, VC is added to inhibit the grain growth of WC. It is observed that the hardness is affected by the amount of addition of VC. Controlling the ratio of C/W less than unity at low Co concentrations will result in the production of W2C phase. The hardness of WC–Co is affected by the amount of W2C phase in the sample and W2C is stable during the normal cooling process.

Rare earth doped new cemented carbide with Ni-Co binder for mining

A method, doping WC with La(NO3)3, of producing cemented carbide with rare earth was introduced. The effects of lanthanum on the mechanical properties and microstructure of WC-9(Co-75%Ni) cemented carbide were studied and a rock drilling experiment was carried out. The experimental results show that both transverse rupture strength (TRS) and hardness of WC-9(Co-75%Ni) rare earth cemented carbides can match that of WC-9Co cemented carbide, when La2O3/(Co + Ni) ratio is 0.3%, the abnormal growth of WC grain in the cemented carbide can be restrained effectively, the homogeneity of grain size in microstructure and the wear resistance are improved, which can be matchable to that of WC-9Co cemented carbide for mining.

Anisotropic grain growth based on the atomic adsorption model in WC-25 pct Co alloy

The process of triangular prism formation and abnormal grain growth of WC was modeled using pseudo-Monte-Carlo simulation based on atomic adsorption and the coalescence mechanism. Grains of WC evolved into a triangular prism shape due to {10 % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9vqpe0x% c9q8qqaqFn0dXdir-xcvk9pIe9q8qqaq-dir-f0-yqaqVe0xe9Fve9% Fve9qapdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabGymayaara% aaaa!39F1! $$\bar 1$$ 0} and {1 % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9vqpe0x% c9q8qqaqFn0dXdir-xcvk9pIe9q8qqaq-dir-f0-yqaqVe0xe9Fve9% Fve9qapdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaacbaGab8Nmay% aaraaaaa!39F2! $$\bar 2$$ 10} planes of fast growth rate. Coalescence of {10 % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9vqpe0x% c9q8qqaqFn0dXdir-xcvk9pIe9q8qqaq-dir-f0-yqaqVe0xe9Fve9% Fve9qapdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabGymayaara% aaaa!39F1! $$\bar 1$$ 0} and {1 % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9vqpe0x% c9q8qqaqFn0dXdir-xcvk9pIe9q8qqaq-dir-f0-yqaqVe0xe9Fve9% Fve9qapdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabGymayaara% aaaa!39F1! $$\bar 1$$ 00} planes subsequent to the anisotropic evolution was the main reason for the abnormal grain growth. The probability of coalescence computed by the Monte-Carlo method agreed well with a theoretical prediction. Experimental evaluation of the computational model was made in sintered WC-25 wt pct Co alloy. The experimental alloy was made with WC powder of different particle size, 0.8 µm and −325 mesh, respectively, and with two different sintering conditions: solid-phase sintering and liquid-phase sintering. The sample made from the coarse powder (−325 mesh) showed the same morphological characteristics as those of the original milled state, whereas the sample made from the fine powder (0.8 µm) assumed a triangular prism shape quickly during solid-phase sintering. The anisotropic growth process of the latter sample could be explained by using the adsorption and coalescence model.

High resolution transmission electron microscopy study in VC-doped WC–Co compound

Microstructure evolution in VC-doped WC–Co was investigated using high-resolution transmission electron microscopy (HRTEM) associated with X-ray energy dispersive spectroscopy (EDS) with a special interest in WC/Co and WC/WC boundaries. It was found that the morphology of carbide grains changed largely by the addition of VC. The WC/Co interfaces tend to form facetting with fine multi-steps of (0001) and {} habits by VC-doping. In addition, the facetting morphology of WC/Co interfaces was confirmed to be already formed in solid state from an examination with a quenched compound from 1200˚C, which is below the eutectic temperature of 1320˚C between WC and Co system. EDS analysis with the sub-nano scale probe revealed that the doped V was strongly concentrated to the two habits. However, the amount of concentrated V was different among them, i.e. more at (0001) habit than at {} habits. V is considered to be concentrate at the boundary during grain growth to accompany the migration of the two habits because most of the doped V solves into the Co-phase and not into WC grains. Thus it can be supposed that the retardation of the grain growth of WC grains is due to the concentration of V at the migration front of the two habits.Meanwhile, WC/WC boundaries were found to be directly in contact each other and free from the second phase such as the amorphous phase whereas the segregation of Co and also V could be detected by EDS analysis. This fact suggests that the grain boundary migration between the adjacent WC grains may be mainly controlled by the solid–solid diffusion. © 2000 Elsevier Science Ltd. All rights reserved.

Air showers reduce lint defects

Fine grained WC-Co-Ni cemented carbides with a low binder content have been successful manufactured via the powder metallurgy method. The WC-Co-Ni composite powder with homogeneous distributions of Co and Ni was synthesized by chemical co-precipitation with the raw materials of WC powder, oxalic acid and chlorides of Co and Ni. In this study, the effects of cobalt and nickel contents on the properties of cemented carbides were investigated systematically. The experimental results demonstrated that the alloy prepared by vacuum sintering had uniform grain size distribution and no abnormal growth of WC grains. When the cobalt content was 4 wt% and 5 wt%, the obtained composites almost completely consolidated with excellent hardness and fracture toughness. Among them, for the sample WC-4 wt%Co, the relative density could reach 99.37%, and the Vickers hardness and fracture toughness were 2010 HV30 and 8.55 MPa·m1/2, respectively. When Ni was added to replace part of Co, the relative density of WC-Co-Ni decreased and the fracture toughness was improved without basically sacrificing the hardness. For the sample WC-2 wt%Co-2 wt%Ni, the hardness decreased to 1921 HV30, while the fracture toughness increased to 8.97 MPa·m1/2.

Consolidation of titanium tri-aluminide by spark plasma sintering: K.Kobayashi et al. (National Industrial Research Inst., Nagoya, Japan.) J. Jpn Soc. Powder Powder Metall., vol 44, no 6, 1997, 554–559. (In Japanese.)

Pure WC was sintered by spark plasma sintering (SPS) process for a binderless cemented carbide application. The relative density of spark plasma sintered WC was over 98% when the SPS temperature was 1700 °C under 50 MPa pressure. Grain growth of WC could be suppressed with full densification by shortening sintering time. When the initial WC powder size was varied from 0.57 to 4.06 μm, the sintered density decreased with decreasing WC powder size. However, WC with an initial powder size of 0.57 μm could be sintered to densification by addition of free carbon. The higher amount of surface oxide in the finer WC powder is considered to have caused decarbonization during the sintering process. For WC powders of 4.06 μm, abnormal grain growth occurred when the sintering time was over 1 min if the sintering temperature was over 1700 °C. Also, with the sintering temperature and sintering time where no abnormal grain growth occurred, abnormal grain growth occurred by addition of carbon. This result shows that the abnormal grain growth in WC sintered by SPS process can be controlled by carbon addition. The abnormal grain growth in sintered WC somewhat increased fracture toughness by crack deflection.

Anisotropic atomic packing model for abnormal grain growth mechanism of WC-25wt.%Co alloy

During liquid phase sintering, cemented carbide particles grow into either faceted or non-faceted grain shapes depending on ally system. In case of WC-Co alloy, prism-shape faceted grains with (0001) planes and {l_brace}1{bar 1}00{r_brace} planes on each face are observed, and furthermore an abnormal grain growth has been reported to occur. When abnormal grain growth occurs in WC crystals, dimension ratio, R, of the length of the side of the triangular prism face to the height of the prism is higher than 4 whereas that for normal grains is approximately 2. Abnormal grain growth in this alloy is accelerated by the fineness of starting powders and by high sintering temperature. To account for the mechanism of the abnormal grain growth, there are two proposed models which drew much research attention: nucleation and subsequent carburization and transformation of {eta} (W{sub 3}Co{sub 3}C) phase into WC, and coalescence of coarse WC grains through dissolution and re-precipitation. Park et al. proposed a two-dimensional nucleation theory to explain the abnormal grain growth of faceted grains. There are questions, however, on the role of {eta} phase on abnormal grain growth. The mechanism of coalescence of spherical grains as proposed by Kingery is also unsuitable for facetedmore » grains. So far theories on abnormal grain growth do not provide a satisfactory explanation on the change of R value during the growth process. In the present work a new mechanism of nucleation and growth of faceted WC grains is proposed on the ground of anisotropic packing sequence of each atom.« less

粗粒ＷＣ‐Ｃｏ合金の性質に及ぼすＶＣ添加の影響

Microstructures and mechanical properties of the coarse-grained low-carbon WC-lomass%Co alloy having carbide grain size of 1.5-2.0 μm were mainly studied in relation to the amount of additional VC up to 5mass% in binder. It was found that the carbide grain size became uniform with increasing the amount of VC, because of suppression of the anomalous grain growth of WC. It was also found that transverse-rupture strength of the alloy was improved with increasing the amount of VC up to about 2-3mass%; however, it sharply decreased with additional amount of VC over about 3mass%. The phenomenon of this strength decrease, being never observed in micro-grained alloy, was attributed to the fact that (W, V)C phases crystallized so largly in the size in coarse-grained alloy, in contrast to micro-grained alloy, that it easily acted as a fracture source.

Life prediction methods for low-cycle torsional fatigue: Curioni, S., Freddi, A. and Caligiana, G. Proc. Conf. Testing of Metals for Structures, Naples, Italy, 29–31 May 1990, pp 162–173

Functionally graded WC-TiC-Co cemented carbides with a Co content gradient and not comprising the η-phase were prepared employing hot-pressing sintering technique by introducing pre-designed both gradients of Co contents and WC grain sizes. The effects of initial hard phase particle size distribution and sintering parameters on the microstructure and mechanical properties of functionally graded cemented carbides were investigated by fabricating coarse-particle, fine-particle and hybrid-particle (combining coarse-particle and fine-particle) functionally graded cemented carbides employing hot-pressing sintering technique. Various hot sintering temperatures (1325 ℃, 1350 ℃, 1375 ℃ and 1400 ℃) and soaking times (15 min, 30 min, 45 min, 60 min) were tested in order to determine the optimal parameters of hybrid-particle functionally graded WC-TiC-Co cemented carbides with the assistance of VC and Cr3C2 as grain growth inhibitors and PVP as dispersant. The experimental results showed that excellent mechanical properties are achieved for sintering at 1375 ℃ soaked for 45 min with a hardness of 1986 kgf/mm2, a TRS of 1752 MPa and a fracture toughness of 13.05 MPa m1/2. Hybrid-particle functionally graded WC-TiC-Co cemented carbides generated a good liquid-phase sintering at 1375 ℃ soaked for 45 min. Specimens sintering for 1325 ℃ and 1350 ℃ maintained the pre-designed Co gradient, whereas the specimens sintering for 1375 ℃ maintained a smaller Co gradient and the specimen sintering for 1400 ℃ had no Co gradient. The excessive grain growth of fine-grained WC resulted the WC size difference disappear of coarse-grain and fine-grain, which weaken the Co phase migration pressure from surface layer to core layer. Furthermore, Co liquid phase distribution behavior is normally related with temperature, soaking time and pressure. The five-layer structure developed in this paper provides the surface with exceptional combination of high wear resistance and high toughness, which is favorable for the application as metal cutting tools.

Study of the liquid‐phase sintering process by probabilistic models: Application to the coarsening of WC‐Co cermets

SUMMARYA new method using probabilistic models is used to study the growth of WC grains in WC‐Co cermets. Two different models are tested: a Boolean model and a two‐colour mosaic model. The Boolean Poisson model is the simplest for describing and predicting material evolution, and depends only on two independent parameters. They allow the estimation of the connectivity numbers and, moreover, are used to determine the type of reaction which controls the WC‐Co coarsening kinetics.

Relations between Transverse-Rupture Strength of WC-Co Cemented Carbides and Cooling Rate after Sintering

The WC-(10, 20, 30)%Co alloys were minutely vacuum-sintered, so that the defect acting as a fracture source in each alloy might almost consist of coarse WC grains smaller than about 20μ. Two sorts of cooling rates after sintering, about 15°and 0.5°C/min, were adopted in the temperature range from 1360°to 1300°C for 10%Co alloy, 1350°to 1300°C for 20%Co alloy and 1340°to 1300°C for 30%Co alloy, respectively. Two sorts of specimens different in cooling rates in each alloy were ground with a diamond wheel, and transverse-ruptured according to JIS. After the test, the dimension (2a) and location of coarse WC grains as a fracture source were measured on the ruptured surface.The results obtained were as follows: 1) The average transverse-rupture strength (σm), and also the external stress (σd) corresponding to σm were always higher in rapidly cooled specimen (R-specimen) than in slowly cooled specimen (S-specimen). 2) The 2a of R-specimen was generally smaller than that of S-specimen, showing that of an anomalous grain growth of WC also occurred during the time of cooling specimens, when the cooling rate was decreased. 3) The distance from the tension surface to the defect (Δt) of R-specimen was larger in 10%Co alloy than that of S-specimen. However, the difference in Δt was hardly observed in (20, 30)%Co alloys. It was found in a slowly cooled 30% Co alloy that the location of the defect was always on the domain boundary of binder phase. 4) The increase in Δm and σd due to increasing cooling rate was considered to be affected mainly by the increase in the strength of WC-Co matrix including that of the domain boundary, and partially by the changes in 2a and Δt.

Grain Size of WC in Sintered WC-VC-Co Alloys

The restriction effects of the additional VC on the grain growth of WC in WC-Co alloy were in detail investigated in relation to the grain size of starting WC powder, and Co and carbon contents of the alloy. The WC powder was prepared by heating the mixture of W powder (-0.5μ) and carbon black powder at 1000-1300°C for 1.5 hr in hydrogen atmosphere. The grain size of this WC powder was reduced to various sizes by ball-milling. WC-(0-2)%VC-(5-20)%Co alloys with various grain sizes and 'carbon contents were vacuum-sintered mainly at 1400°C for various times.The results obtained were as follows: (1) The restriction effect was found to be controlled almost by the ratio of VC/Co, and not by the ratio of VC/WC. Even under the same ratio of VC/Co, the effect was affected by the carbon content of the alloy. (2) When the mean grain size of starting WC powder exceeded a certain critical value, the addition of VC more than a definit value resulted in the normal grain growth of WC in VC contained alloys. However, in the case of the mean grain size smaller than the critical value, it resulted in the abnormal grain growth of WC (with fine grain size of WC in the matrix). For instance, in the usual WC powder having grain size larger than -0.3μ, addition of VC more than -5% in the binder checked the abnormal grain growth (mean grain size of WC in the matrix decreased with increasing amount of VC). However, in the fine grained WC powder having mean grain size smaller than -0.2μ, such a restriction method of adding VC was by this time invalid because of the occurrence of the abnormal grain growth, leading to the impossibility of obtaining micro-grained alloys. The above critical grain sizes (0.2-0.3μ) and the critical amount of VC were naturally considered to vary according to size distributions of the starting WC powder, sintering temperatures, Co contents, etc. (3) The three phase region and the compositions of the binder phase in WC-VC-Co alloys were also examined.

Effects of Addition Carbides on the Grain Size of WC-Co Alloy

The grain size of WC-20%Co alloy affected by the addition carbides such as TiC, VC, Cr3C2, ZrC, NbC, Mo2C, HfC and TaC was in detail investigated. Specimens were sintered mainly at 1400°C for 1 hr. The mean grain size of starting WC powder was about 0.6μ.Results obtained were as follows: (1) When the liquid phase was saturated by the addition carbides at sintering temperatures, the restriction effect of VC on the grain growth of WC was the largest, followed by Mo2C, Cr3C2, NbC, TaC, TiC, ZrC(≅HfC). In this case, there existed a strong correlation. between the restriction effect of addition carbides and the solubility limit in the liquid phase (or the formation free energy). (2) On the other hand, when the liquid phase contained a certain amount of dissolved metals of addition carbides, i.e., about 1.5at% for the starting Co, the effectiveness was in the following order; VC>NbC>TaC>TiC>Mo2C>Cr3C2>ZrC≅HfC. (3) Considering the restriction effect and the shape of carbides precipitated, VC addition was considered to be the most suitable for the grain growth inhibitation of WC, followed by Cr3C2, NbC and TaC.

Study on the Change of Grain Size of WC Powder during Ball Milling of Cemented Carbide

The mixing phenomena of WC and Co powders have not yet been made clear enough in spite of their importance in the Cemented Carbide industry. Therefore, in this paper the crushing of WC powders and the behaviour of their grain growth during sintering were examined using variousWC powders, i.e., coarse single crystal, coarse polycrystalline and medium single crystalline WC powders.The obtained results were as follows;(1) Coarse single crystal WC powders were crushed markedly by chipping in the early ball milling stage. There-after, average grain size of WC continued to decrease with the appearance of fine chipping powders. Therefore, the grain size distribution of the coarse single crystal WC powder grew wider with the increase of ball milling time.(2) Polycrystalline WC powders were crushed in the same way as the above mentioned (single crystal) in the early ball milling stage. However, the grain boundary destruction seemed to be caused after having been WC crushed into the definite size.(3) Single crystal WC powder of medium size were more difficult to be crushed with chipping than the coarse one.(4) The grain growth of coarse single crystal WC during sintering is more rapid than polycrystalline one because the size distribution of the former was wider than that of the latter. Moreover the average grain size of WC in alloys formed medium single crystal WC powders in coarser than that from coarse one, because the former was less crushed than the latter.(5) In sum, the crushbility of WC in ball milling and its grain growth in sintering did not only depend upon WC grain size, but also the manufacturing process.

Relations between Some Properties of Sintered WC-10%Ni Alloy and its Binder Phase Composition

Relations between basic properties of sintered WC-Co base alloys at the room temperature and the composition of the binder phase, that is, the carbon content of the alloys, have been investigated. It was found that the properties were strongly affected by the binder phase composition, although any harmful phase was not formed in-the structures of alloys. On the other hand, researches on the subject for sintered WC-Ni.alloys have never been carried out and it is still vague whether Co is superior to Ni or not as the binder metal of cemented carbides.Therefore, studies on the properties of the WC-10%Ni alloy in relation to the composition of the binder phase were carried out. The results were compared with those already known for WC-10%Co alloy, to get an accurate knowledge on the superiority of Co or Ni as the binder metal. Specimens were vacuum-sintered at mostly 1450°C for lhr. The carbon content of alloys was closely controlled. Results obtained are summarized as follows.(1) Sintering temperature of WC-10%Ni alloy was higher by about 70°C than that of 10%Co alloy. This shows that the temperatures at which the liquid phase is formed, are in this case higher by about 70°C than corresponding temperatures of WC-10%Co two phase alloys. (2) The two phase range in WC-10%Ni alloy extended from about 5.77 to 6.06%C in WC and the width of the range corresponded to about 0.3%C (the values in WC-10%Co alloy are about 6.04-6.22%C and 0.15-0.18%C, respectively). Based on the former result, it is clear that the free carbon phase is formed more easily in Ni-binding alloy than the other. (3) The amount of W dissolved in the binder phase varied abruptly from about 10% to 31% according to the carbon content of the two phase alloys (the value in Co-binding alloy is in the range from 2-3% to 9.10%). (4) Properties such as density, hardness, transverse-rupture strength, magnetic saturation and resistance to acidic solution, etc. showed regular changes in the phase range. These changes were explained by the composition changes in the binder phase. The maximam strength of the alloy was obtained at about the highest carbon side of the range ; however, the value was inferior to that of the Co-binding alloy. The reason may be that the content of the W dissolved in the binder phase in Ni-binding alloy is much higher than that of the other. The alloy having carbon content of less than 5.95% was found to be non-magnetic. (5) Aging phenomena taken place during annealing at temperatures as low as 800°C were not observed in the Ni-binding alloy. (6) The rapid grain growth of WC was observed in the high carbon alloys. (7) From these results, Co was confirmed to be by far superior to Ni as the binder metal of cemented carbides, except for a few cases.