JP7161677B2 - WC-Based Cemented Carbide Cutting Tool and Surface-Coated WC-Based Cemented Carbide Cutting Tool with Excellent Fracture Resistance - Google Patents

Description

The present invention provides a WC-based cemented carbide cutting tool (also referred to as "WC-based cemented carbide tool") and a surface-coated WC-based cemented carbide cutting tool that exhibit excellent fracture resistance in interrupted cutting of alloy steel and the like. Regarding.

Since WC-based cemented carbide has high hardness and toughness, WC-based cemented carbide tools based on it exhibit excellent wear resistance and have a long life over long-term use. Known as a cutting tool.
However, in recent years, various proposals have been made to further improve the cutting performance and tool life of WC-based cemented carbide tools according to the type of work material, cutting conditions, and the like.

For example, in Patent Document 1, a hard phase containing tungsten carbide as a main component and an iron group element (including cobalt, and the cobalt content is preferably 8% by mass or more in the cemented carbide) are used as main components. In a cemented carbide comprising a binder phase, where A is the number of tungsten carbide particles and B is the number of tungsten carbide particles having one or less contact points with other tungsten carbide particles, B / A By satisfying ≦0.05, the plastic deformation resistance of the cemented carbide is improved, and as a result, the life of the WC-based cemented carbide tool is extended in continuous wet cutting of carbon steel and stainless steel. It is proposed to

In Patent Document 2, the Co amount is 10 to 13% by mass, the ratio of the Cr amount to the Co amount is 2 to 8%, and at least one of TaC and NbC is used, and the total amount of TaC and NbC is 0.2 to 0.5% by mass. In a WC-based cemented carbide tool having a hardness of 88.6 HRA to 89.5 HRA, the balance is made of WC, and the area ratio on the polished surface is 80% of the WC cumulative grain size, the diameter D80 and the cumulative grain size of 20 The ratio D80/D20 of the % diameter D20 is in the range of 2.0 ≤ D80/D20 ≤ 4.0, D80 is in the range of 4.0 to 7.0 μm, and the degree of WC adhesion c is 0.36 ≤ c It has been proposed that by setting the ratio to ≦0.43, adhesion of the work material can be prevented and chipping resistance can be improved in cutting difficult-to-cut materials such as stainless steel.

In Patent Document 3, in the WC-based cemented carbide tool, when the chemical composition of the WC-based cemented carbide is represented by WC-x mass % Co-y mass % Cr ₃ C ₂ -z mass % VC, 6 ≤ x ≤ 14, 0.4 ≤ y ≤ 0.8, 0 ≤ z ≤ 0.6, (y + z) ≤ 0.1x, and the WC adhesion C of the WC-based cemented carbide is C = 1-V When represented by _b ^α exp (0.391 L), the value V _b of the binder phase volume fraction of the WC-based cemented carbide in this formula is 0.11 ≤ V _b ≤ 0.25, and (WC particles The value L of the particle size distribution (standard deviation of the particle size distribution)/(average WC particle size) is within the range of 0.3 ≤ L ≤ 0.7, and the coefficient α has a value of 0.3 ≤ α ≤ 0.55 By using a WC-based cemented carbide having a satisfactory WC-adhesion degree C, a WC-based cemented carbide with improved fracture resistance and improved toughness without lowering hardness and rigidity in cutting Al alloys, carbon steel, etc. Carbide tools have been proposed.

In Patent Document 4, in the WC-based cemented carbide tool, when the WC-WC bonding interface length is L1 and the WC-Co bonding interface length is L2,
R>(0.82−0.086×D)×(10/V)
It has been proposed to improve the thermal plastic deformation resistance and toughness of WC-based cemented carbide tools in cutting Ni-based heat-resistant alloys by satisfying the following formula.
Note that R=(L1)/((L1)+(L2))
D: WC area average particle diameter (μm), in the range of 0.6≦D≦1.7.
Here, D is the grain size of WC when the area ratio of WC is 50%.
V: Bound phase volume (vol%), in the range of 9≤V≤14.

In Patent Document 5, in weight %, Cr or/and Cr compound: 0 to 4% (in terms of Cr), V or/and V compound: 0 to 4% (in terms of V), TaC: 0 to 2%, TiC: 0-2%,
N or/and N compounds: 0 to 1% (in terms of N), Co: 0.1 to 10%, WC and unavoidable impurities: balance, and a Co average of 0.06 to 30 nanometers It has a thickness (CFP), and during sintering, a high pressure of 3 atm to 200 atm is applied using gas as a pressure medium in part or all of the temperature range of 900°C to 1600°C during heating. WC—Co based cemented carbide parts for cutting tools with increased density have been proposed, and these WC—Co based cemented carbide parts preferably have an average WC grain size of 1 μm or less and a CFP of 0.06 to 30 nm. It is said that the toughness of ultrafine grained low Co cemented carbide parts in the range of can be increased.
However, CFP is Co average thickness (nm),
CFP = 0.58*A/(100-A)*R
A: Co (%), 2R: WC average grain size (nm).

Japanese Patent No. 6256415 JP 2017-88999 A JP 2017-148895 A JP 2017-179433 A JP-A-7-305136

According to the conventional WC-based cemented carbide tools proposed in Patent Documents 1 to 5, by controlling the number of contact points between WC-WC particles, the grain size of WC, the degree of WC adhesion, manufacturing conditions, etc., WC-based We are trying to improve the cutting performance and tool characteristics of cemented carbide tools.
However, with the above-mentioned conventional tools, in interrupted cutting such as end milling of alloy steel, crack extension at the interface of WC-WC particles or crack generation due to stress concentration in the binder phase may cause chipping. The occurrence could not be sufficiently suppressed, so the tool life was short-lived.

The present inventors focused on the morphology of the binder phase of WC-based cemented carbide in order to develop a WC-based cemented carbide tool that exhibits excellent fracture resistance in interrupted cutting such as end milling of alloy steel. As a result of intensive research, the following findings were obtained.

The WC-based cemented carbide tools shown in Patent Documents 1 to 4 have been improved mainly by focusing on WC particles, and the WC-based cemented carbide tools shown in Patent Document 5 have mainly focused on CFP. However, the present inventors changed their point of view from the conventional technology and conducted repeated research focusing on the morphology of the binder phase, and found that fine binder phase particles (mainly are Co particles), by adjusting the sintering conditions so that the circularity is within the range of 0.3 to 0.6, sintering of the WC-based cemented carbide Sometimes, the binder phase particles wrap around the WC particles, and the binder phase is uniformly present in the WC-based cemented carbide, improving the toughness of the WC-based cemented carbide, and cracking occurs due to the load during cutting. Alternatively, since the propagation and progress of the generated cracks in the WC-based cemented carbide are suppressed, the occurrence of defects is suppressed, and the aggregates of WC particles in the WC-based cemented carbide are reduced. Therefore, the inventors have found that the occurrence of defects originating from this is reduced.
In other words, for the fine binder phase particles of the binder phase of the WC-based cemented carbide, a WC-based cemented carbide tool having a circularity within the range of 0.3 to 0.6 is used for intermittent cutting of alloy steel, etc. It was found that when used for machining, the life of the tool can be extended due to improved toughness and fracture resistance.

The present invention has been made based on the above findings,
"(1) In a WC-based cemented carbide cutting tool based on a WC-based cemented carbide,
The composition of the WC-based cemented carbide contains 6 to 14% by mass of Co and 0.1 to 1.4% by mass of Cr ₃ C ₂ as binder phase forming components, and the balance is WC and unavoidable impurities. , where A10 is the particle area at 10% of the total number of binder phase particles measured on the cross section of the WC-based cemented carbide, the average roundness of the fine binder phase particles having an area of A10 or less is 0.3 to A cutting tool made of WC-based cemented carbide, characterized by being within the range of 0.6.
(2) The WC-based cemented carbide further contains at least one selected from TaC, NbC, TiC, ZrC and VC in a total amount of 4% by mass or less. A WC-based cemented carbide cutting tool as described.
(3) Surface-coated WC-based cemented carbide cutting, characterized in that a hard coating layer is formed on at least the cutting edge of the WC-based cemented carbide cutting tool according to (1) or (2). tool. ”
It is characterized by
The contents of Cr ₃ C ₂ , TaC, NbC, TiC, ZrC, and VC in (1) and (2) above are the amounts of Cr, Ta, Nb, and Ti measured on the cross section of the WC-based cemented carbide. The amount, Zr amount, and V amount are all converted to carbide values.

The WC-based cemented carbide tool and the surface-coated WC-based cemented carbide cutting tool of the present invention contain Co, Cr ₃ C ₂ , or further TaC, NbC, TiC, which are components of the WC-based cemented carbide constituting the substrate. , ZrC, and VC have a specific composition range, and when the particle area of the binder phase grains in the WC-based cemented carbide at a cumulative 10% grain size is A10, fine binder phase particles having an area of A10 or less Since the average roundness is in the range of 0.3 to 0.6, the binder phase particles wrap around the WC particles in the WC-based cemented carbide, and the binder phase is uniformly present. , the toughness of the WC-based cemented carbide is improved, and as a result, the occurrence of cracks due to the load during cutting, or the propagation and progress of the generated cracks in the WC-based cemented carbide is suppressed. , chipping resistance is improved.
In addition, since the aggregates of WC particles are reduced in the WC-based cemented carbide, the occurrence of defects originating from such aggregates is also reduced.
Therefore, the WC-based cemented carbide tool and the surface-coated WC-based cemented carbide cutting tool of the present invention have improved toughness and fracture resistance in interrupted cutting such as end-milling of alloy steel, resulting in a long tool life. is planned.

The present invention will be described in detail below.

Co:
Co is contained as a main binder phase forming component of the WC-based cemented carbide, but if the Co content is less than 6% by mass, sufficient toughness cannot be maintained, while the Co content exceeds 14% by mass. When the Co content in the WC-based cemented carbide is 6 to 14% by mass, the Co content in the WC-based cemented carbide is set to 6 to 14% by mass. determined.

_{Cr3C2 :}
Cr ₃ C ₂ forms a solid solution of Cr in Co that forms the main binder phase, suppresses the growth of the WC phase that forms the hard phase, and refines the grain size of the WC phase, resulting in a WC-based cemented carbide. to a fine grain/uniform grain structure to increase toughness. However, this effect is insufficient when the Cr ₃ C ₂ content is less than 0.1% by mass. is precipitated, the toughness is lowered, and it becomes the starting point of chipping.
In the present invention, the upper limit of the Co content is 14% by mass, so the upper limit of Cr ₃ C ₂ is 1.4% by mass, which is 10% of the upper limit of the Co content.
Therefore, the Cr ₃ C ₂ content in the WC-based cemented carbide is set at 0.1 to 1.4% by mass.

TaC, NbC, TiC, ZrC, VC:
The WC-based cemented carbide of the present invention may further contain at least one selected from TaC, NbC, TiC, ZrC and VC in a total amount of 4% by mass or less.
All of Ta, Nb, Ti, Zr, and V have the effect of increasing the hardness by solid-solving in Co forming the main binder phase, but when the total content of them in terms of carbide exceeds 4% by mass , decrease the toughness due to carbide precipitation, and become the starting point of chipping.
Therefore, when at least one selected from TaC, NbC, TiC, ZrC and VC is contained as a component in the WC-based cemented carbide, the total content thereof should be 4% by mass or less. desirable.
The contents of Cr ₃ C ₂ , TaC, NbC, TiC, ZrC, and VC are the amounts of Cr, Ta, Nb, Ti, Zr, and V measured by EPMA on the WC-based cemented carbide. are all values converted into carbide.

Average Circularity of Fine Binder Phase Particles:
The average roundness of the fine binder phase particles of the WC-based cemented carbide referred to in the present invention refers to the individual fine binder phases identified by observation using a scanning electron microscope (SEM) for the cross section of the WC-based cemented carbide. It is the average value of the circularity obtained by obtaining the circularity of the particles.
Here, the fine binder phase particles are, for example, a binder phase (mainly composed of Co A SEM image in which the contrast of the phase) can be clearly separated from the contrast of the other phases is obtained, and the image is processed to determine the area and number of individual binder phase particles, and the area of the binder phase particle is taken as the horizontal axis, In addition, when the number of binder phase particles is taken as the vertical axis, a cumulative distribution is created by stacking the number of particles from the smaller binder phase area, and the particle area at 10% of the number accumulation is A10, the bond having an area of A10 or less. The phase grains are referred to as fine bonding phase grains.
Then, regarding the roundness of the fine binder phase particles, for example, using a scanning electron microscope (SEM), a cross section of the WC-based cemented carbide is observed at a magnification of 3000 to 4000 times to obtain an SEM image. By specifying and extracting the fine binder phase particles in the SEM image and measuring using the image analysis software ImageJ, the circularity of each fine binder phase particle can be determined.

More specifically, it is as follows.
When n fine binder phase particles are identified in one observation field of the cross section of the WC-based cemented carbide, the individual fine binder phase particles are numbered 1 to n, and the fine binder phase particles numbered 1 to n. are the areas of A ₁ to A _n , respectively, and the perimeters of the fine binder phase particles numbered 1 to n are L ₁ to L _n , the circularity C _m of the fine binder phase particles numbered m is
_Cm = _4π x _Am / ^Lm2
defined by
Then, the values of C ₁ to C _n are obtained with m=1 to n, and the average values C _{1 to n of} these C ₁ to C _n are obtained. It becomes the circularity of the phase particles.
Then, in a plurality of observation fields (for example, 10 observation fields), the roundness of the fine binder phase particles in each observation field is obtained, and the average value of these is the value of the WC-based cemented carbide referred to in the present invention. The average circularity of the fine binder phase particles in the cross section.
As is clear from the definition of circularity, the closer the circularity or average circularity value is to 1, the closer the shape of the fine binder phase grains of the WC-based cemented carbide is to a perfect circle. approaches 0, the shape of the fine binder phase particles becomes elongated instead of circular. It can be said that it is an index.

In the present invention, the average circularity of the fine binder phase particles is set within the range of 0.3 to 0.6 for the following reasons.
When the average circularity of the fine binder phase particles in the WC-based cemented carbide is less than 0.3, the fine binder phase particles wrap around the WC particles more, but on the other hand, the WC-WC particles are separated from each other. As the length of the contact interface becomes shorter, stress concentration occurs at the tips of the fine binder phase particles, reducing the resistance to plastic deformation. Since the voids become starting points for deformation and fracture of the WC-based cemented carbide tool, the toughness, chipping resistance, etc. are lowered.
On the other hand, when the average roundness of the fine binder phase particles exceeds 0.6, the fine binder phase particles do not sufficiently wrap around the WC particles, resulting in a decrease in toughness and abnormal damage such as chipping. easier to do.
Therefore, in the present invention, the average circularity of the fine binder phase particles is set within the range of 0.3 to 0.6.
As a result, in interrupted cutting such as end milling of alloy steel, the toughness is improved, the occurrence of chipping is suppressed, and the life of the cutting tool can be extended.

The WC-based cemented carbide tool of the present invention can be produced, for example, by the following steps.
First, a raw material powder consisting of WC powder, Co powder, and Cr ₃ C ₂ powder having a predetermined average particle size, or, if necessary, TaC powder, NbC powder, TiC powder, ZrC powder, and VC powder. Raw material powders containing one or more kinds of powders are blended and mixed so as to have a predetermined composition to prepare a mixed powder.
Next, the mixed powder is molded to produce a compact, and the compact is placed in a vacuum atmosphere at a liquid phase appearance temperature of the binder phase (depending on the composition of the compact, but generally 1300 to 1360 ° C.), a step (hereinafter referred to as a cycle step) is repeated about 10 to 30 times, and then sintering is performed by holding at a temperature of 1360 to 1500 ° C. for a predetermined time. to produce a WC-based cemented carbide.
By performing a cycle process under conditions where the temperature is repeatedly raised and lowered with the liquid phase appearance temperature of the binder phase sandwiched between them, fine bonding mainly composed of Co with an average circularity of 0.3 to 0.6 is formed between WC grains. Phase particles are formed.
Then, the WC-based cemented carbide can be machined and ground to produce a WC-based cemented carbide tool having a desired size and shape.

In the WC-based cemented carbide tool produced by the above process, the average roundness of the fine binder phase particles of the WC-based cemented carbide is in the range of 0.3 to 0.6, and the binder phase is formed around the WC particles. It wraps around and the binder phase comes to exist uniformly in the WC-based cemented carbide.
As a result, the toughness of the WC-based cemented carbide is improved, and the generation of cracks due to the load during cutting, or the propagation and propagation of the generated cracks in the WC-based cemented carbide, is suppressed, resulting in breakage resistance. improve sexuality.
Furthermore, since the aggregates of WC particles are reduced, the occurrence of defects originating from such aggregates is reduced.

Further, at least the cutting edge of the WC-based cemented carbide tool is coated with a hard coating such as Ti--Al-based, Al--Cr-based carbides, nitrides, carbonitrides, or Al ₂ O ₃ by PVD, CVD, or the like. A surface-coated WC-based cemented carbide cutting tool can be produced by forming a coating by a film method.
In the production of the surface-coated WC-based cemented carbide cutting tool, the type of the hard coating and the method of forming the hard coating may be those already well known to those skilled in the art. not something to do.

The WC-based cemented carbide tool and the surface-coated WC-based cemented carbide tool of the present invention will be specifically described with reference to examples.

<<WC-based cemented carbide tool of the present invention>>
(a) First, WC powder having an average particle size (d50) of 0.8 to 4.0 μm shown in Table 1 and an average particle size (d50) of 1.0 to 3.0 μm shown in Table 1 were used as powders for sintering. 0 μm Co powder, Cr ₃ C ₂ powder, TaC powder, NbC powder, TiC powder, ZrC powder and VC powder are prepared.
These powders were blended so as to have the composition shown in Table 1 to prepare a powder for sintering.
Table 1 shows the composition (% by mass) of various powders.

(b) The sintering powder blended in the formulation shown in Table 1 is wet-mixed in a ball mill for 72 hours, dried, and then press-molded at a pressure of 100 MPa to produce a compact having a predetermined shape. did.

(c) Then, the inside of the furnace is set to a vacuum atmosphere of 10 ¹ Pa or less, and the conditions shown in Table 2, that is, the appearance temperature of the liquid phase of the binder phase (depending on the composition of the compact, but generally 1300 to 1360 ° C. ), the cycle step was performed under the condition that the temperature was repeatedly raised and lowered 10 to 30 times.

(d) Subsequently, the temperature is raised to 1,360 to 1,500° C. under the conditions shown in Table 3 in a vacuum atmosphere of 10 ¹ Pa or less, and the WC-based cemented carbide is produced by maintaining the same temperature for a predetermined time and sintering. did.

(e) Next, the WC-based cemented carbide is machined and ground, and WC-based cemented carbide tools 1 to 10 (hereinafter referred to as present invention tools 1 to 10) having an insert shape of AOMT123608PEER and XDGX175008PDER WC-based cemented carbide tools 11 and 12 having an insert shape (hereinafter referred to as inventive tools 11 and 12) were produced. Table 4 shows the production conditions and composition of the tool of the present invention.

<<WC-based cemented carbide tool of comparative example>>
For comparison, WC-based cemented carbide tools 1 to 12 of comparative examples (hereinafter referred to as comparative tools 1 to 12) were produced.
The manufacturing process is that in the manufacturing process of the present invention tools 1 to 5 and 11, the cycle process (c) is not performed, and sintering is performed under normal conditions, and the present invention tools 6 to 10 and 12, in the cycle step (c) above, treatment was performed outside the recommended conditions of the present invention.

That is, the comparative tools 1 to 5 and 11 shown in Table 5 were obtained by wet-mixing the sintering powder blended in the composition shown in Table 1 in a ball mill for 72 hours, drying, and press molding at a pressure of 100 MPa. and sintered under normal conditions of heating temperature: 1360° C. or higher and 1500° C. or lower and heating and holding time: 30 to 120 minutes in a vacuum atmosphere to obtain a WC-based cemented carbide sintered body. were machined and ground, Comparative Example Tools 1 to 5 had an insert shape of AOMT123608PEER, and Comparative Example Tool 11 had an insert shape of XDGX175008PDER.
Comparative tools 6 to 10 and 12 shown in Table 5 were obtained by wet-mixing sintering powders blended in the formulation shown in Table 1 for 72 hours in a ball mill, drying, and press-molding at a pressure of 100 MPa. After producing a round bar compacted body, the step (c) was performed under the conditions shown in Table 2, and then the heating temperature was 1360°C or higher and 1500°C or lower, and the heating and holding time was 30 to 120 minutes, vacuum. A WC-based cemented carbide sintered body was produced by sintering under normal conditions of an atmosphere, and this was machined and ground. It is an insert shape.

The contents of Co, Cr, Ta, Nb, Ti, Zr, and V, which are components of the cross sections of the WC-based cemented carbides of the present invention tools 1 to 12 and comparative example tools 1 to 12, were measured at 10 points by EPMA. and the average value was taken as the content of each component.
The contents of Cr, Ta, Nb, Ti, Zr, and V were calculated in terms of respective carbides.
Tables 4 and 5 show the respective average contents.

Next, the cross sections of the WC-based cemented carbides of the present invention tools 1 to 12 and the comparative example tools 1 to 12 were examined using a scanning electron microscope (SEM) at a magnification of 3000 to 4000 times. Observing the SEM image with an image size of 120 × 96 mm and a pixel number of 1280 × 1024 pixels, the image is processed, and the area and number of individual binder phase particles in one observation field are obtained, and the binder phase particles A cumulative distribution of binder phase particles is created with the area of the abscissa and the number of binder phase particles on the ordinate, and the particle area at a cumulative number of 10% is A10, and the fine binder phase particles having an area of A10 or less , the circularity of individual fine binder phase particles was measured using image analysis software ImageJ, and the average value of the circularity of the individual fine binder phase particles in the one observation field was obtained.
From the relationship between the observation magnification and the number of pixels, the minimum bonded phase area is 977 nm ² when observed at 3000×, and 549 nm ² when observed at 4000×. Further, the observation field magnification was selected so that 150 to 400 bonded phase particles were included in the field of view. In the present invention, each individual binder phase separated by WC grains is regarded as one grain.
Then, by further averaging the average values of the respective roundness obtained in the ten observation fields, the average roundness of the fine binder phase grains in the cross section of the WC-based cemented carbide was calculated.
Tables 4 and 5 show the A10 value and the average roundness value.

Next, a hard coating layer having an average layer thickness shown in Table 6 was formed by PVD on the cutting edge surfaces of the tools 1 to 10 of the present invention and the comparative tools 1 to 10, and the surface-coated WC-based cemented carbide of the present invention was formed. Alloy cutting tools (hereinafter referred to as "coated tools of the present invention") 1 to 10 and comparative surface-coated WC-based cemented carbide cutting tools (hereinafter referred to as "comparative coated tools") 1 to 10 were produced.
Each of the above coated tools was clamped to the tip of a tool steel cutter with a cutter diameter of 25 mm with a fixing jig, and the following dry shoulder cutting test, which is a type of high-feed interrupted cutting of alloy steel, was performed. did.

Cutter diameter: 25 mm,
Work material: JIS/SCM440, block material with a width of 100 mm and a length of 400 mm,
Cutting speed: 200 m/min,
radial cut: 5 mm,
axial cut: 3 mm,
Feed amount per blade: 0.3 mm/blade,
In the cutting test, the cutting length was measured until the flank wear width reached 0.2 mm, and the state of wear of the cutting edge after the cutting test was observed.
Table 7 shows the results of this test.

In addition, the present invention tools 11 and 12 and the comparative example tools 11 and 12 were both clamped to the tip of a tool steel cutter having a cutter diameter of 40 mm with a fixing jig, and a type of high-feed intermittent cutting of an aluminum alloy shown below was performed. A wet shoulder cutting test was carried out. The flank wear width of the cutting edge was measured and the state of wear of the cutting edge was observed.
Cutter diameter: 40mm,
Work material: JIS A7075, block material with a width of 100 mm and a length of 400 mm,
Cutting speed: 500 m/min,
radial cut: 6 mm,
axial cut: 30 mm,
Single blade feed amount: 0.15 mm/blade,
In the cutting test, the cutting length was measured until the flank wear width reached 0.2 mm, and the state of wear of the cutting edge after the cutting test was observed.
Table 8 shows the results of the cutting test.

According to the test results shown in Tables 7 and 8, the tool of the present invention and the coated tool of the present invention exhibit excellent wear resistance without causing chipping, whereas the comparative example tool and the comparative tool It can be seen that coated tools have a short tool life due to chipping.

As described above, the tool of the present invention and the coated tool of the present invention exhibit excellent chipping resistance when subjected to interrupted cutting of alloy steel, etc., but when applied to other work materials and cutting conditions, It is expected to exhibit excellent cutting performance over long-term use and to extend tool life.

Claims (3)

In a WC-based cemented carbide cutting tool based on a WC-based cemented carbide,
The composition of the WC-based cemented carbide contains 6 to 14% by mass of Co and 0.1 to 1.4% by mass of Cr ₃ C ₂ as binder phase forming components, and the balance is WC and unavoidable impurities. , where A10 is the particle area at 10% of the total number of binder phase particles measured on the cross section of the WC-based cemented carbide, the average roundness of the fine binder phase particles having an area of A10 or less is 0.3 to A cutting tool made of WC-based cemented carbide, characterized by being within the range of 0.6. The WC according to claim 1, wherein the WC-based cemented carbide further contains at least one selected from TaC, NbC, TiC, ZrC and VC in a total amount of 4% by mass or less. Cemented carbide cutting tool. A surface-coated WC-based cemented carbide cutting tool according to claim 1 or 2, wherein a hard coating layer is formed on at least the cutting edge of the WC-based cemented carbide cutting tool.