JP5804380B2 - Cutting tool made of ultra high pressure sintered body - Google Patents

Description

The present invention relates to the cutting edge bonding strength of a cutting tool having an ultrahigh pressure sintered material such as a cubic boron nitride (hereinafter referred to as cBN) sintered body or a polycrystalline diamond (hereinafter referred to as PCD) sintered body. Regarding improvement.

In recent years, as a tool for processing molds used in the manufacture of casings for mobile phones, smartphones, etc., it exhibits high productivity and long life and is second only to PCD sintered bodies having the same hardness as diamond. Cutting tools such as inserts and end mills using cBN sintered bodies having hardness for cutting edges are provided.
However, the cBN sintered body and the PCD sintered body themselves are difficult and expensive to process, and the sintered body shape is limited to a disk shape, so that the tool shape cannot be freely formed, and its use is restricted. However, in recent years, the use of cBN sintered bodies and PCD sintered bodies has increased with the increase in the amount of difficult-to-cut materials used, despite the difficulty in tool processing. As a method for overcoming the price and workability, brazing the WC-based cemented carbide tool body, which is inexpensive and excellent in workability, and a cutting edge portion made of a cBN sintered body or PCD sintered body, Alternatively, the WC-based cemented carbide tool body and the cBN sintered body may be joined by diffusion bonding the WC-based cemented carbide tool body and the cBN sintered body or the PCD sintered body as a raw material. Or the cutting tool which joined the cutting-blade part which uses a PCD sintered compact as a raw material is provided.

  For example, in Patent Document 1, a substantially cylindrical chip in which a cBN sintered body layer and a cemented carbide layer are integrally formed, and a cemented carbide layer on the rear end side of the chip with the same axis as the chip are connected. An end mill having a cutting edge formed at the tip end portion of the tip, and an attachment shaft portion is formed at least on the tip end side of the tool body, and the outer diameter of the tip surface of the attachment shaft portion is The outer diameter of the rear end surface of the chip is the same as the outer diameter, and a joint portion is disposed between the rear end surface of the chip and the front end surface of the mounting shaft portion. With the bonding layer including the diffusion layer diffused to at least one of them, the life is long and stable without detaching the tip from the tool body, and the length of the neck is easily adjusted to adjust the processing depth. An adjustable end mill is disclosed There.

  Further, in Patent Document 2, the blade portion at the tip of the tool is substantially made of an ultra-high hardness sintered body, and a part of the cemented carbide material integrally sintered with the ultra-high hardness sintered body is a shank hole portion. Is a small-diameter end mill that is brazed and fixed using a Ni—Cr brazing material, an Ag—Cu—Ti brazing material, or an Ag—Cu—Zn brazing material as a brazing material, and the inside of the shank hole The tip end portion of the tool made of a super-hard sintered body tip, particularly when the ratio Dh / Dc of the circumscribed circle diameter Dh of the cemented carbide material portion inserted into the maximum diameter Dc of the blade portion is 2 or more, A small-diameter end mill having excellent cutting characteristics capable of high-precision and high-efficiency machining with high rigidity in the lateral direction of a portion from the blade portion to the neck portion and high attachment strength of the neck portion is disclosed.

JP 2007-268647 A JP 2004-268202 A

However, the end mills disclosed in Patent Document 1 and Patent Document 2 are said to provide a strong joint strength by using a Ni-based metal, but if Ni diffuses too much, the carbide shank and the cutting edge side super There existed a subject that the mechanical characteristic of a hard base material fell and it became a cause of breakage.
Moreover, in the Ag type brazing material disclosed in Patent Document 2, sufficient mechanical strength was not obtained due to the low mechanical strength of Ag.
Moreover, in the joining using the conventional brazing material, since the melting point is high, there is a problem that the cBN sintered body and the PCD sintered body are deteriorated at the time of joining.
Therefore, the technical problem to be solved by the present invention, that is, the object of the present invention, is to provide a cutting edge portion made of a cBN sintered body or a PCD sintered body joined via a joining alloy and a WC-based carbide. In a cutting tool made of an ultra-high pressure sintered body having a tool body, the cBN sintered body and the PCD sintered body may be deteriorated by heat at the time of joining as well as having excellent joining strength with little breakage from the joint. There is no need to provide a cutting tool made of ultra high pressure sintered body.

  Therefore, the present inventors have a cBN sintered body or a PCD sintered body (hereinafter simply referred to as a sintered body) made of a cutting blade and a WC-based cemented carbide tool body joined via a joining alloy. As a result of diligent research on improving the joint strength of the ultra high-pressure sintered body cutting tool, the following knowledge was obtained.

(1) In joining the sintered body cutting edge and the shank tip of the WC-based carbide tool body, the sintered body constituting the cutting edge is previously lined with a WC-based carbide support piece. deep. And after coating Cr in advance on the joint surface of the WC-base cemented carbide support piece and the WC-base cemented carbide tool body, a Ni-based joining alloy is inserted between the two and joined under predetermined conditions. Thereby, the Cr layer becomes a barrier for Ni diffusion, and it becomes possible to prevent excessive diffusion of Ni. Further, Cr is alloyed with W contained in the WC-based carbide to form a strong bonding layer between the WC-based carbide support piece and the WC-based carbide tool body and the bonding alloy. The present inventors have found that the Cr—W alloy does not need to be continuously present after the completion of the joining, and the presence of the Cr—W alloy can sufficiently contribute to the improvement of the joining strength.

(2) For the Cr layer, for example, the Cr layer can be obtained on the joint surface by electrolytically depositing chromic anhydride as a solution. At this time, if the Cr layer is too thick, Ni cannot be diffused into the WC-based cemented carbide, and a Ni diffusion layer that contributes to improving the bonding strength is not formed. I found. On the other hand, it was also confirmed that when the thickness is less than 0.1 μm, the original function of suppressing excessive diffusion of Ni cannot be sufficiently exhibited. That is, as the Cr layer is thickened, Ni diffusion is suppressed, and as the Cr layer is thinned, Ni diffusion increases. However, if the Cr layer is too thin, Ni is excessively diffused and the mechanical strength of the WC-based carbide is lowered. Therefore, it has been found that controlling the thickness of the Cr layer is a key factor for improving the bonding strength.

(3) As a result of repeating a number of must-sees based on hypotheses and verifications regarding the components contained in the bonded alloy, it is said that an alloy containing Ni-Cr-B-Si components and containing inevitable impurities including Fe has excellent bonding strength. I found out. In particular, it has been found that by adding B and Si to the bonding alloy, the melting point can be reduced, and deterioration of the sintered body can be prevented.

(4) Observing the state of the joint, as shown in FIG. 2, the Ni—Cr—B—Si alloy inserted as a joining alloy was melted, but Ni was formed on the carbide surface. Excessive diffusion is prevented by the Cr layer. It was confirmed that a Ni diffusion layer having a depth of 2 μm or more and 15 μm or less was formed on the joining surface of the WC-based cemented carbide support piece and the cemented carbide tool body of the cutting edge.

The present invention has been made based on the above findings,
“(1) A cutting blade portion composed of a cBN sintered body or a PCD sintered body lined with a WC-based cemented carbide support piece and a WC-based cemented carbide tool body are locally heated with a joining alloy interposed therebetween. In a cutting tool having joined joints,
The cutting edge part and the WC-based carbide tool body each have a Cr layer on the joint surface with the joint alloy,
The alloy composition obtained by measuring and averaging five points in the bonding layer between the Cr layers was Cr: 14-18 at%, B: 20-26 at%, Si: 1-5 at%, Ni: 32-40 at%, and the balance was Fe. A cutting tool characterized by being an inevitable impurity.
(2) The cutting tool according to (1), wherein an average layer thickness of the Cr layer is 0.1 to 1.0 μm.
(3) The Ni diffusion layer formed by diffusing the Ni component of the bonding alloy in the WC-based cemented carbide support piece and the WC-based cemented carbide tool body of the cutting edge, and the Cr layer. The cutting tool according to (1) or (2), wherein the total average layer thickness of the joint is 5 to 50 μm. "
It is characterized by.

The present invention is described in detail below.
In the present invention, a cutting tool is configured by joining a cutting edge portion made of a cBN sintered body or a PCD sintered body and a WC-based carbide tool body with a joining alloy interposed therebetween.
An example of the manufacturing method of this cutting tool is as follows, when using a cBN sintered compact as a raw material of a cutting edge part.
(A) 65 volume% cBN and the remaining TiN, TiCN, TiC, and Al ₂ O ₃ bonded phases are wet mixed in a ball mill for 24 hours using acetone.
(B) The obtained mixed powder is dried and then molded with a hydraulic press at a molding pressure of 100 MPa.
(C) The obtained molded body is heat-treated in vacuum at 1 × 10 ⁻² Pa, a temperature of 1000 ° C., and a holding time of 30 minutes to remove volatile components and components adsorbed on the powder surface.
(D) A compact and a cemented carbide base material are laminated, and typically subjected to ultra-high pressure and high temperature treatment under conditions of a pressure of 5 GPa, a temperature of 1500 ° C., and a holding time of 30 minutes to obtain a cBN sintered body.
(E) After grinding the upper and lower surfaces of the obtained cBN sintered body, a cBN sintered body disc is obtained.
(F) The cBN sintered compact disc is cut into a predetermined dimension with a wire electric discharge machine to obtain a cBN sintered compact for a cutting edge with a WC-based carbide support.
(G) Cr is coated in advance on the surface of the joint surface of the WC-based cemented carbide support piece of the cBN sintered compact and the WC-based cemented carbide tool body. For example, a Cr layer can be obtained on the carbide surface by electrolytically depositing chromic anhydride as a solution. If the Cr layer is too thick, the bonding alloy cannot be diffused into the WC-based cemented carbide support body and the WC-based cemented carbide tool body of the cBN sintered body piece, so 1.0 μm or less is preferable.
(H) The bonding alloy is weighed so as to have a predetermined composition and melted in a vacuum arc melting furnace to obtain a button-shaped ingot. This is hot-rolled into a plate shape, and further cold-rolled to obtain a thin plate having a predetermined thickness, for example, 50 μm.
(I) A thin plate-shaped bonding alloy obtained by the method (h), for example, Ni—Cr—B—Si, at the tip of the WC-based carbide tool body coated with Cr in the step (g). The alloy is installed, and the cBN sintered body piece is further installed so that the WC-based cemented carbide support comes on the bonding surface side. Similarly, Cr is coated on the surface of the WC-based cemented carbide support body of the cBN sintered body piece. In this state, pressurization is performed at a pressure of 100 MPa, and a joint is formed by locally heating the joint at a high frequency in an inert gas.
(J) The upper and lower surfaces and the outer peripheral surface are polished to obtain a long neck type ball end mill shape.
(K) Further honing is provided by chamfering.
(L) Thereafter, if necessary, for example, a hard coating layer made of TiAlN or the like may be provided by PVD to improve wear resistance or the like.

The state of the bonding layer between the WC-based cemented carbide support body and the WC-based cemented carbide tool body of the cutting edge portion made of the cBN sintered body having the Cr layer formed on the bonded surface as described above. As a result of visual observation, the Ni—Cr—B—Si alloy inserted as a bonding alloy disappeared, as if a composite material in which the WC-based carbide tool body and the cBN sintered body piece were integrated was formed. However, when the structural components and distribution of the bonding layer were investigated in detail using Auger electron spectroscopy (AES), in the vicinity of the bonding surface with the WC-based carbide tool body, the WC-based The W component of the WC particles of the hard tool body and the Cr coated on the surface are alloyed to form a strong bonding layer between the WC-based carbide and the bonding alloy, and the bonding alloy component Ni is formed on the joint surface of the WC-based carbide tool body Was turned Cr layer is the barrier, it was confirmed that remains on the joint surface near without excessively diffused in WC-based cemented carbide tool body. On the other hand, in the vicinity of the WC-based cemented carbide support surface of the cBN sintered compact, the WC particles W and Cr coated on the surface are alloyed to form a strong bonding layer between the WC-based cemented carbide and the bonding alloy. In addition, Ni of the bonding alloy component is excessively diffused in the WC-based cemented carbide support piece, with the Cr layer formed on the bonding surface of the WC-based cemented carbide support piece serving as a barrier. It confirmed that it remained in the joint surface vicinity (refer FIG. 2).
In the present invention, the bonding layer means a layer between the Cr layer formed on the WC-based cemented carbide tool body and the Cr layer formed on the surface of the WC-based cemented carbide support of the cBN sintered body piece. doing. In addition, the joining portion refers to the Ni diffusion layer formed in the WC-based cemented carbide support body of the WC-based cemented carbide tool body and the BN sintered body piece, the WC-based cemented carbide tool body, and the BN sintered body. Joining of a WC-based cemented carbide tool body formed from a Cr layer formed on the surface of a joining surface of a piece of a WC-based cemented carbide support and a bonding layer formed between the Cr layers and a BN sintered body piece It means an area.

  Furthermore, the alloy composition was obtained by Auger electron spectroscopy at the five points in the bonding layer, the average value was calculated, and extensive research was conducted on the relationship with bonding characteristics (tensile strength, bending strength, shear strength, etc.). However, when Cr: 14 to 18 at%, B: 20 to 26 at%, Si: 1 to 5 at%, Ni: 32 to 40 at%, and the balance is Fe and inevitable impurities, the joint has excellent joint characteristics. It has been found.

As described above, a bonding alloy is installed on the WC-based cemented carbide tool body, a cBN sintered body having a WC-based cemented carbide support is installed, and a pressure of 100 MPa is applied, for example, Ar gas By locally heating the vicinity of the joint at a high frequency in an inert gas such as, a Ni diffusion layer is formed on both the WC-based cemented carbide tool body and the WC-based cemented carbide support of the cBN sintered body piece. The junction part which has can be formed.
At this time, the thickness of the bonding alloy used for forming the bonded portion is desirably 50 μm or less because the bonding strength decreases if the thickness is too large. In addition, the Ni diffusion layer not only obtains a strong bonding strength but also has the purpose of relaxing the stress generated in the bonded portion, so that the thickness is desirably 2 μm or more. On the other hand, if the thickness is too large, the strength of the joint portion is lowered, so that the thickness is desirably 15 μm or less.
Further, the Ni diffusion layer formed by diffusing the Ni component of the bonding alloy in the WC-based cemented carbide support piece and the WC-based cemented carbide body of the cutting edge, the Cr layer, and the bonding layer between the Cr layers When the total average layer thickness of the joints consisting of the above exceeds 50 μm, a force such as bending and pulling is directly applied to the joints themselves, the strength of the joints is lowered, and the problem of breakage occurs. On the other hand, when the thickness is less than 5 μm, the thicknesses of the Ni bonding layer, the bonding layer, and the Cr layer are each reduced, so that the bonding strength cannot be sufficiently exhibited. Therefore, the total average layer thickness of the joint part of the joint part was determined to be 5 to 50 μm.

  Ni in the bonding alloy is integrated by diffusion in the Co binder contained in the WC-based carbide tool body, and has the effect of obtaining a strong bond, but formed on the bonding surface of the WC-based carbide tool body. Since the excessive diffusion is suppressed by the Cr layer, the deterioration of the mechanical characteristics of the WC-based cemented carbide tool body is prevented. Since B and Si have an effect of lowering the melting point of the bonding alloy, the temperature applied at the time of bonding can be lowered, and the deterioration of the cBN sintered body and the PCD sintered body can be prevented. Furthermore, Cr is alloyed with the W component in the WC-based cemented carbide support body lined with the WC-based cemented carbide tool body and the cBN sintered body or PCD sintered body, thereby forming a WC-based cemented carbide tool. A strong bonding layer is formed between the main body and the WC-based cemented carbide support piece and the bonding alloy.

Here, the reason why the average value of the alloy composition measured at five points in the bonding layer is determined as described above will be described.
Cr:
Both WC and Ni elements have good wettability and have the effect of improving the strength of the joint. However, if the content exceeds 18 at%, the high temperature strength is reduced. Moreover, when it is less than 14 at%, sufficient wettability cannot be obtained. Therefore, the Cr content is determined to be 14 to 18 at%.
B, Si:
Bonding needs to be performed at a temperature lower than 950 ° C. This is because the characteristics of the cBN sintered body or the PCD sintered body deteriorate at 950 ° C. or higher. In particular, when a metal such as Co is used as the binder, the deterioration becomes remarkable, so it is necessary to perform the treatment at 950 ° C. or lower.
However, Ni and Cr have melting points of 1455 ° C. and 1903 ° C., respectively, which are too high for joining a cBN sintered body and a PCD sintered body, and thus the melting point needs to be lowered. Since B and Si undergo a eutectic reaction with both Ni and Cr, the melting point can be lowered. Therefore, the melting point is lowered using B and Si. However, if B is less than 20 at%, the melting point cannot be lowered sufficiently, and if it exceeds 26 at%, embrittlement occurs. Further, if Si is less than 1 at%, the melting point cannot be lowered sufficiently, and if it exceeds 5 at%, it causes embrittlement. Therefore, the contents of B and Si are determined as B: 20 to 26 at% and Si: 1 to 5 at%.
Fe:
Fe is an inexpensive material, which leads to a reduction in the price of the bonding alloy and can be expected to have the same effect as Ni. Therefore, it is added in several at%, but it was not detected by AES analysis. However, as shown in Table 3, several wt% is added to the bonded alloy.
Ni:
In the alloy composition of the bonding layer, it is a component that occupies the remainder excluding the above components, and since the high-temperature strength is high, a strong bonding strength can be obtained. Further, since Ni has a high mobility at the time of melting, it diffuses over the entire joint and firmly joins the WC-based cemented carbide tool body and the cBN sintered body or PCD sintered body. When Ni is less than 32 at%, the effect of improving the strength cannot be sufficiently obtained, and when it is more than 40 at%, the melting point becomes too high and the performance of the cBN sintered body or PCD sintered body deteriorates.

According to the present invention, in a cutting tool having a joined portion obtained by joining a cutting blade portion made of a cBN sintered material or a PCD sintered material and a WC-based carbide tool body with a joining alloy interposed therebetween, Part and WC-based cemented carbide tool body have a Cr layer on the joint surface with the joint alloy, and an alloy composition obtained by measuring and averaging five points in the joint layer between the Cr layers is Cr: 14 to 18 at%, B : 20 to 26 at%, Si: 1 to 5 at%, Ni: 32 to 40 at%, the balance being Fe and inevitable impurities, the Cr layer of the joint surface becomes a barrier for Ni diffusion, and excessive Ni diffusion Since it becomes possible to prevent, the joining strength of a cutting blade part and a WC base carbide tool main body improves remarkably.
As a result, in an end mill or drill that uses cBN or a PCD chip as a cutting edge, it is possible to obtain a strong joint without breakage from the joint. Further, in high load machining of not only rotating tools but also high hardness steel or Al—SiC composite material by insert, it is possible to obtain a strong bond without flying edge at low cost.

It is the perspective view which showed the external appearance of the long neck type ball end mill. It is the photograph which observed the whole junction part of this invention end mill 1.

  Next, the present invention will be specifically described with reference to examples.

As raw material powders, WC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder and Co powder all having an average particle diameter of 0.5 to 1 μm were prepared. These raw material powders are shown in Table 1. It is blended into the blended composition, wet mixed in a ball mill for 24 hours, dried, and then pressed into a green compact at a pressure of 100 MPa, and this green compact is vacuumed at 6 Pa, temperature 1400 ° C., holding time 1 hour. Sintering was performed under conditions to form four types of WC-based carbide tool bodies (hereinafter simply referred to as carbide tool bodies) A-1 to A-4 shown in Table 1.

Next, cBN powder, TiN powder, TiCN powder, TiB ₂ powder, TiC powder, AlN powder, Al ₂ O each having an average particle size in the range of 0.5 to 4 μm as the raw material powder of the cBN sintered body ₃ powders were prepared, these raw material powders were blended in a prescribed composition, wet mixed with acetone for 24 hours in a ball mill, dried, and then pressure having a size of 15 mm diameter × 1 mm thickness at 100 MPa pressure. Press compacted into powder, and then the green compact is sintered in a vacuum atmosphere at a pressure of 1 × 10 ⁻² Pa at a temperature of 1000 ° C. and a holding time of 30 minutes to adsorb the volatile components and the powder surface. The components were removed, and a pre-sintered body for cutting edge pieces was formed. And this cutting edge piece pre-sintered body was prepared separately with Co: 16% by mass, WC: WC-based cemented carbide support piece having the remaining composition, diameter 15 mm × thickness 2 mm, In a superposed state, it was charged into a normal ultra-high pressure sintering apparatus, and sintered at a high pressure and high temperature in a vacuum atmosphere at a pressure of 5 GPa at a temperature of 1500 ° C. and a holding time of 30 minutes. -B-6 was produced. The composition of the sintered bodies of the cBN sintered bodies B-1 to B-6 was determined by taking the area% of cBN determined by image analysis of the SEM observation result of the sintered body cross-section polished surface as the volume%. About components other than cBN, it stopped only to confirm the component which comprises the main binder phase and other binder phases. The results are shown in Table 2.

  Next, Cr is coated on the joint surface of the WC-based cemented carbide support piece of the cBN sintered body (hereinafter simply referred to as a sintered body) and the cemented carbide tool body. For the Cr coating, a normal coating method can be used. In this example, the electrolytic plating method described below was used. That is, a Cr layer was formed on the joint surface by electrolytically depositing chromic anhydride as a solution. The thickness of the Cr layer is such that an appropriate amount of bonding alloy necessary for securing the bonding strength required for the bonded portion is suppressed in the sintered body and cemented carbide tool body while suppressing excessive diffusion of Ni. It is necessary to have a thickness that can be diffused into the surface. As a result of diligent investigations on the thickness, it was found that if the Cr layer is too thick, the bonding alloy cannot be diffused into the WC-based cemented carbide, so that it is preferably 1.0 μm or less. On the other hand, it was also confirmed that when the thickness is less than 0.1 μm, the original function of suppressing excessive diffusion of Ni cannot be sufficiently exhibited. Therefore, the thickness of the Cr layer is preferably 0.1 to 1.0 μm. The longitudinal section of the Cr layer forming surface was observed by surface analysis by Auger electron spectroscopy (AES), and the average layer thickness of the Cr layer was determined. The results are shown in Table 4.

  Next, the raw material powder is weighed so as to have the composition shown in Table 3, and the bonding alloy is melted in a vacuum arc melting furnace to form a button-shaped ingot. This was hot-rolled into a plate shape, and then cold-rolled to obtain 50 μm thin plate-shaped joining alloys C-1 to C-6.

  Next, the bonding alloy in the form of a thin plate obtained by the above-described method is installed at the tip of the cemented carbide tool main body whose Cr is coated on the bonding surface in the above-described process, and further on the bonding surface in the above-described process. A sintered body lined with a support piece made of WC-based cemented carbide coated with Cr is installed. In this state, pressurization is performed at a pressure of 100 MPa, and the vicinity of the joint is locally heated at a high frequency in an inert gas, thereby forming a joint composed of the Ni diffusion layer, the Cr layer, and the remaining joint alloy. Depending on the joining conditions, all of the joining alloy may diffuse and disappear in the WC-based cemented carbide support piece and the cemented carbide tool body.

As described above, the upper and lower surfaces and the outer peripheral surface are polished to form a long neck type ball end mill as shown in FIG. 1, and further, honing is provided by chamfering so that the present invention end mill as shown in Table 4 is obtained. 1-10 were produced.

  Further, for comparison purposes, a bonding alloy C-7 in which the Cr layer deviates from the range of 0.1 to 1.0 μm by the same process as described above, and the alloy composition of the bonding alloy is different from that used in the present invention. Comparative end mills 1 to 6 using -C-10 were produced.

About each of this invention end mills 1-10 and comparative end mills 1-6, the junction longitudinal section was observed by surface analysis by Auger electron spectroscopy (AES). A part of the result is shown in FIG. FIG. 2 is a photograph observing the entire joint portion of the end mill 1 of the present invention. Ni is visible, the center is a bonded alloy, the left side is a WC-based cemented carbide support part with a cutting edge, and the right side is a WC cemented carbide tool body. Although it can be confirmed that Ni has diffused into the cemented carbide part of the cutting edge and the tool body made of WC carbide, an alloy layer of Cr and W is formed at the boundary part between the bonded alloy and the cemented carbide. Thus, it can be confirmed that excessive diffusion of Ni is prevented. The entire area where Ni is diffused corresponds to the joint. When the thickness of the joint is calculated from this photograph, the average layer thickness of the Ni diffusion layer in the cemented carbide part of the cutting edge on the left side of the photograph is 7.3 μm, and the average layer thickness of the Cr layer adjacent thereto is 0.6 μm. The average layer thickness of the bonding layer is 5.2 μm, the average layer thickness of the Ni diffusion layer in the WC cemented carbide tool body is 8.8 μm, and the average layer thickness of the adjacent Cr layer is 0.7 μm. The average layer thickness was 22.6 μm. Similarly, the thickness of the joint was measured for the other samples. Moreover, the average value of the alloy composition measured by the surface analysis by Auger electron spectroscopy (AES) was calculated | required about five points in a joining layer. In addition, the semiquantitative analysis which used the average matrix relative sensitivity coefficient (AMRSF) as shown in Table 4 was performed for the measurement of the alloy measurement by surface analysis by Auger electron spectroscopy (AES). Since AMRSF includes almost all matrix corrections such as density, electron escape depth, backscattering effect, and elastic scattering correction, it is the most accurate of several relative sensitivity factors (RSFs). Therefore, AMRSF was used in the present invention. The results are shown in Table 4.

Next, for each of the present invention end mills 1 to 10 and comparative end mills 1 to 6, a bending test was performed, the bending strength was measured, and the fractured portion was visually observed. The results are shown in Table 4. The bending test was performed using a sample shape smaller than JIS by a three-point bending test according to the bending strength test method of cemented carbide defined in JIS R1601.

  From the results shown in Table 4, the present invention end mills 1 to 10 have a joining layer obtained by joining a cutting edge portion made of a cBN sintered material and a WC-based carbide tool body with a joining alloy interposed therebetween. The cutting edge portion and the WC-based cemented carbide tool body have a Cr layer on the joining surface with the joining alloy, and the average value of the alloy composition measured at five points of the joining layer is Cr: 14 to 18 at%, B : 20 to 26 at%, Si: 1 to 5 at%, Ni: 32 to 40 at%, the balance being Fe and inevitable impurities, the Cr layer of the joint surface becomes a barrier for Ni diffusion, and excessive Ni diffusion Since it becomes possible to prevent, the joining strength of a cutting blade part and a WC base carbide tool main body improves remarkably. As a result, it shows a bending strength of 2.7 GPa or more, and since the fracture occurs at a place other than the joint (a cemented carbide member), it is clear that the composite material has excellent joint strength. It is.

  In particular, when the average layer thickness of the Cr layer provided on the bonding surface with the bonding alloy is 0.1 to 1.0 μm, or when the total average layer thickness of the bonding portion is 5 to 50 μm, the bending strength is 3 Excellent bond strength of 7 GPa or more.

  On the other hand, the comparative end mills 1 to 6 in which the alloy composition of the bonding layer and the average layer thickness of the Cr layer depart from the scope of the present invention have a bending strength as low as 0.7 to 1.8 GPa, and all of the bonding surfaces Or the fracture | rupture has arisen in the junction part and it is inferior in the point of joining strength.

  In the present embodiment, the end mill has been specifically described as an example. However, the present invention is not limited to the end mill, and all cutting tools having a joint portion between a cutting blade portion such as a drill and an insert and a tool body. Needless to say, this is applicable. Moreover, although what concretely demonstrated what used the cBN sintered compact for the raw material of a cutting blade part was confirmed, even if it was a PCD sintered compact, it confirmed that the same effect was acquired.

  As described above, the cutting tool of the present invention has a cutting edge portion made of a cBN sintered body or a PCD sintered body and a WC base even in high-load cutting such as various types of steel, cast iron, and Al—SiC composite materials. Because it has excellent bonding strength with the carbide tool body, it will exhibit stable cutting performance over a long period of time. Furthermore, it can cope with cost reduction sufficiently satisfactorily.

Claims (3)

Cutting having a joining portion obtained by joining a cutting edge portion formed of a cBN sintered body or a PCD sintered body backed by a WC-based cemented carbide support piece and a WC-based cemented carbide tool body via a joining alloy. In the tool
The cutting edge part and the WC-based carbide tool body each have a Cr layer on the joint surface with the joint alloy,
The alloy composition obtained by measuring and averaging five points in the bonding layer between the Cr layers was Cr: 14-18 at%, B: 20-26 at%, Si: 1-5 at%, Ni: 32-40 at%, and the balance was Fe. A cutting tool characterized by being an inevitable impurity. The cutting tool according to claim 1, wherein an average layer thickness of the Cr layer is 0.1 to 1.0 μm. The joining portion is composed of a Ni diffusion layer formed by diffusing the Ni component of the joining alloy in the cutting edge portion and the WC-based carbide tool body, the Cr layer, and a joining layer between the Cr layers, The cutting tool according to claim 1 or 2, wherein a total average layer thickness of the joint portion is 5 to 50 µm.