JPH07197146A - Sintered compact for tool and its production - Google Patents

Abstract

PURPOSE:To provide a sintered compact for tools satisfying all of toughness, strength, workability, hardness, wear resistance, etc., which are the characteristics required for a cutting tool material, etc. CONSTITUTION:This sintered compact consists of 20 to 85vol.% carbide, nitride or boride of transition metals of any among the Periodic Table groups 4a, 5a, 6a or a mixture composed thereof or a solid soln. thereof, 2 to 30vol.% ferrous metal and 10 to 50vol.% fine granular diamond of a grain size of 1 to 40mum. The surfaces of the fine granular diamond are coated with the carbide of the transition metals of the Periodic Table groups 4a, 5a, 6a. The sintered compact for tools precipitated with carbon in or on the transition metals constituting the sintered compact is prepd. As a result, the production cost is reduced and the excellent sintered compact for tools is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered body suitable for use as a material for a cutting tool and a method for producing the same, and more particularly to a sintered body for a tool having excellent toughness, strength, wear resistance and the like. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Cutting tools made of non-ferrous metals such as aluminum alloys and copper alloys, non-metallic materials such as ceramics, concrete, rubber and plastics have excellent toughness, strength, workability, hardness and wear resistance. Is requested. Cermet, which is widely used as a material for cutting tools at present, is a composite material of ceramics and metal, and has considerable wear resistance and excellent toughness, strength, and workability. Even so, it cannot be said that the recent severe requirements for high-speed cutting have been sufficiently satisfied.

Due to the recent tendency toward high-speed cutting, a diamond sintered body obtained by adding a small amount of a binder such as Co to a fine-grained diamond powder of about 2 to 20 μm and sintering it as a material for a cutting tool under ultrahigh pressure. Despite its extremely high price due to its manufacture, it has attracted attention due to its high wear resistance.

However, the diamond sinter cutting tool cannot be said to have sufficient toughness and strength as compared with cemented carbide, and depending on the work material, chipping wear,
There was a problem that the blade edge was damaged.

Further, in the manufacturing process of the diamond sintered body, an ultrahigh pressure of 50 kb or more is usually required, and the manufacturing cost is remarkably increased, and therefore improvement in this point has been strongly desired.

[0006]

SUMMARY OF THE INVENTION The present invention provides a sintered body for a tool, which satisfies all the required properties as a material for a cutting tool, such as toughness, strength, workability, hardness and wear resistance.
It is intended to be economically obtained by sintering under a low pressure as compared with a diamond sintered body.

[0007]

A first invention is a carbide of a transition metal of any one of groups 4a, 5a and 6a of the periodic table,
A sintered body comprising a nitride, a boride or a mixture thereof or a solid solution thereof in an amount of 20 to 85% by volume, an iron group metal in an amount of 2 to 30% by volume, and a fine diamond particle having a particle size of 1 to 40 μm in an amount of 10 to 50% by volume. The fine diamond surface is coated with a carbide of a transition metal of any one of Groups 4a, 5a and 6a of the Periodic Table, and carbon is deposited in the iron group metal constituting the sintered body or on the surface thereof. A featured sintered body for a tool [claim 1], a second invention is a periodic table, a fourth aspect.
a, 5a, 6a transition metal carbides, nitrides, borides or mixtures thereof or solid solutions thereof 20 to 85% by volume, iron group metals 2 to 30% by volume, Periodic Tables 4a and 5a. , A raw material mixture obtained by mixing 10 to 50% by volume of fine diamond particles having a particle size of 1 to 40 μm, which is coated with 0.1 to 5% by volume of a transition metal of any of 6a groups, at a temperature of 950 to 1150 ° C. and a pressure of 1 To 30 kb, the method for producing a sintered body for a tool [claim 2], the third invention is a carbide of a transition metal of any one of Groups 4a, 5a and 6a of the periodic table, 20 to 85% by volume of a nitride, a boride or a mixture thereof or a solid solution thereof,
A particle size in which an oxide of an iron group metal is 2 to 30% by volume in terms of iron group metal, and 0.1 to 5% by volume of the transition metal of any one of groups 4a, 5a, and 6a of the periodic table is externally coated. 1-40μ
A raw material mixture in which 10 to 50% by volume of fine diamond particles of m are mixed is subjected to a reduction treatment in a reducing atmosphere at a temperature of 500 to 900 ° C., and then a temperature of 950 to 1150 ° C. and a pressure of 1 to 30 k.
In the method for manufacturing a sintered body for a tool [claim 3], which is characterized in that the basic composition is WC, the basic composition is WC.
On a substrate formed of a raw material of a cemented carbide that is —Co or a substrate formed of a raw material of cermet mainly composed of (Mo, W) C and an iron group metal, the periodic table 4a,
Carbides, nitrides of transition metals of either 5a or 6a,
Boride or mixture thereof or solid solution thereof 20
~ 85% by volume, iron group metal 2 to 30% by volume, Periodic Table No. 4
a molded plate molded with a raw material mixture in which 10 to 50% by volume of fine diamond particles having a particle size of 1 to 40 μm, which is coated with 0.1 to 5% by volume of a transition metal of any one of a, 5a, and 6a, is mixed. It is a sintered body for a tool [claim 4] which is laminated, sintered at a temperature of 950 to 1150 ° C and sintered at a pressure of 1 to 30 kb.

These inventions will be further described below. The sintered body for a tool of the first invention is 4a, 5a of the periodic table,
Coated with carbides, nitrides, borides or mixtures thereof of any of the Group 6a transition metals or solid solutions thereof, iron group metals and carbides of the transition metals Group 4a, 5a, 6a of the Periodic Table. Composed of fine diamonds.

Among these, the substance constituting the binder phase is a carbide, nitride, boride of a transition metal of any one of Groups 4a, 5a and 6a of the Periodic Table or a mixture thereof or a solid solution thereof. With iron group metals.

Carbides, nitrides, borides or mixtures thereof of transition metals of any of Groups 4a, 5a and 6a of the Periodic Table or solid solutions thereof, when used as a tool, have high hardness, strength, It has excellent thermal conductivity and chemical stability, and is essentially the same as that used in sintered compacts for tools such as cemented carbide and cermet. Of these, tungsten carbide is preferably used, but titanium carbide and the like can also be preferably used.

The content of these is 20 to 85% by volume. If this content is less than 20% by volume, the hardness, rigidity and wear resistance of the binder phase will be reduced, which is not preferable. Also, this is 85
When the content exceeds the volume%, the contents of the iron group metal and the fine-grained diamond relatively decrease, and the strength, toughness, and wear resistance of the sintered body decrease, which is not preferable.

In addition to the above, iron group metal is contained in an amount of 2 to 30% by volume as a substance constituting the binder phase. This iron group metal is a carbide of a transition metal of groups 4a, 5a and 6a of the periodic table,
It has very good wettability with nitrides and borides, promotes densification by viscous flow, and strengthens the retention of fine-grained diamond dispersed in the binder phase.

If the content of the iron group metal is less than 2% by volume, the binder phase cannot be densified and the binder phase cannot be toughened and strengthened. Further, if it exceeds 30% by volume, the hardness, rigidity and wear resistance of the binder phase decrease, which is not preferable.

Other than the above, the periodic table 4a, 5
It is a fine-grained diamond coated with carbides of a and 6a group transition metals. Due to its inherent hardness, fine-grained diamond serves to improve the wear resistance of the sintered body and to strengthen the sintered body by being dispersed in the sintered body. The content rate is 1
It is 0 to 50% by volume. If it is less than 10% by volume, a sintered body having sufficient wear resistance cannot be obtained, and the toughness cannot be improved by dispersing fine diamond particles. Also this is 50
When the content exceeds the volume%, densification of the binder phase is hindered and a dense sintered body cannot be obtained. The fine-grained diamond used here has an average grain size in the range of 1 to 40 μm. If the particle size is less than 1 μm, the fine diamond particles are likely to fall off, resulting in reduced wear resistance. If the particle size exceeds 40 μm, the tool edge strength is reduced, and the tool edge is easily damaged. It is not preferable because the tool life of the tool obtained in step 1 will be shortened. By using the coated fine-grained diamond, the wettability of the substance forming the binder phase with the carbide-coated fine-grained diamond is improved, and the part which is difficult to be plastically deformed is directly contacted by the diamond comrades and the binder phase is eliminated. The voids between the diamond particles are filled and densified by the plastic deformation of the substance that is easily plastically deformed to form a sintered body having excellent mechanical properties.

A second invention is a method for manufacturing a sintered body for a tool according to the first invention. The raw materials used here and their compounding ratios are set to the carbides, nitrides, borides or mixtures thereof of transition metals of any of Groups 4a, 5a and 6a of the Periodic Table, 20 to 85% by volume of solid solution thereof, iron. Group metal 2-30
%, 10% to 50% by volume of fine diamond having a particle size of 1 to 40 μm, which is coated with 0.1 to 5% by volume of a transition metal of any one of groups 4a, 5a, and 6a of the periodic table. The same as described above.

As will be described later, the coated transition metal and the carbon produced by the phase transition of the diamond surface easily react during sintering to form a carbide so as to enclose the fine-grained diamond. PVD as a method of coating with a transition metal
Method, CVD method, etc., but the coating amount is 0.1 to 5% by volume as an outer percentage of fine grain diamond. The coating amount is 0.
If it is less than 1% by volume, the effect of the coating is not recognized, and if it exceeds 5% by volume, carbides are not effectively formed on the diamond surface as described later, and unreacted coating transition metal remains and dense sintering occurs. I can't get a body.

A third invention uses an oxide of an iron group metal in place of the iron group metal in the raw material used in the second invention, and mixes the raw material mixture by 2 to 30% by volume in terms of iron group metal. ,
After reduction treatment in a reducing atmosphere at a temperature of 500 to 900 ° C., sintering is performed under high temperature and high pressure. As a result, the transverse rupture strength, that is, the strength of the sintered body can be further increased. The reason why the iron group metal oxide is set to 2 to 30% by volume in terms of the iron group metal is the same as that described in the first invention. A hydrogen atmosphere is preferable as the reducing atmosphere, and the processing temperature is 500 to 900 ° C. If the temperature is lower than 500 ° C, the oxide of the iron group metal is not reduced, and if the temperature is higher than 900 ° C, a remarkable phase transition occurs on the surface of the raw material diamond, and a large amount of graphite is generated, which is not preferable. The following reaction proceeds by this reduction treatment. M−O + H ₂ → M + H ₂ O Here, M is an iron group metal. The iron group metal oxide preferably has a particle size of 1 μm or less in consideration of dispersibility in the binder phase.

The reason why the strength of the sintered body is improved by using the iron group metal oxide instead of the iron group metal is that the mixing method such as an ordinary ball mill causes the raw materials to be slightly pulverized at the same time. Although mixed, the iron group metal such as Co has a problem that the metal particles easily adhere to each other during mixing due to their inherent malleability and ductility like water candy.
However, since the oxide of the iron group metal is used at the time of mixing because the oxide has good friability, the oxides are mixed uniformly without adhering, and the iron group metal that has undergone the reduction treatment is uniformly distributed in the structure. Will be dispersed. It is considered that this improves the strength of the sintered body.

According to the results obtained based on the third invention, 20% or more of the transverse rupture strength of the iron group metal oxide raw material was superior to that of the iron group metal oxide raw material.

In a fourth aspect of the present invention, a raw material molded substrate of cemented carbide having a basic composition of WC-Co or Mo is a main component (M).
o, W) A molded plate of the raw material mixture used in the second invention is laminated and arranged on a cermet raw material molded substrate composed of C and an iron group metal, and these are simultaneously baked at a temperature of 950 to 1150 ° C. and a pressure of 1 to 30 kb. It is one that is tied and joined. Cemented carbide and cermet, which are substrates, are excellent in toughness, rigidity, thermal conductivity and corrosion resistance, and are suitable for use as cutting tools. This tool sintered body has a sintering temperature of 950 to 1
Since it can be obtained at a low temperature of 150 ° C, it can be used for ordinary cemented carbide,
The liquid phase observed in the sintering process of cermet or commercially available diamond sintered body does not appear in the cemented carbide or cermet substrate, but since it is sintering under high pressure, solid phase sintering is sufficient, The bonding strength with the hard layer containing diamond is also sufficient. When the hard layer containing diamond and the substrate layer are co-sintered in this way, the strength of the substrate layer is higher than that of the hard layer, so that the transverse rupture strength, that is, the strength of the integrated body can be further increased. . Further, since the substrate layer is significantly easier to process than the hard layer containing diamond, it has an advantage that the cost for producing the tool can be reduced. The thicknesses of the hard layer containing diamond and the substrate layer may be determined in consideration of economical efficiency, tool specifications and strength, but it is sufficient if each is 0.5 mm or more.

These raw material mixtures are mixed by a mixer such as a ball mill, and are mixed as a powder or after being pressed and molded, and then at a high temperature and high pressure generator such as a HIP device and a piston cylinder device at 950 to 1150 ° C. 30 kb
Solid-state sintering in the thermodynamically stable region of graphite. As a result, the fine-grained diamond dispersed in the raw material undergoes a minute amount of phase transition from the surface due to the catalytic action of the iron group metal, and carbon produced by this phase transition and the diamond coated on the surface of the periodic table It reacts easily with a transition metal to form a carbide so as to wrap the fine-grained diamond, and a small amount of carbon precipitates in or on the surface of the iron group metal to strengthen the binder phase. And this sintering condition, compared with the sintering conditions of commercially available diamond sintered body, temperature,
Both pressures are extremely low. The thermodynamic graphite and diamond stability regions for pressure and temperature are shown in Fig. 1.
As shown in.

When the temperature is lower than 950 ° C., the sintered body is not densified, and when the temperature is higher than 1150 ° C., remarkable diamond phase transition occurs, a large amount of graphite is generated, and abrasion resistance peculiar to diamond is impaired. Absent.

When the pressure is less than 1 kb, 950 to 1150
Since the binder phase is not densified in the temperature range of ℃, a high-density sintered body cannot be obtained, and when it exceeds 30 kb, carbon is not generated by the phase transition on the diamond surface because it is sintering in the diamond stable range. Therefore, it is not preferable because carbide is not easily generated on the surface of the fine-grained diamond and the toughness of the binder phase is not achieved.

In the sintered body of the present invention, a peak of graphite was hardly recognized by a method such as X-ray diffraction, but a binder phase was formed by observation with a transmission electron microscope (TEM) and Auger electron spectroscopy. It was confirmed that very fine carbon of nanometer order was deposited in the iron group metal or its surface near the dispersed diamond. Such carbon is commercially available as WC-Co.
It is not found in the cemented carbide, cermet and diamond sintered bodies in the iron group metal or on the surface thereof. The reason why the binder phase is toughened in the sintered body of the present invention has not necessarily been clarified, but it is presumed as follows. That is, by the precipitation of fine carbon, it acts as a pin to suppress the movement of the transition existing in or on the surface of the iron group metal, macroscopically stopping the progress of microcracks, and as a whole sintered body. It is considered to be toughened. Also TE
According to M observation, the size of the iron group metal crystal grains in the commercially available WC-Co cemented carbide, cermet and diamond sintered body is several hundreds of microns in the submicron to large size, whereas the sintered body of the present invention. In the case of, it is recognized that the size of the iron group metal crystal grains is made to be subgrain due to the sintering at a low temperature in which a liquid phase does not occur, and the precipitation of fine carbon makes it extremely small and below submicron. It was It is thought that this disperses the stress concentration in the iron group metal or on the surface thereof, which also contributes to the toughness. Furthermore, the sintering conditions are the sintering temperature of commercially available diamond sintered bodies (140
0 ° C. or higher) and the sintering pressure (50 kb or higher) are significantly lower in both temperature and pressure.
It is also possible that the amount of strain generated in the sintering process is small. This is also considered to have contributed to strengthening.

[0025]

As described above, a binder phase forming material composed of a transition metal carbide, a nitride, a boride or a mixture thereof or a solid solution thereof and an iron group metal, and a fine grain diamond coated with a transition metal are predetermined. When a raw material mixture uniformly blended in the proportion of is heated thermodynamically at a stable temperature and pressure of graphite, a part of the fine-grained diamond undergoes a phase transition, and the resulting carbon reacts with the transition metal to produce the fine-grained diamond. A carbide is formed on the surface, and this is precipitated in the iron group metal or on the surface thereof, so that a sintered body for a tool having a high toughness and high strength binder phase can be obtained.

[0026]

EXAMPLE A raw material mixture obtained by using a binder phase forming raw material having a particle size of 1 μm or less, mixing fine diamond particles coated with a transition metal of Groups 4a, 5a and 6a of the periodic table and thoroughly mixing them in a pot mill. Was molded to obtain a preform having a diameter of 30 mm and a thickness of 2 mm. This compact and a preliminarily produced cemented carbide preform of WC-15 wt% Co having a diameter of 30 mm and a thickness of 2 mm are laminated and subjected to reduction treatment in a hydrogen atmosphere at 800 ° C., and then a piston cylinder type It was inserted into a high temperature and high pressure generator. A graphite heater was used as the heating element, and pyroxene and hexagonal boron nitride were used as the solid pressure medium. The raw material mixing ratios and sintering conditions are as shown in Tables 1 to 3, and the heating and holding time was 10 minutes. When the iron group metal oxide (average particle size 0.2 μm) was used, it was converted to the compounding ratio when it was reduced. Also, Table 1
Table 2 also shows the test results of the inventive sintered body, and Table 3 also shows the test results of the comparative sintered body.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

The obtained co-sintered body of the present invention was one in which the hard layer containing diamond and the cemented carbide portion were firmly integrated. Moreover, all the transition metals coated with the fine-grained diamond were changed to carbides. This co-sintered body was cut by electric discharge machining to prepare a cutting tool and a bending strength test piece. Tool shape is ISO millimeter nominal TNGN1
No. 60304, and the bending strength test piece shape is JIS R
According to 1601, the size of the test piece was set to 2 mm × 1.5 mm × 20 mm (± 0.05 mm) and the span was set to 15 mm due to the limitation of the size of the sintered body. For comparison, commercially available K10
A seed cemented carbide (Comparative Example No. 13 in Table 3) and a commercially available diamond sintered body (Comparative Example No. 14 in Table 3) were prepared and processed into the same shape. Cement mortar was used as the work material. The cutting conditions are cutting speed 75
m / min, depth of cut: 0.5 mm, feed: 0.13 mm / revolution, and life was determined when the average flank wear width was 0.3 mm. The transverse rupture strength test was conducted by measuring the three-point bending strength (kg / mm ² ) according to JIS R 1601.

In the case of the comparative sintered material whose composition and sintering conditions are out of alignment according to the present invention and the commercially available sintered material, the tool edge may be broken in some cases, and the tool life is short. Since it has excellent strength, toughness, and wear resistance, the wear state of the tool flank was steady wear, and the tool life was also significantly excellent.

[0032]

According to the present invention, a sintered body for a tool satisfying all of the toughness, strength, workability, hardness and wear resistance required as a cutting tool material is thermodynamically made of graphite. Since it is possible to sinter in a low-pressure region, which is a stable region, the manufacturing cost is significantly reduced compared to the conventional diamond sintered body, and an excellent sintered body for tools can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a thermodynamic graphite stable region and a diamond stable region related to pressure and temperature.

Claims (4)

[Claims] 1. A carbide, nitride, boride of a transition metal of any one of Groups 4a, 5a and 6a of the Periodic Table, a mixture thereof or a solid solution thereof in an amount of 20 to 85% by volume and an iron group metal in an amount of 2 to 30% by volume. %, And 10 to 50% by volume of fine diamond having a particle size of 1 to 40 μm, the fine diamond surface is coated with a carbide of a transition metal of any one of Groups 4a, 5a and 6a of the periodic table, Further, a sintered body for a tool, characterized in that carbon is deposited in or on the surface of an iron group metal constituting the sintered body. 2. A carbide, nitride, boride of a transition metal of any one of Groups 4a, 5a and 6a of the Periodic Table, or a mixture thereof or a solid solution thereof in an amount of 20 to 85% by volume and an iron group metal in an amount of 2 to 30% by volume. % And finely divided diamond 10-5 having a particle size of 1-40 .mu.m, which is coated with a transition metal of any one of groups 4a, 5a, and 6a of the periodic table in an amount of 0.1-5% by volume.
The raw material mixture in which 0% by volume was mixed was heated to a temperature of 950 to 115.
A method for producing a sintered body for a tool, which comprises sintering at 0 ° C. and a pressure of 1 to 30 kb. 3. A carbide, a nitride, a boride of a transition metal of any one of Groups 4a, 5a and 6a of the Periodic Table, or a mixture thereof or a solid solution thereof in an amount of 20 to 85% by volume and an oxide of an iron group metal. 2-30% by volume in terms of iron group metal, 0.1-5% by volume of the transition metal of any of Groups 4a, 5a, and 6a of the Periodic Table, finely divided diamond 10 having a particle size of 1-40 μm 10 A sintered material for a tool, which is obtained by reducing a raw material mixture containing 50% by volume to 50% by volume in a reducing atmosphere at a temperature of 500 to 900 ° C., and then sintering at a temperature of 950 to 1150 ° C. and a pressure of 1 to 30 kb. Manufacturing method. 4. A substrate formed by molding a raw material of a cemented carbide having a basic composition of WC-Co or having Mo as a main component (Mo,
W) On a substrate obtained by molding a cermet raw material composed of C and an iron group metal, a carbide, a nitride, a boride of a transition metal of any one of Groups 4a, 5a and 6a of the Periodic Table or a mixture thereof, or 20 to 85% by volume of these solid solutions, 2 to 30% by volume of the iron group metal, and 0.1 to 5% by volume of the transition metal of any one of Groups 4a, 5a, and 6a of the Periodic Table, which are externally coated. 1 to 40 μm fine diamond 10 to 50
A sintered body for a tool, which is obtained by stacking formed plates formed of a raw material mixture mixed with each other in a volume percentage, and sintered and bonded at a temperature of 950 to 1150 ° C and a pressure of 1 to 30 kb.