JP2011235370A - Surface-coated wc-based cemented carbide insert - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-coated cemented carbide insert which exhibits superior chipping resistance and thermal plastic deformation resistance.SOLUTION: The surface-coated cemented carbide insert is formed by vapor depositing a hard coating layer on a base which is made of a WC-based cemented carbide obtained by forming and sintering a compound material containing as a material: at least WC powder and Co powder; and further, one or two of carbide of Zr, carbonitride, and nitride powder; and one or two of carbide of Ta, carbonitride, and nitride powder; or solid solution powder of one or two of carbide of Zr and Ta, carbonitride, and nitride. A Co-enriched surface area is formed on the surface of the base. The Co content in the Co-enriched surface area satisfies 1.30-2.10 (by mass ratio) of the Co content in the cemented carbide, and the Ta content in the Co-enriched surface area is 0.026-0.086 (by mass ratio) of the Co content in the Co-enriched surface area.

Description

  The present invention shows excellent chipping resistance and heat-resistant plastic deformation with a hard coating layer in intermittent heavy cutting of steel, cast iron, etc. where impact and intermittent high loads act on the cutting edge, and is excellent over a long period of use. The present invention relates to a surface-coated WC-based cemented carbide insert (hereinafter referred to as a coated cemented carbide insert) that exhibits high wear resistance.

Conventionally, as a cutting tool for steel or cast iron, for example, as shown in Patent Document 1, the cutting edge temperature is increased by including a hard phase of carbides of Zr and Hf as a component of cemented carbide. A cemented carbide tool that prevents plastic deformation of the cutting edge during heavy cutting and has improved wear resistance is known, and a surface on which a hard coating layer is formed on the cemented carbide tool base Coated carbide inserts (referred to as conventional coated carbide inserts 1) are also widely known.
For example, as shown in Patent Document 2, as the components of the cemented carbide, all are 4 to 12% Co, 0.3% or more Ti, 0.5% or more Nb, 0 by weight ratio. Further, a Co-enriched region having a Co enrichment ratio of 1.20 to 3.00 and a thickness of 10 to 50 μm is formed on the cemented carbide surface. A cemented carbide insert based on a cemented carbide containing a large amount of cubic carbide is known just below the Co-enriched region (known as conventional coated carbide insert 2). And it is known that the conventional coated carbide insert 2 has high cutting edge strength and excellent thermal shock resistance.

JP 2003-113437 A JP 2003-205406 A

In recent years, the performance of cutting machines has been remarkable. On the other hand, there are strong demands for labor saving, energy saving, and cost reduction for cutting, and along with this, cutting is becoming increasingly faster and more efficient. However, in the above-mentioned conventional coated carbide inserts 1 and 2, there is no particular problem when this is used for cutting under normal conditions. For example, impact and intermittent high loads are applied to the cutting edge. When it is used for intermittent heavy cutting in which is applied, chipping, partial wear, etc. cause the service life to be reached in a relatively short time.
For example, in the conventional coated carbide insert 1, chipping and chipping are likely to occur because the toughness of the cutting edge is not sufficient, and in the conventional coated carbide insert 2, the heat resistant plastic deformation of the cutting edge is not sufficient. There is a problem that uneven wear is likely to occur, and these cause the tool life.
Therefore, even in intermittent heavy cutting of steel and cast iron where impact and intermittent high load are applied to the cutting edge, it has excellent chipping resistance and heat plastic deformation, and exhibits excellent wear resistance over a long period of use. Development of surface-coated WC-based cemented carbide inserts (coated cemented carbide inserts) is desired.

  In order to meet the above-mentioned problems, the present inventors diligently studied the components and sintering conditions of a substrate made of a WC-based cemented carbide, and obtained the following knowledge.

  That is, conventional inserts made of WC cemented carbide (for example, conventional coated cemented carbide inserts 1 and 2) are usually WC powder, Co powder, TiC powder, TiN powder, TaC powder, NbC having a predetermined particle size as a raw material powder. A powder and the like are blended at a predetermined ratio, a binder and a solvent are added and mixed, dried, and then pressed into a green compact of a predetermined shape with a predetermined pressure. The green compact is subjected to predetermined sintering conditions. It is obtained by sintering to produce a WC cemented carbide insert material, grinding it and processing it into a predetermined insert shape and honing amount.

In the above-described conventional method for producing a WC cemented carbide insert, the present inventors have used at least Zr carbide, carbonitride, nitride as a WC cemented carbide raw material powder, WC powder with a predetermined particle size, and Co powder. One or more of powders, and one or more of Ta carbide, carbonitride, nitride powder, or Zr and Ta carbide, carbonitride, nitride powder One or two or more solid solution powders are added as essential powder components, and then a green compact is produced by press molding. For example, the temperature rise rate is 2 to 10 ° C./min, and the N ₂ pressure is 0.00. The temperature was raised to 1300 ° C. at 06 to 2.0 KPa, and 35 to 80% of N ₂ was replaced with Ar while maintaining the pressure to obtain a N ₂ / Ar mixed atmosphere. 1400 at ℃ / min Sintering is performed under the condition that the temperature is raised to a predetermined temperature of 1500 ° C., and then cooled after holding and firing for 45 minutes, and then this is ground and processed into a predetermined insert shape and honing amount. By vapor-depositing a hard coating layer thereon, a Co-enriched surface region having an average thickness of 5 to 35 μm substantially free of Zr is formed on the surface of a WC cemented carbide insert substrate, The Co content of the Co-enriched surface region is 1.30 to 2.10 (where mass ratio) of the Co content inside the cemented carbide, and the Ta content of the Co-enriched surface region is the same. A WC cemented carbide insert of the present invention having a Co content of 0.026 to 0.086 (however, a mass ratio) in the Co-enriched surface region can be obtained.
An example of a structure photograph of the Co-enriched surface region of the WC-based cemented carbide insert substrate is shown in FIG.

  The coated carbide insert of the present invention having the Co enriched surface region having the predetermined Co mass ratio and Ta mass ratio is an intermittent weight of steel or cast iron in which impact and intermittent high load act on the cutting blade. Even when used for cutting, the cutting edge combines toughness and heat-resistant plastic deformation that satisfy this requirement, and therefore it has been found that it exhibits excellent chipping resistance and wear resistance over a long period of use. It was.

The present invention has been made based on the above findings,
“At least WC powder and Co powder as raw materials, and one or more of Zr carbide, carbonitride, nitride powder and Ta carbide, carbonitride, nitride powder More than one WC group obtained by molding and sintering a compound raw material containing one or more of these, or one or more of Zr and Ta carbide, carbonitride, and nitride solid solution powder In a surface-coated cemented carbide insert in which a hard alloy is used as a base and a hard coating layer is vapor-deposited on the base,
A Co-enriched surface region having an average thickness of 5 to 35 μm is formed on the surface of the substrate of the WC-based cemented carbide, and the Co content in the Co-enriched surface region is the Co content inside the cemented carbide. The Ta content in the Co-enriched surface region is 0.026 to 0.0.1 of the Co content in the Co-enriched surface region. Surface-coated cemented carbide insert characterized by being 086 (but mass ratio). "
It is characterized by.

  The configuration of the present invention will be described below.

The cemented carbide substrate of the present coated cemented carbide insert is, for example, one or more of at least Zr carbide, carbonitride, nitride powder in WC powder and Co powder having a predetermined particle size, and One or more of Ta carbide, carbonitride and nitride powder, or one or more solid solution powders of Zr and Ta carbide, carbonitride and nitride are essential powders After adding a component and forming a raw material powder of a predetermined blending ratio, a binder and a solvent are added and mixed, dried, pressed into a green compact of a predetermined shape with a predetermined pressure, and then the green compact For example, the temperature is raised to 1200 ° C. at a temperature raising speed of 2 to 10 ° C./min and an N ₂ pressure of 0.06 to 2.0 KPa (referred to as primary temperature raising), and then 35 to 80 while maintaining the pressure. % N ₂ with Ar and N ₂ / A Under the condition that the mixed atmosphere is heated to a predetermined temperature between 1400 ° C. and 1500 ° C. at a temperature rising speed of 10 to 20 ° C./min (referred to as secondary heating), and then cooled after holding and firing for 45 minutes. It is obtained by carrying out sintering and then grinding and processing into a predetermined insert shape and honing amount.
The mixing ratio of the raw material powder is a mass ratio,
WC powder: Co powder: Zr compound powder: Ta compound powder
= (70.0-93.0%): (4.0-11.0%): (1.0-6.5%): (2.0-12.5%)
It is desirable that

A hard coating layer (TiN layer, TiCN layer, Al ₂ O ₃ layer) widely known to those skilled in the art is applied to the cemented carbide substrate of the present invention containing the Zr compound and Ta compound obtained by the above production method. Etc.) is coated by chemical vapor deposition to produce the coated carbide insert of the present invention.
When the vicinity of the interface between the carbide substrate surface and the hard coating layer of the obtained coated carbide insert of the present invention was observed using an optical microscope, the substrate surface had an average of 5 to 35 μm as shown in FIG. It is observed that a thick Co-enriched surface region is formed.
The thickness of the Co-enriched surface region to be formed is affected by the temperature, time, pressure, etc. during sintering, but if the Co-enriched surface region becomes thinner than 5 μm, chipping resistance in intermittent heavy cutting processing On the other hand, when the Co-enriched surface region is thicker than 35 μm, the heat-resistant plastic deformability is lowered and uneven wear tends to occur. Therefore, the average thickness of the Co-enriched surface region is not expected. Is 5 to 35 μm.

Next, the Co enriched surface region of the coated cemented carbide insert WC-based cemented carbide substrate and the Co content and Ta content inside the WC cemented carbide substrate are measured as follows.
The Co content and the Ta content were measured on the longitudinal section of the WC-based cemented carbide substrate using an electron beam microanalyzer (hereinafter referred to as EPMA).
According to the above measurement, the Co content of the Co-enriched surface region is 1.30 to 2.10 of the Co content inside the cemented carbide, and the Ta content is equal to that of the Co-enriched surface region. It turns out that it is 0.026-0.086 of Co content (however, all are mass ratios).

The Co content in the Co-enriched surface region depends on the sintering conditions, in particular, the N ₂ pressure at the time of primary temperature rise, the secondary temperature rise and the mixing ratio of N ₂ and Ar in the N ₂ / Ar mixed gas at the time of firing. It is greatly affected as follows.
And N ₂ pressure during primary heating, the difference of the secondary heating and baking time of N _{2 /} Ar N ₂ partial pressure in the mixed gas is large, Co content of Co-enriched surface region is relatively high Become. Conversely, the N ₂ pressure during primary heating, the difference of the secondary heating and baking time of N _{2 /} Ar N ₂ partial pressure in the mixed gas is small, Co content of Co-enriched surface region relative Lower.
Further, the Ta content in the Co-enriched surface region is determined by the sintering conditions, in particular, the N ₂ pressure during the primary temperature rise, and the N ₂ and Ar in the N ₂ / Ar mixed gas during the secondary temperature rise and firing. In addition to the mixing ratio, it is greatly influenced by the temperature increase speed at the time of secondary temperature increase as follows.
And N ₂ pressure during primary heating, large differences in the secondary heating and baking time of N _{2 /} Ar N ₂ partial pressure in the mixed gas, the high Atsushi Nobori speed at the time of the secondary heating, Co wealth The Ta content in the chemical surface area becomes relatively high. Conversely, the N ₂ pressure during primary heating, small difference in secondary Atsushi Nobori and baking time of N _{2 /} Ar N ₂ partial pressure in the mixed gas, when the low heating speed during the secondary heating The Ta content in the Co-enriched surface region is relatively low.

If the Co content in the Co-enriched surface region is less than 1.30, the toughness of the Co-enriched surface region is insufficient, and improvement in chipping resistance and fracture resistance cannot be expected. When the Co content in the Co-enriched surface region exceeds 2.10, the heat-resistant plastic deformability of the Co-enriched surface region tends to decrease, so that uneven wear is likely to occur and the wear resistance is improved. Because of deterioration, the Co content in the Co-enriched surface region was determined to be 1.30 to 2.10 (however, mass ratio) of the Co content inside the cemented carbide.
Furthermore, the Ta component and the Ta content existing in the Co-enriched surface region greatly affect the quality of the heat-resistant plastic deformation property of the Co-enriched surface region. That is, if the Co-enriched surface region of the cemented carbide substrate after sintering contains 0.026 to 0.086 (however, mass ratio) of Ta relative to the Co content in the Co-enriched surface region, Co The heat-resistant plastic deformation property of the enriched surface region is improved. However, when the Ta content relative to the Co content in the Co-enriched surface region is less than 0.026, the effect of improving the Co strength by Ta becomes insufficient, and the desired heat-resistant plastic deformation property of the Co-enriched surface region. In the case where the Ta content of the Co-enriched surface region exceeds 0.086, the toughness of the Co-enriched surface region is relatively lowered. Therefore, chipping and defects are likely to occur, so the Ta content of the Co-enriched surface region is 0.026 to 0.086 (however, mass ratio) with respect to the Co content of the Co-enriched surface region. Determined.
In addition, about the Zr compound contained as an essential component of the cemented carbide of the present invention, a strong skeleton structure of carbide containing WC is formed, and as a result, the heat-resistant plastic deformability is improved, but Co enrichment When a large amount of Zr is present in the surface region, not only the sinterability is lowered, but also the toughness is lowered, which tends to be a starting point for occurrence of chipping.
However, according to the sintering conditions of the cemented carbide of the present invention described above, the Zr content in the Co-enriched surface region is substantially zero, which adversely affects chipping resistance and heat-resistant plastic deformation. There is nothing.

  According to the insert made of the surface-coated cemented carbide of the present invention, in particular, the Co content in the Co-enriched surface region is 1.30 to 2.10 (however, mass ratio) of the Co content inside the cemented carbide. And the Co-enriched surface region has a Ta content of 0.026 to 0.086 (however, a mass ratio) of the Co-enriched surface region, and the Co-enriched surface region has a toughness. Combined with heat-resistant plastic deformation, it has excellent chipping resistance and heat-resistant plastic deformation in the hard coating layer in intermittent heavy cutting such as steel and cast iron where impact and intermittent high load are applied to the cutting edge. As a result, excellent wear resistance can be exhibited over a long period of use.

The cross-sectional optical microscope photograph of the cemented carbide substrate surface of the surface coating cemented carbide insert 6 of this invention is shown.

  Next, the surface-coated cemented carbide insert of the present invention will be specifically described with reference to examples.

Table 1 shows WC powder, Co powder, ZrC powder, ZrCN powder, TaC powder, TaCN powder, and Cr ₃ C ₂ powder, all having a predetermined average particle diameter in the range of 0.5 to 3 μm. The mixture was blended at the indicated ratio, and further a binder and a solvent were added, mixed in a ball mill for 24 hours in acetone, dried under reduced pressure, and then pressed into a green compact of a predetermined shape at a pressure of 100 MPa.
The green compact obtained by this press molding was sintered under the sintering conditions shown in Table 2 to produce coated carbide insert materials 1 to 10 of the present invention.
The coated carbide insert bases 1 to 10 of the present invention were manufactured by grinding from these coated cemented carbide insert materials into an insert shape and a honing amount defined in CNMG12041 (honing amount 0.07 mm).

Furthermore, various hard coating layers are formed on the surfaces of the coated cemented carbide insert bases 1 to 10 of the present invention, and the surface coated cemented carbide inserts 1 to 10 or less of the present invention shown in Table 3 are used. 10 was produced.
For the surface-coated cemented carbide inserts of Examples 1 to 10, the thickness of the Co-enriched surface region of the surface of each cemented carbide insert substrate was observed with an optical microscope after the cemented carbide insert was mirror-wrapped in the longitudinal section direction. Sought by.
FIG. 1 shows a cross-sectional optical micrograph of the surface of the cemented carbide substrate of the surface-coated cemented carbide insert 8 of the present invention.
Further, the Co content, Ta content, Zr content inside the surface-coated cemented carbide inserts of Examples 1 to 10, and the Co content, Ta content, and Zr content of the Co-enriched surface region In the longitudinal section of the cemented carbide insert of the present invention, the location is measured by EPMA, the Co content of the Co-enriched surface region, the Ta content, the Co content inside the insert, the ratio of the Ta content The value was determined.
These measurement results are shown in Table 3.

For comparison, WC powder, Co powder, ZrC powder, ZrCN powder, TaC powder, TaCN powder, Cr ₃ C ₂ powder each having a predetermined average particle diameter in the range of 0.5 to 3 μm are used as raw material powders. The mixture is blended in the proportions shown in Table 4, and a binder and a solvent are added, followed by ball mill mixing in acetone for 24 hours, dried under reduced pressure, and then press-molded into a green compact of a predetermined shape at a pressure of 100 MPa. The green compact obtained by the above was sintered under the sintering conditions shown in Table 5 to produce coated carbide insert materials 1 to 10 as comparative examples.
The coated carbide insert bases 1 to 10 of the comparative example were manufactured by grinding from these coated carbide insert materials into an insert shape and a honing amount defined in CNMG120212 (honing amount 0.07 mm).

Further, various hard coating layers are formed on the surfaces of the coated cemented carbide insert bases 1 to 10 of the comparative example, and the surface coated cemented carbide inserts 1 to 10 or less of the comparative examples shown in Table 6 are compared to comparative examples 1 to 10. 10 was produced.
For the surface-coated cemented carbide inserts of Comparative Examples 1 to 10, the thickness of the Co-enriched surface region of the surface of each cemented carbide insert substrate was determined by optical microscope observation after the comparative cemented carbide insert was mirror-wrapped. .
Further, the Co content, Ta content, Zr content inside the surface-coated cemented carbide inserts of Comparative Examples 1 to 10, and the Co content, Ta content, and Zr content of the Co-enriched surface region , The location in the longitudinal section of the comparative cemented carbide insert is measured by EPMA, the Co content of the Co-enriched surface region, the Ta content, the Co content inside the insert, the ratio of Ta content The value was determined.
These measurement results are shown in Table 6.

Next, for the above Examples 1-10 and Comparative Examples 1-10, both are screwed to the tip of the tool steel tool with a fixing jig,
Work material: JIS S50C round bar with 1 groove slit,
Cutting speed: 350 m / min. ,
Cutting depth: 2.5 mm,
Feed: 0.45 mm / rev. ,
Dry intermittent high feed cutting test of carbon steel under the following conditions (hereinafter referred to as cutting condition 1) (normal feed is 0.3 mm / rev),
Work material: JIS / SCM440 round bar with 1 groove slit,
Cutting speed: 350 m / min. ,
Cutting depth: 3.0 mm,
Feed: 0.3 mm / rev. ,
Dry intermittent high cutting cutting test of alloy steel under the following conditions (hereinafter referred to as cutting condition 2) (normal cutting is 1.5 mm),
And
The time until the flank wear width reached 0.3 mm was measured.
These cutting test results are shown in Table 7.

  From the results of Tables 3, 6, and 7, in the surface-coated cemented carbide insert of the present invention, the Co-enriched surface region in which the mass ratio of Co content is 1.30 to 2.10. In addition, a Co-enriched surface region in which the mass ratio of the Ta content to the Co content in the Co-enriched surface region is 0.026 to 0.086 is formed. Exhibits excellent chipping resistance and heat-resistant plastic deformation in intermittent heavy cutting of steel and cast iron where intermittent and shocking high loads are applied to the blade. In contrast, the surface-coated cemented carbide inserts of the comparative examples can exhibit excellent wear resistance without being chipped, and the life of the insert can be shortened in a short time due to chipping or wear resistance degradation. joy It is.

  When the surface-coated cemented carbide insert of the present invention is used for intermittent heavy cutting, not only can excellent cutting performance be maintained over a long period of use, but also the tool life can be extended. Furthermore, the surface-coated cemented carbide insert of the present invention can be used as an insert for various work materials that require chipping resistance, chipping resistance, heat plastic deformation, wear resistance, etc. It can cope with energy saving and cost reduction.

Claims (1)

The raw material contains at least WC powder and Co powder, and further, one or more of Zr carbide, carbonitride, and nitride powder, and Ta carbide, carbonitride, and nitride powder. WC-based cemented carbide obtained by molding and sintering a compound raw material containing one or more of Zr and Ta carbide, carbonitride, or nitride solid solution powder In a surface-coated cemented carbide insert in which an alloy is used as a base and a hard coating layer is vapor-deposited on the base,
A Co-enriched surface region having an average thickness of 5 to 35 μm is formed on the surface of the substrate of the WC-based cemented carbide, and the Co content in the Co-enriched surface region is the Co content inside the cemented carbide. The Ta content in the Co-enriched surface region is 0.026 to 0.0.1 of the Co content in the Co-enriched surface region. Surface-coated cemented carbide insert characterized by being 086 (but mass ratio).

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