JPH108182A - Impact resisting cemented carbide and surface coated cemented carbide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of the conventional cemented carbide of a type containing coarse grains and fine grains as a mixture that it is unsatisfactory because impact resistance is deteriorated even though strength and toughness are well-balancedly improved. SOLUTION: This impact resisting cemented carbide has a composition consisting of 5-15wt.% of binding phase of metal or alloy, composed essentially of Co, and the balance hard phase of tungsten carbide with inevitable impurities. At this time, the tungsten carbide contains a laminar tungsten carbide having >=3 aspect ratio of tungsten carbide grains in the arbitrary cross-sectional structure of the cemented carbide and coarse tungsten carbide having <3 aspect rario and also having average grain size larger than that of the laminar tungsten carbide, and the proportion of the laminar tungsten carbide to the whole tungsten carbide and the proportion of the coarse tungsten carbide to the whole tungsten carbide are regulated to 5-50vol.% and 10-50vol.%, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact-resistant cemented carbide and a surface-coated cemented carbide suitable for cutting tools, wear-resistant tools and civil engineering tools, and more particularly to heat-resistant impact represented by thermal cracks in cutting tools. Carbide and coated cemented carbide with excellent mechanical impact resistance such as chipping and chipping resistance in cutting tools and long life when used in interrupted turning and milling of steel among cutting tools The present invention relates to an impact-resistant cemented carbide and a surface-coated cemented carbide exhibiting the following.

[0002]

2. Description of the Related Art Generally, cutting tools made of cemented carbide are required to have not only wear resistance, but also improvement in chipping resistance, chipping resistance, thermal crack resistance, and the like. Particularly, intermittent turning and milling of steel are required. In such cases, the occurrence of mechanical and thermal fatigue cracks and their development lead to breakage, so that improvement of the impact resistance has become an important issue.

In general, the impact resistance of a cemented carbide can be improved by making tungsten carbide coarser or increasing the amount of Co. However, there is a problem that the wear resistance is reduced due to a decrease in hardness. . Therefore, in order to maintain a balance between impact resistance and wear resistance, a type of cemented carbide in which coarse particles and fine particles are mixed has been conventionally studied, and a new proposal has been made. A representative example is JP-A-7-252579.

[0004]

Japanese Patent Application Laid-Open No. 7-252579, which is a prior art of a cemented carbide of a type in which coarse and fine grains are mixed, discloses that fine tungsten carbide of 0.1 to 1 μm and fine tungsten of 3 to 10 μm are used. Cutting with a hard coating on the surface of a cemented carbide in which the area ratio on the cross-sectional structure with the coarse-grained tungsten carbide is 0.22 to 0.45 and the alloy carbon content is limited to the low carbon side in the healthy phase region Coated cemented carbide for tools is described. The coated cemented carbide described in this publication is limited to low-carbon alloys in addition to coarse-grained mixture in order to improve the strength and toughness in a well-balanced manner and achieve a long life at high speed cutting. However, there is a problem in that they are not satisfied because the impact resistance is reduced.

The present invention has solved the above-mentioned problems. Specifically, in a coarse-grained cemented carbide, plate-like tungsten carbide which forms relatively fine grains is used. Accordingly, it is an object of the present invention to provide an impact-resistant cemented carbide having excellent impact resistance and a surface-coated cemented carbide, which suppress the occurrence and progress of mechanical and thermal fatigue cracks during cutting.

[0006]

Means for Solving the Problems The inventors of the present invention have studied the simultaneous improvement of wear resistance and impact resistance of coarse and fine mixed grain cemented carbides for many years. The purpose is achieved by forming tungsten carbide, which forms fine grains, into a plate-like crystal, so that mechanical and thermal fatigue cracks are less likely to occur, and its growth is suppressed by the plate-like tungsten carbide crystal together with the coarse tungsten carbide particles. As a result, the inventors have found that the improvement in impact resistance is remarkable, and have completed the present invention.

The impact-resistant cemented carbide according to the present invention comprises 5 to 15% by weight of a binder phase of a metal or alloy containing Co as a main component,
In a cemented carbide having the remainder of a hard phase of tungsten carbide and unavoidable impurities, the tungsten carbide is a tungsten carbide plate having an aspect ratio of tungsten carbide particles in an arbitrary cross-sectional structure of the cemented carbide of 3 or more,
A coarse tungsten carbide having an aspect ratio of less than 3 and an average particle diameter larger than the average particle diameter of the plate-like tungsten carbide, wherein the ratio of the plate-like tungsten carbide to the entire tungsten carbide is 5 to 50% by volume. The ratio of the coarse tungsten carbide is 10 to 50% by volume.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The binder phase in the impact-resistant cemented carbide according to the present invention is substantially composed of Co or 5% of the binder phase.
0% by weight or more is Co and contains other metals or alloys. Of these, the latter case is specifically exemplified by a solid solution of 15% by weight or less of W, Cr, V and Ni. Co alloys can be mentioned. The amount of this bonded phase is
When the content is less than 5% by weight of the entire cemented carbide, the impact resistance is deteriorated due to a decrease in toughness, and when the content exceeds 15% by weight, wear resistance and plastic deformation resistance are deteriorated due to a decrease in hardness. Therefore, it is set to 5 to 15% by weight.

When the amount of the binder phase is the same, the relative saturation magnetization value of the cemented carbide varies mainly due to the metal or alloy dissolved in the binder phase. The relative saturation magnetization value is preferably 70 to 90% of the binder phase substantially made of Co, because the impact resistance and the plastic deformation resistance are improved. The saturation magnetization value of the binder phase varies depending on the amount of solid-dissolved W, that is, the amount of alloy carbon. However, it is preferable to use a low-carbon alloy because the solid-solution W in Co increases and the binder phase is strengthened. is there.

[0010] Tungsten carbide as a hard phase in the impact-resistant cemented carbide of the present invention is larger than the average particle diameter of plate-like tungsten carbide particles (hereinafter referred to as "plate-like WC particles") and plate-like tungsten carbide particles. It is composed of coarse tungsten carbide particles (hereinafter, referred to as “coarse WC particles”) and the remaining tungsten carbide (hereinafter, referred to as “WC”) that does not correspond to both of these tungsten carbides. The particles have a rod-like or needle-like shape on the cross-sectional structure, and have an aspect ratio [showing (the longest diameter / shortest diameter) of one crystal. Specifically, in the case of a polygonal crystal, the side from the vertex where the side intersects the side From the vertical length to the vertex, the longest and the shortest in the length from vertex to vertex] is 3 or more, and the coarse WC particles usually have a triangular or quadrangular shape and an aspect ratio of Below, in which preferably consists of 1.5 to 2.

The plate-like W with respect to the whole tungsten carbide
When the volume ratio of the C particles is less than 5%, the effect of improving the hardness and toughness of the plate-like WC crystal is reduced, so that the wear resistance and impact resistance are reduced. In addition, the impact resistance decreases due to the decrease in coarse WC particles, and the production of a large amount of plate-like WC particles having an aspect ratio of 3 or more becomes difficult. The volume ratio is determined to be 5 to 50% by volume.

On the other hand, if the volume ratio of the coarse WC particles to the whole tungsten carbide is less than 10%, the effect of improving the toughness by the coarse WC crystal is reduced, so that the impact resistance is reduced. Since the wear resistance is significantly deteriorated due to the decrease in hardness, the volume ratio of the coarse WC particles to the entire tungsten carbide is set to 10 to 50% by volume. Among these, in particular, the volume ratio of the plate-like WC to the whole tungsten carbide is 20 to 50%, and the volume ratio of the coarse WC particles to the whole tungsten carbide is 2%.
It is preferable that the content is 0 to 40% or that the volume ratio of both of these tungsten carbide particles to the entire tungsten carbide is 50% or more, since the effect of the present invention is most exhibited. It is preferable that the volume ratio of the plate-like WC to the entire tungsten carbide is 20% by volume or more, because both the wear resistance and the impact resistance are improved. Furthermore, when the average particle diameter of the plate-like WC particles is 1 μm or more and less than 3 μm, and the average particle diameter of the coarse WC particles is 3 μm or more and 7 μm or less, a good balance between wear resistance and impact resistance is obtained. Preferred for practical performance.

The impact-resistant cemented carbide according to the present invention includes a case where the binder phase is substantially composed of the above-mentioned binder phase and a hard phase, and a case where a cubic compound is dispersed in addition to the binder phase and the hard phase. is there. Specifically, the cubic compound is, for example, (WT
i) C, (WTiTa) C, (WTiZr) (CN),
TaC, NbC and the like can be mentioned. The amount of the cubic compound improves wear resistance and plastic deformation resistance in steel cutting, but when it exceeds 30% by weight, mechanical and thermal impact resistance is remarkably reduced. %
It is defined as follows.

The impact-resistant cemented carbide of the present invention can be used as a substrate, and the surface of the substrate can be coated with a conventional hard film to obtain an impact-resistant coated cemented carbide. The hard film in the impact-resistant coated cemented carbide is specifically made of, for example, carbides, nitrides, carbonates, nitrides of the elements of the 4a, 5a and 6a groups of the periodic table and their mutual solid solutions, and compounds of TiAl. , Aluminum oxide, diamond, diamond-like carbon, cubic boron nitride, and hard boron nitride. Among these, there is a combination that is more effective due to the relationship between the base material and the hard film. One of them
The surface-coated cemented carbide according to the present invention is obtained by coating the surface of the above-mentioned impact-resistant cemented carbide with a hard film. Specifically, TiC, Ti (CN), TiN, TiCO, Ti
NO, TiCNO, (TiAl) N, (TiAl) C
Examples thereof include a single-layer film made of one kind of N and Al ₂ O ₃ and a multilayer film of two or more kinds.

Among these hard films, a specific example of a multilayer film is TiN—Ti (CN) —TiC—Al ₂ O ₃ by chemical vapor deposition (hereinafter referred to as “CVD”).
When five layers of TiN are sequentially coated on a base material, TiN- (TiN-TiN) by physical vapor deposition (hereinafter referred to as "PVD") is used.
Al) N 2 layers or TiCN-TiC-TiCN 3
For example, a case where layers are sequentially coated on a base material may be mentioned. The thickness of the single-layer film or the multilayer film is 2 to 20 μm, depending on the application.
Is preferable.

In order to produce the impact-resistant cemented carbide of the present invention, specifically, for example, plate-like WC particles and coarse WC particles are separately prepared as raw materials, and a predetermined WC particle is prepared together with other necessary raw materials. Mixing, molding, pre-firing if necessary, and then sintering in a non-oxidizing atmosphere in the same manner as the conventional powder metallurgy method, or forming plate-like WC particles as a raw material A method of preparing a predetermined composition using a plate-like WC particle precursor, coarse WC particles, and other necessary raw materials to be prepared in the same manner as described above can be used. The impact resistant cemented carbide thus obtained is polished, corroded,
After cleaning, drying, etc., the conventional CV
The hard film can be coated on the surface of the substrate by using one or more of the D method, the plasma CVD method, or the PVD method.

[0017]

In the impact-resistant cemented carbide of the present invention, the plate-like WC particles contained therein act to improve hardness and toughness, thereby improving wear resistance and impact resistance. It acts to improve the impact resistance, and the action of both the plate-like WC particles and the coarse WC particles makes it possible to improve the impact resistance and the thermal shock resistance, which were impossible in the past. In addition to the action, both of them have the effect of increasing other properties such as hardness, toughness and wear resistance.

[0018]

Example 1 A commercially available average particle size is 1.5 μm,
2.5 μm, 4.5 μm, and 7.0 μm WC [WC (15), WC (25), WC (45), W
C (70)], W of 1.3 μm and 2.2 μm [written as W (13) and W (22) in the table in order], and 6
μm graphite (denoted as G in the table) and 1.2 μm Co
And 1.0 μm of a composite carbide of (WTi) C (weight ratio: WC / TiC = 70/30) and 1.0 μm of TaC were weighed to the composition shown in Table 1, An acetone solvent and a cemented carbide ball were inserted into a stainless steel pot, mixed and pulverized for 48 hours, and then dried to obtain a mixed powder. Using this mixed powder, a 2-ton SPGN120302 mold described in JIS-B4120 was used.
/ Cm ² , and the resulting powder compact was heated and sintered at a temperature shown in Table 1 for 1 hour in a vacuum at an atmospheric pressure of 10 Pa, to thereby obtain products 1 to 5 of the present invention and a comparative product. 1-6 were obtained.

Each of the cemented carbide chips thus obtained is ground and lapped with a 1 μm diamond paste, and then subjected to a load of 19 using a Vickers indenter.
The hardness at 6N, the fracture toughness value K1C (IM method) and the relative saturation magnetization value with the comparative product were measured, and the results are shown in Table 2. Next, a photograph of the structure was taken with an electron microscope, and the weight ratio of the binder phase (Co), the cubic compound, and the total WC was measured by an image processing apparatus. The results are also shown in Table 2. In the same manner, the volume ratio and average particle diameter (equivalent area diameter) of the plate-like WC particles having an aspect ratio of 3 or more and the relatively coarse WC particles relative to the whole WC were measured.
It was shown to.

In Table 3, the cemented carbide chips of the products 3 and 5 of the present invention and the comparative products 3, 5 and 6 were ground using a 230 # diamond grindstone to produce a cutting tip of SPGN120308. Using this tip, work material: SCM440, cutting speed: 100 m / min, depth of cut: 2.0 mm, feed: 0.40 mm / tooth, cutting distance:
After performing a dry milling test under the condition of 2m, the number of vertical cracks (perpendicular to the flank) and horizontal cracks (parallel to the flank) and the depth at the cross section of the rake face of the cutting edge were measured. Table 4 shows the results. In addition, a test was performed under the above cutting conditions using three chips for each sample, and the maximum wear amount of the flank reached 0.40 mm, or the average cutting distance until chipping / breakage of the cutting edge was obtained. The results are shown in Table 4.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

[Table 4]

[0025]

Example 2 The cemented carbide chips of the products 1 and 2 of the present invention and the comparative products 1 and 2 obtained in Example 1 were ground using a 230 # diamond grindstone to produce cutting tips of SDKN43ZTN. Then, using a PVD coating apparatus, the film thickness and the film quality are sequentially increased from the base material side to 0.5 μm T
iN, 2.0 μm TiCN and 0.5 μm TiN were coated to a total of 3 μm, and the products 6 and 7 of the present invention and the comparative products 7 and 8 were coated.
Was obtained respectively.

Using three pieces of the surface-coated cemented carbide tool tip thus obtained, a work material: SCM44
0, cutting speed: 150m / min, depth of cut: 2.0m
A dry milling test was performed under the conditions of m, feed: 0.25 mm / blade, and the average cutting distance until the chipping / breakage of the cutting blade or the average flank wear width became 0.30 mm was determined. As a result, the products 6 and 7 of the present invention were each 10.5.
m and 9.7 m, whereas the comparative products 7 and 8 were 4.1 m and 3.3 m, respectively.

[0027]

Example 3 Using the mixed powder of the product 4 of the present invention and the comparative product 4 obtained in Example 1, the C powder described in JIS-B4120 was used.
With the mold of NMG120408 (with breaker), 2
After press-forming at a pressure of ton / cm ² , sintering and grinding under the same conditions as in Example 1, and using a CVD coating device, the film thickness and the film quality are sequentially determined from the base material side,
1.0 μm TiN, 6.0 μm TiCN, 1.0 μm
m TiC, 3.0 μm Al ₂ O ₃ , 1.0 μm Ti
N was coated with a total of 12 μm to obtain a product 8 of the present invention and a comparative product 9.

Workpiece: S48C (with four grooves), cutting speed: 200 m / min, depth of cut: 2.
A wet intermittent turning test was performed under the conditions of 0 mm, feed: 0.30 mm / rev, and the average life time until chipping / breakage of the cutting edge or the average flank wear width became 0.30 mm was determined. As a result, the product of the present invention 8 and the comparative product 9 were 43 minutes and 25 minutes, respectively.

[0029]

The impact-resistant cemented carbide according to the present invention comprises plate-like WC particles composed of fine particles and coarse W particles composed of particles larger than the plate-like WC.
It is present as a mixed particle with C particles, and has a remarkably high hardness and fracture toughness value in the same composition component as compared with a conventional cemented carbide made of mixed-grain tungsten carbide,
The thermal shock resistance, abrasion resistance, chipping resistance and chipping resistance in the cutting test are remarkably excellent, and have an effect of extending the life. In addition, the surface-coated cemented carbide of the present invention has excellent peel resistance between the hard film and the base material, and the effects of the hard film and the base material are maximized. This has the effect of extending the life.

Claims (6)

[Claims] 1. A cemented carbide comprising 5 to 15% by weight of a binder phase of a metal or an alloy containing Co as a main component and a balance of a hard phase of tungsten carbide and unavoidable impurities. The ratio of the longest diameter to the shortest diameter of the tungsten carbide particles in any cross-sectional structure of the alloy (hereinafter, referred to as
("Aspect ratio") of 3 or more, and coarse tungsten carbide having an aspect ratio of less than 3 and an average particle size larger than the average particle size of the plate-like tungsten carbide, The ratio of the plate-like tungsten carbide to the whole tungsten carbide is 5 to 50.
% By volume, and the proportion of the coarse tungsten carbide is 10 to 50% by volume. 2. A cubic crystal comprising 5 to 15% by weight of a binder phase of a metal or alloy containing Co as a main component and at least one of carbon nitrides, carbon oxides and carbonitrides of W and Ti. In a cemented carbide comprising 30% by weight or less of a system compound and the balance being a hard phase of tungsten carbide and unavoidable impurities, the tungsten carbide has the longest diameter and the shortest diameter of tungsten carbide particles in an arbitrary sectional structure of the cemented carbide. Ratio to the diameter (hereinafter,
("Aspect ratio") of 3 or more, and coarse tungsten carbide having an aspect ratio of less than 3 and an average particle size larger than the average particle size of the plate-like tungsten carbide, The ratio of the plate-like tungsten carbide to the whole tungsten carbide is 5 to 50.
% By volume, and the proportion of the coarse tungsten carbide is 10 to 50% by volume. 3. The impact-resistant cemented carbide according to claim 1, wherein the total content of the plate-like tungsten carbide and the coarse tungsten carbide with respect to the entire tungsten carbide is 50% by volume or more. alloy. 4. The impact resistance according to claim 1, wherein the cemented carbide has a relative saturation magnetization of 70 to 90% with respect to a case where the binder phase is made of Co. Cemented carbide. 5. The plate-like tungsten carbide has an average particle diameter of 1 μm or more and less than 3 μm, and the coarse tungsten carbide has an average particle diameter of 3 μm or more and 7 μm or less. The impact-resistant cemented carbide according to 2, 3 or 4. 6. The impact-resistant cemented carbide according to claim 1, 2, 3, 4 or 5, wherein titanium carbide, nitride, carbonitride, carbonate, nitroxide, carbonitride, A surface-coated cemented carbide characterized by being coated with one kind of single layer or two or more kinds of titanium-aluminum nitride, carbonitride, carbonitride, and aluminum oxide.