JPH09241826A - Cemented carbide structural body, its production and cutting tool using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To show excellent cuttability in a cemented carbide structural body by directly coating the surface of a specified cemented carbide substrate with a hard ceramic layer composed of specified coating substance. SOLUTION: This cemented carbide structural body is the one in which the surface of WC base cemented carbide substrate contg. Co or bonding phase metal consisting essentially of Co with a hard ceramic layer without interposing an embrittled layer. This hard ceramic layer is formed of coating substance selected from one or more kinds of groups among the groups 4a, 5a and 6a elements in a periodic table of elements, the carbide, nitride, carbon nitride of Al and two or more kinds of solid solutions thereamong. The embrittled layer denotes the part in the substrate surface in which the amt. of the bonding metal phases is reduced to <=30% for some reason compared to that at the inside of the substrate. The hard ceramic layer is coated by a PVD method. In this way, excellent wear resistance can be obtd. without the peeling of the hard layer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a cemented carbide structure,
It belongs to a manufacturing method thereof and a cutting tool using the same. This cemented carbide structure is suitable for a cutting tool used under severe conditions that require wear resistance and fracture resistance.

[0002]

2. Description of the Related Art A WC-based cemented carbide obtained by sintering hard phase particles containing tungsten carbide (WC) as a main component together with a binder phase metal composed of an iron group metal such as cobalt (Co) and (Ni) is a ceramic material. It has high toughness as compared with the above. However, heat resistance, wear resistance, and corrosion resistance are insufficient to use this as it is as a cutting tool required for high-speed cutting currently in practical use. Table 4 Group 4a metal or Al compounds, such as alumina (Al ₂
O ₃ ), aluminum oxynitride (AlON), aluminum nitride (Al
N), titanium nitride (TiN), titanium carbonitride (TiC)
N), titanium carbide (TiC), zirconium nitride (Zr
N), hafnium nitride (HfN), and other hard ceramic layers are often used by coating one or more layers.

When the hard ceramic layer to be coated is an insulating substance such as alumina, it is generally formed by a vapor phase chemical vapor deposition method (CVD method). On the other hand, when the hard ceramic layer to be coated is a titanium compound, for example, a substance exhibiting conductivity such as titanium nitride,
Besides the CVD method, it can be formed by a PVD method such as arc vapor deposition, sputtering, or ion plating.

However, in the case of the CVD method, the raw material gas is 1
Since the hard ceramic layer is deposited in a film form on the surface of the substrate by heating to a high temperature of about 000 ° C., tensile stress acts on the surface of the hard ceramic layer after cooling, weakening the bending strength of the substrate itself and cutting tool. However, there is a drawback that the cutting edge is likely to be damaged.

On the other hand, the PVD method has a low reaction temperature for forming a hard ceramic layer of about 400 to 500 ° C. and a low base material heating temperature, and thus has no such drawbacks and has been favorably used for coating cutting tools. There is. Moreover, a compressive stress of about 0.1 to 1 GPa remains in the hard ceramic layer after cooling. When compressive stress is applied to the hard ceramic layer formed on the surface of the substrate, the progress of cracking of the hard ceramic layer is reduced, which is advantageous for fracture resistance.

By the way, as described above, Co and Ni are mainly used as the binder phase metal of the WC-based cemented carbide.
Among these, when Ni is used as the binding metal phase, it is superior to the one using Co in that the corrosion resistance is high. However, since it is inferior in heat resistance and hardness, WC using Co or a bonded metal phase mainly containing Co as a base material for a cutting tool.
Base cemented carbide is preferably used.

[0007]

However, in the WC-based cemented carbide using Co as a binder phase metal, P
When the hard ceramic layer is coated by the VD method, the hard ceramic layer may be suddenly peeled off. Especially TiN,
It has been found that when a hard ceramic layer made of a Ti compound such as TiCN is coated, sudden peeling is likely to occur.

Therefore, it was considered that when a strong compressive stress acts on the hard ceramic layer, this layer is likely to peel off. Therefore, in order to reduce the residual compressive stress of this layer, the thickness of this layer was made thin to 1 μm or less. However, such abrupt detachment could not be eradicated.

On the other hand, WC using Ni as a binder metal
When the base cemented carbide is similarly coated with a hard ceramic layer, such abrupt peeling is unlikely to occur. From this, Co is more likely to corrode than Ni, so Co is removed from the binder phase of the surface portion in the acid or alkali cleaning treatment that is performed after grinding into a predetermined shape and before PVD treatment. It is considered that this is because a processed layer (embrittlement layer) in which the amount of WC-based cemented carbide particles is large and the amount of binder phase metal is small is generated.

The present invention has been made to solve the above problems, and provides a WC cemented carbide structure containing Co as a binder phase metal coated with a hard ceramic layer having stable delamination resistance. It is in. Another object of the present invention is to provide a method for producing such a WC cemented carbide structure.

[0011]

The object of the present invention is to provide a substrate made of WC-based cemented carbide having Co or a Co-based binder phase metal on the surface from which the embrittlement layer has been removed, and to 4a of the periodic table of elements. , 5a, 6a group elements and Al carbides, nitrides,
This is achieved by a cemented carbide structure obtained by directly coating a hard ceramic layer composed of a carbonitride, an oxide, and one or more coating materials selected from the group of two or more solid solutions thereof.

That is, the cemented carbide structure of the present invention is C
On the surface of a substrate made of a WC-based cemented carbide having a binder phase metal mainly composed of o or Co, 4a, 5
carbides, nitrides, carbonitrides of a and 6a group elements and Al,
A hard ceramic layer composed of an oxide and at least one coating material selected from the group consisting of two or more solid solutions thereof is directly coated without interposing an embrittlement layer. Here, the embrittlement layer refers to a portion of the surface of the substrate where the amount of the bound metallic phase is reduced to 30% or less as compared with the inside of the substrate due to some circumstances.

A suitable method for producing the cemented carbide structure of the present invention is to use a WC-based cemented carbide having a Co or Co-based binder phase metal on the surface of a substrate as 4a, 5a of the Periodic Table of Elements. , 6a group elements and Al carbides, nitrides, carbonitrides, oxides, and a hard ceramic layer comprising one or more coating materials selected from the group consisting of two or more solid solutions thereof. The cutting tool substrate is ground into a desired shape, (2) the substrate surface is washed with an acid or alkali, (3) the embrittlement layer formed on the substrate surface by such washing is removed, and (4) the hard It is characterized in that the ceramic layer is coated by the PVD method.

The reason why the cemented carbide structure of the present invention is stable and has excellent peel resistance will be described below. First, when a conventional tool having a sudden reduction in peeling resistance was investigated, it was found that an embrittlement layer was formed on the surface of the substrate on which the hard phase was formed, in which the bonding metal phase was significantly reduced compared to the inside. It was And
Since the compressive stress remains in the hard layer formed by the PVD method as described above, it was presumed that the embrittlement layer failed to withstand the stress and was broken, and the hard layer was peeled off. Further investigation revealed that most of the above-mentioned embrittlement layers corroded the bonding metal phase on the substrate surface by a cleaning solution such as alkali or acid during the cleaning operation for forming the hard layer by the PVD method after grinding. It turned out that it was caused.

In the present invention, the embrittlement layer is removed by the blast method. According to this method, not only the surface of the substrate after removing the embrittlement layer can be made equal to the internal structure of the substrate, but also the surface of the substrate is Leaving very small scratches on the PV
It is considered that it becomes a kind of active nucleus in the initial stage of the formation of the hard ceramic layer by the D method, and it also exerts an anchoring effect to synergistically further improve the peel resistance of the hard ceramic layer.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION
Examples thereof include those made of N, TiCN or (Ti, Al) N.

A typical method for removing the embrittlement layer is as follows.
It is a blast process. In the case of blasting, the processing conditions such as the grain size of the abrasive grains used, the material of the abrasive grains, the injection pressure, and the injection time should be set within the range that does not impair the shape of the cemented carbide as the base. In particular, if coarse abrasive grains are used, there is a high possibility that chipping or chipping will occur at the ridge angle of the substrate. When the application of the cemented carbide structure is a cutting tool, the ridge angle of the substrate serves as the cutting edge, and chipping or chipping at that portion during the blasting process leads to product defects. Therefore, it is desirable that the abrasive grains used have a grain size of 50 μm or less.

[0018]

EXAMPLE A cemented carbide throwaway tip of ISO standard SNGN432 shape obtained by grinding a sintered body of WC-10 wt% Co composition (WC hard particle diameter 0.8 to 1.8 μm). Got ready. The cross section of this throwaway tip is shown schematically in FIG. In addition, the surface of the surface is left with traces of the grinding process, and the electron microscope (S
EM). This throwaway chip was used as a substrate and immersed in a 2N hydrochloric acid aqueous solution for a predetermined time.
When the surface of the substrate was observed again by SEM, as shown in FIG. 2, an embrittlement layer having irregularities that was considered to be caused by elution of Co was recognized. The degree of unevenness was more remarkable as the time of immersion in acid was longer.

After that, the Co amount at four points on the surface of the substrate was measured by ED.
It was measured at X, and the average value of Co amount was calculated for each substrate. And for the hard layer made of TiN,
The average value is 7.0 to 10.0% by weight, 3.0 to 7.0.
It is divided into 3 groups of weight% and 0 to 3.0 weight%,
100 substrates in each group were evaluated. For the hard layer made of TiCN or (Ti, Al) N, 100 substrates having a Co average value in the range of 0 to 3.0 wt% were evaluated.

Next, each of the substrates after measuring the amount of Co on the surface was set in a blasting device and blasted under the following conditions. When the surface of the blast-treated substrate was observed again by SEM, as shown in FIG. 3, it was recognized that the unevenness was smoothed and the embrittlement layer was removed.

Blasting conditions: Abrasive grains # 320 Alundum Pressure 0.2 MPa Time 10 seconds The blasted substrate is coated with various hard layers shown in Table 1 to a thickness of 4 μm using an ion plating device. Sample No. 100 pieces of 1 to 5 cemented carbide structures of the present invention were manufactured.

For comparison, the samples No. 1 and No. 3 were treated except that the substrates of the three groups were not blasted. Sample No. 1 under the same conditions as the alloys 1 to 5. 100 cemented carbide structures for comparison of R1 to R5 were manufactured.

The obtained cemented carbide structure No. Nos. 1 to 5 and Nos. Rockwell hardness tester (HR
Using A), the diamond indenter was punched in, and those without peeling of the hard layer were evaluated as having good peeling resistance, and those with peeling of the hard layer were evaluated as having poor peeling resistance, and the rate of non-defective products = (number of non-defective products)
/ (100 pieces) was calculated and is also shown in Table 1.

[0024]

[Table 1] As shown in Table 1, the cemented carbide structures within the scope of the present invention had good peel resistance regardless of the amount of Co on the surface before blasting. It is considered that this is because the blast treatment removed the embrittlement layer having a small amount of Co, and the Co amount on the surface of each sample was recovered to the same level as before embrittlement. On the other hand, in the comparative cemented carbide structure, the surface was not embrittled. Although R1 exhibited almost the same peeling resistance as the cemented carbide structure of the present invention, the peeling resistance markedly deteriorated as the amount of Co on the surface decreased.

Next, sample No. 3 and No. 3 A wet cutting test was performed on the cemented carbide structure of R3 under the following conditions. Work material FCD600 Cutting speed 300 m / min Depth of cut 1.0 mm Feed 0.2 mm / rev As a result, sample No. The amount of VB wear after 3 minutes for Sample No. 3 was only 0.05 mm. V 3 minutes after R3
The B wear amount reached 0.3 mm. Therefore, it is clear that the treatment for removing the embrittlement layer contributes to the improvement of the wear resistance of the cemented carbide structure.

[0026]

As described above, the cemented carbide structure of the present invention has a stable and excellent delamination resistance of the hard layer. Therefore, when it is used as a cutting tool for high-feed cutting or intermittent cutting, etc. In addition, excellent wear resistance can be obtained without the hard layer peeling off. When the substrate is an ultrafine particle cemented carbide, particularly excellent cutting performance is exhibited by the combination of the high-strength substrate and the hard layer having excellent wear resistance.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a substrate after grinding and before cleaning.

FIG. 2 is a schematic cross-sectional view showing a substrate after cleaning and before blasting.

FIG. 3 is a schematic cross-sectional view showing a substrate after a blast treatment.

Claims (8)

[Claims] 1. A carbide, nitride, or carbonitride of a 4a, 5a, or 6a group element of the periodic table of elements and Al on the surface of a substrate made of WC-based cemented carbide having a Co or Co-based binder phase metal. Cemented carbide structure formed by directly coating a hard ceramic layer composed of a coating material, an oxide, and one or more coating materials selected from the group of two or more solid solutions thereof without interposing an embrittlement layer. 2. The hard ceramic layer comprises TiN, TiC
The cemented carbide structure according to claim 1, comprising either N or (Ti, Al) N. 3. A cutting tool comprising the cemented carbide structure according to claim 1. 4. A carbide, nitride or carbonitride of 4a, 5a, 6a group elements of the periodic table of elements and Al on the surface of a substrate made of WC-based cemented carbide having a Co or Co-based binder phase metal. Object, an oxide, and a method for coating a hard ceramic layer made of one or more coating materials selected from the group of two or more solid solutions thereof, (1) grinding a cutting tool substrate into a desired shape, ) The surface of the substrate is washed with an acid or alkali, (3) the embrittlement layer generated on the substrate surface by such washing is removed, and (4) the hard ceramic layer is coated by a PVD method. Method for manufacturing hard alloy structure. 5. The hard ceramic layer is made of TiN, TiCN.
The method for manufacturing a cemented carbide structure according to claim 4, comprising either (Ti, Al) N. 6. The method for manufacturing a cemented carbide structure according to claim 5, wherein the embrittlement layer is removed by a blast method. 7. The method for producing a cemented carbide structure according to claim 6, wherein the grain size of the abrasive grains used in the blasting method is 50 μm or less. 8. A method for manufacturing a cemented carbide structure according to claim 4, wherein a cemented carbide tool substrate is used as the substrate.