JPH08188846A - Coated cemented carbide - Google Patents

Abstract

PURPOSE: To remarkably improve the balance between wear resistance and breaking resistance by forming a beta removal layer on the surface of a WC- base super hard base material of a coated sintered hard alloy and specifying the lattice constant of B1 type crystals in the region inside the beta removal layer and also the half-breadth in the X-ray diffraction plane, respectively. CONSTITUTION: In a coated sintered hard alloy in which a WC-base sintered hard alloy is used as base material, this base material contains, by weight, 5-40% of B1 type crystals consisting of the carbides, nitrides, and carbonitrides of the group IVa, Va, and VIa metals and solid solutions thereof and 5-14% of iron group metals. A beta removal layer of about 5-50μm thickness is provided to the vicinity of the surface of this base material. The difference in the lattice constant between the B1 type crystals in the region of 10-200μm thickness inside this beta removal layer and the B1 type crystals in the part inside the region above is regulated to 0-0.01. Moreover, the proportion of the half-breadth in the (422) diffracting plane at X-ray diffraction is regulated to 70-90%. Further, a coating layer is composed of a substance selected from among the carbide, nitride, carbonitride, boron nitride, carbon nitride, carbon oxide, etc., of Ti.

Description

Detailed Description of the Invention

[0001]

This invention is suitable for cutting tools,
Coated cemented carbide with excellent wear resistance and fracture resistance, especially WC
The present invention relates to a coated cemented carbide having a base cemented carbide as a base material.

[0002]

2. Description of the Related Art A coated cemented carbide used for a cutting tool must satisfy the contradictory properties of wear resistance and fracture resistance.

By the way, on the outermost surface of the WC-based cemented carbide base material, a layer (de-beta layer) consisting of WC and a binding metal is provided.
By reducing the size of the B1-type crystal in the region inside it,
Conventionally, it has been proposed to improve wear resistance and fracture resistance.

However, when the grain size of the B1 type crystal in the inner part of the debeta layer is reduced, the wear resistance is improved, but the strength,
That is, there is a problem that chipping resistance is lowered. This is because, after the crack has passed through the deβ-layer, the crack growth is rapidly promoted immediately below it, so that the effect of the deβ-layer is not sufficiently exerted.

On the other hand, if the grain size of the B1 type crystal is increased,
Although the strength is improved, there is a problem that the plastic deformation resistance is lowered.

Therefore, according to the present invention, by devising the grain size distribution of the B1 type crystal in the inner portion of the deβ-layer, a WC-based material suitable for a cutting tool, in which wear resistance and fracture resistance are well balanced. It is intended to obtain a coated cemented carbide having a cemented carbide as a base material.

[0007]

Means for Solving the Problems and Its Actions The WC-based cemented carbide base material of the present invention contains B1 type crystals in an amount of 5 to 40 w.
t% included. When it is less than 5 wt%, the B1 type crystal in 0 to 100 μm inside the deβ-layer has a half-value width ratio of 90 as compared with the B1 type crystal sufficiently inside the β1 layer.
%, The difference becomes small, the propagation of cracks passing through the deβ-layer cannot be prevented, and there is almost no effect of improving the strength. On the other hand, when the content is 40 wt% or more, the strength of the interior of the alloy is significantly reduced.

The WC-based cemented carbide base material according to the present invention contains 5 to 15 wt% of an iron group metal as a binder phase. When it is less than 5 wt%, the sinterability is lowered and the strength is lowered, and when it is 15 wt% or more, the plastic deformation resistance is lowered.

Further, in the vicinity of the surface of the WC-based cemented carbide base material in the present invention, 5 to 50 μm, preferably 10 to 3
It has a 0 μm de-beta layer. If it is thinner than 5 μm,
Since the resistance to the introduction of cracks is insufficient, the fracture resistance cannot be sufficiently improved, and when it is 50 μm or more, the plastic deformation resistance decreases.

In the WC-based cemented carbide base material according to the present invention, the B1-type crystal in the region of 10 to 200 μm inside the de-β layer is compared with the B1-type crystal in the inner part of this region, and the lattice constant is Difference of 0 to 0.01, preferably 0 to 0.
In addition, the ratio of the full width at half maximum on the (422) diffraction plane of X-ray diffraction is 70 to 90%. If the thickness of this region is less than 10 μm, the effect of improving the strength becomes small, and if it exceeds 200 μm, the wear resistance decreases. The reason why the difference in lattice constant is 0 to 0.01 and the ratio of full width at half maximum is 70 to 90% is as follows. If the difference in lattice constant exceeds 0.01, this region and
The difference in the composition of the B1 type crystal between the inside of this region and the inside becomes too large, and the balance between wear resistance and strength is lost. Further, when the ratio of the full width at half maximum is less than 70%, the difference in grain size between this region and the inner portion of this region becomes too large, that is, B1 in the region immediately below the de-β layer.
The grain size of the type B crystal is too coarse, or conversely, the grain size of the B1 type crystal in the inner portion of this region becomes too fine,
The balance between strength and wear resistance will be lost. On the contrary, when the ratio of the half width is larger than 90%, the effect of improving the strength due to the coarsening of the B1 type crystal in the region immediately below the de-β layer cannot be sufficiently obtained.

Next, it is preferable that the absolute value of the full width at half maximum in the inner portion of the region immediately below the debeta layer is 0.4 to 1.0. When it is greater than 0.4, the effect of improving both the performance balance by improving the wear resistance of the inner portion of the area and improving the strength of the area becomes large. However, when the half-value width of the B1 type crystal in the inner portion of the region exceeds 1.0, the half-value width of the B1 type crystal in the region also increases accordingly, and the balance between the above two performances tends to be lost. Show. That is,
The wear resistance is greatly improved, but the fracture resistance tends to decrease.

The B1 type crystal is composed of a group IVa element and a V
It is composed of a metal carbide, a nitride, a carbonitride and a solid solution thereof containing a group a element as a main component, and the amount of the group IVa metal component (M1 “mol”) and the amount of the group Va metal component (M2 “mo”).
When l ") is represented by a mol ratio, if the following relation is satisfied, it becomes easy to balance wear resistance and fracture resistance.

0.2 ≦ M1 / (M1 + M2) ≦ 0.9
(Preferably 0.7) Especially, it is more effective when the group IVa metal is Zr and the group Va metal is at least one of Ta and Nb as main components.

By the way, the coated cemented carbide of the present invention can be manufactured as follows.

First, raw materials of WC, iron group metal and B1 type crystal carbide are blended and molded within the range of the present invention, and 1350 to 1
Sinter in the range of 500 ° C. However, the lattice constant inside the alloy is adjusted by blending the raw materials. Further, the full width at half maximum is adjusted by the particle size of the blended raw material, the sintering temperature and the time. At this time, the temperature of nitrogen is gradually changed (increased) between the temperature of 1250 ° C. or higher during heating and the sintering keep, and the nitrogen content is gradually changed (increased) in accordance with the increase of the equilibrium nitrogen partial pressure accompanying the temperature increase. keep. And keep it in this atmosphere even during sintering keep, 5 ℃ per minute
Cool at the above speed.

The above equilibrium nitrogen partial pressure varies depending on the alloy system (type of B1 type crystal), but B1 type crystal (TiTaNb)
In the case of N type, empirically, at 1500 ° C., about 10 torr, 1
It is considered to be about 1 torr at 250 ° C.

Therefore, the formation of the de-β layer is a dissolution of the B1 type crystal in the bonding layer near the surface of the cemented carbide by denitrification and a re-precipitation immediately below the de-β layer. By controlling the deposition rate, it is possible to control the B1 type crystal immediately below the de-β layer itself.

The de-β layer controlled by the above method, and the B1 type crystal immediately below the de-β layer change during cooling when the cooling rate is slowed down, and the structure of the present invention maintained until sintering is maintained. I can't keep it. Therefore, a cooling rate of 5 ° C./min or more is required.

The thickness of the deβ-layer and the half-value width immediately below the β-layer can be adjusted by adjusting the nitrogen partial pressure and the sintering keep time by the above method.

[0020]

【Example】

(Example 1) As a raw material powder, WC, TiC, TiN,
TaC, TaN, NbC, NbN, VC, VN and C
o, Ni was prepared, and the complete powder having the composition shown in Table 1 was converted into C
125 mm after being pressed into a chip in the shape of NMG120408
From 0 ° C to 1450 ° C in a reduced pressure N ₂ atmosphere at 5 ° C / min, as the temperature rises, the N ₂ partial pressure is continuously increased from 0.05 torr to 1 torr, and then the temperature is raised and maintained in a nitrogen atmosphere for 2 hours. Then, it cooled at 5 degree-C / min.

Then, using this alloy as a base, ordinary C
The inner layer was coated with 5 μm TiC, TiCN, and TiN, the intermediate layer was coated with TiBN, TiCNO, and the outer layer was coated with 2 μm of aluminum oxide, zirconium oxide, and hafnium oxide, and a cutting test was conducted under the following cutting conditions.

For comparison, Samples 2'and 3'having the same composition as Sample Nos. 2 and 3 and subjected to vacuum sintering (both heating, keeping and cooling in vacuum) which is a conventional sintering method are also provided. It was prepared and coated with the same coating film as above.

As for the inside, the sample is placed 5 from the surface.
After rough grinding with a flattening of not less than 00 μm, the surface is mirror-finished by buffing with # 1500 and # 3000 diamond paste.
Buffing with a diamond paste of a coarser number than 500 is sequentially carried out from the surface, and after confirming that the de-β layer disappears with an optical microscope, # 3000 diamond paste buffing is used for mirror finishing. About this side X
Using a line diffractometer, the lattice constant and the half width are measured at the diffraction peak of the (422) plane.

These samples were cut under the conditions of Test 1 and Test 2 shown below, and the flank wear amount (mm) and the defect rate (%) at that time were measured.

Test 1 (wear resistance test) Cutting speed 220 m / min Work material SCM435 Feed 0.45 mm / rev Cutting time 20 min Cutting depth 2.0 mm Test 2 (Toughness test) Cutting speed 100 m / min Work material SCM435 4 grooves Material feed 0.45 mm / rev Cutting time 30 seconds Cut 2.0 mm Repeated 8 times In Table 1, the amount of IVa group metal component is M1 mol, Va
M1 / (M1 +) when the amount of group metal component is M2mol
The value of M2) is also shown.

The test results, the lattice constant of the B1 type crystal, the full width at half maximum and the like are shown in Table 2 together with those of the comparative product.

A, B, C and D in Table 2 are: | AB |: Inner part (A) of the de-β layer and fully internal (B)
Difference in lattice constant of B1 type crystal at C: Half width at (422) diffraction plane of B1 type crystal inside de-β layer D: Half width at (422) diffraction plane of B1 type crystal sufficiently inside 100 * C / D: B1 inside the de-beta layer and well inside
Ratio of full width at half maximum on (422) diffraction plane of type crystal E: Thickness of region inside de-β layer (μm) F: Thickness of de-β layer (μm)

[0028]

[Table 1]

[0029]

[Table 2]

(Example 2) As a raw material powder, WC, Zr
C, ZrN, TaC, TaN, NbC, NbN, VC,
VN, CO, and Ni were prepared, and the finished powder having the composition shown in Table 3 was pressed into a chip in the shape of CNMG120408, and then N2 was added at 1 ° C to 1450 ° C at 2 ° C / min.
The temperature rises in a depressurized atmosphere of + H2, and as the temperature rises, N2
After raising the partial pressure continuously from 0.01 torr to 2 torr (H2 partial pressure is constant at 5 torr),
Hold in a nitrogen p atmosphere of 2 torr for 1 hour at 10 ° C /
Cooled at min.

Then, based on this alloy, the usual C
The inner layer was coated with 5 μm TiC, TiCN, and TiN, the intermediate layer was coated with TiBN, TiCNO, and the outer layer was coated with 2 μm of aluminum oxide, zirconium oxide, and hafnium oxide, and a cutting test was conducted under the following cutting conditions. Also, sample 1
Conventional comparative product 1 obtained by performing vacuum sintering (both temperature rising, keeping, and cooling) which is the conventional sintering with the compositions of 2 and 13 by changing the degree of vacuum.
2 ', 13' and 12 ", 13" are also listed in Table 4.

Test 1 of Example 1 using these samples
And the cutting evaluation was performed under the same conditions as Test 2. Sample No.12
And 13 are the amount of B1-type crystal, the amount of bonding layer, M1 / (M1 +
The values of M2) are almost the same as those of Nos. 3 and 4 of Example 1, and Zr and Ta are only for B1 type crystal compositions 12 and 13.
It is understood that the effect of the present invention is more remarkable by comparing these with a metal carbonitride compound containing as a main component.

[0033]

[Table 3]

[0034]

[Table 4]

[0035]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, in the portion immediately below the deβ-layer of the WC-based cemented carbide base material, the difference in composition from the inside is small, and the crack propagation resistance that is coarser than that inside is excellent. A type crystal is arranged to improve the strength (damage resistance) and wear resistance, and further, the B1 type crystal having a thinner inside is arranged to improve the wear resistance. It is possible to obtain a coated cemented carbide suitable for a cutting tool, which has a significantly improved balance between wear resistance and fracture resistance.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of a coated cemented carbide according to the present invention.

Claims (4)

[Claims] 1. A carbide, a nitride, a carbonitride, a boronitride, a carbonitride, a carbonate of Ti, an oxide of Al, Zr, and Hf on the surface of a WC-based cemented carbide base material, and oxides of these. In the coated cemented carbide having one or more coating layers selected from oxide composite films, the WC-based cemented carbide base material is a periodic table.
IVa, Va, VIa group metal carbides, nitrides, carbonitrides,
And 5 to 40 wt% of B1 type crystal composed of these solid solutions
%, 5 to 15 wt% of iron group metal, and 5 near the surface
˜50 μm de-beta layer, inside the de-beta layer 10
The B1 type crystal at ˜200 μm has a lattice constant difference of 0 to 0.01 as compared with the B1 type crystal inside the B1 type crystal, and the half width ratio on the (422) diffraction plane of X-ray diffraction is 70. ~ 90% coated cemented carbide. 2. The coated cemented carbide according to claim 1, wherein the half-value width of the B1 type crystal in the inner portion of the inner region of the β-free layer is 0.4 to 1.0. 3. The B1-type crystal is composed of a carbide, a nitride, a carbonitride of a metal containing a group IVa element and a group Va element as a main component, and a solid solution thereof, and the amount of the group IVa metal component (M1 "m
ol ”) and the amount of the Va group metal component (M2“ mol ”)
The coated cemented carbide according to claim 1 or 2, which has the following relationship when expressed by an ol ratio. 0.2 ≦ M1 / (M1 + M2) ≦ 0.9 4. The B1 type crystal according to claim 3, wherein the Br type crystal is Zr.
A coated cemented carbide, which comprises a metal carbide, a nitride, a carbonitride, and a solid solution thereof containing, as a main component, at least one of Ta and Nb.