JPH06228702A - Nitrogen-containing sintered hard alloy - Google Patents

Abstract

PURPOSE:To provide a high-quality nitrogen-containing sintered hard alloy used for cutting tool and having superior strength. CONSTITUTION:This alloy is composed of a hard phase consisting, e.g. of the carbides of at least two transition metals selected from the group IVa, Va, and VIa metals of the periodic table and a binding phase of Ni, Co, etc. As to the amount of the binding metal phase, the maximum part of the amount of binding phase exists in the range of depth between the position at a depth of 3mum from the surface and the position at a depth of 500mum from the surface. As to the hard phase, when the composition of the metals constituting the hard phase is represented by (TixWyMc), (x) in the surface part is >=1.01 times the average (x) in the alloy, (y) is 0.1-0.9 times the average (y) in the alloy, and also the above (x) and (y) return the average (x) and average (y) of the whole alloy, respectively, within a depth of 800mum. Moreover, WC grains do not exist in the surface part, or, even if they do exist, the amount is <=0.1vol%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-quality nitrogen-containing sintered hard alloy having extremely high strength as a material for cutting tools.

[0002]

2. Description of the Related Art Sintered hard alloys containing nitrogen composed of a carbonitride containing Ti as a main component and a hard layer bonded with a metal composed of Ni and Co have already been put to practical use as cutting tools. In this nitrogen-containing sintered hard alloy, the high-temperature creep resistance is significantly improved because the hard phase becomes significantly finer than that of the conventional nitrogen-free sintered hard alloy.
It has been widely used as a cutting tool along with so-called cemented carbide containing C as a main component.

However, this nitrogen-containing sintered hard alloy has a thermal conductivity as an alloy due to the fact that the carbonitride of Ti which is the main component has a significantly lower thermal conductivity than that of WC which is the main component of the cemented carbide. The degree of thermal expansion is about 1/2, and the coefficient of thermal expansion is 1.3 times as high as that of cemented carbide containing nitrogen depending on the characteristic value of the main component. Resistance to shock is low. Therefore, it must be used with sufficient reliability for cutting under conditions where thermal shock is severe, such as milling, cutting with a lathe for square timber, and wet copying cutting where the depth of cut changes greatly. It was the current situation.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The inventors have conducted detailed research on analysis of cutting phenomena such as temperature distribution and stress distribution in a tool in various cuttings and arrangement of material components in the tool. As a result, the following findings were obtained. Cemented carbide has a high thermal conductivity, so the high heat generated on the tool surface during cutting diffuses quickly through the inside of the tool, making it difficult for the surface to reach a high temperature and suddenly spinning idle or water-soluble cutting. Even if this high temperature part is suddenly exposed and rapidly cooled where oil is applied, tensile stress is generated in the surface layer part and is unlikely to remain, due to the small thermal expansion coefficient.

However, since the nitrogen-containing sintered hard alloy containing Ti as its main component has a low thermal conductivity, it is difficult for the heat to diffuse from the portion of the cutting edge where the cutting edge easily reaches the highest temperature and the cutting surface hits the surface. However, the inside has a steep temperature gradient such that the temperature suddenly decreases. Therefore, once cracks occur, this alloy, which has a low internal temperature, is extremely susceptible to chipping. Furthermore, in the case of such a material, when cutting oil is applied and rapidly cooled, a so-called temperature gradient reversal phenomenon occurs in which only the pole surface is cooled and the temperature immediately below remains high, which also affects the large coefficient of thermal expansion. Tensile stress is generated in the surface layer, and thermal cracking is very likely to occur. That is, in the nitrogen-containing sintered hard alloy, it was naturally limited to improve the thermal conductivity and the thermal expansion coefficient while containing Ti necessary for improving the cut finished surface. Then, the inventors arrived at the present invention as a result of various studies to solve this problem.

[0006]

That is, in the nitrogen-containing sintered hard alloy of the present invention, a large amount of Ti component is arranged in the extreme surface layer portion that determines the properties of the cutting finish surface of the tool, and a specific distance from immediately below it. A large amount of a bonding metal such as Ni or Co having high toughness is arranged in the thickness of to increase the strength just below the cutting edge. This Ni / Co
Since the enriched layer has a high coefficient of thermal expansion, it also has an effect that compressive stress can be generated in the surface layer portion during cooling after sintering or when the cutting tool is removed. In addition, W, which is an essential component of the hard layer, is enriched from the surface to the inside. It is considered that the main heat conduction medium of the nitrogen-containing sintered hard alloy is the binder phase, but the hard phase also contributes to the heat conduction particularly inside by enriching W. Inside the binder phase-enriched layer, the binder phase is decreased and the hard phase is increased in order to more effectively exhibit the heat conduction improving effect.

For this reason, the nitrogen-containing sintered hard alloy is
The maximum amount of the binder phase exists in the depth range of 3 μm or more and 500 μm or less from the surface, and the value is 1.1 times or more and 4 times or less of the average binder phase amount of the alloy, and the alloy is formed up to a depth of 800 μm. The average binder phase amount of the whole is restored, and the binder phase amount of the surface portion is set to 0.9 times or less of the maximum binder phase amount. The depth of 800 μm is used to prevent a decrease in thermal conductivity and to improve the plastic deformation resistance of the tool during cutting. As for the hard phase, Ti and Ta, Nb, and Zr, which have the similar effect of improving wear resistance to steel cutting, are enriched in the surface portion, and instead, W and Mo, which have little effect, are reduced, and especially W is added to the surface. It has been found that the WC particles do not exist, or even if they exist, the content is 0.1 vol% or less.

The reasons for limitation in the present invention will be described in detail below. It is said that the existence depth range of the highest part of the amount of binder phase and its amount of binder phase enhance the tool strength, and that compressive stress can be generated in the surface layer part during cooling after sintering or when the cutting tool is released. It is necessary to have an effect, and the maximum depth is 3
If it is less than μm, the wear resistance as a tool is poor, and it is 500 μm.
If it exceeds, the effect of applying compressive stress to the surface is not sufficiently exhibited. If the ratio of the amount of the binder phase at the highest part to the average amount of the binder phase is 1.1 times or less, the desired strength improving effect cannot be obtained, and 4
If it exceeds 2 times, the plastic deformation during cutting or the inside becomes too hard and the strength becomes insufficient, which is not preferable.

Surface Binder Phase Content The surface section must have wear resistance and be subjected to compressive stress due to a smaller coefficient of thermal expansion than the interior, so that the maximum binder phase ratio exceeds 0.9 times. If so, these desired effects cannot be obtained. Amount of Ti, Ta, Nb, and Zr in the hard phase on the surface part The surface must have high wear resistance, and Ti and Ta, Nb, and Zr, which have the same effect of improving wear resistance, are rich in the surface part. However, if the average ratio of the alloy is less than 1.01, the desired wear resistance cannot be obtained. In particular, Ta and Nb are preferable because they can have high-temperature oxidation resistance.
Further, due to this enrichment, there is an effect that the properties of the cut finish surface are extremely excellent. W and Mo content in the hard phase at the surface

The amounts of W and Mo in the hard phase are (Ti _x W _y
M _c ) and (Ti _x W _y Mo _b M _c ) are represented by y and b. WC and / or Mo ₂ C, which have poor wear resistance, are reduced on the surface portion, and as a result, W and / or Mo in the hard phase is enriched toward the inside. If this amount is less than 0.1 as an average ratio as an alloy, it is practically impossible to make it, and if it exceeds 0.9, the wear resistance is poor, which is not preferable. M
o exhibits almost the same behavior as WC in the hard phase.

Only the WC will be described here. The morphology of W enrichment in the hard phase from the surface to the interior of the alloy is
It may be present as C particles, or the peripheral structure of the composite carbonitride solid solution may be W-rich. Also,
As the existence form of the hard phase, a solid solution of W-rich may be partially present or may be more than the surface texture, and hard particles (white core with a white center and a dark periphery are observed in a scanning electron microscope). Called particles, white areas are Ti
Even if the ratio of the -rich portion in the gray portion of the -rich portion is the W-rich portion) increases, the desired effect of improving the heat conduction characteristics and the strength can be obtained. The range of 0.5 <x ≦ 0.95 and 0.05 <y ≦ 0.5 is to maintain wear resistance and heat resistance. If it deviates from these ranges, the wear resistance and the heat resistance are deteriorated, so that the object of the present invention cannot be achieved. Hereinafter, a detailed description will be given in examples.

[0012]

【Example】

(Example 1) As a raw material powder, (T
i _0.8 W _0.2 ) (C _0.7 N _0.3 ) powder 48% by weight, 1.5%
μm (TaNb) C powder (TaC: NbC = 2: 1)
(Weight ratio)), 24% by weight, 19% by weight of WC powder of 4 μm, 3% of Ni powder and Co powder of 1.5 μm, respectively.
Wt%, after the wet mixing 6 wt%, embossing molding, ^10-2
After degassing in a Torr vacuum at 1200 ° C, nitrogen gas partial pressure 5
The temperature was raised to 1400 ° C. with Torr and hydrogen gas partial pressure of 0.5 Torr, and once evacuated to 10 ⁻² Torr, the gas atmosphere was returned again and sintering was carried out for 1 hour. CO ₂ from 1330 ° C. After quenching with nitrogen 1
Sample 1 was prepared by gradually cooling at 2 ° C./minute while flowing 00 Torr. The structure of this sample is shown in Table 1.

[0013]

[Table 1]

For comparison, the same embossed compact was used as a sample by several conventional manufacturing methods, and the nitrogen partial pressure was 5 To.
Sample 2 sintered at 1400 ° C. at rr, sample 3 cooled at the same post-sintering CO partial pressure of 200 Torr as sample 2 and sample 4 the same as sample 2 cooled at the nitrogen partial pressure of 180 Torr after sintering . These structures are shown in Table 2.

[0015]

[Table 2]

Table 4 shows the results of the judgments made on the nitrogen-containing sintered hard alloys of Samples 1 to 4 under the cutting conditions 1 to 3 shown in Table 3 together.

[0017]

[Table 3]

[0018]

[Table 4]

Example 2 As raw material powder, 51 wt% of (Ti _0.8 W _0.2 ) (C _0.7 N _0.3 ) powder having an average particle size of 2 μm and (TaNb) C powder (TaC: Nb) of 1.2 μm were used.
C = 2: 1 (weight ratio)), 27% by weight, 11% by weight of WC powder of 5 μm, 3% by weight and 8% by weight of Ni powder and Co powder of 1.5 μm, respectively. Press-molded, degassed in a vacuum of 10 ^-2 Torr at 1200 ° C, then sintered at 1450 ° C for 1 hour at a nitrogen gas partial pressure of 10 Torr, and then 10
Sample 5 was prepared by cooling under a high vacuum of ^-5 Torr and sample 5 by cooling under CO ₂ . For comparison, samples 7 and 8 having the structures shown in Table 5 were prepared from the same molded body. These were evaluated under the cutting conditions shown in Table 6 and the results are shown in Table 7.

[0020]

[Table 5]

[0021]

[Table 6]

[0022]

[Table 7]

Example 3 As a raw material powder, 42 (Ti _0.8 W _0.2 ) (C _0.7 N _0.3 ) powder having an average particle size of 2.5 μm was used.
% By weight, 1.5 μm of (TaNb) C powder (TaC:
NbC = 2: 1 (weight ratio)) 23 wt%, W of 4 μm
C powder 25 wt%, 1.5 μm of Ni powder and Co powder of 2.5 wt% and 6.5 wt% respectively were wet-mixed and then press-molded, and nitrogen gas partial pressure was 15 Torr and 1430 ° C.
After sintering for 1 hour, the sample 9 was cooled with CO ₂ and the dew point was −40.
Sample 10 was prepared by cooling with hydrogen gas at 0 ° C. For comparison, sample 1 was prepared from the same raw material powder so that the average amount of the binder phase and the internal hard phase composition (Ti + Nb, W) in Table 8 were obtained.
1-13 were also created. Samples 14 to 19 are comparative structural alloys using the same molded body as Samples 9 and 10. Table 9 shows the conditions and results of these cutting tests.

[0024]

[Table 8]

[0025]

[Table 9]

(Example 4) With an average particle diameter of 2 μm, the outer portion of the cored structure looks white in a reflection electron microscope image, and the core looks black (Ti _0.75 Ta _0.04 Nb _0.04 W _0.17 ) (C _0.56 N
_0.44 ) powder and the same 1.5 μm Ni powder and Co powder of 85% by weight, 8% by weight and 7% by weight, respectively, after wet mixing,
After embossing, degassing at 1200 ° C. in a vacuum of 10 ⁻² Torr, sintering at 1450 ° C. for 1 hour at a nitrogen gas partial pressure of 10 Torr, and CO ₂ cooled alloy sample 20, Ti (CN), T
Sample 21 was prepared by mixing aC, WC, NbC, Co, and Ni so as to have the same composition as sample 20, mixing and sintering. For comparison, samples 22 and 23 having the structure shown in Table 10 were prepared from the same molded body as sample 20, and sample 24 having the structure shown in Table 10 was also prepared from the same molded body as sample 21. First
Table 1 shows these cutting test conditions and evaluation results.

[0027]

[Table 10]

[0028]

[Table 11]

Example 5 (Ti having an average particle size of 2 μm)
_0.8 W _0.2 ) (C _0.7 N _0.3 ) powder, 1.5 μm TaC powder, 4 μm WC powder, 2 μm ZrC powder, 1.5 μm Ni powder and Co powder And structural alloys were made. Table 13 shows the characteristics of each alloy sample.

[0030]

[Table 12]

[0031]

[Table 13]

Example 6 (Ti having an average particle size of 2 μm)
_0.8 W _0.2 ) (C _0.7 N _0.3 ) powder, 1.5 μm TaC powder, 3 μm NbC powder, 4 μm WC powder, 3
An alloy having the average composition and structure shown in Table 14 was prepared by using Mo ₂ C powder of μm, Ni powder and Co powder of 1.5 μm. Table 15 shows the characteristics of each alloy sample.

[0033]

[Table 14]

[0034]

[Table 15]

[0035]

As described above, according to the present invention, as a cutting tool, cutting under particularly severe conditions of thermal shock, for example, milling cutting or cutting with a lathe of square timber, and wet copying with greatly varying cutting depth. It has an effect that a highly reliable nitrogen-containing sintered hard alloy can be provided for cutting and the like.

[Brief description of drawings]

1 to 4 are diagrams schematically showing composition distributions in the depth direction from the surface of Samples 1 to 4 in Example 1. [Brief description of drawings]

FIG. 1 is a composition distribution diagram of the surface depth of Sample 1 in Example 1.

FIG. 2 is a compositional distribution diagram of the surface depth of sample 2 in the first embodiment.

FIG. 3 is a compositional distribution diagram of the surface depth of Sample 3 in Example 1.

FIG. 4 is a composition distribution diagram of the surface depth of sample 4 in the first embodiment.

Claims (5)

[Claims] 1. A hard phase comprising at least one kind of carbides, nitrides, carbonitrides of at least two kinds of transition metals selected from groups 4a, 5a and 6a of the periodic table, or composite carbonitrides thereof. And a nitrogen-containing sintered hard alloy consisting of a binder phase containing Ni and Co and unavoidable impurities, the maximum value of the binder phase amount exists in the depth range of the binder metal phase amount from 3 μm to 500 μm from the surface. Is 1.1 times or more and 4 times or less the alloy average binder phase amount, and the depth is 800 μm.
To the average binder phase amount of the entire alloy, and the binder phase amount of the surface part is 0.9 times or less than the binder phase highest part, and for the hard phase, the metal forming the hard phase The component composition is (Ti _x W _y M _c ), where M is a transition metal component forming a hard phase other than Ti and W, and x, y, and c are atomic ratios x +
When expressed as y + c = 1 (satisfying 0.5 <x ≦ 0.95, 0.05 <y ≦ 0.5)), x of the surface portion is 1.01 times or more the alloy average x, and y is 0 relative to the alloy average y. .1 or more and 0.9 or less, and returns to the average x and y of the entire alloy by the depth of 800 μm, and WC particles are not present on the surface portion or are 0.1 volume% or less even if they are present. A nitrogen-containing sintered hard alloy characterized by the following. 2. A hard phase comprising at least one kind of carbides, nitrides, carbonitrides of at least two kinds of transition metals selected from the groups 4a, 5a and 6a of the periodic table, or composite carbonitrides thereof. And a nitrogen-containing sintered hard alloy consisting of a binder phase containing Ni and Co and unavoidable impurities, the maximum value of the binder phase amount exists in the depth range of the binder metal phase amount from 3 μm to 500 μm from the surface. Is 1.1 times or more and 4 times or less the alloy average binder phase amount, and the depth is 800 μm.
To the average binder phase amount of the entire alloy, and the binder phase amount of the surface part is 0.9 times or less than the binder phase highest part, and for the hard phase, the metal forming the hard phase The composition of the components is (Ti _x W _{y M'b} M _c ) (where M is Ti, W, T
Hard phase forming transition metal components other than a and Nb, M'is T
a, or Nb, where x, y, b, and c are atomic ratios x + y + b + c = 1 (0.5 <x ≦ 0.95, 0.05
<Y ≦ 0.5, 0.01 <b ≦ 0.4) is satisfied), x + b of the surface portion is 1.01 with respect to the alloy average x + b.
X or more, y is 0.1 or more and 0.9 or less with respect to the average y of the alloy, and the average x of the entire alloy is up to 800 μm in depth.
A nitrogen-containing sintered hard alloy characterized by returning to + b, y, and having no WC particles on the surface portion or 0.1% by volume or less even if they are present. 3. A hard phase comprising at least one kind of carbides, nitrides, carbonitrides of at least two kinds of transition metals selected from groups 4a, 5a and 6a of the periodic table, or composite carbonitrides thereof. And a nitrogen-containing sintered hard alloy consisting of a binder phase containing Ni and Co and unavoidable impurities, the maximum value of the binder phase amount exists in the depth range of the binder metal phase amount from 3 μm to 500 μm from the surface. Is 1.1 times or more and 4 times or less the alloy average binder phase amount, and the depth is 800 μm.
To the average binder phase amount of the entire alloy, and the binder phase amount of the surface part is 0.9 times or less than the binder phase highest part, and for the hard phase, the metal forming the hard phase The composition of the components is (Ti _x W _y Ta _a Nb _b M _c ) (where M is Ti,
Hard phase forming transition metal components other than W, Ta, Nb, x,
y, a, b, c are atomic ratios x + y + a + b + c = 1
(0.5 <x ≦ 0.95, 0.05 <y ≦ 0.5, 0.01 <a ≦ 0.
4, 0.01 <b ≦ 0.4) is satisfied), x + a + b of the surface part is 1.01 times or more the alloy average x + a + b, and y is 0.1 or more and 0.9 or less of the alloy average y. , The average x of the whole alloy up to a depth of 800 μm
A nitrogen-containing sintered hard alloy characterized by returning to + a + b, y, and having no or no WC particles on the surface portion, or 0.1% by volume or less. 4. A hard phase comprising at least one kind of carbides, nitrides, carbonitrides of at least two kinds of transition metals selected from the groups 4a, 5a and 6a of the periodic table, or composite carbonitrides thereof. And a nitrogen-containing sintered hard alloy consisting of a binder phase containing Ni and Co and unavoidable impurities, the maximum value of the binder phase amount exists in the depth range of the binder metal phase amount from 3 μm to 500 μm from the surface. Is 1.1 times or more and 4 times or less the alloy average binder phase amount, and the depth is 800 μm.
To the average binder phase amount of the entire alloy, and the binder phase amount of the surface part is 0.9 times or less than the binder phase highest part, and for the hard phase, the metal forming the hard phase The component composition is (Ti _x W _y Zr _b M _c ) (where M is Ti, W, Z
Hard phase forming transition metal components other than r, x, y, b, c are atomic ratios x + y + b + c = 1 (0.5 <x ≦ 0.95, 0.0
5 <y ≦ 0.5, 0.01 <b ≦ 0.4)), x + b of the surface portion is 1.01 with respect to the alloy average x + b.
X or more, y is 0.1 or more and 0.9 or less with respect to the average y of the alloy, and the average x of the entire alloy is up to 800 μm in depth.
A nitrogen-containing sintered hard alloy characterized by returning to + b, y, and having no WC particles on the surface portion or 0.1% by volume or less even if they are present. 5. A hard phase comprising at least one kind of carbides, nitrides, carbonitrides of at least two kinds of transition metals selected from the groups 4a, 5a and 6a of the periodic table, or composite carbonitrides thereof. And a nitrogen-containing sintered hard alloy consisting of a binder phase containing Ni and Co and unavoidable impurities, the maximum value of the binder phase amount exists in the depth range of the binder metal phase amount from 3 μm to 500 μm from the surface. Is 1.1 times or more and 4 times or less the alloy average binder phase amount, and the depth is 800 μm.
To the average binder phase amount of the entire alloy, and the binder phase amount of the surface part is 0.9 times or less than the binder phase highest part, and for the hard phase, the metal forming the hard phase The composition of the components is (Ti _x W _y Mo _b M _c ) (where M is Ti, W, M
Hard phase forming transition metal components other than o, x, y, b, c are atomic ratios x + y + b + c = 1 (0.5 <x ≦ 0.95, 0.0
5 <y ≦ 0.5, 0.01 <b ≦ 0.4) is satisfied), x of the surface portion is 1.01 times or more the x of the alloy average,
y + b is 0.1 or more and 0.9 or less with respect to the average y + b of the alloy, returns to the average x, y + b of the entire alloy by a depth of 800 μm, and WC particles are not present or present on the surface portion. Also, the nitrogen-containing sintered hard alloy is characterized by being 0.1% by volume or less.