JPH08199283A - Titanium carbonitride-base alloy - Google Patents

Abstract

PURPOSE: To improve the performance of a titanium carbonitride-base alloy at the time of use as a cutting tool for high-speed cutting and high-feeding cutting by specifying a hard titanium carbonitride-base alloy, to which specific metals are added, and the grain sizes and contents of solid-solution grains, respectively. CONSTITUTION: This alloy consists of 80-95wt.% of hard phase consisting of the carbide, nitride, carbonitride of Ti and at least one metal, other than Ti, selected from the group IVa, Va, and VIa metals of the periodic table and the balance binding phase composed essentially of iron group metal with inevitable impurities. Further, when this alloy is observed by means of a scanning electron microscopic structure photograph, the grains of the hard phase in the alloy are essentially constituted of grain A whose core part has a black color enriched in Ti and grain B whose core part has a white color deficient in Ti, and the average grain size of the grains A and the average grain size of the grains B are regulated to 0.7-1.5μm and 0.1-0.7μm, respectively. Further, it is preferable to regulate the area ratio of the grains A comprising in the hard phase to 60-90%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of titanium carbonitride based alloy (so-called cermet), which is particularly required to have heat crack resistance and plastic deformation resistance such as high speed cutting, high feed and high depth of cut. The present invention relates to a cermet that can be used as a cermet tool that exhibits excellent performance over a long period in heavy cutting.

[0002]

PRIOR ART Titanium carbonitride based alloy (cermet) is WC
Since it has superior oxidation resistance and abrasion resistance compared to the base alloy,
Widely used as a cutting tool. However, the conventional cermet is mechanically liable to be damaged and weak in thermal shock, so that its use is limited. Therefore, various methods for improving fracture resistance have been proposed. Japanese Unexamined Patent Publication (Kokai) No. 5-186843 discloses that coarse particles having an average particle diameter of 2 to 8 μm are dispersed in an amount of 10 to 50% by volume in a fine particle matrix of a hard component having an average particle diameter of less than 1 μm.
A titanium-based carbonitride-sintered alloy in which the average grain size difference between fine grains and coarse grains is 1.5 μm or more is described. This alloy has improved toughness and wear resistance. However, in the alloy described in this patent, when intermittent cutting is carried out under a rather large load, defects often occur starting from coarse grains of 6 μm or more, and the toughness is not sufficient.

Further, in recent cutting processes, high efficiency of cutting is required, and high-speed cutting and high-feed cutting tend to be used. However, known TiCN-based cermet cutting tools were used for high-speed cutting and high-feed cutting. In the present case, the service life is reached in a relatively short time.

The present inventors have found that TiC, TiCN, or TiN among these components forming the hard phase, or Va, VIa
By optimizing the particle size of the solid solution containing one or more of group metals, it exhibits excellent durability against thermal cracks and thermal shocks that occur in high-speed cutting, high-feed cutting, and high-cut cutting. I found out that. Also, VIa
It has been found that when the solid solution of the group metal to the binder phase progresses sufficiently, the hardness of the binder phase increases and an excellent wear resistant alloy is obtained. The present invention has been made based on these findings.

[0005]

It is an object of the present invention to provide a TiCN based alloy for cermet cutting tools which has a long service life.

[0006]

DISCLOSURE OF THE INVENTION The present invention relates to a carbide, a nitride, and a carbonitride of Ti and at least one metal selected from the group IVa, Va, and VIa metals other than Ti. In the hard carbonitride-based alloy consisting of 80-95% by weight of the hard phase and the balance being the unavoidable impurities and the binder phase having the iron group metal as the main component, a scanning electron microscope microstructure photograph is obtained after polishing the alloy cross section. When observed, the particles of the hard phase in the alloy appear as black with the core rich in Ti.
And a particle B whose core has a poor Ti content and which looks white. The average area of the particle A in the polished cross section is in the range of 0.7 to 1.5 μm ² , and the average area of the particle B is
A hard titanium carbonitride-based alloy characterized by being in the range of 0.1 to 0.7 μm ² .

The composition of the hard phase titanium carbonitride can be represented by [Equation 1]: [Equation 1] (Ti, M) ₁ (C _u N _V ) _z (where M is IVa other than Ti, Represents at least one metal selected from the group consisting of Va and VIa metals, u,
v and z represent numbers in the following range: u + v = 1, 0.2 ≧ v ≧ 0.6, 0.75 ≧ z ≧ 0.95)

When the group VIa metals Mo, W and Cr are selected as M, these metals dissolve in the hard phase as well as in the binder phase and exhibit solid solution strengthening. When the V group metals V, Nb, and Ta are selected as M, these metals mainly form a solid solution in the hard phase and form a double structure to improve wear resistance. When a group IVa metal, Zr or Hf, is selected as M, these metals are effective for strengthening the binder phase, but on the other hand, they significantly reduce the sinterability and easily generate vacancies. The addition amount is preferably 2% or less. N
Is effective for improving the strength of cermet, but the value v of N is
If it exceeds 0.6, the sinterability is impaired, and if it is 0.3 or less, the effect of N addition is small. The value of Z should be 0.95 or less. By doing so, it is possible to form a low carbon alloy to promote the solid solution of M metal in the binder phase and strengthen the solid solution. If it exceeds this value, an FC precipitation alloy is likely to be formed. Also, set the value of Z to 0.
If it is less than 75, the intermetallic compound is precipitated, the toughness is lowered or the transverse rupture strength is greatly varied, and the performance is varied.

The binder phase can be at least one iron group metal and has a ratio of 5 in a hard titanium carbonitride based alloy.
~ 20% by weight.

When observed by scanning electron micrograph, the particles of the hard phase in the alloy of the present invention are, as shown in FIG. 1, particles having a black core (that is, particles A whose core is rich in Ti or Black core particles) and particles having a white core (that is, particles B or white core particles having a poor Ti core).
They can be divided into types. The feature of the present invention resides in that the average particle area of these particles is in the following range: Black core particles 0.7 to 1.5 μm ² White core particles 0.1 to 0.7 μm ²

Here, the "particle area" is the area occupied by individual particles of the hard phase in the alloy as seen when the cross section of the alloy is polished and the polished cross section is observed with a scanning electron micrograph. The "average particle area" is its average (for example, the geometric average of the particle areas of the particles in the field of view of the scanning electron microscope), and the "maximum particle area" is the maximum particle area.

This average particle area can be calculated with the naked eye from a microstructure photograph, but it can also be calculated using an image processing technique in the following procedure. That is, (1) First, the cermet alloy is polished and a 5,000 times structure photograph is taken with a scanning electron microscope. (2) After identifying grain boundaries in a region of 14 μm × 17 μm, an image is read into a computer using a scanner. (3) Next, in the image after the identification of the grain boundaries, the particles having the black core are painted black to the grain boundaries, and again read into the computer by using the scanner. (4) The white core particles are extracted by taking the difference between the image read first and the image painted black. (5) The number of pixels occupied by each particle is calculated, the area of one pixel is calculated from the magnification, and the area of each particle is calculated. (6) Obtain the distribution of the area of each particle from the area of all white core particles. (7) Obtain the area and distribution of the black core by the same method. (8) Obtain the average particle area and the maximum particle area from the obtained distribution.

In the actual scanning electron microscope observation, the hard phase can be distinguished into particles having a black core and particles having a white core as shown in FIG. 1, and 10 fields of view per 1 cm ^{2 of} 4,800 times photograph are analyzed by image analysis. Then, the area and number of individual particles of the hard phase are calculated.

[0014]

When the average particle size of the white core particles is 0.7 μm ² or more, the abrasion resistance is significantly reduced. On the other hand, when the average particle size of the white core particles is 0.1 μm ² or less, the particles are likely to come off and the crater wear increases. On the other hand, if the average particle size of the black core particles is 0.7 μm ² or less, crack propagation cannot be suppressed, sufficient fracture toughness cannot be obtained, and the black core particles are broken in a short life. Conversely, the average particle size of the black core particles is 1.5 μm ²
In the case above, the hardness is lowered, the wear resistance is lowered, and it becomes a starting point of fracture, so that a desired effect cannot be obtained. The maximum particle size of the white core particles is 5 μm ² . If the maximum particle size exceeds this value, the wear resistance decreases. The area ratio of the white core particles in the hard phase is preferably 10 to 40%. If the ratio of the white core particles exceeds 40%, the wear resistance decreases.

Coarse-grained black core particles improve wear resistance, and when the particle size becomes large, the toughness is improved due to the effect of suppressing crack propagation. However, the maximum particle area is 20
If particles exceeding μm ² are present, the impact and vibration during cutting of the tool cannot be completely absorbed, and it tends to become the starting point of fracture.

The binder phase of the alloy of the present invention preferably has a lattice constant of the binder metal in the range of 3.590 to 3.620, particularly 3.600 to 3.615 (X-ray analyzer XRD / RU-300, Cu.
-K line, excitation condition 50 kv -200 mA, 2θ = 40 to 45 °,
(Analysis of Co ・ Ni (111) plane). If the lattice constant is 3.590 or less, solid solution strengthening is insufficient, and if it is 3.615 or more, intermetallic compounds are likely to be formed and the strength becomes unstable. In addition, alloys in this range have high hardness at high temperature, and the cutting edge during cutting is also difficult to deform.

[0017]

Example Production of Sintered Body Commercially available TiCN, TiC, TaC, NbC, WC, Mo ₂ C, Ni and Co powders were used. TiCN, TiC, TaC and Nb
C is a black core particle constituent powder, which was used after being mixed and then roughened in N ₂ at 1,400 to 2,000 ° C. On the other hand, Ta
C, NbC, WC and Mo ₂ C are white core particle constituent powders, which were preliminarily crushed in a wet ball mill by using superhard balls, and atomized to adjust the particle size. After adding 3 to 5% of paraffin as a molding aid to a mixture of the powders shown in [Table 1] and [Table 2] in the composition ratios shown in each table, in an stainless steel container using an alcohol or acetone solvent. Then, it was mixed and ground with a WC-based cemented carbide ball. In addition,
Table 2 shows comparative examples.

[0018]

[Table 1]

[0019]

[Table 2]

[0020] After the evaporative drying of the solvent from the obtained mixed powder, the mixed powder was compression molded at a pressure of ^{0.5ton / cm 2 ~5ton / cm 2} , 10 -3 ~10 -2 mmHg vacuum (or mixed (Equal to the equilibrium nitrogen partial pressure of the powder, the nitrogen partial pressure is 0.1 to 100 Torr).
Liquid phase appearance temperature ~ maximum temperature 1,400 ~ 1600 ℃ 60 ~ 90
After holding for 1 minute, vacuum or carbon monoxide atmosphere for 1 to 300
It was made Torr and cooled to 1,100 ° C or lower (sintering). Two peak distributions were obtained by adjusting the particle size distribution. The amount of solid solution in the bonding layer was adjusted by blending metal W instead of WC. The obtained sintered body is chemically analyzed and hard phase components (Ti, T
a, Nb, Mo, W), the binder phase components (Ni, Co) and the light elements (C, N) were quantified, and the values of v and z were obtained.

Evaluation of Sintered Body After the obtained sintered body was flat-polished and buffed, 10 fields of view of a scanning electron microscope at 4,800 times were image-analyzed to analyze the grain size of the hard phase (white core). Calculate maximum particle size, average particle size and area of particles and black core particles). Further, the lattice constant of the binder phase was obtained by X-ray diffraction. The results obtained are shown in [Table 3] and [Table 4].

[0022]

[Table 3]

[0023]

[Table 4]

Cutting test From the obtained sintered body samples 1 to 18, a cutter tip SNMN
432 was prepared and a cutting test was conducted under the following conditions. (1) milling wear test work SCM435 HS37 (100 × 300mm) dry at 10 pass, the cutting speed v = 200 m / min Feed rate f = 0.2 mm / blade cut d = 2.0 mm measurement items V _B wear amount ([mu] m)

(2) Milling toughness test work S50C φ16 (78 holes) (150 × 300) Wet, 3 passes / 1 corner, n = 4, cutting speed v = 200 m / min Feed speed f = 0.2 mm / blade cutting d = 2.0 mm measurement Cutting length up to fracture / 3,600 mm = breakage rate The results are summarized in [Table 5] and [Table 6].

The results of the wear resistance test of Samples 1 to 9 of the present invention show that the flank wear amount V _B is 200 μm or less, the fracture rate in the toughness test is 35% or less, and the fracture toughness value K1C It is a very strong alloy as shown in. When the content of N is reduced (Comparing Sample 3 and Sample 11), the wear resistance decreases. On the other hand, if the Z value is too low, an intermetallic compound is formed, so that the fracture toughness is significantly reduced (Sample 10). The presence of coarse particles of white-core particles and black-core particles (Sample 14) appears as an increase in the fracture rate in the toughness test due to the initial defect, and causes variations in the toughness.

[0027]

[Table 5]

[0028]

[Table 6] ☆: Large crater wear

[0029]

From the above results, the titanium carbonitride-based alloy of the present invention markedly improves the heat crack resistance in cutting such as a milling cutter and greatly improves the fracture toughness, so that it can be used as a cermet cutting tool having a long service life. Can be used.

[Brief description of drawings]

FIG. 1 is a conceptual explanatory view of particles observed when a hard titanium carbonitride-based alloy of the present invention is observed by a scanning electron microscope structure photograph.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Nobuyuki Kitagawa 1-1-1 Kunyokita, Itami City, Hyogo Prefecture Sumitomo Electric Industries, Ltd. Itami Works

Claims (5)

[Claims] 1. A hard phase composed of carbides, nitrides, and carbonitrides of Ti and at least one metal selected from metals of the IVa, Va, and VIa groups of the periodic table other than Ti has a hard phase of 80 to 80.
95% by weight, the balance consisting of a binder phase mainly composed of iron group metal and unavoidable impurities, when observed in a scanning electron microscope structure photograph in a hard titanium carbonitride-based alloy, particles of the hard phase in the alloy The core is mainly composed of two kinds of particles A, which is rich in Ti and looks black, and particle B whose core is poor in Ti, which looks white.
In the range of 1.5 [mu] m ^2, 0.1 to the average area of the particles B 0.
A titanium carbonitride based alloy characterized by being in the range of 7 μm ² . 2. The area occupied by the hard phase of the particles A is 60 to 90%.
The alloy according to claim 1, wherein 3. The maximum particle area of the particle A is 20 μm ² or less when observed with a scanning electron microscope structure photograph,
The maximum particle area of particle B is 5 μm ² or less.
Or the alloy according to 2. 4. The alloy according to any one of claims 1 to 3, wherein the hard phase is titanium carbonitride having a composition represented by [Formula 1]: [Formula 1] (Ti, M) ₁ ( C _u N _V ) _z (where M represents at least one metal selected from the group IVa, Va and VIa metals other than Ti, u, v and z represent a number in the following range: u + v = 1.0, 0.2 ≧ v ≧ 0.6, 0.75 ≧ z ≧ 0.95) 5. The alloy according to claim 4, wherein the binder phase is composed of a metal of Ni and / or Co, and the lattice constant of the binder metal is 3.590 to 3.620Å.