JP2001139375A - Tib2-ti(cn)-based composite and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly obtain a TiB2-Ti(CN)-based composite which does not require the use of fine raw material powder controlled to several μm order or below as sintering powder, allows the easy control of a non-stoichimetric property by changing the mixing ratio of the powder in spite of the raw mate rial powder having the non-stoichiometric property and has a high density, high hardness and excellent fracture toughness value. SOLUTION: This TiB2-Ti(CN)-base composite is prepared by sintering the powder mixture essentially consisting of titanium powder (Ti), boron carbide (B4C) powder and boron nitride (BN) powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates is a high density and high hardness, and excellent fracture toughness TiB 2 _-Ti (CN)
The present invention relates to a system composite and a method for producing the same.

[0002]

2. Description of the Related Art Titanium carbides, borides, nitrides, and composites thereof are promising as structural materials because of their relatively light weight and excellent mechanical properties, and many syntheses have been studied. These include cutting tools, target materials, drawing dies, nozzles, electrodes, automotive parts,
It can be used for molds and the like. Under such circumstances, the TiB ₂ —Ti (CN) -based composite has attracted special attention because of its high hardness and excellent fracture toughness.
(Note that the ratio of C to N in Ti (CN) varies over a wide range, and does not always correspond to 1: 1. Therefore, unless otherwise specified in the present specification, those variables vary. The mixing ratio of TiB ₂ and Ti (CN) can be variously changed and does not always correspond to 1: 1 and unless otherwise specified in this specification. However, it is generally assumed that the above-mentioned materials are all appropriately changed.) However, it is generally difficult to sinter the above materials without adding a sintering aid, and it is difficult to perform hot pressing or HI.
Sintering by P is performed. In addition to such a sintering method of applying pressure and heating, a method of simultaneously performing synthesis and sintering, for example, pressure self-combustion sintering in which solidification is performed by sintering synthesis while applying pressure or solid phase replacement while hot pressing Reactive hot pressing, which causes a reaction, has also been applied to solidification of these compounds.

[0003] These methods are of interest because they solidify while causing mass transfer by a chemical reaction, so that a tissue that cannot be formed by simple mixing can be obtained. In recent years, spark plasma sintering, which is a type of current pressure sintering, has begun to be applied to densification of difficult-to-sinter materials. This is an attractive method of energy saving because a pulsed current is applied while the powder is being pressed to directly heat the sample and the mold, enabling rapid temperature rise. If the technique of reactive hot pressing can be applied to this spark plasma sintering, there is a possibility that this method can be widely applied to densification of difficult-to-sinter materials.

On the other hand, in the conventional TiB ₂ -Ti (CN) -based composite, a TiB ₂ powder, a TiC powder, a TiN powder or a Ti (CN) powder is mixed and sintered at a high temperature (normal pressure sintering, Hot pressing, HIP, etc.) have been used to produce sintered bodies. However, when such a powder is used, the target hardness, density, and fracture toughness value cannot be achieved unless a fine raw material powder controlled to the order of several μm or less is used and uniformly mixed. There is a problem that the cost increases.

In addition, TiC or Ti mixed with TiB ₂
N has a strong nonstoichiometric property, which greatly affects the strength of the sintered body. For this reason, when the TiB ₂ powder is mixed with the TiC powder, TiN powder or Ti (CN) powder and directly sintered as described above, the sintering process cannot control the non-stoichiometric property. There is a problem that the specificity greatly affects the properties of the product. Of stable quality TiB ₂ -
In order to produce a Ti (CN) -based composite, the raw material itself needs to have excellent sinterability, and at the same time, has a low non-stoichiometric ratio, that is, x = 1 or very low. It must be close raw material powder. However, in general, there is a contradictory relationship that the sinterability deteriorates as x = 1, which is a condition where the non-stoichiometric ratio is small, and there has been a problem that manufacturing becomes difficult. From the above, TiB ₂ -Ti
The (CN) -based sintered composite itself was considered to be a material having high density and high hardness and excellent properties such as fracture toughness, but its production was not always easy, and a satisfactory sintered body was obtained. I could not say that it was obtained.

[0006]

From the above, it is not necessary to use a fine raw material powder controlled to the order of several μm or less as the sintering powder, and even if the raw material powder has non-stoichiometric properties, TiB ₂ -Ti which can easily control non-stoichiometric properties by changing the mixing ratio of powders, and has high density, high hardness and excellent fracture toughness in a short time.
It is an object of the present invention to provide a production method and a sintered composite capable of obtaining a (CN) -based composite.

[0007]

As described above, the present invention provides: 1) sintering a mixed powder containing titanium powder (Ti), boron carbide (B ₄ C) powder and boron nitride (BN) powder as main components. wherein the _TiB 2 -Ti (CN) composites of the production method 2) 1, characterized in that 99% or more relative density) _TiB 2 -Ti (CN) based composite production method 3 described ) V, Cr, Mn, Fe, Co, Ni, Cu, Zr,
It is characterized by containing 0.001 to 20% by weight of at least one element selected from Nb, Mo, Ta, and W 1).
Or 2), wherein the _TiB 2 -Ti (CN) based _TiB 2 -Ti according to each of 1) to 3), wherein the method for manufacturing a composite body 4) is a sintered with the solid phase substitution reaction ( CN)
5) TiB ₂ —Ti (C) according to any one of 1) to 4), characterized in that sintering is performed by pulse current pressure sintering.
Preparation of N) Composites method _{6) TiB 2 -Ti (C x} N x-1) y ( where, 0 <x <
1, 0.7 ≦ y ≦ 1.0) TiB ₂ —Ti (C) described in each of 1) to 5), which is a composite.
N) Method for producing a composite 7) TiB ₂ particles having an average particle diameter of 20 μm or less and an average particle diameter of 2
0μm following _{Ti (C x N x-1} ) particles (where, 0 <x <
1) characterized in that it has the mixed structure of 1).
6) The method for producing a TiB ₂ —Ti (CN) -based composite according to each of the items 6).

Furthermore, the present invention relates to 8) TiB₂-Ti (C_xN_x-1)_y(However, 0 <x <
1, 0.7 ≦ y ≦ 1.0) Sintered structure
TiB characterized by the following₂—Ti (CN) -based composite 9) Titanium powder (Ti), boron carbide (B₄C) Powder and
Powder mixed with boron nitride (BN) powder as the main component
With a sintered composite structure obtained by sintering.
8) The TiB as described in 8) above.₂-Ti (CN)
10) characterized by having a relative density of 99% or more
TiB according to 8) or 9)₂—Ti (CN) based composite 11) V, Cr, Mn, Fe, Co, Ni, Cu, Z
at least one element selected from r, Nb, Mo, Ta, and W
Characterized by containing 0.001 to 20% by weight of
8) TiB according to 10)₂—Ti (CN) based composite 12) Sintering accompanied by a solid phase substitution reaction
8) to 11) each of TiB₂-Ti (C
N) series composite 13) pulse current pressure sintering 8)
To 12).₂-Ti (CN) -based
Composite 14) TiB₂-Ti (C_xN_x-1)_y(However, 0 <
x <1, 0.7 ≦ y ≦ 1.0).
TiB described in each of 8) to 13)₂-T
i (CN) -based composite 15) TiB having an average particle size of 20 μm or less₂Particles and average particle size
Ti (C _xN_x-1) Particles (however, 0 <
characterized by having a mixed structure of x <1) 8)
To 14).₂-Ti (CN) -based
A complex.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As a mixed powder for sintering, titanium powder (Ti), boron carbide (B ₄ C) powder and boron nitride (BN) powder are used. Although B ₄ C has non-stoichiometric properties,
Not in N. Therefore, if the analytical values are known, the nonstoichiometry can be easily controlled by changing these mixing ratios, and the nonstoichiometry of the raw material does not affect the product. A hot press method can be used as a sintering method. However, when a pulse current pressure sintering method (discharge plasma sintering method) is used, a high temperature can be obtained in a short time, and the time until a product is obtained can be greatly reduced. Has features.

[0010] Pulse current pressure sintering is a method in which a sintering material is put into a graphite mold and heated by applying a large pulse-like current while pressurizing the sintering material. Current flows through the device and the temperature rises locally.
It is considered that the diffusion of atoms is promoted by the local high temperature, and a solid-phase reaction occurs efficiently. Titanium carbides, borides, and nitrides are difficult-to-sinter materials and originally difficult to densify without the addition of sintering aids.
₄ C, can be solidified in a short period of time while causing solid phase substitution reaction of BN, obtain a dense _TiB 2 -Ti (CN) based sintered complex.

[0011] The sintering temperature is 1600 ° C or more, and the pressing force is 2
Although 0 MPa or more is required, in particular, 1800 ° C. or more,
The pressure is desirably 30 MPa or more. (Note that the sintering temperature at this time means the temperature of the surface of the graphite mold (beside the portion filled with the sintering material) used in hot pressing and pulse current pressure sintering.) The pressing force can be appropriately determined according to the type of the sintering material and the like.

The movement distance of the substance by the solid-phase displacement reaction is estimated to reach several tens μm to 100 μm. Ti,
B ₄ C and BN powder sintering materials each having a purity of 99% or more are used. The particle size of Ti powder is 30 μm or less (preferably 10 to 30 μm), the particle size of B ₄ C is 10 μm or less.
It is desirable to use a powder of N powder having a particle size of 10 μm or less.
A powder having a particle size of 20 μm or less, a particle size of B ₄ C of 20 μm or less, and a particle size of BN powder of 10 μm or less can also be used. Even when a relatively large raw material powder is used, the structure is rearranged, and a fine TiB ₂ —Ti (CN) -based sintered composite is obtained. It is preferable that the particle size of the Ti powder is larger than the particle sizes of the B ₄ C powder and the BN powder. In this way, it is necessary to use strict raw material powders controlled to the order of several μm or less, and strict control of the raw material powders that the target hardness, density, and fracture toughness value cannot be achieved unless they are mixed uniformly. The method of the present invention has a great advantage in that the manufacturing cost can be significantly reduced as compared with the conventional method in which the manufacturing cost is high.

The structure of the obtained TiB ₂ —Ti (CN) -based sintered composite is composed of TiB ₂ particles having an average particle diameter of 20 μm or less and Ti (C _x N _x−1 ) particles having an average particle diameter of 20 μm or less (however, 0 <x <1) is provided. FIG. 1 shows a micrograph of the structure. In addition, this is Ti, B ₄ C,
The BN powder was sintered at a sintering temperature of 2000 ° C. for a holding time of 20 minutes.
At a pressure of 50 MPa, 2B ₄ C + 2BN + 9Ti → 5T
₁ shows a sintered structure of a TiB ₂ —Ti (CN) -based composite sintered by the reaction of iB ₂ + 4Ti (C _0.5 N _0.5 ). In Figure 1, the white portion is a _{Ti (C x N x-1} ) particles, the black portion is a TiB ₂ particles. The tissue can also be expressed as a mesh-like TiB ₂ tissue _{Ti (C x N x-1} ) particles are uniformly mixed. Such a dense structure has a high hardness and a high toughness, and the reason why the high toughness is particularly exhibited is a network-like structure generated by the reaction. Thus, the sintered composite of the present invention has a 99%
Having the above relative density and a fracture toughness value of 4.0 MPam
TiB ₂ − exceeding ^1/2 and reaching Vickers hardness 2120
A Ti (CN) -based composite can be obtained.

The TiB ₂ —Ti (CN) based composite of the present invention further comprises V, Cr, Mn, Fe, Co, Ni, Cu,
One or more elements selected from Zr, Nb, Mo, Ta, and W can be contained in an amount of 0.001 to 20% by weight. Thereby, the fracture toughness value is further improved, and
A sintered composite reaching Pam ^1/2 can be obtained.
The reason why the lower limit of the addition amount is set to 0.001% by weight is as follows.
If the amount is less than 0.001% by weight, there is no effect of the addition, and the upper limit is set to 20% by weight.

Further, the present invention relates to a method for producing titanium powder (Ti),
Boron (B₄C) Distribution of powder and boron nitride (BN) powder
By changing the ratio, TiB₂-Ti (C_xN
_x-1) _y(However, 0 <x <1, 0.7 ≦ y ≦ 1.0)
TiB of various compositions with sintered structure₂-Ti (CN)
A system complex can be obtained. As shown in the examples below
In addition, the bulk density decreases as x increases, but the relative density becomes
And the Young's modulus increases (the Poisson's ratio decreases
And the fracture toughness and Vickers hardness also increase.
You.

When y increases in the range of 0.7 ≦ y ≦ 1.0, the bulk density increases, the relative density decreases, and the Poisson's ratio slightly decreases, but the Young's modulus increases, and the fracture toughness increases. Values and Vickers hardness tend to increase. In other _words, becomes dense as the value of y is reduced in _{Ti (C x N x-1} ) y, becomes easy sintering. As shown above, in the present invention controls nonstoichiometric in _{Ti (C x N x-1} ) y is merely readily achievable by changing the compounding ratio of raw material powders. Compared to the conventional sintering method in which a raw material having an appropriate non-stoichiometric ratio must be synthesized in advance, it has a great feature that it can be controlled much more easily.

[0017]

Embodiments will be described below with reference to embodiments. The present embodiment shows a preferred example, and the present invention is not limited to these embodiments. Therefore, modifications within the scope of the technical idea of the present invention, other embodiments and modes, etc. are included in the present invention.

Example 1 As sintering powders, B ₄ C powder (average particle size 1.5 μm, purity 99%), BN powder (average particle size 24.5 μm, purity 99.5%), Ti Powder (average particle size 6.0 μm, purity 99.5%) was used.
These powders Scheme _{2xB 4 C + 2 (1-} x) BN
+3 (x + 1) Ti → (3x + 1) TiB ₂ + 2Ti
_{(C x N 1-x)} were mixed variously varied weighed x assumes. This mixed powder was filled into a graphite mold having an inner diameter of 20 mm and an outer diameter of 50 mm, and a pressure of 50 MPa and a heating rate of 50 mm.
° Cmin ^-1 , sintering temperature 2000 ° C, holding time 20
Sintering was performed in vacuum using a discharge plasma sintering apparatus under the conditions of min. About the obtained sintered body, density, Young's modulus,
Poisson's ratio, Vickers hardness, and fracture toughness were measured and analyzed by X-ray diffraction and EPMA.

X = 0 to 1 (for a test sample, x =
Those with 0 and x = 1 were also used. FIG. 2 shows the relationship between x, the relative density and the bulk density of the sample subjected to the reactive discharge plasma sintering using the powder of (2). The bulk density gradually decreased, but the relative density increased rapidly when x increased from 0 to 0.1, and then gradually increased. When x = 0, a constant ratio of TiN _1.0 having poor sinterability adversely affects the densification,
It is presumed that the sinterability was improved by increasing the non-stoichiometric property of TiN with the increase of x. FIG. 3 shows the relationship between Young's modulus and Poisson's ratio and x. As with the relative density, x =
0 has a low Young's modulus due to a low relative density, and x
Increased to 0.1, and then increased gradually. The Poisson's ratio was almost constant between 0.16 and 0.19.

FIG. 4 shows the relationship between Vickers hardness and x.
The hardness of the sintered body at x = 0 was low, but increased as x increased, and reached a maximum at x = 0.5, and the Vickers hardness at that time was 2120. FIG. 5 shows the relationship between the fracture toughness value and x. The fracture toughness value of the sintered body at x = 0 was low, but increased as x increased, and reached a maximum at x = 0.5, at which time the fracture toughness value was 4.0 MPam ^1/2 . X =
At 0.7, there was a tendency to temporarily decrease, but at x = 1, the equivalent fracture toughness value was 4.0 MPam ^1/2 . From the above Young's modulus, hardness and fracture toughness values, it can be seen that the value of x in the above reaction formula is good in the range of 0.3 to 1, especially in the vicinity of 0.5. In particular, although not shown, V, Cr,
Mn, Fe, Co, Ni, Cu, ZrNb, Mo, T
a, one or more elements selected from W
By adding the weight%, the fracture toughness value can be further improved, and its fracture toughness value is 10 to 15 MPam.
It was possible to obtain a sintered composite reaching ^1/2 .

(Example 2) The same powder as in Example 1 was used, and x = 0.5, which takes good values of the Young's modulus, hardness and fracture toughness, was fixed, and the reaction formula B ₄ C + BN + (5 / 2
+ 2 / y) Ti → (5/2) TiB ₂ + 2 / yTi (C
_0.5 N _0.5) assumes the _y were mixed variously varied weighed y. Further, this mixed powder was treated with an inner diameter of 2 as in the example.
Filled in a graphite mold having a diameter of 0 mm and an outer diameter of 50 mm, a pressure of 50 MPa, a heating rate of 50 ° Cmin ⁻¹ , and a sintering temperature of 2
Sintering was performed in vacuum using a discharge plasma sintering apparatus under the conditions of 000 ° C. and a holding time of 20 minutes. The obtained sintered body was measured for density, Young's modulus, Poisson's ratio, Vickers hardness, and fracture toughness, and analyzed by X-ray diffraction and EPMA.

FIG. 6 shows the relationship between y and the relative density and bulk density when y is changed in the range of 0.7 ≦ y ≦ 1.0. As y increases, the bulk density gradually increases, but the relative density conversely reaches a maximum at y = 0.7 and is already 9
Reaches 9.8%. However, thereafter, as y increases, the relative density decreases, dropping to 99.1 at y = 1. It can be seen that reducing the amount of y is effective for increasing the density. Similarly, FIG. 7 shows the relationship between y and Young's modulus and Poisson's ratio. As in the case of the relative density, when the ratio of y decreases from y = 0.7 to 1.0, the Young's modulus tends to decrease. Poisson's ratio was almost constant.

FIG. 8 shows the relationship between Vickers hardness and y.
The hardness of the sintered body at y = 0.7 was low, but increased as y increased, and reached a maximum at y = 1, and the Vickers hardness at that time was 2120. However, it can be seen that the Vickers hardness exceeds 2,000 even at y = 0.7. FIG. 9 shows the relationship between the fracture toughness value and y. Although the fracture toughness value of the sintered body at y = 0.7 is low, it increases as y increases, and y = 0.7
The maximum value is 1.0 and the fracture toughness value at that time is 4.0MP.
am was over ^1/2 . Above relative density, Young's modulus,
From the viewpoint of the hardness and the fracture toughness, it is found that the value of y in the above reaction formula is effective in the range of 0.7 to 1.0.

[0024]

According to the present invention, titanium powder (Ti), boron carbide (B ₄
C) By using a mixed powder mainly composed of powder and boron nitride (BN) powder and performing sintering accompanied by a solid-phase displacement reaction using pulsed current pressure sintering or the like, an order of several μm or less. There is an advantage that it is not necessary to use fine raw material powder controlled,
It has a great feature that a TiB ₂ —Ti (CN) -based composite can be obtained at low cost. In addition, even if the raw material powder has non-stoichiometric properties, it is possible to easily control the non-stoichiometric properties by changing the mixing ratio of the powders, and to achieve a high density, high hardness, and excellent fracture toughness in a short time. It has an excellent effect of obtaining a _2- Ti (CN) -based composite. Also,
From the controllability of the production or the easiness of the operation, V, Cr, Mn, Fe, Co, Ni, Cu, Zr,
One or more elements selected from Nb, Mo, Ta, and W are added in an amount of 0.001 to 20% by weight, and TiB ₂ —Ti (C
It is possible to improve the properties of the N) -based composite, and has a feature that the fracture toughness value and the like can be further improved.

[Brief description of the drawings]

FIG. 1 is a micrograph of the structure of a sintered body of a TiB ₂ —Ti (CN) -based composite.

FIG. 2 is a reaction formula of 2 × B ₄ C + 2 (1-x) BN + 3 (x
+1) Ti → (3x + 1) TiB ₂ + 2Ti (C _x N
₁ is a diagram showing the relationship between x and the relative density and bulk density of a sample subjected to reactive discharge plasma sintering while variously changing x assuming _1-x ).

FIG. 3 is a diagram showing a relationship between Young's modulus and Poisson's ratio and x.

FIG. 4 is a diagram showing the relationship between Vickers hardness and x.

FIG. 5 is a diagram showing a relationship between a fracture toughness value and x.

FIG. 6: Reaction formula B ₄ C + BN + (5/2 + 2 / y) Ti
→ (5/2) TiB ₂ + 2 / yTi (C
FIG. 5 is a diagram showing the relationship between y and relative density and bulk density of a sample subjected to reactive discharge plasma sintering with various values of _y assuming _0.5 N _0.5 ) _y .

FIG. 7 is a view showing the relationship between Young's modulus and Poisson's ratio and y.

FIG. 8 is a diagram showing a relationship between Vickers hardness and y.

FIG. 9 is a diagram showing a relationship between a fracture toughness value and x.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C22C 29/14 C22C 29/14 AB BF term (Reference) 4G001 BA23 BA33 BA61 BA67 BB43 BB44 BB57 BB67 BC13 BC46 BC55 BC61 BD12 BD16 BD18 BD36 BE11 BE22 BE33 4K018 AB02 AB03 AB04 AC01 AD04 BA02 BA03 BA04 BA09 BA11 BA13 DA12 EA06 EA22 KA15 KA18 KA19 KA37 KA62

Claims (15)

[Claims] 1. Titanium powder (Ti), boron carbide (B ₄
C) sintering a mixed powder mainly composed of powder and boron nitride (BN) powder, wherein TiB ₂ -Ti (C
N) A method for producing a composite. 2. The method for producing a TiB ₂ —Ti (CN) -based composite according to claim 1, having a relative density of 99% or more. 3. V, Cr, Mn, Fe, Co, Ni, C
u, Zr, Nb, Mo, Ta, TiB 2 -Ti (CN) based composite according to claim 1 or 2, characterized in that it contains 0.001 to 20 wt% of one or more elements selected from W How to make the body. 4. The TiB ₂ -T according to claim 1, wherein the sintering is accompanied by a solid phase substitution reaction.
A method for producing an i (CN) -based composite. 5. The TiB _{2 according} to claim 1, wherein the sintering is performed by pulse current pressure sintering.
-A method for producing a Ti (CN) -based composite. 6. The composite according to claim 1, wherein the composite is a TiB ₂ —Ti (C _x N _x−1 ) _y (where 0 <x <1, 0.7 ≦ y ≦ 1.0) system composite. TiB described in each of Nos. 1 to 5
_A method for producing a _2- Ti (CN) -based composite. 7. A mixed structure of TiB ₂ particles having an average particle diameter of 20 μm or less and Ti (C _x N _x-1 ) particles having an average particle diameter of 20 μm or less (where 0 <x <1). The TiB ₂ —Ti (C) according to each of claims 1 to 6
N) A method for producing a composite. 8. It is characterized by having a sintered structure of TiB ₂ —Ti (C _x N _x−1 ) _y (where 0 <x <1, 0.7 ≦ y ≦ 1.0). A TiB ₂ —Ti (CN) -based composite. 9. Titanium powder (Ti), boron carbide (B ₄
The TiB _{2 according} to claim 8, comprising a sintered composite structure obtained by sintering a mixed powder containing C) powder and boron nitride (BN) powder as main components.
-Ti (CN) based composite. 10. The TiB ₂ —Ti (C) according to claim 8, having a relative density of 99% or more.
N) -based complex. 11. V, Cr, Mn, Fe, Co, Ni,
Cu, Zr, Nb, Mo, Ta, TiB 2 -Ti (CN) based composite according to claim 8-10, wherein the one or more elements selected from W contains 0.001 to 20 wt% body. 12. The TiB _{2 according} to claim 8, wherein the sintering is accompanied by a solid phase substitution reaction.
-Ti (CN) based composite. 13. The TiB ₂ -T according to claim 8, wherein sintering is carried out by pulse electric current pressure.
i (CN) -based complex. 14. TiB ₂ —Ti (C _x N _x−1 )
_y (where, 0 <x <1,0.7 ≦ y ≦ 1.0) based _TiB 2 -Ti (CN) based composite according to each of claims 8 to 13, which is a complex . 15. A mixed structure of TiB ₂ particles having an average particle diameter of 20 μm or less and Ti (C _x N _x-1 ) particles having an average particle diameter of 20 μm or less (where 0 <x <1). The TiB ₂ -T according to any one of claims 8 to 14,
i (CN) -based complex.