JPH06172913A - Titanium carbide-based cermet alloy - Google Patents

Abstract

PURPOSE:To obtain a TiC-based cermet alloy having both high strength and high toughness by combining a TiC-based hard phase with a Co or Ni-based bonding phase and specifying the Ti and Mo contents of the bonding phase. CONSTITUTION:This TiC-based cermet alloy consists of a TiC-based hard phase which may contain WC as necessary and a Co- and/or Ni-based bonding phase. The Ti and Mo contents of the bonding phase satisfy the conditions of Mo/Ti>=0.85 and Ti+Mo>=6wt.% or Ti+Mo+W>=7wt.%. Feeding sources for Ti and Mo allowed to enter into solid soln. in the bonding phase are TiC in the hard phase and added metallic Mo. The pref. amt. of Co or Ni added is about >=15vol.% and that of WC is about 5-50vol.%. The bonding phase is strengthened, the hardness is made equal to or higher than that of TiCN and excellent toughness can be ensured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to titanium carbide (hereinafter referred to as "T
The present invention relates to a TiC-based cermet alloy having high strength and high toughness by strengthening the binder phase.

[0002]

2. Description of the Related Art At present, a titanium nitride (hereinafter referred to as "Ti (C, N)") base alloy containing nitrogen is predominantly used as a cermet alloy for tools. This Ti (C, N) -based cermet alloy has improved room temperature strength, oxidation resistance, and cutting performance as compared with the conventional TiC-based cermet alloy.

Both TiC-based and Ti (C, N) -based cermet alloys have a core (TiC, Ti (C, N)) and surrounding structures ((Ti, Mo) C, (Ti, Mo)).
The hard phase is formed by particles having a core structure composed of (C, N)), but the particle diameter of the Ti (C, N) -based cermet alloy is made fine by containing nitrogen. And it is said that the room temperature strength is improved by this grain refinement.

It is also known that Ti (C, N) -based cermet alloys have excellent high temperature strength.

"Powder and Powder Metallurgy, Vol. 30, No. 3, (19
83.4) "in it are described in detail regarding the high-temperature strength of the TiC-Mo ₂ C-Ni alloy containing nitrogen, have a high-temperature strength in which the alloy has excellent Mo is more solid solution in the so-called binder phase It is explained that the dynamic recovery of the bonded phase was suppressed. Here, the mechanism of solid solution of Mo in the binder phase is not described in the above document, but it can be presumed to be due to the following. That is, Ti that has been supersaturated by denitrification from Ti (C, N) during vacuum sintering combines with C of Mo ₂ C to form a carbide, and excess Mo dissolves in the binder phase. is there.

Further, it is described in the above-mentioned document that the solid solution amount of Mo in the binder phase increases as the amount of nitrogen increases, and the amount of Mo ₂ C as a source of Mo increases. For _{example, TiC 0.7 N 0.3 -11% Mo} 2 C-24% Ni
Alloy having a composition (wt.%) Of Mo in the binder phase of 3.4 wt.% (Ti solid solution amount of 9.3 wt.%), TiC _0.7 N _0.3 −1
9% Mo ₂ C-24% Ni alloy (blending composition wt.%) Has a Mo content of 1
The amount of Mo in the TiC-11% Mo ₂ C-24% Ni alloy containing no nitrogen (blending composition wt.%) Is 0, whereas the amount of Mo is 0.0 wt.% (Ti solid solution amount is 9.3 wt.%). .2 wt.% (Ti solid solution amount 12.7 wt.
%) And the TiC-19% Mo ₂ C-24% Ni alloy has an Mo amount of 1.8 wt.% (Ti solid solution amount of 16.3 wt.%). From this result, it can be easily understood that it would be extremely difficult to strengthen the binder phase in the TiC-based cermet alloy containing no nitrogen even if the addition amount of Mo ₂ C is increased.

[0007]

As described above, Ti (C,
The N) -based cermet alloy has excellent properties as compared with the TiC-based cermet alloy, but denitrification occurs during vacuum sintering, causing a property change between the surface and the inside of the alloy, and pores in the structure. There is a problem that it easily occurs. When pores are generated in the structure, the Ti (C, N) -based cermet alloy cannot have the original strength.

With respect to this problem, various proposals have been made to introduce nitrogen gas during sintering and to control the temperature rising conditions (for example, Japanese Patent Laid-Open No. 2-9303).
No. 6, No. 2-145741, etc.). However, the above proposal is not desirable in terms of productivity.

Further, the Ti (C, N) -based cermet alloy has a property that it is easy to obtain high hardness but inferior in toughness as compared with the TiC-based cermet alloy. Various improvements have been proposed in this regard as well, and the applicant of the present invention has also proposed JP-A-6
No. 3-83241 proposed a method of adding WC independently from a solid solution with TiCN, but no essential improvement has been made.

Therefore, the present invention strengthens the binder phase of the TiC cermet alloy, which does not have the problem of denitrification during sintering, to have a hardness equal to or higher than that of the Ti (C, N) -based cermet alloy. , TiC with particularly good toughness
The task is to provide a base cermet alloy.

[0011]

According to the above-mentioned prior art, M
Those skilled in the art can easily predict that strengthening of the binder phase will be achieved by increasing the solid solution amount of o. However, as described above, in the case of TiC-based cermet alloy, the amount of Mo solid solution in the binder phase cannot be increased even if the amount of addition of Mo ₂ C is increased like Ti (C, N) -based cermet alloy. is there.

A TiC-based cermet alloy in which a relatively large amount of Mo is solid-solved in the binder phase is referred to as "a cemented carbide and a sintered hard material.
Fundamentals and Applications (Suzuki et al., February 1986, Maruzen) "No. 31
6 to 332. For example, TiC-
10% Mo-30% Ni alloy (blending composition wt.%) Ti about 11
wt.%, Mo about 2 wt.%, TiC-20% Mo-30% Ni alloy (blending composition wt.%) Ti about 10 wt.%, Mo about 4 wt.%, T
iC-30% Mo-30% Ni alloy (blending composition wt%)
The values of about 9 wt.% And Mo about 6 wt.% Are shown, and when Mo is added as metallic Mo, the amount of Mo in the binder phase can be increased as compared with the case where it is added as carbide (Mo ₂ C). Is understood. Therefore, the present inventor has conducted a detailed study on the TiC-based cermet alloy in which metallic Mo is used as the source of Mo for forming a solid solution in the binder phase, instead of carbide (Mo ₂ C).

As a result, the amount of solid solution of Mo in the binder phase increases by increasing the amount of addition of metallic Mo, but not only the amount of solid solution of Mo in the binder phase increases, but also the amount of solid solution of Ti and It has been found that the binder phase is strengthened when there is a predetermined relationship, and as a result, the toughness can be remarkably improved while having the hardness equivalent to that of the Ti (C, N) -based cermet alloy.

The present invention was made based on this finding, and is a titanium carbide based cermet alloy comprising a hard phase mainly composed of titanium carbide and a binder phase, wherein the Ti and Mo contents in the binder phase are 6 wt. % ≦ Ti + Mo and 0.
The titanium carbide based cermet alloy is characterized by satisfying the condition of 85 ≦ Mo (wt.%) / Ti (wt.%). The present invention will be described in detail below.

In the present invention, Ti and M in the binder phase
The content of o is set to 6 wt.% ≦ Ti + Mo because it is the minimum amount necessary for strengthening the binder phase. Where T
The i and Mo contents are% by weight in the binder phase, and are represented by ICP (inductively coup) described in detail in Examples below.
led plasma) can be determined by emission spectrometry.

In order to have both excellent toughness and hardness, not only the total content of Ti and Mo in the binder phase should be within the above range, but also the amount ratio of Mo and Ti should be 0.85≤Mo (wt). .%)
It is necessary to satisfy the condition of / Ti (wt.%). This is because the toughness cannot be improved if it is less than 0.85, as shown in Examples described later.

The hard phase of the cermet alloy of the present invention is mainly composed of TiC, but it is acceptable to include other carbides. In particular, tungsten carbide (hereinafter referred to as "WC") is a substance effective in improving sinterability, and it is desirable to add it. In that case, the amount of WC added is 5 vol.% ≦ WC ≦ 50 v
It is desirable to set it in the range of ol.%. If it is less than 5 vol.%, The effect of improving the sinterability cannot be sufficiently obtained, while 50 vol.
This is because if it exceeds%, the chip welding when used as a cutting tool cannot be ignored.

Next, the binder phase is mainly composed of one or two of Co and Ni, and the hard phase of TiC is used as the strengthening element.
Ti and Mo which are the constituent elements of When WC is used for the hard phase, W is also contained as a hard phase strengthening element. When the amount of one or two of Co and Ni increases, the amount of hard phase decreases relatively and the hardness decreases. Therefore, the addition amount of one or two kinds of Co and Ni is preferably 15 vol.% Or less, more preferably 10 vol.%.

The structure of the cermet alloy of the present invention comprises a hard phase and a binder phase, and the hard phase has a so-called core structure. When TiC and WC are contained as a hard phase, a central structure relatively rich in Ti and poor in W, and (W,
It has a cored structure consisting of peripheral tissues rich in Mo) and poor in Ti. The Mo in the peripheral structure is due to the Mo added to strengthen the binder phase.

Next, a method for producing the cermet alloy of the present invention will be described. A feature of the method for producing the cermet alloy of the present invention is that Mo, which is a binder phase strengthening element, is added not as a carbide (Mo ₂ C) but as a metallic Mo. The reason is that, as already described, the addition as metallic Mo can form more solid solution in the binder phase than the addition as metallic carbide.

It is considered that addition of metallic Mo also has the effect of refining (Ti, W, Mo) C, which is a carbide forming the peripheral structure, and contributes to the improvement of toughness.

Furthermore, the addition of metallic Mo has the effect of reducing the contact between carbide particles (hereinafter referred to as "skeleton"), and contributes to the improvement of toughness. That is, T
Since the surface area of the skeleton of the iC-based cermet alloy is about 2 to 3 times larger than that of the WC-based cemented carbide, the toughness is deteriorated in order to reduce the crack propagation resistance. In particular, when added as Mo ₂ C, Mo tends to remain as a carbide in the surrounding structure, and Mo solid solution in the binder phase is reduced. However, when added as metallic Mo, the amount of Mo that enters the peripheral structure is reduced and the amount of Mo that forms a solid solution in the binder phase is increased as compared with the case where it is added as a carbide, which contributes to the reduction of skeleton.

As the metallic Mo, in addition to pure Mo, an alloy with Co and Ni which are constituent elements of the binder phase can be added.

Further, it is not necessary to add the entire amount of Mo as metallic Mo, and it is also permissible to add carbide (Mo ₂ C) mainly with metallic Mo within the range not departing from the gist of the present invention.

[0025]

EXAMPLES The present invention will be described in detail below based on examples.

TiC, WC, Mo, Co and Ni powders were prepared so as to have the compounding compositions shown in Tables 1 and 2. The average particle size of the powder is TiC: 1.5 μm, WC: 1.5 μm, C
o: 2.0 μm, Ni: 2.5 μm, Mo: 3.0 μm.

These raw material powders were put in denatured alcohol and mixed for 4 hours using an attritor. In addition, the mixing amount when making cermet is Ti which is a component of the hard phase.
C and WC are set to 60 to 90 wt% of the whole, and C which is a component of the binder phase
o, Ni and Mo added alone were blended so as to be 10 to 40 wt% of the whole. About 4 wt% of plasticizer (paraffin) was added to the above mixture as a molding aid, dried, sieved and SN
After being molded into P432 (SNGN120408), it was vacuum-sintered at 1500 to 1550 ° C for 1 hr.

Using this sample, Vickers hardness, crack resistance (kg / mm) indicating toughness, and solid solution amount of elements in the binder phase (wt.% Determined with the dissolved amount in the binder phase as 100%) were determined. .

The Vickers hardness is a, b as shown in FIG. 5 by applying a load of 30 kg with a diamond indenter according to JIS standard.
Was measured and the hardness conversion table was used.

The crack resistance (kg / mm) was determined by applying a load of 50 kg with a diamond indenter as in the case of Vickers hardness.
As shown in, the distances of c, d, e, and f were measured, and the load / (c + d + e + f) was calculated.

The amount of elemental solid solution in the binder phase is determined by dissolving and extracting the binder phase in an aqueous solution of mixed acid, and measuring the ICP (inductive-ly coupled plasma).
a) It was determined by quantifying each element in the binder phase by emission analysis.

Table 3 shows Vickers hardness, crack resistance (kg / mm) indicating toughness, Ti + W content (wt.%) In the binder phase, and Ti + W.
+ Mo amount (wt.%), Mo (wt.%) / Ti (wt.%) Are shown. In Tables 1 to 3, ◯ indicates the alloy of the present invention and Δ indicates the comparative alloy.

All the alloys of the present invention have hardness Hv of 1600 or more and crack resistance of 65 (kg / mm) or more, which are not obtained by the conventional alloys (trial Nos. 11 and 12).

[0034]

[Table 1]

[0035]

[Table 2] FIG. 1 shows the relationship among the Mo addition amount, hardness, and crack resistance in Table 3. Hardness (Hv) and crack resistance (kg / mm) on the vertical axis
Shows the amount of added Mo (vol.%). From FIG. 1, it can be seen that by setting the Mo addition amount to 6% or more and 12% or less, hardness of 1600 or more in Hv and characteristics of crack resistance of 65 (kg / mm) or more can be obtained. Further, it is particularly noticeable in FIG. 1 that the crack resistance increases as the hardness increases. This is because it is common knowledge in the art that hardness and crack resistance are contradictory properties, and generally, the higher the hardness, the lower the crack resistance.

FIG. 2 shows the relationship between the amount of Mo added in Table 3, the total amount of binder phase (wt.%), And the amount of solid solution of Ti, Mo, and W in the binder phase. From this figure, the total amount of binder phase is 7.7 Mo.
Although it tends to decrease as it increases in the range of ˜11.7 vol% (9.8 to 15.3 wt%), the solid solution amounts of Ti and Mo tend to increase. Further, Mo in the binder phase is more solid-solved than Ti in the range, but Ti is Mo in the other range.
It can be seen that more solid solution occurs. Further, the W solid solution amount shows a substantially constant value regardless of the Mo addition amount.

FIG. 3 shows the relationship between the Mo addition amount in Table 3 and the Ti + Mo + W solid solution amount in the binder phase. When the Mo addition amount is up to 11.7 vol.%, The Mo addition amount increases. It can be seen that the Ti + Mo + W solid solution amount also increases as the temperature increases. In addition, the hardness of Hv is 1600 or more, and the crack resistance is 65 (kg /
The solid solution amount of Ti + Mo + W corresponding to the range of the amount of addition of Mo that can obtain the above characteristics is about 7 to 28 wt.%. Next, Fig. 4 shows the amount of Mo added and Mo (wt.%) / Ti (wt.%)
Shows the relationship with. It can be seen from FIG. 4 that Mo (wt.%) / Ti (wt.%) Is about 0.85 or more when the Mo addition amount is 5.5% or more.

Summarizing the above results of FIGS. 1 to 4,
Hardness of 1600 or more in Hv, and crack resistance of 65 (KG / mm)
In order to obtain the above characteristics, the Mo addition amount is about 5.5 Wt.
% To 11% or less (FIG. 1), and within this Mo addition amount range, the Ti + Mo + W solid solution amount in the binder phase is 7 to
It is in the range of 28 wt.% (6 wt.% Or more for Ti + Mo) (Fig. 3), and Mo is more solid-solved in the binder phase than Ti (Fig. 2), and Mo (wt.%) ) / Ti (wt.%) Shows a value of 0.85 or more (FIG. 4).

[0039]

[Table 5] Binder phase analysis of cermet (wt%) Ti + Mo Ti + Mo + W Ti / Mo Hardness crack Test number (wt%) (wt%) Hv resistance Ti W Mo Co Ni kg / mm △ 1 2.8 0.1 0.5 40.7 55.9 3.3 3.4 0.18 1450 75 △ 2 3.4 0.7 2.0 39.2 54.6 5.4 6.1 0.59 1760 65 ○ 3 3.3 1.1 4.2 35.1 56.3 7.5 8.6 1.27 1810 75 ○ 4 3.8 0.9 4.9 35.0 55.5 8.7 9.6 1.29 1720 79 ○ 5 4.9 1.1 6.4 33.2 54.5 11.3 12.4 1.31 1710 84 ○ 6 6.5 1.2 7.5 32.8 51.9 14.0 15.2 1.15 1730 91 ○ 7 8.7 1.1 10.1 31.3 48.9 18.8 19.9 1.16 1670 92 ○ 8 14.0 1.3 12.5 29.4 42.8 26.5 27.8 0.89 1680 78 ○ 9 12.7 1.0 11.6 27.5 47.1 24.3 25.3 0.91 1640 75 △ 10 13.9 1.0 10.4 23.5 51.1 24.3 25.3 0.75 1530 58 Slave 11 2.9 0.9 1.3 65.2 29.7 4.2 5.1 0.45 1740 45 Material 12 2.3 1.5 6.3 60.5 29.4 8.6 10.1 2.3 1525 75

Here, according to FIGS. 1 to 3, Ti + Mo +
The result is that if the amount of W solid solution becomes too large, the crack resistance deteriorates, but this is due to Mo (wt.%) / Ti (wt.
%) Is not appropriate, and Mo (wt.%) / Ti (wt.
%) Within the range of the present invention, it is presumed that excellent crack resistance is exhibited even if the solid solution amount of Ti + Mo + W increases.

That is, in the TiC-based cermet alloy, in order to combine excellent toughness and hardness by strengthening the binder phase, the solid solution amount of Mo and Ti in the binder phase should be 0.85 ≦ M.
Ti + Mo while maintaining the relationship of o (wt.%) / Ti (wt.%)
Is 6 wt.% Or more or Ti + Mo + W is 7 wt.% Or more.

[0042]

As described above, according to the present invention, Ti
It is possible to obtain a TiC-based cermet alloy having hardness substantially equal to that of the CN-based cermet alloy and significantly improved toughness, and this TiC-based cermet alloy has a problem that pores are generated due to denitrification during vacuum sintering. Absent.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of Mo added and the hardness and crack resistance.

FIG. 2 is a graph showing the relationship between the amount of Mo added, the total amount of binder phase, and the amount of solid solution of Ti, Mo, and W in the binder phase.

FIG. 3 is a graph showing the relationship between the amount of Mo added and the amount of solid solution Ti + Mo + W in the binder phase.

FIG. 4 is a graph showing the relationship between the amount of Mo added and Ti / Mo in the binder phase.

FIG. 5 is a diagram showing a Vickers hardness measurement method.

FIG. 6 is a graph showing a crack resistance measuring method.

[Explanation of symbols]

 None

Claims (2)

[Claims] 1. A titanium carbide-based cermet alloy comprising a hard phase mainly composed of titanium carbide and a binder phase mainly composed of one or two of Co and Ni, wherein T in the binder phase.
i and Mo content is 0.85 ≦ Mo (wt.%) / Ti (wt.
%), 6 wt.% ≦ Ti + Mo, a titanium carbide based cermet alloy characterized by satisfying the conditions. 2. A titanium carbide-based cermet alloy comprising a hard phase mainly composed of titanium carbide and tungsten carbide and a binder phase mainly composed of one or two kinds of Co and Ni, wherein Ti and Ti in the binder phase are contained. Mo content is 0.85
A titanium carbide-based cermet alloy characterized by satisfying the following conditions: ≦ Mo (wt.%) / Ti (wt.%), 7 wt.% ≦ Ti + Mo + W.