JPH0483806A - Combined hard alloy material - Google Patents

Abstract

PURPOSE:To provide a complex hard alloy material maintaining excellent toughness as characteristic of high speed tool steel and also drastically improved in wear resistance by constituting the center part of nitrogen-containing titanium base sintered alloy and the outer peripheral part of sintered alloy steel in this center. CONSTITUTION:As an example, at first, this material is obtd. by mixing 15-60vol.% TiN particles having <=0.3mum average particle diameter, 10vol.% VC particles having 0.08mum average particle diameter and <=10vol.% TiN particles having 1-3mum average particle diameter as hard phase, and 30-84vol.% high speed tool powder as combined phase. After applying 1 the mixed alloy steel powder on outer periphery of a bar 2 composed of the nitrogen-containing titanium base sintered alloy, i.e., Ti-base cermet alloy, this is compacted with cold isostatic pressing. This green compact is charged into a mild steel-made cylindrical vessel, and while executing degassing treatment, this is heated, and after vacuum-sealing, hot isostatic pressing treatment is executed to this green compact. The alloy material improved in the wear resistance to the level being equal to a sintered hard alloy under condition of maintaining the toughness of the high speed tool steel, is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a composite hard alloy material used as a material for cutting tools and the like.

[Prior Art] High-speed tool steel or cemented carbide is most commonly used as a material for cutting tools and the like.

High-speed tool steels are mainly made of Cr, Mo, W, and V.

It is an alloy steel containing Co and C as alloy components and having Fe as a matrix. In high-speed tool steel, by adjusting each alloy component, properties suitable for the tool material can be adjusted, and at the same time, the properties can be changed by heat treatment.

- High-speed tool steel for boat fishing has excellent toughness and is therefore used as a material for cutting tools that require high reliability. Manufacturing methods for high-speed tool steel include melt casting,
The atomized powder is subjected to hot isostatic pressing (HIP, Hot
Powder metallurgy methods are widely used in which solidification is performed by, for example, 1sostatic pressing.

Furthermore, in order to add wear resistance to high-speed tool steel which has excellent toughness as described above, a method has been proposed in which the amount of carbides and nitrides is increased. For example, JP-A-55-583
No. 50 and Japanese Unexamined Patent Publication No. 58-181848 disclose that high-speed tool steel powder is mixed with powders such as carbides and nitrides,
A method of sintering has been proposed as a method of increasing the amount of carbides and nitrides in the matrix. Furthermore, Japanese Patent Publication No. 60-18742 proposes a material in which extremely fine TiN particles are dispersed in a matrix of high-speed tool steel. JP-A No. 60-2648 and JP-A No. 61-179845 disclose composites of high-speed tool steel in which extremely fine TiN particles are dispersed in a matrix and alloy steel such as high-speed tool steel. A new tool material has been proposed.

On the other hand, cemented carbide is WCST i CXTaC, Nbc
It is an alloy made by sintering carbides such as Co and N1 as bases. Although this cemented carbide is inferior to high-speed tool steel in terms of toughness, it has excellent high abrasion resistance, making it a tool material that exhibits its characteristics in high-speed cutting. The properties of cemented carbide suitable for use as a tool material can be adjusted by changing its composition, but the properties can also be adjusted by appropriately changing the grain size of its hard phase. In addition,
Cemented carbide can be manufactured by a powder metallurgy method that consists of a series of steps of mixing, pressing, and sintering powder as a raw material.

[Problems to be Solved by the Invention] As described above, although high-speed tool steel has excellent toughness, it has insufficient wear resistance, so it is difficult to use it as a tool material suitable for high-speed cutting.

In order to improve the wear resistance of high speed tool steels, increasing the alloying content and increasing the amount of carbides in the matrix are commonly used.

However, it is not easy to achieve improved wear resistance while maintaining the excellent toughness that characterizes high-speed tool steel.

In other words, by increasing the alloy components, the amount of carbides in high-speed tool steel increases, and the wear resistance increases, but on the other hand,
A rapid decrease in toughness occurs. In particular, when manufactured by the melt casting method, the volume of carbides in high-speed tool steel is at most about 15% by volume, and if more than this amount of carbides is included in the matrix, it cannot be used as a practical tool. Unable to obtain toughness. Further, although the amount of carbides can be increased to some extent by powder metallurgy, the amount of carbides that can be increased is about 30% by volume at most.

By mixing powders such as carbides and nitrides with high-speed tool steel powder,
According to the sintering method, it is theoretically possible to contain any amount of carbide or nitride. However, even in this case, it is inevitable that as the hard phase increases, the toughness will decrease. - When powders with a particle size of several microns are mixed, compression molded, and sintered, the grain boundaries of the powder in high-speed tool steel increase as the amount of hard ceramics such as carbides and nitrides increases. carbides and nitrides aggregate in a network. When carbides and nitrides aggregate in this way, the toughness decreases to an unacceptable degree. As a countermeasure to this problem, it is possible to make carbides and nitrides into ultrafine particles on the order of submicrons. However, such ultrafine particles tend to aggregate, and it is not easy to uniformly disperse them. Therefore, it is currently impossible to obtain a structure of high-speed tool steel in which carbides and nitrides are dispersed so as to have desired properties.

Furthermore, since the elastic modulus of high-speed tool steel is smaller than that of cemented carbide, which will be discussed later, deformation during cutting increases.
There was a problem in that it could not be used for applications such as tools that required high accuracy.

On the other hand, unlike high-speed tool steel, cemented carbide has excellent wear resistance but does not have sufficient toughness.

Therefore, cemented carbide is not used as a material for tools that require reliability. As a method of improving the toughness of cemented carbide, a method of making carbides in the hard phase finer has been adopted. However, this method also has its limitations, and the toughness obtained falls far short of that of high-speed tool steel. Usually, the amount of carbide contained in cemented carbide is about 80 to 90% by volume. In order to improve toughness depending on the application, cemented carbide is manufactured with a composition in which the amount of carbide is reduced to about 60% by volume, but the wear resistance rapidly decreases and it cannot be used as a material for cutting tools. .

As mentioned above, high-speed tool steel and cemented carbide used as materials for conventional cutting tools each have drawbacks.
In practice, they can only be used under conditions that do not cause these drawbacks. Therefore, there was a problem that the characteristics of high-speed tool steel or cemented carbide could not be fully exhibited.

Therefore, an object of the present invention is to provide a composite hard alloy material that maintains the excellent toughness characteristic of high-speed tool steel and at the same time has significantly improved wear resistance.

[Means for Solving the Problems] A composite hard alloy material according to the present invention includes a central portion made of a nitrogen-containing titanium-based sintered alloy, a central portion coated with the central portion,
and an outer peripheral portion made of sintered alloy steel. The nitrogen-containing titanium-based sintered alloy contains Ti in an atomic ratio of 0.45 or more and 0.95
Below, at least one of Mo and W is 0.045
a metal element containing at least one selected from the group consisting of Zr5Hf, V, Nb, Ta, and Cr in an atomic ratio of 0.05 or more and 0.3 or less and 0.05 or more and 0.3 or less;
1 or more and 0.9 or less and a hard dispersed phase consisting of a compound with a nonmetallic element containing N of 0.1 or more and 0.9 or less. Further, the nitrogen-containing titanium-based sintered alloy contains 3.0% by weight or more and 40.0% by weight of a binding metal containing at least one of Fe, Co, and Ni to bind the hard dispersed phase.
Contains the following. The sintered alloy steel that makes up the outer peripheral part is
It consists of a first hard phase, a second hard phase, and a binder phase.

The first hard phase is 15% by volume or more 60% by volume in the outer peripheral portion.
TiN particles are contained in an amount of vol% or less and have a particle size of 0.3 μm or less. The second hard phase is contained in the outer peripheral portion at 1% by volume or more and 10% by volume or less, and has a particle size of 1μm or more and 3μm.
It consists of TiN particles with a size of less than m. The binder phase is contained in the outer peripheral portion at 30% by volume or more and 84% by volume or less, and is made of alloy steel for dispersing and bonding the first hard phase and the second hard phase therein. The alloy steel contains 2.5% by weight or more of Cr and 4.5% by weight or less, and 1.5% or more of Mo by 5.0% by weight.
0% by weight or less, W from 2.0% to 6.0% by weight, C from 0.3% to 1.2% by weight, and Co from 1% to 1.2% by weight.
It contains 5% by weight or more and 15% by weight or less, Mn by 0.5% by weight or less, Si by 0.5% by weight or less, and the remainder consists of Fe and unavoidable impurities.

Preferably, 5 of Ti in TiN in the sintered alloy steel
0 atomic % or less is Zr, Hf, V, and Nb.

It may be substituted with one or more elements selected from the group consisting of Ta, Cr, Mo, W, At, and Si.

Preferably, N in TiN in the sintered alloy steel
50 atomic % or less of may be substituted with one or more elements selected from the group consisting of B, C, and 0. Furthermore, the thickness of the outer peripheral portion made of sintered alloy steel may be 0.05 or more and 0.3 or less of the total thickness of the composite hard alloy material.

In the bonding metal of the nitrogen-containing titanium-based sintered alloy, Fe,
40 atomic % or less of Co and Ni is Cr.

It may be substituted with at least one metal selected from the group consisting of Mo and W. The hard dispersed phase of the nitrogen-containing titanium-based sintered alloy includes one or more of carbides, nitrides, and carbonitrides of Ti, carbides of at least one of Mo and W, Zr, and Hf.

VSNbSTa and Cr may contain at least one of carbides, nitrides, and carbonitrides selected from the group consisting of the metal element and the non-metal element. It may contain a solid solution composed of.

[Function] According to the composite hard alloy material according to the present invention, TiN particles as a hard phase dispersed in the sintered alloy steel constituting the outer peripheral portion have wear resistance that is insufficient in high-speed tool steel alone. enhance TiN has a Vickers hardness of Hv2000k.
g/mm2, - Hv8 of high-speed tool steel for boat fishing.
It has a hardness more than twice that of 00 to 10100Q/mm2. By dispersing this hard TiN, the hardness of the high-speed tool steel becomes Hv 1000 kg/mm2 or more, and a significant improvement in wear resistance is achieved. Also, TiN
has low reactivity with steel, suppresses adhesive wear during cutting, and improves the surface roughness of the cut surface.

According to the conventional technology for dispersing TiN as a hard phase into high-speed tool steel, the strength of the tool steel sharply decreases as the amount of TiN increases because the TiN particles are large. On the other hand, according to the present invention, the particle size of the TiN particles is reduced to 0.
．． By suppressing the thickness to 3 μm or less, the TiN particles are uniformly and finely dispersed, making it possible to reduce the decrease in strength.

The TiN particles serving as the basic hard layer need to be finely dispersed as described above. However, by dispersing some TiN particles as a hard phase to have a constant particle size of 1 μm or more, it is possible to suppress the cracks generated in the matrix from propagating, and as a result, Fracture toughness value improves. In addition, due to the presence of TiN particles having a particle size of 1 μm or more,
Suppressing wear and tear is suppressed. If the particle size of such coarse 118 particles is less than 1 μm, the above effect will not be sufficient;
If the thickness exceeds 3 μm, the strength will decrease.

Furthermore, if the amount of coarse TiN particles is less than 1% by volume, the above effects cannot be achieved, and if it exceeds 10% by volume, the strength will drop sharply as described above. Note that the amount of TiN particles having a particle size of 0.3 μm or less is suitably 15% by volume or more and 60% by volume or less. If it is less than 15% by volume, the effect of improving wear resistance by dispersing TiN as a hard phase will be small, and if it exceeds 60% by volume, the toughness will decrease slightly.

On the other hand, the binder phase for dispersing and bonding the above-mentioned hard phase therein has a matrix composition close to that of the high-speed tool steel during quenching. Basically, it is most important to create a composition that does not precipitate primary carbides during the quenching process. The toughness provided by high speed tool steels is due to this matrix composition. Also in the present invention, the maximum effect can be obtained by employing this matrix composition. If alloy components other than Fe are less than the specified lower limit, sufficient strength cannot be obtained, and if they exceed the upper limit, toughness decreases.

The hard phase to be dispersed in the matrix may be mainly composed of TiN, with some of the components of the binder phase matrix dissolved therein. In addition, up to 50 atomic % of Ti in TiN can be replaced by Zr, Hf, V, Nb, TaSCrSMo,
It is possible to substitute with one or more elements selected from the group of W, At and Si. Similarly, 5 of N in TiN
It is also possible to substitute up to 0 atomic % with one or more elements selected from the group consisting of B, C, and 0. These substitutions are effective in improving the heat resistance, wear resistance, toughness, etc. of the alloy. However, substitution of more than 50 atom %
This is not preferable because it will impair the characteristics of iN.

The sintered alloy steel configured as described above can exhibit satisfactory characteristics as a material for tools such as cutting tools by itself. However, by introducing a composite method using the above-mentioned sintered alloy steel as the outer peripheral portion, it is possible to improve the performance of the -layer. This fact has already been clarified by the present inventor and is disclosed in Japanese Patent Application No. 1-339982. According to this disclosure, by employing cemented carbide as the core material, it is possible to significantly improve the rigidity of the tool material as a whole. As a result, the machining accuracy of the tool improves, and the surface roughness of the surface machined by the tool improves.

However, the difference in thermal expansion coefficient between cemented carbide and the sintered alloy steel that constitutes the outer peripheral portion is quite large, and the present invention shows that the thermal stress generated during heating and cooling during joining and heat treatment becomes so large that it cannot be ignored. revealed by the person.

Therefore, the present invention was made based on the inventor's knowledge that this thermal stress can be alleviated by employing a nitrogen-containing titanium-based sintered alloy, so-called Ti-based cermet alloy, in the central portion. It is.

That is, since cermet alloy has a coefficient of thermal expansion between that of cemented carbide and high-speed tool steel, it works effectively in alleviating thermal stress generated during joining and heat treatment.

On the other hand, cermet alloys have a somewhat lower Young's modulus than cemented carbide, which is disadvantageous from the viewpoint of improving tool rigidity. However, it has sufficiently high rigidity compared to the sintered alloy steel that makes up the outer circumference,
This does not impair the above-mentioned effects of the present invention.

Since the outer peripheral portion is made of the above-mentioned sintered alloy steel, a cutting tool edge with improved wear resistance can be obtained while maintaining the toughness of high-speed tool steel. Note that coating the surface of the sintered alloy steel with a hard ceramic film brings about better results in further improving performance. The material for this film is preferably TiN, but Tl
c or Ti (CN) may be used, and Al, 203 may be further coated thereon.

The sintered alloy steel referred to herein may be produced by either solid-phase sintering or liquid-phase sintering, but solid-phase sintering is preferable from the viewpoint of suppressing grain growth.

[Example] FIG. 1 is a sectional view conceptually showing a composite hard alloy material according to the present invention. According to this figure, an outer peripheral part 1 made of sintered alloy steel surrounds a central part 2 made of nitrogen-containing titanium-based sintered alloy.

Example 1 As the hard phase, 35% by volume of TiN particles with an average particle size of 0.1 μm, 10% by volume of VC particles with an average particle size of 0.08 μm,
TiN particles having an average particle size of 1.5 μm were blended in an amount of 5% by volume, and high-speed tool steel powder as a binder phase was blended in an amount of 50% by volume, and mixed using a dry ball mill. The composition of the high-speed tool steel powder is 4.0% by weight of Cr, 3.5% by weight of Mo, 2.0% by weight of W, 8.5% by weight of Co, and 0% by weight of C.
5% by weight, the remainder being Fe and unavoidable impurities.

After the alloy steel powder mixed in this way is coated on the outer periphery of a rod made of a nitrogen-containing titanium-based sintered alloy, so-called Ti-based cermet alloy, cold isostatic pressing (CIP),
cold 1sostatic pressing
). The composition of the cermet alloy is TiCN
(atomic ratio C/N=515) is 68% by weight, WC is 12.
5% by weight, TaC 6.0% by weight, and Co 13.5% by weight. Also, the diameter of the cermet alloy rod is 5mm.
1 length was 200 mm. In this way, thickness 2
A layer consisting of mm of alloyed steel powder was formed.

This molded body was placed in a mild steel cylindrical container, heated to a temperature of 500° C. while being deaerated, and vacuum-sealed. Then, this molded body is subjected to hot isostatic pressing (HIP).
processed. The conditions for hot isostatic pressing treatment are temperature 1
At 130° C., the pressure of Ar gas used as a pressure medium was set to 1000 kg/cm 2 . A drill with a diameter of 6 mm was prototyped from the sintered body thus obtained.

In the cross-sectional structure of this drill, the center part has a diameter of 5 m.
A portion made of a cermet alloy of m was located, and its outer periphery was surrounded by a portion made of sintered alloy steel with a thickness of 0.5 mm. Predetermined grooves and cutting edges were molded into the drill.

For comparison, a prototype drill made of sintered alloy steel without cermet alloy in its center was manufactured. Cutting tests were conducted using prototype drills of the present invention and comparison products, and commercially available trills made of cemented carbide and high speed tool steel. The cutting conditions were as follows.

Work material: 350C Cutting speed: 60m/min Feed speed + 0.20mm/rev Machining depth: 15 machining The results of the cutting test are shown in Table 1.

(Leaving space below) According to the test results in Table 1, with drills made of cemented carbide, wear is small when the number of holes machined is small, but when the number of holes machined increases, subtle chipping occurs on the cutting edge. It was recognized that this was due to increased wear.

Furthermore, the comparative product was slightly inferior to the invented product. Comparing the enlargement of the processed hole, the inventive product has an enlargement of 30 μm.
In contrast, the comparative product had a thickness of approximately 60 μm.

Example 2 Each particle was uniformly distributed so that the hard phase particles having a predetermined structure form were 40% by volume, the TiN particles with an average particle size of 2.3 μm were 10% by volume, and the matrix of high-speed tool steel was 50% by volume. A cylinder made of sintered alloy steel with a dispersed structure was prepared. The hard phase particles surround the TiN particles (TiWMo)
It had a structure in which a solid solution of (CN) was formed surrounding it. The average particle size of this hard phase particle is 0.12 μm
The thickness of the solid solution surrounding the TiN particles is 0.
It was 0.02 μm. The composition of the high-speed tool steel that constitutes the matrix is 3.8% by weight of Cr and 5.5% by weight of Mo.
, W is 2.5% by weight, Co is 10.0% by weight, C is 0.
45% by weight, the remainder being Fe and unavoidable impurities.

In addition, 60% by weight of TiCN (atomic ratio C/N=8/2)
, Mo2C 8.5% by weight, WC 10% by weight, TaN
A bar made of a cermet alloy having a composition of 5.5% by weight, 8% by weight of Co, and 8% by weight of Ni was prepared.

This cylinder made of sintered alloy steel and the rod made of cermet alloy were integrated by diffusion bonding. A cutting tool having a predetermined shape for an end mill was manufactured from the composite hard metal member thus obtained. A cutting test was conducted using this cutting tool under the following conditions.

Prototype material S KD 11 (HRc 42) Cutting speed
60m/min Feed rate: 0.15mm/1 blade machining width 2.0mm Machining depth 10mm According to the cutting test results, if the end mill made of composite hard alloy material according to the present invention is used, machining can be performed without any particular problem. It is possible, and the deviation of the sides of the machined groove from the vertical line is
The accuracy was extremely high, with a maximum of 0.04 mm. In addition,
For comparison, if an end mill made of cemented carbide is used,
Immediately after machining started, the cutting edge chipped, making cutting impossible. Additionally, if you use an end mill made of high-speed tool steel,
No cutting was possible due to rapid wear.

Example 3 A nitrogen-containing titanium-based sintered alloy having the composition shown in Table 2 was prepared, and a composite hard alloy material centered on this was prototyped using the same outer peripheral material and manufacturing method as in Example 1. At the same time, a composite hard alloy material was prototyped using a nitrogen-containing titanium-based sintered alloy whose composition was outside the range of the present invention, and was used as a comparative example.

As is clear from Table 2, it was confirmed that all the products of the present invention achieved good bonding and could sufficiently withstand the actual cutting test. On the other hand, in the comparative product, a satisfactory nitrogen-containing titanium-based sintered alloy could not be obtained.

Among the comparative products in Table 2, sample No. 8, in which the amount of Ti was smaller than the value within the range specified by the present invention, cracked during cooling during joining. In addition, sample No. 9 in which the amount of Ti is larger than the value within the range defined by the present invention
According to , the toughness was insufficient.

According to sample No. 10, in which the amount of bonded metal was smaller than the value within the range defined by the present invention, cracking occurred during bonding. Further, in Sample No. 11, in which the amount of bonded metal was larger than the value within the range defined by the present invention, sufficient rigidity could not be obtained. In sample No. 12, in which the amounts of Cr, Mo, and W in the bonding metal were too large, sintering was not performed well,
A nest has occurred.

[Effects of the Invention] As described above, according to the present invention, it is possible to obtain an alloy material whose wear resistance is improved to a level comparable to that of cemented carbide while maintaining the toughness of high-speed tool steel. can. Furthermore, when used as a cutting tool, it has high rigidity and enables highly accurate cutting. Therefore, when the composite hard alloy material is used as a cutting tool material, it can contribute to improving the efficiency and reliability of cutting.

[Brief explanation of the drawing]

FIG. 1 is a sectional view conceptually showing a composite hard alloy material according to the present invention. (2 idiots) -g-

Claims (1)

[Scope of Claims] (1) A central portion made of a nitrogen-containing titanium-based sintered alloy; and an outer peripheral portion surrounding the central portion and made of sintered-alloy steel, the nitrogen-containing titanium-based sintered alloy comprising: , Ti in atomic ratio is 0.
45 or more and 0.95 or less, at least one of Mo and W from 0.045 to 0.3, and Zr, Hf,
A metal element containing 0.005 or more and 0.3 or less of at least one selected from the group consisting of V, Nb, Ta, and Cr, and an atomic ratio of C of 0.1 or more and 0.9 or less and N of 0.1
Contains a hard dispersed phase consisting of a compound with a non-metallic element containing 0.9 or less, and in order to bond the hard dispersed phase, Fe,
The sintered alloy steel contains 3.0% by weight or more and 40.0% by weight or less of a bonding metal containing at least one of Co and Ni, and the sintered alloy steel has a grain size of 0.5% in the outer peripheral portion.
The first hard phase consisting of TiN particles with a particle size of 3 μm or less is 15% by volume or more and 60% by volume or less, and the second hard phase consisting of TiN particles with a particle size of 1 μm or more and 3 μm or less is 1% by volume or more and 10% by volume or less.
% by volume or less, and the first hard phase and the second hard phase.
The alloy steel contains 30% by volume or more and 84% by volume or less of a binder phase made of alloy steel for dispersing and bonding a hard phase of Cr, and the alloy steel contains Cr of 2.5% by weight or more and 4.5% by weight. % by weight or less, Mo from 1.5% by weight to 5.0% by weight, W from 2% to 5.0% by weight.
．． 0% to 6.0% by weight, C 0.3% to 1.2% by weight, Co 1.5% to 15% by weight, Mn 0.5% by weight or less, Si 0.5% by weight
A composite hard alloy material containing the following, with the remainder consisting of Fe and unavoidable impurities. (2) TiN in the sintered alloy steel
50 atomic % or less of Ti in the particles is Zr, Hf,
Substituted with one or more elements selected from the group consisting of V, Nb, Ta, Cr, Mo, W, Al and Si,
The composite hard metal material according to claim 1. (3) 5 of N in TiN particles in the sintered alloy steel
Claim 1 or 2, wherein 0 atomic % or less is substituted with one or more elements selected from the group consisting of B, C, and O.
Composite hard alloy material described in . (4) The composite hard alloy material according to any one of claims 1 to 3, wherein the thickness of the outer peripheral portion is 0.05 or more and 0.3 or less of the total thickness of the composite hard alloy material. (5) 40 atomic percent or less of Fe, Co, and Ni in the bond metal of the nitrogen-containing titanium-based sintered alloy is Cr.
5. The composite hard alloy material according to claim 1, wherein the composite hard alloy material is substituted with at least one metal selected from the group consisting of , Mo, and W. (6) The hard dispersed phase of the nitrogen-containing titanium-based sintered alloy includes one or more of Ti carbides, nitrides, and carbonitrides;
Carbide of at least one of Mo and W, Zr, H
The composite hard alloy material according to any one of claims 1 to 5, comprising at least one type of carbide, nitride, and carbonitride selected from the group consisting of f, V, Nb, Ta, and Cr. . (7) The composite hard alloy material according to any one of claims 1 to 6, wherein the hard dispersed phase of the nitrogen-containing titanium-based sintered alloy includes a solid solution composed of the metal element and the non-metal element. .