JPH05302140A - Cermet alloy and its manufacture - Google Patents

Abstract

PURPOSE:To develop a cermet alloy excellent in heat resistance by forming a nitride layer contg. fine TiN on the surface of a cermet alloy contg. hard components and metallic components for bonding. CONSTITUTION:A cermet material constituted of hard components 1 such as TiCN and bonding metal 2 such as Co and Ni is exposed to a gaseous nitrogen plasma atmosphere by high frequency or microwave discharge to form a nitride layer having 10 to 500mum thickness from the surface of the cermet alloy to the inside. The objective cermet alloy in which TiN 3 having <=0.1mum particle size is uniformly dispersed into the metallic components 2 for bonding in the nitride layer and the amt. of saturation magnetism is regulated to a one below 50% that theoretically decided from the bonding metallic components 2 as well as combining excellent toughness and heat resistance can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cermet alloy used for cutting tools and a method for producing the same.

[0002]

2. Description of the Related Art Ti-based hard ceramics (TiC, Ti
N, TiCN, etc.) as a main component, and a cermet alloy composed of IV, V, and VI group carbides other than Ti as hard components, nitrides, carbonitrides, and Fe group metals as bonding metal components. Are known. The main component contributes to wear resistance, the other hard components contribute to sinterability and toughness, and the bonding metal component contributes to toughness and plays a role of connecting the hard components.

Generally, the cermet alloy has a drawback that it has a low thermal conductivity and the temperature of the cutting edge tends to rise during cutting, as compared with cemented carbide which is also a sintered hard alloy. This is because Ti-based hard ceramics, which is the main component of the cermet alloy, has a lower thermal conductivity than WC, which is the main component of the cemented carbide. That is, since the thermal conductivity is low, it is difficult for the heat of the cutting edge to be transferred to other portions during cutting. Therefore, when cutting is performed using a cermet alloy, the temperature of the cutting edge may rise and the cutting edge may be deformed. The deformation of the cutting edge is due to the softening of the bonding metal component in the cermet alloy at high temperatures.

If the amount of the binding metal component is reduced, the deformation of the cutting edge can be prevented, but if this is done, the toughness of the cermet alloy will be reduced, and there will be a problem that the cermet alloy will be lost and cannot be used under severe conditions such as interruption.

[0005]

The following methods are conceivable as methods for improving the heat resistance of cermet alloys.

One is a method of dispersing an intermetallic compound such as Ni ₃ Al or Co ₃ Ti in the bonding metal component of the cermet alloy. This method is disclosed, for example, in JP-A-53-88.
No. 609 and Japanese Patent Laid-Open No. 53-91008. The method of dispersing the intermetallic compound between the bonding metal components to improve the heat resistance is a method generally used in the field of heat resistant alloys, but the effect when applied to sintered hard alloys is not always clear. ..

Another method is to improve the heat resistance of the nitrogen-containing cermet alloy by controlling the sintering atmosphere to change the surface characteristics of the cermet alloy. For example, this method is disclosed in JP-A-54-139815 and JP-A-58-110654. However, this method causes a problem of deterioration of toughness,
In addition, there is a problem that it can be applied only to alloys that are used as it is as a sintered surface.

As another method, there is a method of coating the surface of the cermet alloy by the CVD method or PVD method, ion nitriding or ion implantation. This method is disclosed in, for example, Japanese Patent Laid-Open No. 1-176066. However, the method of coating using the PVD method has a problem of cost increase. Although the ion nitriding method does not increase the cost as compared with the PVD coating, the effect of improving the heat resistance is unknown. The ion implantation method is not practical because the effect of heat resistance is unknown and the cost is higher than that.

The present invention has been made to solve the above conventional problems. An object of the present invention is to provide a cermet alloy having heat resistance and a method for producing the same.

[0010]

According to one aspect of the present invention, in a cermet alloy containing a hard component and a bonding metal component, a thickness of 10 μm or more and 500 μm or less from the surface of the cermet alloy toward the inside of the cermet alloy. There is a nitride layer, and the bond metal component in the nitride layer has a grain size of 0.
The feature is that TiN of 1 μm or less is dispersed.

In another aspect of the present invention, an alloy containing a hard component containing Ti and a bonding metal component in which Ti is dissolved is exposed to a nitrogen gas plasma atmosphere by high frequency or microwave discharge, whereby the alloy is formed. A nitride layer having a thickness of 10 μm or more and 500 μm or less is formed from the surface to the inside, and the grain size is 0.1 in the bonding metal component in the nitride layer.
This is a method for producing a cermet alloy in which TiN having a size of μm or less is dispersed.

[0012]

In the present invention, fine T is contained in the bonding metal component.
iNs are dispersed. TiN as dispersed particles has been used as a hard component of cermet alloys until now,
Its wear resistance and welding resistance are well known. It has been found that when the TiN particles are dispersed in the binding metal component, the heat resistance of the cermet alloy is remarkably improved. The reason why the deformation of the cutting edge is suppressed at high temperature by dispersing TiN in the bonding metal component can be explained by the Orowan model that TiN blocks the movement of dislocations. By dispersing TiN, the hardness of the cermet alloy was also improved, and the wear resistance was also improved.

The principle by which TiN can be dispersed in the binding metal component will be described below. The hard metal components are dissolved in the binder metal component during the sintering process. Among these, regarding Ti, in the bonding metal component of the low carbon alloy,
It has been found to account for 5-10% of the weight of the bound metal component. It is considered that this Ti solid-solution strengthens the bond metal component, but the present inventors considered using Ti dissolved in the bond metal component to disperse TiN in the bond metal component.

Ti has a high affinity with nitrogen and easily reacts with nitrogen to form TiN. Then, it was confirmed that fine TiN was precipitated in the bond metal component when Ti and nitrogen solid-solved in the bond metal component of the cermet alloy were bonded.

In the present invention, it is necessary to activate nitrogen to diffuse the nitrogen into the cermet alloy. As a method of activating nitrogen, it is conceivable to raise the temperature of nitrogen, but with this method, a TiN layer is formed on the surface of the cermet alloy and nitrogen cannot be diffused into the inside of the cermet alloy.

As another method for activating nitrogen, there is a method using low temperature plasma. When nitrogen is activated by using low temperature plasma, nitrogen can be activated at low temperature, so that the problem that the TiN layer is formed on the surface of the cermet alloy described above is eliminated. The method for diffusing nitrogen into the cermet alloy using low temperature plasma is specifically as follows. First, a low-pressure nitrogen-containing gas (N ₂ + H ₂ , NH _3, etc.) is introduced into the furnace, and direct current,
Alternatively, nitrogen plasma is generated by applying high frequency or microwave, and the activated gas is brought into contact with the surface of the cermet alloy, so that nitrogen permeates and diffuses into the cermet alloy.

Nitrogen that has penetrated into the cermet alloy bonds with Ti in the bonding metal component to form TiN nuclei. Although the thickness of the bonding metal component is small, the nucleus of TiN is extremely fine on the order of nanometers, so that it can be dispersed in a large amount in the bonding metal component to strengthen the dispersion of the bonding metal component. The produced TiN is extremely stable, and decomposition or grain growth can be suppressed to a minimum even at high temperatures, so that the effect of dispersion strengthening can be maintained.

As a method of obtaining low-temperature plasma, there is a method of using a DC type ion nitriding device which has been conventionally used, but this method has a tendency that plasma is excessively concentrated on a cutting edge of a tool. Is unknown, but the effect of improving heat resistance is small. On the other hand, it was found that the plasma obtained by a method such as high frequency or microwave generated a uniform plasma over the entire surface of the cermet alloy and had a great effect of improving the heat resistance. In addition, plasma obtained by a method such as high frequency or microwave has an effect of increasing the nitriding speed and shortening the processing time.

As a method of dispersing fine TiN in the bonding metal component, TiN is previously added to Co or Ni powder by a method such as a mechanical alloying method.
It is possible to disperse the above powder and prepare a cermet alloy by the conventional powder metallurgical method using this powder, but in this method, the TiN powder grows during sintering and the effect of dispersion strengthening is obtained. Can not be achieved.

Next, the reason for limiting the numerical values will be described. The thickness of the nitride layer is 10 μm or more is 10 μm
This is because if it is less than the above range, the heat resistance is not improved and the deformation of the cutting edge of the tool cannot be prevented. The reason why it is set to 500 μm or less is that if it exceeds 500 μm, the toughness of the cermet alloy decreases. Further, it takes time to form a nitride layer having a thickness of more than 500 μm, which is not practical.

The particle size of TiN dispersed in the binder metal phase is set to 0.1 μm or less. When the particle size exceeds 0.1 μm, the thickness becomes equivalent to the thickness of the binder metal component layer, and the TiN can be dispersed in the binder metal component. Because you can't. The particle size of TiN is preferably 2 nm or more. If it is less than this, the effect of dispersion strengthening cannot be sufficiently obtained.

The saturation magnetic amount in the cermet alloy is
50 of the saturation magnetic quantity theoretically determined from the bond metal component
% Or less is preferable. This is because in order to disperse TiN in the bond metal component, Ti must be sufficiently dissolved in the bond metal component.

The hard component that can be used in the present invention is at least one selected from the group including carbides, nitrides, carbonitrides of IVa, Va and VIa group metals and solid solutions thereof. As the binding metal component,
There are Fe group metals. The Fe group metal may be one kind or two or more kinds. The proportion of the hard component in the cermet alloy is preferably 70% by weight or more and 95% by weight or less. The proportion of Ti in the hard component is preferably 50% by weight or more.

The proportion of the binding metal component in the cermet alloy is preferably 5% by weight or more and 25% by weight or less. This is because if it is less than 5% by weight, the toughness is deteriorated. This is because if it exceeds 25% by weight, the wear resistance becomes poor.

Further, the volume ratio of TiN dispersed in the bonding metal component is preferably 5% by volume or more and 30% by volume or less with respect to the total amount of TiN and the bonding metal component dispersed.

The nitriding temperature is 300 ° C. or higher and 100.
It is preferably 0 ° C or lower.

[0027]

【Example】

(Example 1) Commercially available TiCN, WC, TaN, NbC and Co, Ni were mixed, molded, and sintered to obtain 85.0% by weight of a hard component, 5.0% by weight of Co, and 10% by weight of Ni.
A 0% by weight cermet alloy was obtained. Co and Ni are binding components. In addition, Ti, Nb, Ta in the hard component, Ti in the whole W is 0.75, Nb is 0.1, Ta is 0.
05 and W were 0.1 (above atomic ratio). Of all C and N, C was 0.65 and N was 0.35 (above atomic ratio).

This cermet alloy was used for high frequency (13.5
Ion nitridation was performed in plasma in which 6 MHz) and DC were superposed. The conditions for ion nitriding are shown in FIG.

When the surface of this cermet alloy was observed, it was nitrided to a depth of 40 μm from the surface, and that portion was 200 Vickers hardness from the inside of the cermet alloy.
The higher the hardness (Hv), the higher the hardness. FIG. 1 is a schematic diagram near the surface of this cermet alloy. Between the hard component 1 is the bond metal component 2. 40μ depth from the surface of the cermet alloy
It is nitrided up to m. A large amount of TiN3 is dispersed in the bond metal component 2 in the nitride layer. Ti
The particle size of N ₃ was 20 to 50 nm.

Tests 1 to 3 were carried out on the cermet alloy and the cermet alloy which was not ion-nitrided. Test 1 is a measurement of the amount of plastic deformation of the cutting edge. If the amount of plastic deformation of the cutting edge is small, it means that it has heat resistance. Test 2 is a measurement of the flank wear width. When the wear width is small, it has wear resistance. Exam 3
Is a measurement of the defect rate in 10 corners. That is, 10 tools were prepared and the number of missing tools was measured. Test 1
The conditions of No. 3 are shown in FIG. The results are shown in Fig. 4. As can be seen from FIG. 4, it was found that the present invention is superior in heat resistance and wear resistance to the conventional example, and has a small tool fracture rate. (Example 2) WC solid solution in TiCN, Mo2
A cermet alloy was prepared from C and Ni. In the same manner, a plurality of carbon materials having different carbon values were produced. The same nitriding treatment as in Example 1 was performed on these cermet alloys. Theoretical saturation magnetism of these cermet alloys, saturation magnetism of alloys, saturation, thickness of nitrided layer, precipitated TiN
The amount is shown in FIG. As can be seen from FIG. 5, the smaller the saturation rate, the larger the amount of TiN deposited. (Example 3) A plurality of cermet alloys before nitriding of Example 1 were produced, and cermet alloys having different nitriding layer thicknesses were produced by changing the nitriding time. The relationship between the nitriding time and the thickness of the nitrided layer is shown in FIG. As can be seen from this graph, it can be estimated that it takes 24 hours, that is, one day to make the thickness of the nitride layer 100 μm. Therefore, 50
If it is 0 μm, it takes more than 5 days, which is not suitable for mass production.

When a cutting test was performed on these cermet alloys, the effect of improving heat resistance was not observed when the thickness of the nitride layer was less than 10 μm.

[0032]

According to the first aspect of the present invention, the cermet alloy has excellent heat resistance while maintaining the toughness of the cermet alloy. Therefore, it is possible to prevent deformation of the cutting edge during cutting. It also becomes a cermet alloy with excellent wear resistance.

Further, according to another aspect of the present invention, such a cermet alloy can be produced.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of the present invention.

FIG. 2 is a table showing conditions of ion nitriding.

FIG. 3 is a diagram showing conditions of tests 1 to 3 in a table.

FIG. 4 is a diagram showing the results of tests 1 to 3 in a table.

FIG. 5 is a table showing the relationship between the saturation rate and the amount of precipitated TiN.

FIG. 6 is a graph showing the relationship between the nitriding time and the thickness of the nitrided layer.

[Explanation of symbols]

 1 Hard component 2 Bonded metal component 3 TiN

Claims (4)

[Claims] 1. A cermet alloy containing a hard component and a bonding metal component, wherein a nitriding layer having a thickness of 10 μm or more and 500 μm or less is present from the surface of the cermet alloy toward the inside of the cermet alloy, and is in the nitriding layer. A particle size of 0.
A cermet alloy characterized in that TiN of 1 μm or less is dispersed. 2. The saturation magnetic amount in the cermet alloy is
The cermet alloy according to claim 1, which has a saturation magnetic amount of 50% or less theoretically determined from the binding metal component. 3. An alloy containing a hard component containing Ti and a bonding metal component in which Ti is dissolved is exposed to a nitrogen gas plasma atmosphere by high frequency or microwave discharge, so that the alloy is directed from the surface to the inside. Thickness 10
A nitride layer having a thickness of 0.1 μm or more and 500 μm or less is formed, and T having a grain size of 0.1 μm or less is formed in the bonding metal component in the nitride layer.
A method for producing a cermet alloy, in which iN is dispersed. 4. The method for producing a cermet alloy according to claim 3, wherein the nitrogen gas plasma is generated using high frequency and direct current.