JP2828512B2 - Coated TiCN-based cermet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated TiCN-based cermet having excellent wear resistance and toughness and a method for producing the same, and more particularly to a coated TiCN-based cermet which is excellent as a cutting tool on a finished surface of a work material after cutting. About cermet.

[0002]

2. Description of the Related Art Conventionally, WC-C has been used as a cutting sintered body.
A cemented carbide mainly containing o is mainly used, but recently, a cermet sintered body mainly containing carbides, nitrides, and carbonitrides of Ti has been used.

As such a cermet-based sintered body, T
The mainstream was a TiC-based cermet containing iC as a main component, an iron group metal as a binder phase, and carbides, nitrides, and carbonitrides of metals of groups 4a, 5a and 6a of the periodic table as hard phase components. . However, since such a TiC-based cermet sintered body is inferior in heat resistance and toughness, it has been proposed to further include a nitride such as TiN or a carbonitride in the above composition. This is intended to impart toughness to the sintered body due to the high toughness of TiN itself, and to improve thermal shock resistance and thermal plastic deformation due to high thermal conductivity.

Accordingly, TiC containing TiN has been conventionally used.
Various improvements have been made to the base cermet. For example, Japanese Patent Publication No. Sho 59-14534 discloses that nitrogen is introduced into a furnace at a temperature lower than the liquid crystal appearance temperature to form a softened layer having a high toughness on the surface of a sintered body.
No. 76, it is possible to form a hard layer having a specific hardness by firing in a CO reducing atmosphere. According to Japanese Patent Publication No. 60-34618, CO
It has been proposed to obtain a cermet having uniform mechanical properties inside the surface by forming an atmosphere.

However, according to the above-mentioned prior art, only the hardness or the toughness is studied, and as a tool material that requires both high hardness and high toughness, it is still insufficient in terms of cutting performance. Not enough.

In order to solve this problem, the present applicant introduces nitrogen at a temperature not lower than the liquid phase appearance temperature, and then reduces the nitrogen gas pressure after reaching the maximum sintering temperature, so that the surface of the sintered body is less than the inside. A TiCN-based cermet having a high hardness and high toughness modified portion was proposed.

[0007]

However, according to the above-mentioned TiCN-based cermet, the T
Due to the low i content ratio as compared with the inside, especially when cutting is performed using an iron-based material as a work material, a large amount of W or bonding metal present on the surface of the sintered body and the work material Has reacted, and there was a problem that the surface of the work material was roughened.

Therefore, the present invention has no pores and voids,
Fully demonstrates the properties of TiN, heat resistance, wear resistance,
An object of the present invention is to provide a material for a tool that has excellent toughness and a good surface after cutting of a work material.

[0009]

The inventors of the present invention have conducted studies on the above-mentioned drawbacks, and as a result, the present inventors have proposed a TiCN having a hardened and toughened modified portion on the surface which is higher than the inside.
The base cermet is used as a base material, and the surface thereof is coated with a hard film containing more Ti than the base material, having an average particle size of 0.4 μm or less, and containing an iron group metal having a content of 100 ppm or less. By utilizing the excellent properties of the cermet base material, the reactivity between the work material and the cermet is reduced as much as possible, and it is found that a cermet having a good surface of the work material after cutting can be obtained. Reached.

The TiCN-based cermet used as the base material in the present invention contains 50 to 80% by weight, particularly 55 to 6% by weight of Ti carbide, nitride or carbonitride as a hard phase component.
5% by weight and 10 to 40% by weight, particularly 15 to 30% by weight of a carbide of a Group 6a element of the periodic table such as W or Mo.

In such a hard phase component, if the amount of Ti is less than 50% by weight, the wear resistance is reduced, and 90% by weight.
If it exceeds sinterability, the sinterability is undesirably reduced. In addition, the 6a
Group elements have the effect of suppressing grain growth and improving the wettability with the binder phase. However, if the content is less than 10% by weight, the above effects cannot be obtained, the hard phase becomes coarse, and the hardness and strength decrease. Also 4
If it exceeds 0% by weight, an unhealthy phase such as an η phase is generated and sintering becomes difficult.

In addition to the above-mentioned hard phase components, other than the above, Ta and Nb for the purpose of improving crater wear resistance, and Zr, V and H for the purpose of improving plastic deformation resistance.
It is possible to contain nitrides, carbides and carbonitrides such as f in a proportion of 5 to 40% by weight, but if it exceeds 40% by weight, deterioration of wear resistance and generation of pores and voids tend to increase remarkably. There is not preferred.

On the other hand, the binder phase is mainly composed of an iron group metal such as Fe, Co, and Ni, and may partially include a hard phase forming component.

The hard phase component is 60 to 9 as a whole of the sintered body.
5% by weight, the binder phase component comprising 5 to 40% by weight.

The feature of the composition in the present invention is that the atomic ratio represented by (nitrogen / carbon + nitrogen) in the hard phase component is in the range of 0.4 to 0.6, particularly 0.4 to 0.5. The point that is set. That is, if this atomic ratio is less than 0.4, improvement in toughness and wear resistance cannot be expected, and the object of the present invention is not achieved.If it exceeds 0.6, pores and voids are generated in the sintered body, The reliability as a tool decreases.

The TiCN-based cermet of the present invention can maintain the effect of improving toughness, wear resistance and heat resistance by containing a large amount of nitrogen for a long period of time due to such a constitution, and has a long tool life. And high reliability can be achieved. Moreover, it is possible to commercialize the sintered body without performing a polishing step or the like on the sintered body after sintering. Further, it is characterized in that a modified portion having higher hardness and higher toughness exists in the surface layer portion up to about 1000 μm from the surface of the cermet than in the inside. The presence of the modified layer makes it possible to greatly improve the wear resistance and chipping resistance of the cutting tool as a base material of the coated tool as compared with the conventional cermet.

However, the cermet described above contains a metal having low reactivity with iron group metals such as Ti in the surface layer of the cermet due to the mechanism of forming a high hardness and high toughness modified layer on the surface layer. Due to a small ratio and a large amount of Group 6a metal and bonding metal such as W, when cutting is performed using, for example, structural alloy steel SCM435 as a work material, W and iron group metal in the cermet react. In some cases, the finished surface after cutting may be rough. Therefore, according to the present invention, such TiCN
The surface of the base cermet is coated with a hard film containing Ti.

In order to suppress the reactivity between the cermet base material and the work material, the hard film is formed of a film in which the amount of Ti in the hard film is larger than the amount of Ti in the base material. The reactivity with the material can be suppressed. Also,
When the aforementioned hard film is formed on the cermet surface, the iron-group metal rich in the cermet surface diffuses into the hard film, and this causes the hardness of the hard film and the inherent properties of the hard film such as low reactivity with the work material to be reduced. Will deteriorate. Therefore, this hard film reduces the amount of iron group metal contained in the film to 100 ppm or less, especially 70 ppm.
pm or less.

Further, the grain size of the crystal constituting the hard film is:
This is a factor that affects the hardness and strength of the film. The smaller the crystal grain size, the harder the film, the higher the strength and the higher the toughness. Therefore, according to the present invention, the crystal grain size of this hard film is 0.4 μm
By controlling the thickness to 0.3 μm or less, the original function as a hard film can be exhibited, and at the same time, it is possible to prevent the falling off of the particles due to the breakage in the film and the peeling of the film.

Incidentally, as the Ti-containing hard film in which the amount of Ti is larger than the amount of Ti in the cermet base material, TiC, TiN,
TiCN and the like are preferable, and oxygen may be contained in these films in some cases.

This hard film has a thickness of 1 to 10 on the cermet surface.
It is desirable to coat with a thickness of 1 μm. If the thickness is less than 1 μm, the effect of suppressing the reactivity with the work material is small, and the surface of the work material is easily roughened. The film tends to peel during use due to the difference in thermal expansion of the film.

In the coated TiCN-based cermet of the present invention, the method for producing the above-mentioned TiCN-based cermet as a base material can be easily produced based on, for example, the method described in JP-A-2-15139.

On the surface of the TiCN-based cermet, Ti
As a method of forming the hard film containing the heat, specifically, the thermal CV
A chemical vapor deposition method (CVD method) such as a D method, a plasma CVD method, or a laser CVD method, a physical vapor deposition method (PVD method) such as a sputtering method or an ion plating method, or a gas phase impregnation method can be employed. In order to control the particle size of the hard film to 0.4 μm or less according to the present invention, an ion plating method and a sputtering method are preferable.

Further, the amount of the iron group metal mixed into the hard film is set to 1
The ion plating method, plasma C
The VD method is preferable. Particularly, according to the ion plating method, it is easy to control the crystal grains of the film due to the low deposition temperature, and the diffusion of the iron group metal from the base material is suppressed. It can be prevented from being mixed in. Further, in film formation, it is necessary to consider that parts made of iron group metal should be eliminated as much as possible in facilities and the like in the reaction furnace.
Hereinafter, the present invention will be described with reference to the following examples.

[0025]

EXAMPLES As raw material powders, Ti (CN), TiN, TiC, WC, Mo ₂ C, Nb having an average particle size of 1 to 1.5 μm
Using C, NbN, VC, Ni and Co, the mixture was blended to the composition shown in Table 1, and then pulverized with a vibration mill, and a binder-added product was press-molded into a TNGA332 chip shape.
After removing the binder at 00 ° C., the formed body was placed in a firing furnace, nitrogen gas at a pressure of 70 atm was introduced after the liquid phase appearance temperature of about 1300 ° C., and the temperature was raised to the maximum firing temperature of 1500 ° C. Was gradually reduced to a vacuum. The hardness and toughness of the surface and the interior of the obtained cermet were measured. In each case, the hardness and toughness were higher in the surface layer, and it was confirmed that the modified portion was formed in the surface layer. did. Further, the obtained sintered body was quantitatively analyzed for carbon and nitrogen in the hard phase, and (N / C +
N) The atomic ratio was determined.

Next, using each cermet as a base material, the base material temperature is set to 300 to 700 ° C. by an ion plating method, and TiN, TiCN, T
An iCNO film was formed. Further, the average crystal grain size in the coating film was determined by an SEM photograph.
Measured by CP analysis.

Next, each sample was subjected to an abrasion resistance test and a fracture resistance test under the following conditions. In the abrasion resistance test, the flank wear amount (mm) was measured. I checked the number.

Abrasion test Work material SCM435 Cutting speed 200m / min Cutting depth 2mm Feed 0.3mm / rev Cutting time 10min Fracture resistance test Work material SCM435 (round bar Ns-40) 4-groove cutting speed 100m / min Cutting time 1min depth of cut 2mm feed 0.2mm / rev

Also, as an evaluation of the finished surface. Using a surface roughness meter, a method of expressing the finished surface state of the work material by Rmax was evaluated as x when the value was 10 s or more and as ○ when less than 10 s.

[0030]

[Table 1]

[0031]

[Table 2]

As is clear from the results shown in Tables 1 and 2, Sample No. 3 in which the (N / C + N) ratio is less than 0.4 has a rough surface on the sintered body and has poor wear resistance. Conversely, in sample No. 4 having a ratio exceeding 0.6, a good sintered body could not be obtained, and a wear resistance test could not be performed.

[0033]

As described in detail above, the coating Ti of the present invention
According to the CN-based cermet, while containing a predetermined amount of nitrogen, the surface portion of the cermet having a modified phase having higher hardness and higher toughness than the inside thereof has a Ti-containing hard film formed on the surface of the cermet. It has abrasion resistance, chipping resistance, and suppresses reactivity with the work material, thereby maintaining the characteristics of the cermet base material and improving the surface of the work material after cutting. be able to.

Claims (1)

(57) [Claims] 1. A titanium carbide, nitride or carbonitride of 50 to 80% by weight and a carbide of a Group 6a element of the periodic table in a ratio of 10 to 40% by weight, and (Nitrogen / carbon + The atomic ratio represented by nitrogen) is 0.4 to 0.6
And from 5 to 40% by weight of a binder phase component containing iron group metal as a main component, and a higher toughness and a higher hardness than the inside in a surface layer portion up to 1000 μm from the surface. On the surface of the TiCN-based cermet in which the modified portion of
A coated TiCN-based cermet characterized by being coated with a hard film containing Ti having an average particle diameter of 0.4 μm or less and an iron group metal content of 100 ppm or less.