JP2001152276A - Cermet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce cermet having toughness and wear resistance at a cutting rate of 50 to 350 m/min. SOLUTION: In titanium carbonitride cermet containing a hard phase having a cored structure, in which the total content of Co and/or Ni is 7 to 30 weight %, particles essentially consisting of Co and/or Ni with a particle size of 30 to 200 nm by observation with an electron microscope to the cermet are dispersed into the hard phase having a cored structure by 0 to 15 pieces per particle on the average.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a titanium carbonitride-based cermet cutting tool having excellent toughness and wear resistance (hereinafter, simply referred to as a cermet tool).

[0002]

2. Description of the Related Art Conventionally, as shown in Japanese Patent Application Laid-Open No. 11-229068, a core structure is formed by observing a microscopic cross-sectional structure, and the core portion is made of titanium carbonitride, and its peripheral portion is formed. Ti and one of Ta, Nb, W, and Mo
Co and / or having a particle size of 50 nm or less throughout the cored structure.
Alternatively, a first hard dispersed phase having a structure in which ultrafine alloy particles containing Ni as a main component are dispersed and distributed: 63 to 97 area%, and Co and / or Ni having a particle size of 50 nm or less in titanium carbonitride are used as a main component. Second hard dispersed phase having a structure in which ultrafine alloy particles are dispersed and distributed: 0.1 to 30 area%, and the balance is a binder phase containing Co and / or Ni as a main component and inevitable impurities. Having a total content of Co and / or Ni of 3 to 7% by weight
Titanium carbonitride-based cermet is described. This conventional example performs cutting at a cutting speed exceeding 500 m / min in order to respond to the recent demand for higher performance and higher output of a cutting device and to meet the demand for labor saving and energy saving of the cutting process. A cermet tool intended to perform.

[0003]

However, the current cermets tend to be slightly inferior in toughness as compared with WC-based cemented carbides. Therefore, in actual cutting, a case of high-speed cutting exceeding 500 m / min is rare. This is because in high-speed cutting, plastic deformation due to cutting heat occurs in the cutting tip. Therefore, as in the above invention, the content of the metal binder phase is reduced to 3 to 7% to prevent plastic deformation. However, when the amount of the metal binder phase is reduced, the toughness is significantly reduced, and thermal cracks are generated. And mechanical micro-chipping occur, resulting in severe chip damage.
An object of the present invention is to provide a cermet having excellent toughness and abrasion resistance under conventional cutting conditions, that is, approximately 50 to 350 m / min in terms of cutting speed.

[0004]

According to the above-mentioned studies, the gist of the present invention is as follows: a hard phase having a cored structure is contained, and the total content of Co and / or Ni exceeds 7% by weight and 30% by weight.
In the following titanium carbonitride-based cermet, an electron microscope section observation of the cermet shows that
Particles containing Co and / or Ni as main components having the following particle diameters are contained in the core-structured hard phase in an average of 0 per particle.
A cermet characterized by dispersing up to 15 cermets.

[0005]

First, attention was paid to the microstructure of the cermet tool from the above viewpoint. FIG. 1 shows an electron micrograph of the cermet microstructure of the present invention.

[0006] As shown in Fig. 1, it was found that ultrafine alloy particles containing Co and / or Ni as main components are dispersed in the hard phase. The number of the ultrafine dispersed particles is large in hard particles having a cored structure, and the number is small in hard particles having no cored structure. Further, in the hard particles having a cored structure, the ultrafine dispersed particles tend to be slightly concentrated at the interface between the core and the outer periphery. From the above, carbides, carbonitrides, and nitrides form a solid solution during sintering, but in the process, Co and / or Ni attached to the surrounding or hard powder are taken into the solid solution double carbide, As a result, it is presumed that ultrafine dispersed particles were formed in the hard particles.

It is a matter of course that the hard phase is responsible for the wear resistance of the cermet, but the presence of dispersed particles mainly composed of Co and / or Ni as the main component of the binder phase exists in the hard phase. Reduces the wear resistance of hard particles. Also, the incorporation of Co and / or Ni into the hard particles is
This relatively lowers the amount of metal bond and consequently lowers the toughness of the cermet. As described above, the dispersion of Co and / or Ni in the hard particles lowers the inherent wear resistance of the cermet, and also lowers the toughness. The index of the adverse effect is Co / N existing in the hard particles.
This is the number of ultrafine dispersed particles mainly composed of i. From the above viewpoints, the present inventors have obtained a high wear-resistant and high-toughness cermet by a technique of limiting the number of ultrafine dispersed particles mainly composed of Co / Ni dispersed in the hard phase. .

In the present invention, the production method for limiting the number of ultrafine dispersed particles mainly composed of Co / Ni does not matter. This is because there are several effective manufacturing methods. For example, it has been confirmed that the use of coarse Co raw material powder reduces the number of ultrafine dispersed particles mainly composed of Co / Ni in the hard phase as compared with the case of using fine Co particles. Also, (Ti
Even when a double carbide such as W) C or (TiWTa) C is used, mutual solid solution during sintering is small, and as a result, Co in the hard phase is reduced.
The number of ultrafine dispersed particles mainly composed of / Ni decreases. The particle size of the hard raw material powder as well as the metal raw material powder also affects the number of ultrafine dispersed particles mainly composed of Co / Ni. In addition, depending on the sintering conditions such as temperature and holding time during sintering, Co
The number of ultrafine dispersed particles mainly composed of / Ni depends.
And, of course, it depends on the composition of the cermet and the particle size of the hard phase. In consideration of the above, the raw material powder used, the sintering conditions, and the like may be adjusted according to the target cermet grade.

[0009] However, despite the fact that various production methods have been confirmed, practical cermets include hard particles having a cored structure almost without exception. The cored structure is formed because the hard phase powder mutually forms a solid solution during the sintering process.
And / or Ni uptake is unavoidable. The present inventors have conducted various studies on the extent to which the incorporation is permitted. As a result, when the number of ultrafine dispersed particles mainly composed of Co / Ni exceeds 15 per hard particle, the abrasion resistance and toughness rapidly increase. It was found to decrease. The particle diameter of the ultra-fine dispersed particles mainly composed of Co / Ni is 30 nm or more and 200 nm or less. If it exceeds 200 nm, wear resistance and toughness will be reduced. Particles smaller than 30 nm cannot be used as indicators because their existence is difficult to confirm. It is practical to impose a limit on the number of particles present for particles larger than 30 nm. The amount of metal is limited to more than 7% by weight and 30% by weight or less. If it is less than 7%, the toughness is poor,
If it exceeds 30%, the abrasion resistance is poor, which is contrary to the gist of the present invention.

[0010]

Next, the cermet of the present invention will be specifically described with reference to examples. First, the average particle size: 0.1.
8-1.4 μm TiCN powder and a predetermined amount of Co and / or
Or Ni, and further, as raw material powder,
TaC having a predetermined average particle size in the range of ~ 2.0 µm
Powder, NbC powder, WC powder, Mo ₂ C powder, and coarse (2 μm) and fine (0.5 μm) Co and Ni powder were prepared. These raw material powders were blended at the ratios shown in Table 1. These were wet-mixed and pulverized by a ball mill for 24 hours, dried, and then pressed into a green compact at a pressure of 100 MPa. The green compact is sintered under two kinds of sintering conditions of A and B, that is, A is a condition for obtaining the present invention, B is a condition for obtaining a non-product of the present invention, and the present invention has a throwaway chip shape of ISO standard CNMG120408. Cermet chip A1
A7 was manufactured as a comparative product B1 to B7 of the present invention.

[0011]

[Table 1]

Using a transmission electron microscope (TEM) at a magnification of 350,000 times, the average particle size of the ultrafine dispersed particles and the average number of ultrafine alloy particles per cored hard particle were measured for the obtained chip. Was measured. The results are also shown in Table 1. The main component constituting this is an energy dispersive X
It was determined using a line spectrometer (EDS), and it was confirmed that the particles were mainly composed of Co and / or Ni.

Further, with respect to the various cermet tools described above, a milling test was performed under the following conditions: work material: S50C, cutting speed: 220 m / min, feed amount: 0.2 mm / tooth, and cutting amount: 2.5 mm. The cutting time until the flank wear width of the blade reached 0.4 mm was measured. Table 1 also shows the results of these measurements.

From the results shown in Table 1, the tools A1 to A7 according to the cermet of the present invention have ultrafine particles dispersed and distributed in hard particles despite having the same composition as the comparative products B1 to B7. Since the number of dispersed particles is small, it is clear that the cutting edge is less damaged, and exhibits a much higher abrasion resistance than conventional cermets B1 to B7 in which not a small amount of ultrafine particles are dispersed in hard particles. In particular, the life of A1 is remarkably prolonged in comparison with B1. This was considered to be because the total amount of Co and Ni was 7.5%, which was smaller than that of other samples, so that the incorporation of Co and Ni into the hard particles had a particularly large effect on toughness.

[0015]

From the above results, the cermet of the present invention is suitable for a cermet tool which exhibits particularly excellent performance at a cutting speed generally used in actual cutting sites.

[Brief description of the drawings]

FIG. 1 shows an electron micrograph of a micro tissue of the present invention.

[Explanation of symbols]

 1 Ultrafine dispersed particles

Claims (1)

[Claims] 1. An electron microscope section observation of a titanium carbonitride-based cermet containing a hard phase having a cored structure and having a total content of Co and / or Ni of more than 7% by weight and not more than 30% by weight. Over 30nm and 200n
A cermet, characterized in that 0 to 15 particles containing Co and / or Ni as main components having a particle size of m or less are dispersed in the cored hard phase on average per particle.