JP2011132057A - Sintered compact - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sintered compact having higher hardness without reducing toughness. <P>SOLUTION: In the sintered compact 1 having a skeleton structure 4 where the outer periphery of a hard phase 2 whose main ingredient is TiCN is enclosed by a matrix 3 whose main ingredient is WC, the average particle diameter of the hard phase 2 is 0.3-5 μm and the ratio (Sp/Sb) of the area Sp of the hard phase 2 to the area Sb of the matrix 3 is 0.5-3 in the cross-sectional observation of the skeleton structure 4 of the sintered compact 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sintered body containing TiCN and WC.

  Currently, cemented carbides mainly composed of WC and cermets mainly composed of TiCN are widely used as wear-resistant materials and cutting tool materials. In order to develop a material with higher wear resistance for such a material, for example, as in Patent Document 1, a mixture of fine powders of titanium carbide, tungsten carbide, and tantalum carbide is mixed and molded, and then pulsed current pressure sintering A binderless cemented carbide that has been densified by a method is disclosed. Patent Document 2 discloses a sintered body having a hard layer made of TiCN and a binder phase made of metallic tungsten. Further, Patent Document 3 discloses a sintered body having a structure in which a periphery of an agglomerated portion made of a cermet sintered body is surrounded by a matrix portion made of a cemented carbide sintered body.

JP 2009-179519 A Japanese Patent Laid-Open No. 11-061319 JP-A-10-219385

  However, in a structure in which titanium carbide particles, tungsten carbide particles, and the like are mixed as in Patent Document 1, the effect of suppressing the progress of cracks is low when cracks occur in the sintered body, and the toughness of the sintered body is sufficient. It turned out not to be able to say. Further, in the sintered body in which the binder phase is made of metallic tungsten as in Patent Document 2, there is a limit in improving the hardness of the sintered body. Further, as disclosed in Patent Document 3, a sintered portion composed of an agglomerated portion made of TiCN cermet bonded with a binder phase made of iron group metal and a peripheral portion made of cemented carbide bonded with a binder phase made of iron group metal. It was found that there was a limit to the improvement in hardness even in the knot.

  Then, this invention is for solving the said problem, and is providing the sintered compact which can improve the hardness further, without reducing toughness.

  The sintered body of the present invention has a skeleton structure in which a matrix mainly composed of WC is surrounded between hard phases mainly composed of TiCN. Here, the hard phase in the skeleton structure has a core portion with a high Ti content ratio in the center, and the outer periphery thereof has a high content ratio of the fourth, fifth, and sixth group metals other than Ti in the periodic table. It is desirable to be constituted by a cored structure made of

  In the cross-sectional observation of the skeleton structure portion, the average particle size of the hard phase is 0.3 to 5 μm, and the ratio (Sp / Sb) of the area Sp of the hard phase to the area Sb of the matrix is 0. 5 to 3 is desirable.

  The sintered body preferably contains an iron group metal in a proportion of 0.5 to 15% by mass, and a dispersed phase containing the iron group metal as a main component is dispersed in the matrix.

  Further, it is desirable that the skeleton structure having an average diameter of 5 to 100 μm has a structure in which it is dispersed in a cemented carbide containing WC particles and Co.

  According to the sintered body of the present invention, it has a skeleton structure in which the outer periphery of the hard phase mainly composed of TiCN is surrounded by a matrix mainly composed of WC, and this skeleton structure is made of conventional cemented carbide or cermet. Thus, since the binder is not made of an iron group metal and the binder is a carbide mainly composed of WC, the hardness is high. In particular, the hard phase has a core portion with a high Ti content ratio in the center, and the outer periphery thereof has a cored structure composed of a peripheral portion with a high content ratio of the fourth, fifth, and sixth group metals other than Ti. This is desirable in terms of improving the toughness of the sintered body.

  In the cross-sectional observation of the skeleton structure portion of the sintered body, the average particle size of the hard phase is 0.3 to 5 μm, and the ratio (Sp / Sb) of the hard phase area Sp to the matrix area Sb is 0. 5 to 3 is desirable in that it has high hardness and toughness that can withstand practicality.

  In addition, the sintered body contains an iron group metal in a proportion of 0.5 to 15% by mass, and that the dispersed phase mainly composed of the iron group metal is dispersed in the matrix. This is desirable in terms of improving the sinterability. Further, the skeleton structure having an average diameter of 5 to 100 μm is composed of a structure dispersed in a cemented carbide containing WC particles and Co, without using a pressure sintering method such as hot pressing. This is desirable in that the sintered body can be fired by the pressure sintering method.

An example of the sintered compact of this invention is shown, It is a scanning electron micrograph about (a) 200 times, (b) 2000 times, (c) 5000 times. It is a principal part enlarged micrograph of the sintered compact of FIG. 1, and a mapping photograph of a specific metal element.

  An example of the sintered body of the present invention will be described on the basis of scanning electron micrographs of (a) 200 times, (b) 2000 times, and (c) 5000 times in FIG.

  As shown in FIGS. 1B, 1C and 2, the sintered body 1 of the present invention surrounds the outer periphery of the hard phase 2 mainly composed of TiCN with a matrix 3 mainly composed of WC. It has a skeleton structure 4 composed of a structure. This skeleton structure 4 has a hardness higher than that of cemented carbide, cermet or conventional binderless cemented carbide. As a result, it was found that the hardness of the sintered body 1 as a whole was high.

  Here, at least a part of the hard phase 2 has a core portion 2a having a high Ti content ratio in the center, and an outer periphery thereof is a peripheral portion having a high content ratio of periodic groups 4, 5, and 6 metals other than Ti. From the cored structure composed of 2b, that is, the cored structure having a high Ti content ratio surrounded by the peripheral part 2b having a high content ratio of the fourth, fifth, and sixth group metals other than Ti It is desirable to be configured in terms of improving the toughness of the sintered body 1. The average particle size of the core portion 2a is preferably 0.1 to 2.0 μm, and the average particle size of the entire hard phase 2 including the peripheral portion 2b is preferably 0.3 to 5.0 μm from the viewpoint of improving toughness. . Moreover, in the scanning microscope observation of the cross section of the sintered compact 1, since the core part 2a of the hard phase 2 has high Ti content ratio, it is observed as black particle | grains, and the peripheral part 2b is periodic table 4th, 5th other than Ti. , Because of the high content of Group 6 metal, it exists as gray white or white. The grayish white color may appear to be a color tone close to white or a color tone close to gray depending on photography conditions, but can be distinguished in a relative comparison between the core part 2a and the peripheral part 2b. .

  In addition, the measurement of the particle size of the hard phase 2 in this invention is measured according to the measuring method of the average particle size of the cemented carbide prescribed | regulated to CIS-019D-2005. At this time, in the case where the hard phase 2 has a cored structure, the particle diameter is measured with the hard phase 2 as a single hard phase 2 up to the outer edge of the peripheral portion including the core portion 2a and the peripheral portion 2b.

  Here, as shown in FIGS. 1 (b) and 1 (c), in the cross-sectional observation of the skeleton structure 4 portion of the sintered body 1, the average particle diameter of the hard phase 2 is 0.3 to 5 μm. The ratio of the area Sp to the area Sb of the matrix 3 (Sp / Sb) is preferably 0.5 to 3 in terms of having high hardness and toughness that can withstand practicality. A desirable range of the average particle diameter of the hard phase 2 is 1 to 3 μm, and a desirable range of the ratio (Sp / Sb) is 1 to 2.

  Further, the sintered body 1 may contain an iron group metal in a proportion of 0.5 to 15% by mass, and as shown in the mapping diagrams of the Co element in FIGS. 1 and 2, the matrix 3 of the skeleton structure 4. It is desirable that the disperse phase 6 containing iron group metal as a main component is dispersed therein in terms of enhancing the sinterability of the sintered body 1.

  Further, in the present embodiment, as shown in FIGS. 1A and 1B, the sintered body 1 has a skeleton structure 4 having an average diameter of 10 to 100 μm in a cemented carbide 7 containing WC particles and Co. It consists of a distributed configuration. If it is this structure, the sintered compact 1 of this invention can be baked with a normal pressureless sintering method, without using pressure sintering methods, such as a hot press.

(Production method)
Next, the manufacturing method of the cutting tool mentioned above is demonstrated.
Two kinds of mixed raw material powders are prepared as raw materials.
The first mixed raw material powder has an average particle size of 1 to 3 μm, preferably 1.5 to 2.5 μm of TiCN powder of 50 to 75% by mass, particularly 50 to 70% by mass, and an average particle size of 0.05 to 1 μm. WC powder of 0 to 12% by mass, particularly 7 to 10% by mass, and Mo ₂ C powder having an average particle size of 1 to 4.5 μm is 0.5 to 10% by mass, particularly 1 to 10% by mass, and the average particle Total amount of any one of carbide powder, nitride powder, or carbonitride powder (other than TiCN, WC, Mo ₂ C) of the above-mentioned other periodic table group 4, 5 and 6 metals having a diameter of 0.1 to 2 μm 1 to 20% by mass, particularly 10 to 15% by mass, and Co powder having an average particle size of 1.0 to 3.0 μm is 0 to 10% by mass, particularly 3 to 7% by mass, and the average particle size is 0.3 to 0.3%. 0.8 μm Ni powder, 0-10% by weight, in particular 3-5% by weight, and optionally M with an average particle size of 0.5-10 μm CO ₃ powder 3 wt% or less, especially a mixed powder mixed in a ratio of 0.5 to 1.0 mass%. TiC powder and TiN powder may be added to the first and second raw materials, but these raw material powders constitute TiCN in the cermet after firing.

On the other hand, the second mixed raw material powder is a cemented carbide material of tungsten carbide (WC) having an average particle size of 1.0 μm or less of 79 to 95% by mass and vanadium carbide (VC) having an average particle size of 0.3 to 1.0 μm. ) 0.1 to 0.3 mass% of powder, 0.1 to 0.3 mass% of chromium carbide (Cr ₃ C ₂ ) powder having an average particle diameter of 0.3 to 2.0 μm, and an average particle diameter of 0.2 It is set to 5 to 15% by mass of metallic cobalt (Co) of ˜0.6 μm, and further mixed metal powder of metallic tungsten (W) or carbon black (C) as desired.

  Next, a binder is added to each of the first raw material powders, molded, and subjected to a firing heat treatment at 1400 ° C. or higher for 0.2 to 1 hour in a vacuum atmosphere. At this time, if the firing heat treatment temperature is lower than 1400 ° C., many voids tend to be generated in the sintered body after the second firing described later. Subsequently, this was pulverized to obtain a cermet powder having an average particle size of 1.0 to 5.0 μm and a cemented carbide powder having an average particle size of 0.1 to 1.0 μm. Thereafter, both the cermet and the cemented carbide powder are mixed and molded into a predetermined shape by a known molding method such as press molding, extrusion molding or injection molding.

  Then, the heat-treated first raw material powder and the non-heat-treated second raw material powder are mixed under wet conditions such as a vibration mill and a rotary mill, and known molding such as press molding, extrusion molding, injection molding and the like. It is formed into a predetermined shape by a method.

Then, according to this invention, the sintered compact of the predetermined structure | tissue mentioned above can be produced by baking the said molded object on the following conditions. As an example of firing conditions,
(A) The temperature is raised to 1050 to 1250 ° C.
(B) In an atmosphere filled with an inert gas such as nitrogen (N ₂ ) of 30 to 2000 Pa, the temperature is increased to 1300 to 1450 ° C. at a temperature increase rate of 0.1 to 2 ° C./min,
(C) While raising the temperature to 1560-1600 ° C. at a temperature increase rate of 3-15 ° C./min in a vacuum atmosphere, maintaining the vacuum atmosphere or an atmosphere filled with an inert gas for 0.5-2 hours,
(D) Firing is performed at a cooling rate of 6 to 15 ° C./min.

  At this time, when the firing temperature is lower than 1560 ° C., element diffusion between the first raw material and the second raw material is insufficient, and the cermet having the iron group metal as the binder phase and the iron group metal as the binder phase. It becomes a mixed structure with the cemented carbide. On the contrary, if it exceeds 1600 degreeC, a sintered compact will be oversintered and the hardness of a sintered compact will fall.

  Then, if desired, a coating layer is formed on the surface of the cermet. A physical vapor deposition (PVD) method such as an ion plating method or a sputtering method can be suitably applied as the coating layer forming method.

TiCN powder having an average particle size (d ₅₀ value) shown in Table 1 as measured by the microtrack method, WC powder having an average particle size shown in Table 1, Mo ₂ C powder having an average particle size shown in Table 1, average particle size 1 TiN powder with an average particle size of 2 μm, NbC powder with an average particle size of 1.5 μm, ZrC powder with an average particle size of 1.8 μm, VC powder with an average particle size of 1.0 μm, an average particle size of 2.4 μm Using a Ni powder and a Co powder with an average particle diameter of 1.9 μm, add isopropyl alcohol (IPA) to the first mixed powder adjusted in the ratio shown in Table 1 using a stainless steel ball mill and a carbide ball. Then, the mixture was wet-mixed, and 3% by mass of paraffin was added and mixed, and then formed into granules by a spray dryer, and further heat treated under the conditions shown in Table 1 and pulverized.

Similarly, WC powder having an average particle size (d ₅₀ value) shown in Table 2, TiC powder having an average particle size of 1.5 μm, TaC powder having an average particle size of 2 μm, NbC powder having an average particle size of 1.5 μm, and average particle size Using the 1.8 μm ZrC powder, the VC powder having an average particle size of 1.0 μm, and the Co powder having an average particle size of 1.9 μm, the second mixed raw material powder shown in Table 1 was prepared, and the above heat treatment was performed. The first mixed raw material powder and a vibration mill were mixed under wet conditions, and a binder was further mixed to obtain a mixed powder for molding.

And using this mixed powder for molding, it was press-molded into a tool shape of CNMG120408 at 200 MPa. Then, (a) the temperature is increased to 1200 ° C. at a temperature increase rate of 10 ° C./min, and (b) the temperature is increased to 1400 ° C. at a temperature increase rate of 0.5 ° C./min in an atmosphere filled with 1000 Pa of nitrogen (N ₂ ). (C) The temperature is raised to the firing temperature shown in Table 2 at a rate of 7 ° C./min in a vacuum atmosphere, maintained in that state for 1 hour, and (d) cooled at a cooling rate of 10 ° C./min. Firing was performed under the firing conditions for firing in the process.

The obtained cermet is observed with a scanning electron microscope (SEM), and image analysis is performed using commercially available image analysis software on any five locations where 10 or more hard phases can be confirmed, and the state of the skeleton structure (average particle size) d _i and proportions), as well as confirm the average particle diameter of the core portion (d ₁ and d ₂₎ for the hard phase forming the hard phase and cored structure in the skeleton structure, the wavelength dispersive spectroscopy (WDS analysis) Then, the distribution state of each metal element in the skeleton structure and the matrix portion was measured, and the abundance ratio of each metal element was calculated. The results are shown in Table 3.

  Next, with respect to the obtained sintered body, the hardness of the skeleton structure portion was measured using a micro Vickers hardness meter, and the hardness of the entire sintered body was measured using the Vickers hardness meter. In addition, fracture toughness (K1c) was measured. The results are shown in Table 3.

  From Tables 1-3, sample No. which does not have a skeleton structure | tissue is shown. Nos. 6 to 9 had low sintered hardness and low fracture toughness.

  On the other hand, Sample No. which is a sintered body having a structure within the scope of the present invention. 1-5 and no. 10 to 12 exhibited excellent wear resistance, good fracture resistance, and long tool life.

DESCRIPTION OF SYMBOLS 1 Sintered body 2 Hard phase 2a Core part 2b Peripheral part 3 Matrix 4 Skeleton structure 6 Dispersed phase 7 Cemented carbide

Claims (5)

  A sintered body having a skeleton structure in which the outer periphery of a hard phase mainly composed of TiCN is surrounded by a matrix mainly composed of WC.   The hard phase in the skeleton structure has a structure in which an outer periphery of a core portion having a high Ti content ratio surrounds a peripheral portion having a high content ratio of Group 4, 5, 6 metals other than Ti. The sintered body described.   In the cross-sectional observation of the skeleton structure portion, the average particle diameter of the hard phase is 0.3 to 5 μm, and the ratio (Sp / Sb) of the area Sp of the hard phase to the area Sb of the matrix is 0.5 to 5 μm. The sintered body according to claim 1, wherein the sintered body is 3.   The sintering according to any one of claims 1 to 3, wherein an iron group metal is contained at a ratio of 0.5 to 10% by mass, and a dispersed phase mainly composed of the iron group metal is dispersed in the matrix. body.   The sintered body according to any one of claims 1 to 3, wherein the skeleton structure having an average diameter of 5 to 100 µm has a structure dispersed in a cemented carbide containing WC particles and Co.