JPH08253836A - Wear resistant tungsten carbide-base cemented carbide having excellent toughness - Google Patents

Abstract

PURPOSE: To produce a WC-base cemented carbide excellent in toughness and wear resistance by specifying the compsn. of a sintered body constituted of Co, Ni, VC and Cr3 C2 as bonding phase forming components and CW as a hard phase forming component and the characteristics of the hard phase. CONSTITUTION: In a sintered body having a blending compsn. contg., as bonding phase forming components, by weight, 5 to 20% Co and/or Ni, 0.1 to 2% VC and 0.1 to 2% Cr3 C2 , and the balance WC as a hard phase forming component, the hard phase constituting the same has various characteristics of <=0.7μm average particle diameter, the assembly of planes and 1×10<8> cm<-2> or below of dislocation density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tungsten carbide (hereinafter referred to as WC) based cemented carbide having excellent toughness and wear resistance.

[0002]

2. Description of the Related Art Conventionally, as described in, for example, Japanese Patent Publication No. 62-56224, in terms of weight% (hereinafter,% means% by weight), Co and //
Or Ni: 5 to 20%, vanadium carbide (hereinafter referred to as VC
): 0.1 to 2%, chromium carbide (hereinafter, Cr ₃ C
₂ ): 0.1 to ₂ %, tungsten carbide as a hard phase forming component (hereinafter referred to as WC): the remainder, and a hard material that constitutes the sintered body. WC-based cemented carbides having an average particle size of the phase of 0.7 μm or less are known, and it is also known that these WC-based cemented carbides are applied as various cutting tools and wear resistant tools such as rolling rolls. There is. The above WC-based cemented carbide is V
C and Cr ₃ C ₂ form a solid solution in the matrix to remarkably suppress the growth of WC as a hard phase forming component, and have an excellent wear resistance by refining the average grain size of the WC to 0.7 μm or less. It is also known that it is a brutal one.

[0003]

On the other hand, in recent years, there is a strong demand for labor saving and energy saving such as cutting work and plastic working, and in connection with this, high speed cutting and Heavy cutting such as feed and high depth of cut is performed, and high-speed rolling and high-pressure rolling are likely to be performed for plastic working.Therefore, cutting tools and wear-resistant tools used for these processing are subject to severe conditions. However, since the conventional WC-based cemented carbide and the other WC-based cemented carbides that compose the same have insufficient toughness, cracks and chips are not generated in practical use. At present, it is likely to occur and has a relatively short service life.

[0004]

Therefore, the present inventors have
From the above viewpoint, the conventional WC-based cemented carbide, which has excellent wear resistance due to the average grain size of the hard phase mainly composed of WC being 0.7 μm or less, is noted, and it has high toughness. As a result of conducting a study to impart a value of 1100 to 1200 during sintering to the sintering temperature.
The temperature is maintained at a temperature equal to or lower than the liquidus appearance temperature of ℃ for a predetermined time (holding process at the time of temperature rise), and the conventional sintering temperature of 1350 to 1
The sintering temperature is 1250 to 1300 ° C., which is relatively lower than 400 ° C. but is higher than the liquid phase appearance temperature, and further heated and held at 1450 to 1500 ° C. higher than the sintering temperature (high temperature heat treatment), When the furnace-cooled sintering was performed, the W
C group cemented carbide, the above temperature-raising-period holding process, the conventional WC based cemented carbide, as exemplified by 100,000 times the tissue replication view by transmission electron microscopy in FIG. 2, 1 × 10 ¹² cm ^- A dislocation density of ² or more was 1 × 10 ⁸ cm ⁻² or less as illustrated in the same tissue copy diagram of FIG. 1, and WC was mainly formed by the high temperature heat treatment. The hard phase, combined with the sintering temperature being low as described above,
As shown in FIG. 2, the surface had a curved aggregate shape, but the surface became a flat aggregate shape as shown in FIG. 1 as a result of self-development. Has a low dislocation density and its surface shape is a plane aggregate WC.
It has been obtained that the base cemented carbide has excellent wear resistance as well as extremely excellent toughness.

The present invention has been made based on the above-mentioned research results, and in each case, Co and / or Ni: 5 to 20%, VC: 0.
_{1~2%, Cr 3 C 2:} 0.1~2%, WC as hard phase forming component: rest, with a sintered body of blend composition consisting of a hard phase constituting the sintered body, (A)
An average particle size of 0.7 μm or less, (b) a plane aggregate surface,
(C) It is characterized by a wear-resistant WC-based cemented carbide with excellent toughness, which has a dislocation density of 1 × 10 ⁸ cm ⁻² or less and the above (a) to (c).

Next, in the WC-based cemented carbide of the present invention, the reason why the composition and the average grain size and dislocation density of the hard phase are limited as described above will be explained. (1) Composition (a) Co and Ni These components have the effect of improving the sinterability and thus the alloy strength, but if the proportion is less than 5%, the desired strength can be secured. No, on the other hand, the ratio is 20
%, The hardness sharply decreases and the wear resistance is unavoidably deteriorated. Therefore, the ratio is set to 5 to 20%, preferably 9 to 13%.

(B) VC and Cr ₃ C ₂ These components all dissolve in Co and Ni, which are binder phase forming components, and in the coexisting state, significantly suppress the grain growth of the hard phase mainly composed of WC. The average particle size is 0.7μ
miniaturized below m, but has the effect of improving the wear resistance have, VC the ratio is respectively: less than 0.1% and Cr ₃ C _2: the desired effect can be obtained in the working is less than 0.1% On the other hand, the proportions are VC: 2% and C, respectively.
If r ₃ C ₂ exceeds 2%, it becomes difficult to form a complete solid solution in the binder phase and the toughness deteriorates. Therefore, the ratio is VC: 0.1 to 2%, preferably 0.4. ~ 0.9%,
Cr ₃ C _2: 0.1~2%, preferably defined 0.5 to 1%.

(2) Average particle size of hard phase This is determined because it is necessary to reduce the average particle size of the hard phase to 0.7 μm or less in order to ensure excellent wear resistance.

(3) Dislocation Density of Hard Phase As described above, in the conventional WC-based cemented carbide, since many dislocations having a dislocation density of 1 × 10 ¹² cm ^-2 or more exist in the hard phase, desired toughness is obtained. Can not be secured, but this is 1 × 10 ⁸ cm ²
This is based on the reason that when the dislocation density is set to the following, it has excellent toughness in combination with the planar aggregate shape of the hard phase surface.

[0010]

EXAMPLES Next, the WC-based cemented carbide of the present invention will be specifically described by way of examples. As raw material powder, 0.1-
Various W having a predetermined average particle size within the range of 0.6 μm
C powder, 1.5 μm VC powder, 2.3 μm Cr
₃ C ₂ powder, 1.3 μm Co powder, and 1.5 C
Ni powder of μm was prepared, and these raw material powders were blended to the blending composition shown in Table 1, respectively, and the powder was wet-ball milled to 72
After mixing for a period of time, drying under reduced pressure, press-molding into a green compact at a pressure of 1 ton / cm ² , and sintering this green compact in a vacuum under the conditions shown in Table 1 (cooling is furnace cooling). According to the present invention, cemented carbides 1 to 5 of the present invention were manufactured. For comparison purposes, Table 1
The conventional cemented carbides 1 to 5 were manufactured under the same conditions, except that the holding treatment at elevated temperature and the high temperature heat treatment were not performed as shown in FIG.

With respect to the various cemented carbides obtained as a result, the Vickers hardness, the fracture toughness value, and the average grain size of the hard phase mainly composed of WC were measured. Further, the dislocation density is taken by a transmission electron microscope at a magnification of 100,000 times to photograph the tissue
The total area of the hard phase existing in the 12 cm x 12 cm frame in this micrograph is determined by an image analyzer, and the number of all dislocation lines existing in the hard phase is counted to determine the dislocation lines per unit area of the hard phase. The number was calculated by calculating the number. Further, in this case, the interface between the hard phase and the binder phase was observed, and if all of them were linear, it was determined that the surface of the hard phase had a planar aggregate shape. Table 2 shows the results.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

From the results shown in Table 2, the cemented carbides 1 to 5 of the present invention have an average grain size of the hard phase of 0.7 μm or less, which is almost equal to that of the conventional cemented carbides 1 to 5, This also appears in the hardness.On the other hand, regarding the surface shape of the hard phase and the dislocation density, the two are significantly different, and this difference appears as the difference in fracture toughness value, and the surface shape of the hard phase is flat. The cemented carbides 1 to 5 of the present invention, which are aggregates and have a low dislocation density of 1 × 10 ⁸ cm ⁻² or less, have the same surface shape as a curved aggregate, and 1
It is clear that the toughness is far superior to that of the conventional cemented carbides 1 to 5 having a high dislocation density of × 10 ¹² cm ^-2 or more. As described above, since the WC-based cemented carbide of the present invention has excellent toughness and excellent wear resistance, various cutting tools such as indexable inserts, drills, end mills, rolling rolls and When used as a wear resistant tool such as a die, it exhibits excellent performance over a long period of time even in practical use under severe conditions.

[Brief description of drawings]

FIG. 1 is a structure copy diagram (magnification: 100,000 times) of a WC-based cemented carbide of the present invention by a transmission electron microscope.

FIG. 2 is a structure copy diagram (magnification: 100,000 times) of a conventional WC-based cemented carbide by a transmission electron microscope.

Claims (1)

[Claims] 1. By weight%, as a binder phase forming component, Co and / or Ni: 5 to 20%, vanadium carbide: 0.1 to 2%, chromium carbide: 0.1 to 2%, hard phase Tungsten carbide as a forming component: a sintered body having a compounding composition consisting of the remainder, and the hard phase constituting the sintered body has (a) an average particle diameter of 0.7 μm or less, (b) a plane aggregate A wear-resistant tungsten carbide-based cemented carbide having excellent toughness, characterized by having a surface, (c) a dislocation density of 1 × 10 ⁸ cm ^-2 or less, and (a) to (c) above.