JPS6112847A - Sintered hard alloy containing fine tungsten carbide particles - Google Patents

Abstract

PURPOSE:To fine WC particles and to develop a sintered hard alloy having excellent wear resistance and toughness by adding V and Cr in combination as a suppressing agent for grain growth to the hard sintered alloy contg. Ni or Co as a binding phase and consisting essentially of WC. CONSTITUTION:5-40% 1 or 2 kinds of powder of Ni or Co as the binding phase and respectively 0.1-2.0% V and Cr as the suppressing agent for grain growth in the form of carbide, etc. are mixed with the WC powder having <=0.7mum average grain size. The powder mixture is press-molded under 1ton/cm<2> pressure and the molding is heated and sintered for 1.5-5 hours at 1280-1430 deg.C in a vacuum atmosphere. The V and Cr are entered into the binding phase Ni or Co and the growth of the WC to >=0.7mum average grain size is suppressed by the property thereof to suppress the grain growth, by which the grains are maintained finely and the WC contg. sintered hard alloy having the excellent wear resistance and toughness is produced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a cemented carbide, and particularly to a cemented carbide with excellent wear resistance and toughness that contains fine tungsten carbide particles with an average grain size of 07 μm or less. It is.

[Conventional technology]

Conventionally, cemented carbide, which has a dispersed phase mainly composed of tungsten carbide (hereinafter referred to as WC) combined with a metal phase such as Co or Ni, has been widely used as a material for cutting tools, wear-resistant tools, impact-resistant tools, etc. , especially WC with an average particle size of about 1 μm.
Cemented carbide containing particles has high hardness and high toughness, so it is attracting attention as a material that is located between general cemented carbide and high-speed steel, and this property makes it easy to form sharp edges. Because of this, it is also used as a material for tools that traditionally used high-speed steel, such as various shear blades, drills for printed circuit boards, and end mills, and has brought significant improvements in the performance of these tools.

[Problem that the invention seeks to solve]

In such applications, there is a need to further improve the properties of the cemented carbide mentioned above in terms of product quality control and tool life. The above improvement is achieved by making the WC particles smaller, since a smaller diameter improves its hardness, while a constant hardness increases its toughness by increasing the proportion of binder phase. considered to be a thing.

By the way, since WC particles generally undergo grain growth due to dissolution/precipitation reactions during sintering, the particle size of the WC particles in the obtained alloy usually tends to be larger than the particle size of the original raw material powder particles. This tendency becomes more pronounced as the particle size of the raw material WC particles becomes smaller. Therefore, research has been carried out to suppress the grain growth of WC by adding various grain growth inhibitors singly to the alloy. It is known to be effective. Therefore, in conventional cemented carbide containing WC particles with an average particle size of about 1 μm, one of the metal carbides mentioned above is added to the alloy based on the above research. The grain growth inhibiting effect of these metal carbides increases as the amount added increases, so if you want to obtain a cemented carbide containing even finer WC particles with an average grain size of 0.7 μm or less, it is necessary to add a large amount of metal carbide. However, if this is done, part of the grain growth inhibitor, which is normally dissolved in the binder phase during sintering, will precipitate during cooling after sintering and become mixed with the WC particles and the metal binder phase. is another third
The problem was that it formed a phase, which reduced the toughness of the alloy.

[Failure to solve the problem]

From the above-mentioned viewpoint, the present inventors have developed a conventional fine-grained WC.
As a result of repeated research in order to obtain a cemented carbide with an even smaller average grain size of WC particles than that of particle-containing cemented carbide without reducing the toughness, we found that an alloy containing Co and/or Ni as a binder phase When V and Cr are added in combination as a grain growth inhibitor, the amount of V and Cr is so large that the third phase is formed in the alloy.
Even without adding r, the average particle size of WC particles is 07 μm.
It has been found that a cemented carbide having the following properties can be obtained.

This invention was made based on the above knowledge, and the weight%
and one or two of Co and Ni: 5 to 40
%, V: 0.1~2.0% and Cr201~
2. 0%, with the remainder consisting of w'c and unavoidable impurities, and the average particle size of the WC in the alloy is 07 μm or less. This provides a cemented carbide with excellent wear resistance and toughness.

Next, the reason why the composition range of the cemented carbide of the present invention is limited as described above will be described.

(1) Co and Ni These components form a liquid phase during sintering and bind the WC particles, thereby achieving densification of the alloy and imparting toughness to the alloy. is 5% by weight
If it is less than that, densification is insufficient and toughness is insufficient.
On the other hand, if it exceeds 40% by weight, the hardness decreases too much and the wear resistance decreases, so the content of these is limited to 5 to 40% by weight.

(2) ■ V acts as a solid solution in the binder phase together with Cr and suppresses the grain growth of we, but if its content is less than 0.1 wt., even if it is added in combination with Or, the desired grain growth cannot be achieved. On the other hand, if the content exceeds 20% by weight, it will precipitate as a third phase in the alloy depending on the cooling rate after sintering, etc.
Since it causes a decrease in toughness, the content is reduced to 01-2.
．． It was limited to 0% by weight.

(3) Cr Cr is dissolved together with V in the binder phase and has the same effect as V, but if its content is less than 0.01% by weight, the desired grain growth suppressing effect cannot be obtained even when it is added in combination with V. On the other hand, 2
．． If the content exceeds 0% by weight, depending on the cooling rate after sintering, it may precipitate as a third phase in the alloy, resulting in a decrease in toughness.

Its content was limited to 0.1 to 2.0% by weight. Furthermore, c
In addition to the above effects, r also has the effect of improving corrosion resistance, so
It can be advantageously used especially in applications where corrosion resistance is required.

The alloy of this invention essentially consists of two phases, a WC phase and a binder phase, and p, v, and cr do not precipitate as a third phase, but are solidly dissolved in the binder phase. Therefore, in manufacturing the alloy of the present invention, ■ and cr are VC powders.

Although it is added as Cr3C2 powder, it is also possible to add powders such as powders of vanadium nitride, chromium nitride, vanadium hydride, chromium hydride, etc., which are finely decomposed and dissolved in solid solution, and also added as metal powder or alloy powder. You can also.

Although the amount of carbon in the alloy has not been mentioned so far, it is necessary to avoid the formation of double carbide phase (η phase) due to an insufficient amount of carbon, or the generation of free carbon due to an excessive amount of carbon. Its carbon content is adjusted.

〔Example〕

Example l First, as raw material powders, WC powder with an average particle size of 06 μm, Co powder with an average particle size of 1.3 μm, and VC powder with an average particle size of 1.5 μm were used.
Cr3C2 powder and 23 μm Cr3C2 powder are prepared, and these raw material powders are mixed to obtain the final composition shown in Table 1.
After mixing in a wet ball mill in acetone for 3 days, the mixture was dried under reduced pressure. 1 of the obtained mixed powder
The compacted powder was press-formed under the pressure of a ton foil and sintered under the sintering conditions shown in Table 1 in a vacuum atmosphere of 0.05 torr to obtain cemented carbide alloys 1 to 1 of the present invention. 7 and comparative cemented carbide 1 having a different composition range from the cemented carbide of the present invention.
-7, and for the present invention cemented carbide 1-3 and comparative cemented carbide 1-7, the atmosphere was changed to 10.
After switching to 00 atm Ar, temperature: 1350℃
Hot isostatic pressing (HIP) was performed under conditions of time holding. Grind these sintered bodies with a diamond grindstone to obtain 4uX
JIS transverse bending specimens of ENijllX24M were manufactured, and the transverse rupture strength of these specimens was measured by three-point bending at a span interval of 20 u, and the Rockwell hardness A scale (HRA) was also measured. Furthermore, WC in these alloys
The average particle diameter was measured by observing the structure with a scanning electron microscope (SEM). These measurement results are summarized in Table 1.

From the results shown in Table 1, the cemented carbide alloys 1 to 7 of the present invention all have a fine average grain size of 07 μm or less.

Compared to a comparative alloy with the same -co content, the hardness is 0.
It can be seen that the transverse rupture strength is approximately the same or slightly higher. Still inventive cemented carbide 2 and comparison cemented carbide 1
Although they have almost the same hardness, inventive cemented carbide 2 has a higher Co content and higher toughness (transverse rupture strength), and inventive cemented carbide 4 and comparison cemented carbide 3 also have a higher Co content and higher toughness (transverse rupture strength). The same is true.

Example 2 First, as a raw material powder, the WC powder used in Example 1, C
In addition to O powder and VC powder, Ni powder with an average particle size of 2.3 pm and Cr2N powder with an average particle size of 2.5 μm were prepared, and these raw material powders were blended so as to have the final composition shown in Table 2. Then, the mixed powder obtained by mixing and drying under the same conditions as in Example 1 was formed into a green compact, and the green compact was heated in the same atmosphere as in Example 1, respectively. Inventive cemented carbide alloys 8 to 10 and comparative cemented carbide alloys 8 to 1o were manufactured by sintering them under the conditions shown in the table and by subjecting them to the same HIP as in Example 1. These alloys were then subjected to the same tests as in Example 1,
The measurement results are shown in Table 2.

From the results shown in Table 2, comparative cemented carbide alloys 8 to 10 to which V and Or are not added in combination have an average grain size of WC of 1.
In contrast, cemented carbide alloys 8 to 10 of the present invention have a fine average grain size of 0.7 μm or less, and still have a small amount of Co and Nl.
Comparing the cemented carbide of the present invention and the comparative cemented carbide with the same amount, it can be seen that the hardness of the cemented carbide of the present invention is 15 to 1.8 higher, and the toughness (transverse rupture strength) is also slightly higher. .

Example 3 The Co powder used in Example 1 was used as the raw material powder.

In addition to the VC powder, WC powder with an average particle size of 0.5 μm and metal Cr powder with an average particle size of 3.0 μm were prepared, and these raw material powders were mixed in the same manner as in Example 1 so that they had the final compositions shown in Table 3. The mixed powder obtained by blending the above powder was molded into a green compact, and the green compact was sintered in vacuum at a temperature of 1360° C. Invention cemented carbide 11 and comparison cemented carbide 1
1 to 13 were produced. The same tests as in Example 1 were then carried out on each of these alloys, and the measurement results are shown in Table 3.

From the results shown in Table 3, the cemented carbide 11 of the present invention is composed of extremely fine WC particles and exhibits high values of both hardness and transverse rupture strength, whereas the comparative cemented carbide 1 with only V added
1 has a transverse rupture strength almost equal to that of the cemented carbide 11 of the present invention, but W
It can be seen that the C grain size is somewhat coarse and the hardness is low, and in Comparative Cemented Carbide 12 to which neither V nor Cr was added, the WC grain growth was remarkable, the hardness was extremely low, and the transverse rupture strength was also low. Comparative cemented carbide 1 with a large amount of added V
Although 3 has a small average particle size of WC and high hardness,
Due to the precipitation of the third phase in the alloy, the toughness (flexural strength) is extremely low.

Next, a two-sided end mill with a diameter of 6 heads φ was cut from these alloys, and the workpiece material: 5KD11 (HRC20),
Cutting speed: 25 rrt/rmc, feed (f):
50 B/m, depth of cut: 10 wI! A wet cutting test was carried out on steel under the conditions of 0.3 rr and flank wear
The cutting length until the end of the life was determined using un as the life standard, and the ratio of the cutting length of each alloy to the cutting length of comparative cemented carbide 11 was calculated to evaluate the cutting performance of each alloy. The results of these tests are also shown in Table 3. According to the test results (cutting length ratio) in Table 3, 5 the present invention cemented carbide 11 is the comparative cemented carbide 11.
It can be seen that it has extremely superior abrasion resistance compared to No. 13.

〔Effect of the invention〕

As mentioned above, the cemented carbide of this invention has both excellent wear resistance and sufficient toughness, so it can be used in various cutting tools, shearing tools, wear-resistant tools, end mills, printed circuit boards, drills, etc. It exhibits excellent performance when used as a tool, and alloys that use Ni as a bonding metal also have excellent corrosion resistance. It is also suitable for applications such as tools that are used for cleaning purposes.

Claims (1)

[Claims] One or two of Co and Ni: 5 to 40%,
A composition containing V: 0.1 to 2.0% and Cr: 0.1 to 2.0%, with the remainder consisting of WC and inevitable impurities (
A cemented carbide with excellent wear resistance and toughness containing fine tungsten carbide particles, characterized in that the average particle size of the WC in the alloy is 0.7 μm or less .