JPS601382B2 - hard alloy - Google Patents

Description

[Detailed Description of the Invention] Tungsten, which is used in cemented carbide, exists in only a small amount on the earth, so it is an expensive metal and has continued to rise in price in recent years as a so-called strategic material.

Therefore, it has become important to replace tungsten in cemented carbide with pond materials. One solution is to use cemented carbide tools or titanium-based cermet tools. However, these tools have poor rutting properties, so in many cases they cannot replace cemented carbide. Therefore, it has been investigated whether tungsten carbide in cemented carbide can be replaced with molybdenum carbide. The present invention relates to the latter.

Tungsten carbide (WC) to molybdenum carbide (MoC)
There has been little consideration in the past to replace it with .

The reason for this is that molybdenum carbide does not stably exist as MoC at room temperature, but exists as Mo2C.
Mo2C has a room temperature hardness (Vickers) of 1800 to 150
0k9/There are only secrets. This is about 2' skelet degree compared to WC's 2400k9/ground. Furthermore, Mo2C is not often used as an additive in cemented carbide raw materials. This is M
When o2C is introduced, the carbide grain size of the cemented carbide becomes finer, and acicular crystals of Mo2C grow, reducing the alloy strength. However, when molybdenum carbide forms a solid face with tungsten carbide, it becomes stable as a monocarbide having a simple hexagonal crystal structure.

If this solid solution carbide of tungsten and molybdenum consisting of (Mox・Wy)C is used as a raw material for cemented carbide, the hardness is W
It becomes a carbide similar to C, and WC forms a solid solution in MoC, which prevents MoC from decomposing into Mo2C and carbon, giving very favorable results. Therefore (Mox・Wy
) If a stable carbide of C can be easily produced, it is considered possible to replace tungsten with molybdenum. In order to make this more concrete, development of a stable manufacturing method for (Mo.W)C is also underway. (Japanese Unexamined Patent Publication No. 51-146306) By the way, not only hardness but also toughness is an important characteristic required of hard materials such as Fumoto hard alloys. The research results reported so far have not investigated how to improve work efficiency when replacing WC with MoC. This is because MoC and WC are stabilized as a solid solution, so the carbide is necessarily uniform and tends to have many defects.In contrast, the purity of WC, which is generally used industrially, is is very high, and the amount of bonded carbon has reached the theoretical value of the stoichiometric composition, so it is easy to make WC powder with strong crystal strength, but it is difficult to make it uniform with the manufacturing method described above. When replacing WC powder with a solid melt of (MooW)C, an important issue is how to prevent a decrease in ballistic properties.
・W) Replaced with C powder without reducing its properties,
Rather, various studies were conducted to improve the characteristics.

As a result, a combination of carbides having two or more simple hexagonal phases with different Mo/W ratios, which are solid solution compositions,
We saw that the toughness improved and released it. Although the details of the reason for this improvement in grade property are unknown, when (Mo/W)C separates into two phases, the solid melt strain of both phases decreases, resulting in higher rutting properties than in the case of one phase. So I thought. At least in the alloy, there is a phase consisting of (Mox・Wy)C(Y>×) close to the properties of WC and a phase consisting of (Mox・Wy)C(X) close to the properties of MoC.
The alloy composed of the phase >Y) has the rutting property of WC and the
Since it has two properties of heat deformation resistance, (Mo・W
)C is advantageous over using a single phase carbide. In the present invention, the most effective one is WC or MoC in WC.
It is preferable to be composed of a solid solution having a slight solid solution of MoC and a solid melt having a composition of MoC in a solid bath of WC.

This corresponds to when the peak of the (1-3) plane is separated into two in X-ray diffraction. Therefore, in the present invention (
As shown in Figure 1, the peak of the IQ3) plane is close to the WC of (Mo/W)C, and the peak position of the X-ray diffraction line due to the C female line is 28, which is near 121o (11a). .

On the other hand, (Moo. Rule Wo.5.) In C, (low a
) and (D-b) peaks. This 0-
The peak of a is near 12r, indicating the peak of WC,
Moreover, the peak of low b indicates the peak of a solid solution of (Mox·Wy)C. Phase separation can be detected by measuring this (10"3) plane. Also, in the present invention, (Mox・Wy)C
Whether or not there are two or more simple hexagonal phases can be determined by observing with an optical microscope after corrosion with red dish salt alkali solution, or by observing the composition using XMA observation.

Figure 2 shows the results. What is observed as white here is W
(Mo.W)C has a composition close to that of C, and the gray color observed indicates a solid solution containing a large amount of Mo. Of course, some of these carbides are Ti, Zr, Hf, V, Nb, Ta,
There is no change in the basic relationship even when replacing with a BI type double carbide containing Cr.

That is, as for the WC type simple hexagonal phase, an alloy with higher rutting properties can be obtained by having two or more phases having different compositions than by having one uniform phase. The above substitution amount is 20% of the carbide of Mo and W.
A content of atomic percent or less is desirable from the viewpoint of toughness.

Note that the same relationship holds true for alloys in which a portion of C in the carbide is replaced with nitrogen or oxygen.

In this case, the amount of oxygen is regulated by the following formula in order not to impede the sinterability of the alloy. W atomic% Oxygen atomic% (INaVaMa group metal atomic%) (N-V Atagawa group a metal atomic%) It is desirable that the amount is less than the greater of either the sound or 0.3 sound of the total WaVa group atomic %.

It is preferable that the binding metal is mainly composed of ferrous metals, and accounts for 3 to 5% by weight of the composition.

If it is less than 3%, it will be too brittle, and if it exceeds 5% by weight, the high temperature properties will deteriorate.

It is natural that this ferrous metal forms a solid solution with group a metals of WaVa when it becomes a binder phase, and also contains iron, Si, Ca, and A.
The effects of the present invention will not be lost even if an element having a hardness equivalent to that of these elements is added. In the present invention, 2
The method for producing an alloy that combines a simple hexagonal type solid solution of (Mo/W)C consisting of more than one phase may involve mixing field melts of two or more phases in the alloy.
Rather than this, it is better to make a solid solution separated into two phases by increasing the particle size of the WC as a starting material and allowing the carbonization reaction to occur without complete reaction during formation of the solid solution carbide.

The reason for this is that it is thought that the strength of each carbide particle itself increases when a WC crystal exists at the center of the carbide and (Mo.W)C is formed around the periphery. Example 1
Add 2A of Mo2C and carbon to Kaze 6 Buddha's WC powder and blend it so that the final carbide composition becomes (Moo.5Wo.5)C. 200,000 for 1 hour.

The carbon content of the carbide is T. C. 7.81%F. C. 0.0
3%, the bonded carbon was close to the theoretical value of (Moo.5Wo.5)C, and was a carbide. When examined by X-ray diffraction, the Mo2C peak completely disappeared, and all (Mo/W)
It was the peak of C. However, when the cross section of the powder was examined, the inside of the powder had a cored structure. When the high-angle peak of the X-rays was examined, it was found to be separated into two phases as shown in FIG. This powder is considered evil. On the other hand, one WC powder and two mountains of Mo2C and carbon (Moo.5Wo.5
)C and Co as a diffusion aid.
0.5% was added and mixed. The mixed powder was heated twice a day in an air stream.
After heating at 000000 for 1 hour, the temperature was lowered to 1400000 and maintained for 1 hour. When examining the carbon content of this powder, T. C7.71%F. C.O. 05%Coo. 5%, which is close to the theoretical carbon content.

When examined by X-ray diffraction, no two-phase separation was detected as shown in Figure 1, and it was found to be completely one phase. This powder is referred to as (B}. An alloy was prepared using carbide by Kaze and Tsukuda's method. It was weighed so that the blended composition was (Mo.W)C-15% by weight Co, and wet-processed in an organic solvent. After mixing, the process of dry stamping was performed and sintered at 1400 qo in vacuum.The properties of the obtained alloy were as follows. It exhibited properties comparable to Co-based cemented carbide.

On the other hand, in the conventional known method 'B', a homogeneous solid solution is obtained, but
When it was made into an alloy, it lacked toughness. Example 2 Compared to the alloy consisting of a single phase of (Mo/W)C in Example 1,
It was found that carbide separated into phases exhibits higher strength and ballability, so it was thought that the same effect could be expected if the desired phase was prepared in advance and mixed during mixing.

By adding Co as a diffusion aid to 2 mm of WC, 2 mm of Mo2C and carbon, two solid solution carbides (Mom, Wo.3
)C and plate (Moo.3, WM)C were prototyped.

The properties of these carbides are shown in Table 2. Both the second table carbide 'C} and the plate had a bonded carbon content that reached the theoretical carbon level, and as a result of X-ray examination, they were completely one-phase.

Therefore, by combining the [C} and the carbide of the plate (Moo.
5W Misaki) O alloy was created in C-. At the same time, an alloy using 'B}(Moo.5Wo.5)C, which had a single phase from the beginning, was also prototyped for comparison. The alloy properties at this time are shown in Table 3. Table 3 It has become clear that a combination of two or more simple hexagonal types has a higher quality than an alloy consisting of one phase.

Example 3 Using raw materials A and B in the same manner as in Example 1 (Moo.
5Wo. 5) C-30% by weight (Tio.7 Moo.3)
A C-10% by weight Co alloy was created.

(2) X-ray diffraction results (Mo/W) of the alloy using the raw material showed two-phase separation in the C phase, whereas when the raw material {B} was used, it was one phase. When this alloy was used to cut a partially grooved SCM Kyodo steel material at a cutting speed of 150 m'mh, a feed of 0.4 ribs/rev, and a depth of cut of 0.2 sails, the alloy using raw material [B] was cut in 15 minutes. However, the alloy made from a general-purpose raw material did not break after 15 minutes, was still machinable, and the amount of wear at that time was the same as {B) the amount of wear for the alloy made from the raw material. Example
4 The alloys shown in Table 4 were prepared in the same manner as in Example 3, and the alloys were evaluated by the same test method as in Example 3, and good results were obtained as shown in the table.

Table 4

[Brief explanation of the drawing]

Figure 1 shows (Moo.o5Wo.95)C carbide and (
Moo. 5oW low o)C carbide by CuK line
It is a chart showing the results of an enlarged examination of the range between 28=120 and 1260 using line diffraction. FIG. 2 is a micrograph showing the composition image of a (Mo.W)C-Co alloy examined using an X-ray microanalyzer. In addition, in Figure 1, I is (Moo.o5Wo.95)
C, mouth indicates (M public W5) C. Outside 2 Zoo Diagram

Claims (1)

[Claims] 1 A composite carbide of tungsten and molybdenum having a simple hexagonal crystal structure and having two or more hard phases with different Mo/W ratios, the binder phase being an iron group metal of 3 to 5
A hard alloy characterized in that it accounts for 0% by weight. 2 A composite carbide of tungsten and molybdenum having a simple hexagonal crystal structure and two or more hard phases with different Mo/W ratios, and 20 at% or less of the composite carbide is composed of Ti, Zr, HfV, Nb, A hard alloy characterized in that the hard material is substituted with one or more B1 type hard carbides selected from Ta and Cr, and the binder phase is comprised of 3 to 50% by weight of an iron group metal.