JPH0517299B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a sintered hard alloy having excellent wear resistance and high-temperature properties as well as toughness, and a method for manufacturing the alloy. In recent years, as cutting processes have become more efficient, tool materials for high-speed cutting or high feed rates are required.Currently, tool materials such as TiC-based cermets or TiN-based cermets are mainly provided. ing. However, all of the above-mentioned tool materials contain a large amount of iron group metal and use this as a binder phase, so the cutting edge does not wear out during high-feed cutting or high-speed cutting, but rather suffers from plastic deformation due to an increase in the temperature of the cutting edge. There is a problem in that the lifespan is shortened. In order to solve some of the above problems, materials with less plastic deformation at high temperatures, such as ceramic tools mainly made of aluminum oxide, are also used, but these materials inherently have low material strength and are prone to chipping. Also, due to its low thermal conductivity, it has the problem of being susceptible to thermal shock, and its range of use is currently limited. In addition, if many iron group metals are contained and used as a binder phase, the problems mentioned above cannot be prevented, so sintered alloys containing tungsten and molybdenum and used as a binder phase have also been developed. However, these are obtained by sintering at a high temperature of 2000℃ or higher or by hot pressing, which has extremely poor productivity, and from the viewpoint of sintering properties, they contain tungsten or molybdenum. The amount has increased and the problems mentioned above have not been solved. The present invention has been made in view of the above-mentioned problems, and is made using an extremely rare iron group metal compared to conventional metals, which has excellent mechanical properties at high temperatures, has particularly wear resistance and toughness, and is capable of high-speed cutting and high-feed cutting. The object of the present invention is to provide a sintered hard alloy suitable for cutting tools containing the following: and a method for manufacturing the alloy. The first gist of the present invention is that tungsten carbide has a weight ratio of 10 to 95%. Titanium carbide 2-80%. Mixtures or intercompounds of 2-80% titanium nitride and iron. Nickel. 0.1 of one or more types of cobalt
Contains ~5%, and contains 0.1 to 15% nitrogen,
It is a sintered hard alloy in which the metallic phase of tungsten is 0.1 to 10% and the above-mentioned iron group metal forms a binder phase.
Titanium carbide 2-80%. 2-80% titanium nitride and iron.
Nickel. A green compact containing 0.1 to 5% of one or more iron group metals such as cobalt is heated in vacuum to denitrify a portion of the titanium nitride, thereby denitrifying the tungsten carbide. This is a method for producing a sintered hard alloy in which tungsten is precipitated by carbonization and the tungsten and the iron group metal are made into a binder phase. The present invention will be described in detail below. In order for a sintered hard alloy to be widely used in cutting tools, it is required that the sintering property is excellent in mechanical properties at higher temperatures than the raw material, and that it also has wear resistance, toughness, and chipping resistance. Therefore, we believe that the above requirements cannot be met with conventional sintered hard alloys that contain a large amount of iron group metals, which have poor heat resistance and wear resistance, and therefore contain extremely small amounts of these metals as a binder phase. The present invention was developed from the viewpoint that the above requirements can be met by precipitating tungsten from tungsten carbide to compensate for the lack of bonding. That is, tungsten carbide 10-95wt%. Titanium carbide 2-80wt%. Titanium nitride 2-80wt% and iron. Nickel. The carbide is made to have a composition containing 0.1 to 5 wt% of one or more iron group metals such as cobalt. Nitride or double carbide. A green compact obtained by mixing and stirring double carbonitride powder and press-forming it is
Tungsten carbide precipitates tungsten when heated and sintered at temperatures above 1300°C under a vacuum of 10 ^-3 mmHg, and the binder phase of this sintered alloy is sinterable, consisting mainly of tungsten and a small amount of iron group metals. It has been discovered that a sintered hard alloy suitable for tools, which has excellent high-temperature properties, excellent wear resistance, toughness, and chipping resistance, can be obtained. For these reasons, see TiN or (W.
Ti)CN denitrifies when sintered in vacuum. Denitrified TiN _1-x becomes unstable when the amount of bonded nitrogen is insufficient, and carbon surrounds it. oxygen. In the presence of a source of nitrogen, it combines to form stable compounds. TiN absorbs carbon from WC to become TiCN,
On the other hand, WC undergoes carbon removal and becomes W via W ₂ C. That is, (W.Ti)CN−N ₂ →W+(W,
W is precipitated by the reaction of Ti)′CN. However, if a large amount of WC is contained, the corresponding
The amount of TiN decreases and the amount of precipitated W decreases, making it impossible to obtain sufficient strength. So 0.1~5wt%
It is presumed that when the iron group metal was added, this promoted sintering and bonded the hard substances together with the precipitated W, resulting in the high-strength sintered alloy as described above. In addition to the above-mentioned iron group metals, it is also effective to add aluminum and chromium, which are usually used in cemented carbide or cermets. This sintered hard alloy manufacturing method can be carried out using a conventional vacuum sintering furnace, and the conditions are as follows:
The compacted powder is heated under a vacuum of 1 to 10 ^-3 mmHg.
After heating to 1300 to 1500°C to precipitate a part of the tungsten in the compact, further heating to 1500 to 1700°C.
Sintered hard material obtained by sintering at an elevated temperature, which can be easily manufactured at a relatively low temperature and does not require the use of special equipment, and is advantageous in terms of quality and cost. Becomes an alloy. Next, the reasons for limiting the sintered hard alloy according to the present invention will be explained. In this sintered hard alloy, tungsten carbide is essential because it decarburizes and precipitates tungsten. If its content is less than 10 wt%, the desired tungsten will not be precipitated, and therefore the desired content of the alloy will not be achieved. It exhibits no toughness and is unsuitable as a cutting material, and if it exceeds 95 wt%, the amount of titanium nitride is correspondingly insufficient, making it difficult for tungsten to precipitate, making it impossible to obtain sufficient alloy strength. Titanium carbide reacts with tungsten carbide and titanium nitride during sintering to form TiCN or (W.
Ti) forms CN to promote sintering, but the amount
If it exceeds 80wt% or falls below 2wt%, sinterability will deteriorate. Titanium nitride is also essential in this alloy because it denitrides and combines with the carbon of tungsten carbide, resulting in the precipitation of tungsten. However, if the amount is less than 2 wt%, tungsten will not be sufficiently precipitated, and if it exceeds 80 wt%, the amount of tungsten carbide will be correspondingly insufficient, which is not appropriate. In addition, 80wt% of titanium carbide in the above components
up to ZrC.HfC and VC.NbC. or _Mo2C .
It may be used in substitution with one or more of Cr ₃ C ₂ . In particular, substitution with ZrC.HfC.VC.Cr ₃ C ₂ yields a sintered alloy with high hardness and high toughness, and substitution with TaC yields the alloy with high toughness. In addition, 80wt of titanium nitride in the ingredients mentioned above
Even if up to % is replaced with one or more of ZrN.HfN.VN.TaN.NbN, the same effects as described above can be obtained and a preferable sintered hard alloy can be obtained. The carbides and nitrides of the sintered hard alloy described above may each exist alone in the alloy, or may be a composite solid solution. In addition, the tungsten metal phase that precipitates during sintering acts as a binder phase for this alloy and is a factor that increases toughness, but if the amount is less than 0.1wt%, the desired toughness cannot be obtained. If you try to precipitate more than %, sintering conditions, that is, heating at high temperature for a long time, will be required, which will not only cause problems in productivity, but also reduce toughness and deteriorate the hardness and wear resistance, which are the characteristics of this alloy. This is not desirable because it damages the And nitrogen is a nitride. Although it exists in the alloy as carbonitride, it is denitrified during sintering, so the lower limit of the amount of nitrogen remaining in this alloy is set to 0.1 wt%.
If it is less than this value, the toughness of the alloy will decrease, and if it exceeds 15 wt%, the composition or sintering conditions according to the present invention will result in very little tungsten precipitation, making it unsuitable as a binder phase. We believe that the reason for the above is largely due to the properties of nitrides, similar to the fact that TiN-based cermets have better toughness than TiC-based cermets. Next, iron. Nickel. The purpose of iron group metals such as cobalt is to improve the sinterability of the sintered alloy of this invention and to strengthen the alloy together with tungsten as a binder phase, but the content is 0.1wt.
If it is less than 5% by weight, the above effect will not be seen, and if it exceeds 5wt%, the hardness of the alloy will decrease and the amount of deformation at high temperatures will increase, which is not preferable. Note that this iron group metal may be used in a relatively small amount (approximately 2 wt% or less) in a composition range where the content of both tungsten carbide and titanium nitride in the alloy is appropriate and tungsten precipitation is sufficient. When the amount of tungsten carbide exceeds 80 wt% or when the amount of tungsten carbide is less than about 15 wt%, the content of the iron group metal should be as high as about 5 wt%. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 As raw materials, commercially available tungsten carbide powder with a particle size of about 0.6μ, titanium carbonitride powder with a different C/N ratio of 1 to 2μ, and double carbonitride of tungsten and titanium with a particle size of 1 to 2μ, and a particle size of 1 to 2μ. 5μ iron. Nickel. cobalt. A mixture of chromium and aluminum according to the composition shown in Table 1 is mixed in a conventional wet ball mill, molded in a mold to obtain a green compact, and then the green compact is vacuum sintered. It was heated in a furnace under vacuum. The conditions were a vacuum value of 10 ^-2 mmHg and a temperature of 1300℃ for about 30 minutes.
A sintered hard alloy according to the present invention was obtained by heating at 1600° C. for about 30 minutes. In addition, for comparison, Samples 1, 2, and 3, which were outside the composition range of the alloy of the present invention, and Table
Samples 4, 5, and 6 were obtained by sintering green compacts having the same composition as Samples 2, 6, and 8 according to the present invention in 1 in a nitrogen atmosphere of 100 Torr under the above conditions. Resistance of each sample obtained as above. The fracture toughness value (load 10
The calculated values (Kg) are also shown in the same table. The table also shows that each sample is diffracted using an X-ray diffraction device to identify the phase of the sample, and for samples with tungsten precipitated, a scanning electron microscope with an X-ray analyzer (X-ray analyzer) is used.
Observe the structure using MA), calculate the amount of precipitated tungsten from the microstructure photograph, and calculate the amount of tungsten precipitated.
The amount of _N2 was also analyzed and the results are also shown.

[Table] As is clear from Table 1, the alloy of the present invention exhibits extremely good values for hardness, transverse rupture strength, and fracture toughness, indicating that it has high toughness. On the other hand, comparative alloys 1, 2, and 3, which are outside the composition range of the invention alloy, were created for comparison with the invention alloy.
was an unsintered body. Comparative alloys 4, 5, and 6 sintered in a nitrogen atmosphere had no tungsten precipitation and exhibited relatively good values for transverse rupture strength, but extremely low fracture toughness values. Example 2 The same tungsten carbide powder and titanium carbonitride powder as in Example 1 were used as raw material powders, and the particle size was 1 to 1.
Table using 3μ carbide and iron group metal with grain size of 1 to 5μ
2 was prepared using the same method as in Example 1 (heating conditions were 1600°C x 1hr).
Samples 12 to 21 according to the present invention were obtained. In addition, Samples 7 and 8 without titanium carbide were obtained using the same manufacturing method as the above-mentioned alloy of the present invention.

[Table] As is clear from Table 2, some of the titanium carbide
Substitution with carbides of groups 4a, 5a, and 6a also produced the same effect as described above, and substitution with tantalum carbide increased transverse rupture strength and fracture toughness values. In addition, replacement with vanadium carbide or chromium carbide resulted in high hardness. Incidentally, a method in which titanium nitride was replaced with tantalum nitride also had an effect. Samples 7 and 8, which did not contain titanium carbide and were used for comparison with the alloy of the present invention, had poor sinterability and were unsintered bodies. Example 3 Conventional titanium nitride-based cermet, titanium carbide-based cermet and aluminum oxide coated alloy A,
SUG432 chips were made from B and C, the invention alloys 2, 5, and 11, and the comparative alloys 4 and 5 in Table 1, and their cutting performance was compared. The cutting conditions are V=198m/min.d=2.0mm.
f=0.18mm, cutting width is 50mm, and cutting length is 500mm.
I passed it. The workpiece material is S55C and is milled. These results are shown in Table-3.

[Table] As shown in Table 3, it is clear that the alloy of the present invention has excellent wear resistance and chipping resistance and is suitable as an alloy for cutting tools.

Claims (1)

[Claims] 1. Tungsten carbide 10 to 95% by weight. Titanium carbide 2-80%. Mixtures or intercompounds of 2-80% titanium nitride and iron. Nickel. Contains 0.1 to 5% of one or more of cobalt, 0.1 to 15% of nitrogen, and 0.1 to 10% of tungsten metal phase and the iron group metal form a bonding phase. A sintered hard alloy with excellent high-temperature properties. 2 Tungsten carbide 10-95% by weight. Titanium carbide 2-80%. 2-80% titanium nitride and iron. Nickel. A green compact containing 0.1 to 5% of one or more iron group metals such as cobalt is heated in vacuum to denitrify a portion of the titanium nitride, thereby denitrifying the tungsten carbide. A method for producing a sintered hard alloy with excellent high-temperature properties, characterized by precipitating tungsten through carbonization and using the tungsten and the iron group metal as a binder phase.