JPH05247626A - Sintered compact incorporating silicon nitride coated with boron nitride containing film and/or silicon carbide and manufacture therefor - Google Patents

Abstract

PURPOSE:To provide a sintered compact to the sintered compact itself, which incorporates silicon nitride or silicon carbide, being superior in friction resistance, wear resistance and seizuring resistance and being coated with a film which enables to stably exhibit the performance for a long period by excellently sticking to the sintered compact itself, and its manufacturing method. CONSTITUTION:The sintered compact 1 is incorporated with the silicon nitride and/or silicon carbide in which a part or whole of the surface is coated with a boron nitride containing film 11 which is formed by using vacuum deposition and/or sputtering and ion irradiation jointly and also the manufacturing method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a sintered body containing a silicon nitride or a carbide having high hardness and excellent strength at high temperature, and further improved in friction resistance and wear resistance. The present invention relates to a sintered body and a manufacturing method thereof. The “sintered body” in the present specification includes not only a sintered body as a material for various articles, but also a cutting tool, a molding die and the like, parts thereof, parts and the like using the same.

[0002]

2. Description of the Related Art Sintered bodies containing nitrides and carbides of silicon (Si) have the characteristics of lightness, hardness, and high strength when silicon nitride is taken as an example, and particularly excellent in high temperature strength. .. In addition, when used as a cutting tool material, it has high toughness and is less likely to cause "chips" in the base material during cutting. Also, taking silicon carbide as an example, it has high hardness and high thermal conductivity, and has the characteristics of high temperature strength as well as silicon nitride. Therefore, they are widely used in the fields of abrasion resistance and abrasion resistance.

[0003]

However, Si nitrides such as silicon nitride and silicon carbide and Si carbides are
Since it is a substance that is difficult to sinter itself, it is necessary to add a sintering aid to obtain a sintered body. After sintering, this sintering aid remains at the grain boundaries of the sintered body. For example, in the case of a sintered body of silicon nitride, a material such as Y ₂ O ₃ or MgO is used as a sintering aid, and these are oxides (SiO ₂ ) existing on the surface of the silicon nitride raw material powder. Reacting,
A liquid phase is formed during sintering and remains as a glass phase at the grain boundaries after sintering. This grain boundary glass phase component is poor in high temperature strength,
Further, when the sintered body is used as a cutting tool or a metal mold, it may cause adhesion to a work material or a molded body, which may lead to a situation in which the characteristics of silicon nitride cannot be sufficiently obtained.

The same applies to the case of silicon carbide, and a substance made of boron (B) element or carbon (C) element is often used as a sintering aid. Although this sintering aid does not form a liquid phase during sintering like silicon nitride, it remains at the grain boundaries of the sintered body and adversely affects the characteristics of the sintered body. Similarly, when an oxide is used as a sintering aid, the grain boundary phase component of the sintered body adversely affects the characteristics of the sintered body.

As described above, the control of the grain boundary phase of the Si non-oxide sintered body has become a technically large problem, and in order to improve this, the hot pressing method or the HIP (hot isostatic pressing) method is used. Or by reaction sintering,
Attempts have been made to develop a material having a small amount of grain boundary phase components, but there are problems that the manufacturing cost is high, a large quantity cannot be produced at one time, or the density of the sintered body cannot be sufficiently increased.

For this reason, attempts have been made to solve the above-mentioned problems by forming a film on the surface of the sintered body, but silicon nitride and silicon carbide have a small coefficient of thermal expansion and are therefore generally used. A large internal stress is generated in the film formed by the CVD method or the PVD method, which causes problems such as poor adhesion of the film and cracks in the film.

Therefore, the present invention is a sintered body containing silicon nitride or silicon carbide, which is more excellent in abrasion resistance, wear resistance and seizure resistance than the sintered body itself, and It is an object of the present invention to provide a sintered body coated with a film capable of closely adhering to the sintered body and exhibiting the above-mentioned performance stably over a long period of time, and a method for producing the same.

[0008]

Means for Solving the Problems The present inventor has conducted extensive research to achieve the above-mentioned object, and has focused on a boron nitride-containing film as the film. Boron nitride (hereinafter referred to as “BN”) is a cubic zinc blende type (hereinafter referred to as “c-B” depending on its crystal structure).
N)), a structure similar to hexagonal graphite (hereinafter referred to as “h-BN”), or a hexagonal wurtzite type (hereinafter referred to as “w-BN”). It

Since c-BN has the second highest hardness after diamond and is excellent in thermal and chemical stability, c-BN is applied to a field requiring wear resistance such as a cutting tool, Further, it is used as a heat sink material by taking advantage of its insulating property and high thermal conductivity. Further, w-BN also has excellent chemical stability, thermal shock resistance, and high hardness,
It has been applied to various fields where abrasion resistance is required.

The inventor of the present invention initially proposed a film of the same quality, namely, silicon nitride and silicon carbide, and high-temperature stability, hardness, Attention was paid to those having excellent thermal shock resistance, such as diamond and c-BN. However, since the silicon nitride and silicon carbide films are of the same quality as the base material, the problem of internal stress does not occur, but they are inferior in hardness and thermal conductivity as compared with c-BN.

Further, diamond has an affinity with iron group elements and is inferior to the chemical stability of h-BN and c-BN. Based on such a background, the present inventor considered that the BN-containing film was optimal as a film to be coated on the sintered body of silicon nitride or silicon carbide. In addition, c-BN has a small coefficient of thermal expansion, and even if it is formed on a sintered body made of silicon nitride or silicon carbide, an excessive internal stress is not applied, so that the compatibility between the film and the sintered body is excellent. ..

Next, regarding the method for producing a BN-containing film, c-B
Both N and w-BN are usually artificially synthesized under high temperature and high pressure. Therefore, so far c-BN
Attempts to synthesize thin films of w-BN at low temperature
This has been done by various PVD and CVD methods. As an example of the CVD method, in the method, a substrate to be formed a film is placed in a reaction chamber and heated to a temperature close to 1000 ° C., and then a gas containing a boron element (B) and a nitrogen element (N) are contained. The raw material gas to be introduced is introduced into the reaction chamber to cause a thermal decomposition reaction to form a BN film on the surface of the substrate. further,
Also in the PVD method, for example, reactive sputtering in which boron is sputtered in nitrogen gas to form a BN film on the surface of the substrate has been attempted. However, h-BN could be constructed by any of the methods, but c-B
It was impossible to synthesize N or w-BN.

Therefore, the inventors of the present invention have conducted extensive research and, as a method of forming a BN-containing film on a sintered body, simultaneously with forming a film containing a boron element on the sintered body, alternately, or after forming the film. If you use the method of irradiating ions, at low temperature,
It was found that a boron nitride-containing film having good adhesion to a sintered body can be formed. Based on the above findings, the present invention is characterized in that a part or all of the surface is covered with a boron nitride-containing film formed by using vacuum deposition and / or sputtering and ion irradiation in combination. The present invention provides a sintered body containing silicon nitride and / or silicon carbide.

Further, in the present invention, as a manufacturing method thereof, a boron element-containing substance is applied onto a sintered body containing silicon nitride and / or silicon carbide by a vacuum vapor deposition method and / or a sputtering method, A boron nitride-containing film is formed by irradiating ions from an ion source simultaneously with the application, alternately or after the application, and the ratio of boron atoms and nitrogen ions reaching the sintered body in the film formation. And a method for producing a sintered body of a boron nitride-containing film coating, which comprises controlling the atomic ratio of boron and nitrogen in the boron nitride-containing film by controlling the acceleration energy of the irradiation ions. is there.

It is desirable that the acceleration energy of the ions to be irradiated in forming the boron nitride-containing film in the above method is 40 KeV or less. When the ion acceleration energy exceeds 40 KeV, excessive ion defects are introduced into the film and the characteristics of the film deteriorate. There is no particular lower limit to the acceleration energy. The atomic ratio of boron to nitrogen present in the film in the boron nitride-containing film-coated sintered body is preferably 0.1 or more and 50 or less.

When a film is formed such that the atomic ratio of boron to nitrogen existing in the film is smaller than 0.1, the film formation time becomes abnormal due to excessive sputtering, resulting in an increase in cost. On the other hand, if it exceeds 50, the BN content in the film decreases, and the BN characteristics cannot be sufficiently obtained. Therefore,
Also in the method, the atomic ratio of boron atoms to nitrogen ions reaching the sintered body and the acceleration energy of the irradiation ions are adjusted so that the atomic ratio of boron to nitrogen existing in the boron nitride-containing film is 0.1 or more and 50 or less. It is desirable to control so that

The atomic ratio of boron to nitrogen in the film containing boron nitride may be constant in each part of the film, or
It may be gradually decreased (continuously, stepwise or a combination thereof) from the surface of the sintered body toward the surface of the film. In this case, when carrying out the method, the ratio of boron atoms and nitrogen ions reaching the sintered body and the acceleration energy of the irradiation ions may be controlled so that the atomic ratio has such a distribution.

When the film is formed so that the atomic ratio of boron to nitrogen present in the boron nitride-containing film gradually decreases from the surface of the sintered body as the base toward the surface of the boron nitride-containing film, The internal stress can be further reduced, the adhesiveness of the film can be further improved, and the influence of the underlying sintered body can be reduced, and c-BN and w-BN can easily grow.

As the boron element-containing substance used in the above method, simple substance of boron, oxide of boron, nitride of boron, carbide of boron and the like can be considered. Further, the method of the evaporation source is not particularly limited, and for example, a method using means such as electron beam (EB), resistance, laser, high frequency can be appropriately adopted. Further, the boron element-containing substance may be formed into a film on the sintered body by sputtering, but in this case, the method of sputtering is not particularly limited, and it can be sputtered by a means such as ion beam, magnetron, or high frequency.

Further, as the ions used in the above-mentioned method, in addition to nitrogen ions from the nitrogen element, it is conceivable that these are mixed with an inert gas ion such as an inert gas or a hydrogen atom gas or a hydrogen ion. When an inert gas ion or hydrogen ion is used, the vaporized boron atom can be more highly excited, which is advantageous for the formation of c-BN. The angle of incidence of ions on the sintered body is not particularly limited. The ion source system is also not particularly limited, and, for example, a Kauffman type, a bucket type, etc. can be considered.

In the film formation, the ratio of boron atoms to nitrogen ions reaching the substrate (B / N transport ratio) is adjusted by, for example, monitoring the amount of vapor deposition on the substrate using a film thickness monitor and using an ion current measuring device. This can be done by monitoring the irradiation amount of ions on the substrate. The film thickness monitor may be, for example, a quartz vibration film thickness meter, and the ion current measuring device may be, for example, a Faraday cup equipped with a secondary electron suppressing electrode, but is not particularly limited. With these, the film can be formed to have an arbitrary thickness.

[0022]

According to the sintered body of the present invention, since it is coated with a boron nitride-containing film having good adhesion, it is more excellent in abrasion resistance, wear resistance and seizure resistance than the sintered body itself. ,
Moreover, such performance can be stably exhibited over a long period of time.
Further, according to the method for producing the sintered body, the boron element-containing substance is applied to the sintered substrate by the vacuum deposition method and / or the sputtering method, and at the same time as the application, alternately or after the application, ions are added. A boron nitride-containing film is formed on the sintered substrate by irradiation with ions from a source, and the ratio of boron atoms to nitrogen ions reaching the substrate and the acceleration energy of the irradiation ions are controlled in the film formation. This controls the atomic ratio of boron to nitrogen in the boron nitride-containing film.

Further, in the above-mentioned film forming method, the irradiated ions collide with the vaporized atoms, so that the vaporized atoms are pushed into the substrate and recoil within the substrate, so that the vaporized atoms recoil at the interface between the substrate and film. The adhesion of the film is improved by forming the mixed layer of the constituent atoms, and the vaporized atoms are excited by the collision of the vaporized atoms with the ions, resulting in c-BN and w-
BN is formed in the film. Therefore, a BN film having excellent adhesion can be obtained at a low temperature.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a sintered substrate 1 having a boron nitride-containing film 11 formed on its surface, which is an embodiment of the present invention.
FIG. 2 shows a schematic structure of an example of a film forming apparatus used for manufacturing the sintered base 1 of FIG.

In FIG. 2, 1 is a substrate, 2 is a holder for supporting the substrate 1, 3 is an evaporation source for evaporating a substance containing a boron element, 4 is an ion source for irradiating ions,
Reference numeral 5 is a film thickness monitor for measuring the number of boron vapor deposited on the substrate 1 and its film thickness, and 6 is an ion current measuring device for measuring the number of ions irradiated on the substrate 1. These are housed in the vacuum container 7. The inside of the container 7 can be made to have a desired vacuum degree by the exhaust device 8.

In making the substrate 1 according to the present invention,
First, after the substrate 1 is supported by the holder 2, the inside of the vacuum container 7 is evacuated to a predetermined vacuum degree. After that, the evaporation source 3 is attached to the substrate 1.
Using, the substance 3a containing the boron element is vacuum-deposited. It should be noted that instead of vacuum vapor deposition, a film may be formed on the substrate 1 by sputtering a boron element-containing substance.

Simultaneously with, or alternately with, vacuum deposition (or sputtering) of the substance containing the boron element, or after the deposition, the ions 4a containing nitrogen ions are supplied from the ion source 4.
Is irradiated on the vapor deposition surface. At this time, the atomic ratio (B / N composition ratio) of boron and nitrogen in the formed boron nitride-containing film 11 is adjusted by monitoring the deposition amount on the substrate 1 using the film thickness monitor 5 and measuring the ion current. The irradiation amount of ions to the substrate 1 is monitored using the container 6.

In the film formation, the acceleration energy of irradiation ions is set to 40 KeV or less, and the atomic ratio of boron and nitrogen (B / N composition ratio) existing in the formed film.
Is controlled to be 0.1 or more and 50 or less, the ratio of boron atoms and nitrogen ions reaching the substrate 1 and / or the acceleration energy of irradiation ions is controlled. The acceleration energy of the ions may be constant during film formation, or may be changed continuously, intermittently, or a combination thereof.

Further, by such control, the atomic ratio of boron to nitrogen existing in the formed boron nitride-containing film becomes constant at each part in the film or the surface of the sintered substrate 1 is nitrided. The boron-containing film is formed so that the surface of the boron-containing film decreases continuously, stepwise, or a combination thereof. By the film forming operation described above, a thin film 11 containing boron nitride is formed on the surface of the substrate 1 as shown in FIG. Further, in the film forming method, the irradiated ions 4
When a and evaporating atoms collide with each other, the evaporating atoms are pushed into the substrate 1 and recoil within the substrate, and a mixed layer composed of both constituent atoms is formed at the interface between the substrate 1 and the film formed thereon. By doing so, the adhesion of the film is improved, and the vaporized atoms are excited by the collision between the vaporized atoms and the ions 4a,
As a result, c-BN and w-BN are easily formed, and a BN-containing film having excellent adhesion at low temperature is formed.

Next, a specific example of a method for producing a sintered body according to the present invention by the film forming apparatus shown in FIG. 2 and a boron nitride-containing film-coated sintered body obtained thereby will be described. It should be noted that each of the sintered substrates described below is of a press type having a press molding recess having a predetermined curvature. Example 1 Using the apparatus shown in FIG. 2, a sintered substrate 1 made of silicon nitride
Was placed on the substrate holder 2, and the vacuum container 7 was held at a vacuum degree of 5 × 10 ⁻⁷ Torr. Then, the boron pellet 3a having a purity of 99.7% was vaporized using the electron beam evaporation source 3 to form a film on the substrate 1. At the same time, nitrogen gas having a purity of 5N (99.999%) is introduced into the ion source 4 until the inside of the vacuum container 7 reaches 5 × 10 ⁻⁵ Torr and ionized, and the substrate 1 is accelerated with an acceleration energy of 15 KeV. Irradiation was performed at an angle of 0 ° with respect to the normal line that was set up. As the ion source 4, a bucket type ion source using a cusp magnetic field was used.

The substrate 1 is composed of silicon nitride raw material powder and Y ₂ O ₃ powder.
And a sintering aid made of Al ₂ O ₃ were added and sintered under normal pressure. The sintering aid was added at 5% by weight with respect to the raw material powder. Then, the whole was sintered at 1800 degrees under a nitrogen atmosphere. The film is formed to a thickness of about 500 nm by adjusting the evaporation amount of boron atoms and the irradiation amount of nitrogen ions in consideration of the sputtering rate of nitrogen atoms of boron atoms so that the composition ratio of B / N is 20. Went to get.

After that, the acceleration energy of ions is 2 KeV,
A film having a thickness of about 5000 nm was formed under the condition of B / N composition ratio = 1. Example 2 Using the same substrate as in Example 1, ion acceleration energy-1
A film having a thickness of about 500 nm is formed under the conditions of 5 KeV and B / N composition ratio = 20, and thereafter, ion acceleration energy is 200 eV, B
A film having a thickness of about 500 nm was formed under the condition of / N composition ratio = 1. The other conditions were the same as in Example 1.

Example 3 Using the same substrate as in Example 1, ion acceleration energy 35
A film having a thickness of about 1000 nm was formed under the conditions of KeV and B / N composition ratio = 1. Example 4 A sintered substrate 1 made of silicon carbide was used, and the acceleration energy of ions was 20 KeV and the B / N composition ratio was 20.
nm thick film formation, and then ion acceleration energy 2 Ke
A film having a thickness of about 250 nm is formed under the conditions of V and B / N composition ratio = 4,
Further, the ion acceleration energy is 2 KeV and the B / N composition ratio =
A film having a thickness of about 500 nm was formed under the condition of 1. The other conditions were the same as in Example 1.

This substrate was β-SiC sintered by adding 0.3% and 0.5% by weight of B and C, respectively, to a SiC raw material and sintering at 2000 ° C. in an Ar atmosphere under atmospheric pressure. It was a union. Comparative Example 1 Approximately 1000 n on the same silicon nitride sintered substrate as in Example 1 under the conditions of ion acceleration energy of 50 KeV and B / N composition ratio = 1.
A film having a thickness of m was formed. The other conditions were the same as in Example 1.

Comparative Example 2 The same silicon carbide sintered substrate as in Example 4 was used, and the ion acceleration energy was 15 KeV and the B / N composition ratio was 50.
A film having a thickness of 00 nm was formed. After that, the ion acceleration energy 2
A film having a thickness of about 500 nm was formed under the conditions of 00 eV and B / N composition ratio = 1. The other conditions were the same as in Example 4.

Using each of the sintered substrates of Examples 1 to 4 and Comparative Examples 1 and 2, 70 wt% of lead oxide (PbO), 27 wt% of silicon oxide (SiO ₂ ) and 3 wt% of trace components. Glass mass in a nitrogen atmosphere at a temperature of 500 ° C and a pressing pressure of 40K
Pressed at g / cm ² . Further, in addition to Comparative Examples 1 and 2, the same press test as above was performed using the same substrate as in Examples 1 and 4 in which a film was not formed as a comparative example.

When pressing, maintain this condition for 2 minutes,
Then, after cooling to 300 ° C., the glass was taken out. When the state of the glass after molding was confirmed, Example 1
No discoloration was observed in the samples Nos. 4 to 4, but discoloration was observed in the glass in the press using the silicon nitride sintered substrate on which no film was formed. Further, in the case of using the silicon carbide sintered substrate on which a film was not formed, although the discoloration was not observed, the adhesion of the sintering aid was recognized on the glass surface after molding. Further, the hardness of the films of Example 1 and Comparative Examples 1 and 2 was measured with a 10 g load Micro Vickers hardness tester, and it was found to be 550 respectively.
0, 2200, 2000, and the hardnesses affecting the wear resistance of Comparative Examples 1 and 2 were inferior to those of Example 1.

[0038]

According to the present invention, a sintered body containing a nitride of silicon or a carbide of silicon, which is more excellent in abrasion resistance, wear resistance and seizure resistance than the sintered body itself, and It is possible to provide a sinter that is coated with a film that adheres well to the sinter itself and can stably exhibit the above performance for a long period of time, and a method for producing the sinter.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a film forming apparatus 1 used for manufacturing the sintered body shown in FIG.
It is a figure which shows schematic structure of an example.

[Explanation of symbols]

 1 Substrate 11 Boron Nitride Containing Film 2 Substrate Holder 3 Evaporation Source 3a Boron Element-Containing Substance 4 Ion Source 4a Ion 5 Film Thickness Monitor 6 Ion Current Measuring Device 7 Vacuum Container 8 Exhaust Device

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kiyoshi Ogata 47 Umezu Takaunecho, Ukyo-ku, Kyoto City Nissin Electric Co., Ltd.

Claims (9)

[Claims] 1. A silicon nitride characterized in that a part or all of the surface is covered with a boron nitride-containing film formed by using vacuum evaporation and / or sputtering and ion irradiation in combination. And / or a sintered body containing a carbide of silicon. 2. The sintered body according to claim 1, wherein the atomic ratio of boron to nitrogen in the boron nitride-containing film is 0.1 or more and 50 or less. 3. The sintered body according to claim 1, wherein the atomic ratio of boron to nitrogen present in the boron nitride-containing film is constant in each part of the film. 4. The sintering according to claim 1, wherein the atomic ratio of boron to nitrogen existing in the boron nitride-containing film is gradually decreased from the surface of the sintered body toward the surface of the boron nitride-containing film. body. 5. A boron element-containing substance is applied onto a sintered body containing a nitride of silicon and / or a carbide of silicon by a vacuum vapor deposition method and / or a sputtering method, and at the same time as the application.
Alternately or after the application, ions are irradiated from an ion source to form a boron nitride-containing film, and the ratio of boron atoms and nitrogen ions reaching the sintered body in the film formation and the irradiation ions The method for producing a sintered body according to claim 1, wherein the atomic ratio of boron to nitrogen in the film containing boron nitride is controlled by controlling the acceleration energy. 6. The method according to claim 5, wherein the acceleration energy of the ions to be irradiated in the film formation is 40 KeV or less. 7. The ratio of boron atoms to nitrogen ions reaching the sintered body and the acceleration energy of the irradiation ions in the film formation are such that the atomic ratio of boron to nitrogen present in the boron nitride-containing film is 0.1. The method according to claim 5 or 6, wherein the control is performed so as to be 50 or less. 8. In the film formation, the ratio of boron atoms and nitrogen ions that reach the sintered body and the acceleration energy of the irradiation ions are such that the atomic ratio of boron and nitrogen present in the boron nitride-containing film is The method according to claim 5, 6 or 7, wherein the control is performed so as to be constant in each part. 9. In the film formation, the ratio of boron atoms to nitrogen ions reaching the sintered body and the acceleration energy of the irradiation ions are determined by the atomic ratio of boron to nitrogen existing in the boron nitride-containing film. 8. The method according to claim 5, 6 or 7, which is controlled so as to decrease gradually from the surface of the body toward the surface of the film.