JPH11199325A - Hbn sintered product and production of heat-resistant coating film on hbn sintered product and sliding part comprising hbn sintered product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the employment of a hexagonal boron nitride(hBN) sintered product having a solid lubricating action in both water and sea water. SOLUTION: This hBN sintered product is obtained by adding 1-10 wt.% of calcium powder as a sintering auxiliary to hBN powder and subsequently sintering the mixture by use of a hot press. The auxiliary-added hBN sintered product is used on the sliding surface of a sliding part, when used in a fluid containing NaCl. When the auxiliary-added hBN sintered product is rubbed with the same kind of material to be rubbed under a load of 62-245 kg/mm<2> in water, a water-resistant calcium hydroxide coating film is produced on the surface of the auxiliary-added hBN sintered product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sintered body made of hexagonal boron nitride (hBN) (hereinafter referred to as an hBN sintered body), a method for forming a water-resistant film on the surface of the hBN sintered body, and a method for producing the same. The present invention relates to a sliding component made of a hBN sintered body.

[0002]

2. Description of the Related Art Generally, graphite, molybdenum disulfide, hexagonal nitride, and the like are used in a special environment in which a liquid lubricant or grease cannot be used in order to provide a lubricating effect to a sliding surface of a machine component. A self-lubricating solid lubricant made of a layered lattice material such as boron (hereinafter referred to as hBN) is used.

In recent years, hBN sintered bodies have been increasingly used as materials for use as the fixed lubricant because of their excellent wear resistance.

[0004]

However, this h
In a BN sintered body, boron nitride (BN), which is a main component, is water-soluble and bonds with OH to form ammonia (NH) as shown in the following formula.
₃ ) and (boric acid) H ₃ BO ₃ and elute. _{BN + 3 / 2H 2 O =} 1 / 2B 2 O 3 + NH 3 1 / 2B 2 O 3 + 3 / 2H 2 O = H 3 BO 3 ( elution) Therefore hBN sintered body, the sliding surface such as with water, For example, it could not be used for a seal member such as a fluid bearing.

Further, hBN not only binds to water due to the above-mentioned chemical reaction, but also has good water absorption due to its layered lattice shape, so that hBN is used in seawater such as pumps, bearings and seals for ships. Under the water absorption and the heat generated by the sliding friction, a large amount of salt (NaCl) adheres to the sliding surface of hBN in a short time. This attached Na
Since Cl causes an increase in friction coefficient and abnormal wear, it cannot be used in sliding parts used in seawater.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to form a sintered body made of hBN which can be used as a sealing member for a sliding surface in an environment where water or seawater is used. In order to achieve the above object, the invention of claim 1 is characterized in that hexagonal boron nitride (hBN) is a main component, and calcium is added and sintered as a sintering aid.

[0007] The invention described in claim 2 is characterized in that the amount of calcium added as the sintering aid is in the range of 0.8 wt% to 10 wt%. The invention according to claim 3 is characterized in that the sintered body is rubbed in a fluid having an OH group by a material to be rubbed having at least the same abrasion resistance as that of the sintered body, thereby providing a surface of the sintered body. In which a calcium hydroxide film is formed.

The invention according to claim 4 is characterized in that the fluid having an OH group is pure water (H ₂ O). According to a fifth aspect of the present invention, the load applied to the material to be rubbed against the hBN sintered body is from 62 kg / mm ² to 24 kg / mm ^2.
It is characterized by 5 kg / mm ² .

According to a sixth aspect of the present invention, a surface of a sintered body containing hexagonal boron nitride (hBN) as a main component and calcium added as a sintering aid is coated with a calcium hydroxide film. It is assumed that. The invention according to claim 7 is a sliding component which has the hBN sintered body according to claim 1 or 2 on a sliding surface and is used in a fluid containing NaCl.

[0010]

Next, a first embodiment of the present invention will be described. In the present embodiment, by mixing calcium oxide CaO powder 1.5 wt% and a ₂ 0 ₃ powder 2.5 wt% boron oxide B to the hBN powder as sintering aids, sintered by hot pressing as a test piece. In addition, calcium Ca
At room temperature, calcium oxide is combined with oxygen to form calcium oxide CaO. Therefore, in this embodiment, this CaO is used, but simple Ca may be used.

Here, calcium oxide added to the hBN powder
CaO powder and boron oxide B_Two0 _ThreeThe amount of powder
Friction resistance of hBN sintered body which is sintered with increase increases
Calcium oxide CaO powder and B_Two0_ThreePowdered
Calcium hydroxide film from about 0.8 wt% for both
Can be formed, and at 10 wt% or more, the frictional resistance is large and solid
0.8 wt% or more due to impairing the function as a lubricant
Is considered to be practically preferable to be 10 wt% or less.
Can be

The auxiliary material-added hBN sintered body thus formed is mounted on a pressing device 10 shown in FIG. 1 and pressed. As shown in FIG. 1, the pressurizing device 10 is provided with a rotatable table 12 on a base 11, and the table 12 is driven to rotate by a motor 22. An auxiliary material-added hBN sintered body 13 is fixed to the table 12.
A cylindrical wall 14 is set up so as to surround the N sintered body, and the inner periphery of the wall 14 is filled with pure water (H ₂ O).

The pressing mechanism main body 1 for applying a load to the auxiliary material-added hBN sintered body 13 is placed on the auxiliary material-added hBN sintered body 13.
5 are arranged. The pressing mechanism main body 15 mainly includes a pin 16, a weight support 17, and a side block 18 that holds the pin 16 and the weight support 17. The pin 16 is a sintered body formed of the same material as the hBN sintered body 13 with the auxiliary material, and the hBN sintered body 1 with the auxiliary material.
3 transmits frictional force to the surface.

The pin 16 is fixed to a weight support portion 17, and a support bar 23 is erected at the center of the weight support portion 17 at the center, and a disk-shaped weight 19 supported by the support bar 23 is provided. Is arranged. One end of an arm 20 is connected to the side surface of the weight support portion 17, and the other end of the arm 20 is held by a side block 18.

The table 12 or the arm 20 of the pressing device 10 is connected to the hBN sintered body 13 with the auxiliary material and the pin 1.
If a feed mechanism is attached so that 6 moves relative to the center of rotation in the radial direction, a frictional force can be applied to the entire surface of the hBN sintered body 13 with the additive. A strain measuring device 21 is mounted at the center of the arm 20, and the frictional force of the hBN sintered body 13 with the auxiliary material is measured based on the measured value of the strain measuring device 21.

Using the pressurizing device 10 having the above structure,
While applying a load to the hBN sintered body 13 with the auxiliary material,
HBN sintered body 1 when auxiliary material moves on the circumference
The electron beam microanalyzer (hereinafter referred to as EPMA)
). The test conditions at this time are as follows. Pin (material to be rubbed) material: hBN sintered body with auxiliary material Sliding speed: 0.13 m / s Total sliding distance: 700 m FIG. 2 (a) shows the addition of auxiliary material when the test was performed under the above test conditions. The surface of the hBN sintered body 13 is indicated by a symbol α in the figure.
Is a portion rubbed by the pin 16.

Further, when the surface of the hBN sintered body 13 with the additive was analyzed using EPMA from FIG. 2 (a), the portion where calcium was rubbed with the pin 16 as shown in FIG. Only as shown in FIG. 2 (c), oxygen was also observed only in the portion rubbed with the pin 16 as in the case of calcium. Accordingly, by rubbing the hBN sintered body 13 with the aid with the pins 16 in water (H ₂ O), the calcium Ca of the hBN sintered body 13 with the aid was converted to water (H ₂ O).
OH and combined with calcium hydroxide ₂ O) (Ca (O
It is considered that the film of H) ₂ ) is formed.

When a similar test was performed in air, calcium and oxygen were slightly observed not only from the portion rubbed with the pin 16 but also from the entire surface of the hBN sintered body 13 with the additive. No film of (OH) ₂ ) was formed. It is proved by the graph of FIG. 3 that calcium hydroxide is superior in water resistance to BN which is a main component of the hBN sintered body 13 with the additive.

FIG. 3 shows the hBN sintered body 13 with the additive added with the calcium hydroxide film and the pure hBN sintered film without calcium hydroxide film formed by sintering pure hexagonal boron nitride alone. This is a result of measuring the concentration of ammonia (NH ₃ ) in water (H ₂ O) when the pin is slid while changing the load by the pin 16 by the pressurizing device 10 shown in FIG. .

Ammonia (NH ₃ ) is produced as described above when the hBN sintered body is dissolved in water. The higher the concentration of ammonia, the more the hBN sintered body is dissolved in water. , Indicating no water resistance. As shown in FIG. 3, the hBN sintered body 13 with the auxiliary material formed with the calcium hydroxide film slides the pin 16 by applying the same load to the pure hBN sintered body without the calcium hydroxide film. When this was done, it was found that only about 1/2 to 1/3 of ammonia was produced.

From this, the hBN sintered body 13 with the additive formed with the calcium hydroxide film has about two to three times the water resistance of the pure hBN sintered body without the calcium hydroxide film. You can see that there is. FIG. 4 shows the addition of auxiliary material.
The observation was made on the load applied to the BN sintered body 13 and the ratio of oxygen to calcium on the surface of the hBN sintered body 13 with the auxiliary material added.

In FIG. 4, the ratio β of oxygen to calcium shown by the solid line is the calcium hydroxide (C
It is considered that the closer to the theoretical value of a (OH) ₂ ), the more the calcium hydroxide film is formed on the surface of the hBN sintered body 13 with the additive.
A calcium hydroxide film is formed between (N).

That is, since the contact area between the pin 16 and the hBN sintered body 13 with the auxiliary material is 0.8 mm ² , the hBN sintered body 13 with the auxiliary material has a thickness of 61.25 kg / mm ² to 245 kg / mm ^2. It was observed that a calcium hydroxide film was formed by applying a load of. In addition,
The high ratio of oxygen to calcium between 0 (N) and 5 (N) is caused by the initial addition of C to the hBN sintered body 13 with the additive.
It is considered that the ratio of oxygen to calcium contained in a and B ₂ O ₃ was detected as it was. At this stage, it was observed that no film was formed on the surface of the hBN sintered body 13 with the additive. I have.

From these results, calcium is added to hBN to form an auxiliary material-added hBN sintered body 13, and this calcium-added auxiliary material-added hBN sintered body is subjected to the same auxiliary material addition in water (H ₂ O). By rubbing with the material-added hBN sintered body, a water-resistant calcium hydroxide film can be formed on the surface. Also,
The load when rubbing the hBN sintered compact with auxiliary material is 62 kg / m.
From a m ² and 245 kg / mm ^2, it can form a film of reliably calcium hydroxide.

In the above embodiment, the addition of an auxiliary material in water
Although calcium hydroxide is formed by rubbing the BN sintered body, a calcium hydroxide film can be formed not only by water (H ₂ O) but also by a fluid having an OH group, for example, alcohol.
Further, it is not always necessary to use the same auxiliary material-added hBN sintered body to rub the auxiliary material-added hBN sintered body, and a material having a higher wear resistance than the auxiliary material-added hBN sintered body such as ceramic is effective. .

Further, it is considered that calcium hydroxide is resistant to corrosion since it is known to have high alkali resistance. Next, a second embodiment of the present invention will be described. In the second embodiment, hBN (hexagonal boron nitride) powder was used as a test piece and Ca was used as a sintering aid.
1.5 wt% of O (calcium oxide) powder and 2.5 wt% of B ₂ O ₃ (boron oxide) powder were mixed and sintered by hot pressing.

The sintering conditions at this time were as follows: sintering temperature: 2000 ° C. pressure: 150 kgf / cm ² sintering time: about half a day.

Here, the amount of the CaO powder and the amount of the B ₂ O ₃ powder added to the hBN powder, as in the first embodiment, increase with the increase in the frictional resistance of the hBN sintered body. Increase. From about 0.8 wt% of both calcium oxide CaO powder and B ₂ O ₃ powder, a calcium hydroxide film is formed in water, and Ca
Can be gradually eluted into the aqueous NaCl solution, and also has a function of solid lubrication of hBN. When the content is 10 wt% or more, the frictional resistance increases and the function as a solid lubricant is impaired. Therefore, it is considered that the content of 0.8 wt% or more and 10 wt% or less is practically suitable.

As a comparative example with the hBN sintered body with the auxiliary material of the present invention, a pure hBN sintered body consisting only of hBN powder was prepared under the same sintering conditions. These additives are added
Pressing device 1 shown in FIG. 1 for BN sintered body and pure hBN sintered body
0 and pressurized. About this pressurizing device 10,
Except that the inner periphery of the wall 14 is filled with an aqueous NaCl solution, the same as in the first embodiment described above, and the description is omitted.

The state of the hBN sintered body 13 when the pin 16 is moved on the circumference while applying a load to the pure hBN sintered body and the auxiliary material-added hBN sintered body 13 using the pressurizing device 10 is described. The analysis was performed using a line microanalyzer (hereinafter referred to as EPMA). The test conditions at this time are as follows. Material of pin (member to be rubbed): Same sintered body as test piece Sliding speed: 0.13 m / s Total sliding distance: 700 m FIG. 5 (a) shows pure hB when the test was performed under the above test conditions.
The surface of the N sintered body is shown, and a portion indicated by a symbol α in the figure is a portion rubbed by the pin 16.

Further, when the surface of the hBN sintered body 13 was analyzed using EPMA from FIG. 5 (a), as shown in FIG. Further, as shown in FIG. 5 (c), chlorine was observed only in the portion rubbed with the pin 16 similarly to sodium. This indicates that NaCl was adsorbed by rubbing the hBN sintered body 13 with the pin 16 in an aqueous NaCl solution.

FIG. 6 similarly shows the hB added with the auxiliary material after the above test.
The surface of the N sintered body was analyzed by EPMA. Neither sodium Na (b) nor chlorine Cl (c) was observed in the portion α rubbed by the pin 16. 7 and 8
7 shows the change in the coefficient of friction between the pure hBN sintered body and the hBN sintered body with the additive added according to the change in the concentration of NaCl.
In the case of the pure hBN sintered body of the above, the friction coefficient is increased by about 0.04 in the 9 wt% NaCl aqueous solution as compared with the pure water, but in the hBN sintered body with the additive added in FIG. No change was observed in the friction coefficient at all.

Next, FIGS. 9 and 10 show changes in the amounts of elements of Na (sodium) and Cl (chlorine) on the friction surfaces of the pure hBN sintered body and the hBN sintered body with the auxiliary material accompanying the change in the concentration of the NaCl aqueous solution. Is shown by a graph. In the pure hBN sintered body of FIG. 9, Na also sharply increases when the concentration of Cl exceeds about 0.5 wt%, and it can be seen that NaCl aggregates on the sliding surface. However, in the hBN sintered compact with the aid added in FIG. 10, even if the concentration of NaCl changed, the element amounts of Na and Cl on the sliding surface hardly changed. That is, there is almost no aggregation of NaCl and pure water (N
(aCl concentration: 0 wt%) and no difference from the non-sliding surface were not observed at all.

From this, in the hBN sintered body with the auxiliary material added, there is almost no aggregation of NaCl, so that the friction coefficient can be maintained and abnormal wear does not occur. Therefore, the lubrication performance of hBN is not impaired. In addition, in the hBN sintered body with the additive added, a large amount of Ca on the friction surface is detected in pure water, but extremely reduced in the NaCl aqueous solution. This is because in pure water, CaO, which is a sintering aid, is combined with water as shown in the following chemical formula, and a Ca (OH) ₂ film is formed on the sliding surface of CaO + H ₂ O = Ca (OH) _2. It is thought to be. In NaCl, Na and Cl are affected by Na and Cl.
It is considered that Ca gradually elutes into the Cl aqueous solution, so that Ca on the friction surface decreases.

FIG. 11 is a graph showing the pH of test water (NaCl aqueous solution) after the above test. It can be seen that while the pure hBN sintered body is almost neutral, the hBN sintered body with the additive added has an increased pH. This is considered to be because the pH increased due to the elution of Ca as described above. FIG. 12 shows the results of measuring the water absorption of each hBN sintered body. The test piece at this time was 30 × 30 × 5 mm, and the water absorption time was 2 hours, which is the same as the sliding time. HBN sintered compact with additive is pure h
It can be seen that only about 1/5 or less of the BN sintered body absorbs water.

From these facts, it is considered that since the pure hBN sintered body has a large water absorption, NaCl gradually aggregates on the sliding surface due to sliding friction. However, in the hBN sintered body with the additive, in addition to the elution of Ca, the water absorption rate is extremely small as compared with the pure hBN sintered body.
It is considered that there is almost no aggregation of l. Therefore, by forming a sliding part with this auxiliary material-added hBN sintered body,
The hBN can be used without impairing the solid lubricating performance of a hBN even in a bearing member or a seal member of a pump for a ship used in seawater.

[0037]

As described above, the hBN sintered body according to the first aspect of the present invention contains hexagonal boron nitride (hBN) as a main component, and is sintered by adding calcium as a sintering aid. Therefore, it can be used for sliding parts used in water or seawater. Further, the hexagonal boron nitride sintered body according to claim 2 has a water resistance without impairing the solid lubricating performance of hBN by setting the amount of calcium added as a sintering aid to 0.8 wt% or more and 10 wt% or less. Thus, an hBN sintered body having seawater resistance can be obtained.

The invention according to claims 3 and 4 is characterized in that the hBN sintered body is rubbed with a friction material in a fluid having an OH group or in pure water (H ₂ O).
A corrosion-resistant calcium hydroxide film can be formed on the surface of the sintered body. The invention according to claim 5 is characterized in that the load applied to the material to be rubbed against the hBN sintered body is 62K.
By setting the range of g / mm ² to 245 Kg / mm ^2, a calcium hydroxide film can be efficiently formed.

Further, the invention according to claim 6 is characterized in that hBN
Since the calcium hydroxide film is formed on the sintered body, the water resistance is superior to that of the hBN sintered body having no calcium hydroxide film on the surface. It can be used as a solid lubricant even in a liquid having an OH group such as a seal member of a fluid bearing.

The invention according to claim 7 is characterized in that the hBN sintered body obtained by adding Ca to hBN and sintered is applied to a sliding component used in a fluid containing NaCl.
A sliding part having the solid lubrication performance of BN and no adsorption of NaCl can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an appearance of a pressurizing device used in an embodiment of the present invention.

FIG. 2 is a diagram showing a surface state when friction is applied to a pure hBN sintered body in pure water using a pressurizing device.

FIG. 3 shows the results of measuring the concentration of ammonia (NH ₃ ) in an hBN sintered body having a calcium hydroxide film formed thereon and in a pure hBN sintered body having no calcium hydroxide film.

FIG. 4 shows the load applied to the hBN sintered body 13 and the hBN
5 is a graph relating to the ratio of oxygen and calcium on the surface of a sintered body 13.

FIG. 5 is a diagram showing a surface state when friction is applied to a pure hBN sintered body in a NaCl aqueous solution using a pressurizing device.

FIG. 6 is a diagram showing a surface state when friction is applied to an auxiliary material-added hBN sintered body in a NaCl aqueous solution using a pressurizing device.

FIG. 7 is a graph showing a change in friction coefficient due to a change in NaCl concentration of a pure hBN sintered body.

FIG. 8 is a graph showing a change in friction coefficient due to a change in NaCl concentration of the hBN sintered body with an additive.

FIG. 9 is a graph showing a change in the amount of elements on a friction surface of a pure hBN sintered body in an aqueous NaCl solution.

FIG. 10 is a graph showing a change in the amount of elements on a friction surface of an hBN sintered body with an additive added thereto in an aqueous NaCl solution.

FIG. 11 is a graph showing a change in pH value of an aqueous NaCl solution after a pressure sliding test.

FIG. 12 is a table showing the water absorption of the hBN sintered body with the additive added and the pure hBN sintered body.

[Explanation of symbols]

 Reference Signs List 10 pressure device 11 base 12 table 13 hBN sintered body 14 wall 15 pressure mechanism main body 16 pin 18 side block 20 arm

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koichi Nakajima 1-19-16 Harukidai, Togo-cho, Aichi-gun, Aichi Prefecture (72) Inventor Fumihiro Honda 3-620 Kanzawa, Midori-ku, Nagoya-shi (72) Inventor Yasuo Imada 13-333 Kagamida, Narumi-cho, Midori-ku, Nagoya-shi (72) Inventor Toshiyuki Saito 1-1-1, Asahi-cho, Kariya-shi, Aichi Pref.

Claims (7)

[Claims] 1. An hBN sintered body comprising hexagonal boron nitride (hBN) as a main component, and sintered by adding calcium as a sintering aid. 2. The hBN sintered body according to claim 1, wherein the amount of calcium added as the sintering aid ranges from 0.8 wt% to 10 wt%. 3. The sinter comprising hBN according to claim 1 or 2 is rubbed in a fluid having an OH group by a material to be rubbed having at least the same abrasion resistance as the sinter. A method for forming a water-resistant film on an hBN sintered body, comprising forming a calcium hydroxide film on the surface of the sintered body. 4. The fluid having an OH group is pure water (H ₂ O).
The method for producing a water-resistant coating on a hBN sintered body according to claim 3, wherein: 5. A load applied to a material to be rubbed which rubs the hBN sintered body from 62 kg / mm ² to 245 kg / mm ^2.
The method for producing a water-resistant film on a hBN sintered body according to any one of claims 3 to 4, characterized in that: 6. A hBN sintered body comprising hexagonal boron nitride (hBN) as a main component and a calcium hydroxide film coated on the surface of a sintered body to which calcium is added as a sintering aid. 7. The hB according to claim 1 or 2,
A sliding component made of an hBN sintered body, characterized in that the sliding part has a sintered body made of N on a sliding surface and is used in a fluid containing NaCl.