JP2000001372A - Ceramic sliding parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain ceramic sliding parts not causing defects such as peeling and having stable quality by specifying the iron content of a ceramic material contg. a sintering aid. SOLUTION: A silicon nitride-base ceramic powder contg. a prescribed amt. of a sintering aid is mixed with a binder to prepare a slurry, metallic components including iron in the slurry are removed by passing the slurry through a screen with a magnet and then the slurry is shaped into particles by spray drying or other method. The particles are press-molded in a prescribed shape, freed of the binder by heating and sintered by further heating to obtain the objective ceramic sliding parts such as ball bearings comprising a silicon nitride-base ceramic material contg. the sintering aid and having <=2,000 ppm, preferably <=200 ppm iron content. At least one selected form Y2O3, Al2O3, TiO2, etc., is used as the sintering aid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ceramic sliding part.

[0002]

2. Description of the Related Art In recent years, attempts have been made to use ceramic materials having excellent properties such as wear resistance, heat resistance and acid resistance as various sliding members. For example, a ball bearing made of a ceramic material is expected to be used as a bearing member for various machines because it does not seize even if the lubricating oil runs out during operation and has excellent wear resistance, as compared with a metal ball bearing. ing.

Conventionally, as a ceramic material constituting such a ball bearing, a silicon nitride-based, silicon carbide-based, alumina-based, or titanium nitride-based ceramic material having excellent mechanical strength has been mainly used. Various methods of manufacturing ball bearings using these ceramic materials have also been implemented. For example, as an example of a case of forming a ball bearing, first, a predetermined raw material ceramic powder is mixed with a binder, molded by a predetermined means, sintered, and subjected to a necessary post-treatment. .

[0004]

SUMMARY OF THE INVENTION It has been found that ceramic sliding parts obtained by conventional methods, such as ball bearings, often cause peeling of the material on the ball surface in a short period of time during use. I have. The appearance of such a peeling phenomenon is fatal to ceramic ball bearings, and poses a problem in terms of stability of component quality and reliability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and it is an object of the present invention to provide a ceramic sliding part, particularly a ball bearing, which has a stable quality without a defect such as peeling. Aim.

[0006]

The ceramic sliding component according to the present invention is characterized in that the content of iron in the ceramic material containing the sintering aid is 2,000 ppm or less. Further, in claim 2, the ceramic contains silicon nitride as a main component. In claim 3, the content of iron is 200 ppm or less. In claim 4, the sintering aid includes Y ₂ O ₃ , Al _{According to a} fourth aspect of the present invention, the ceramic sliding component is a ball bearing, which contains at least one of ₂ O ₃ , AlN, and TiO ₂ .

In the method for manufacturing a ceramic sliding component according to the present invention, a raw ceramic powder containing silicon nitride and a sintering aid is slurried, then granulated and formed into a predetermined shape.
The method for manufacturing a ceramic sliding component to be sintered is characterized in that a removing step and a polishing step are provided so that the iron content in the ceramic sliding part becomes 2000 ppm or less.

According to the study of the present inventors, as a result of analyzing the surface of a ceramic sliding part, for example, a part that has peeled off during the use of a ball bearing with an X-ray microanalyzer, a large amount of iron (Fe) ) Was detected. Focusing on this fact, further research revealed that due to iron inevitably present in the raw ceramic material, some cohesion phenomena with these iron particles as nuclei occurred during sintering,
This was found to precipitate on the surface of the component and form an aggregate of about 30 to 100 μm on the surface layer. The aggregates were easily peeled, and peeled in a scale-like manner with mechanical stress, which was the cause of the deterioration of the quality of the sliding parts.

The present invention has been made based on the above findings, and is characterized in that metal components which are inevitably present in a ceramic material and cause the above-mentioned separation are positively eliminated. The above-described peeling phenomenon in the component surface layer occurs not only in iron but also in metal components such as Cr, Ni, and W, and can also occur due to the presence of a metal compound such as WC. Therefore, in the present invention, such a component is also included as the metal component.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As a raw material ceramic material constituting a ceramic sliding component of the present invention, a ceramic conventionally used as a material for a sliding component can be appropriately used.
Specifically, for example, a silicon nitride-based ceramic material, a silicon carbide-based, alumina-based, or titanium nitride-based ceramic material is used depending on the application, and a mixed material thereof may also be used.

When the ceramic sliding component of the present invention is manufactured, usually, first, the raw ceramic powder is slurried, then granulated, formed into a predetermined shape, and sintered to obtain the ceramic sliding component. Although the method of obtaining can be taken, the contained metal component is substantially removed in at least one of the above steps.

[0012] Such active removal of the metal component can be performed, for example, by slurrying the raw ceramic powder and then filtering the slurry using a screen filter provided with a magnet.

As a method of removing the metal component at the raw material stage, for example, before the raw ceramic powder is slurried, the raw ceramic powder is brought into contact with a magnet so that the metal component in the raw ceramic powder can be previously removed. The method of sorting and removing is effective.

Further, a method is also effective in which after the above-mentioned slurry is granulated by a predetermined method, the granulated material is brought into contact with a magnet to select and remove metal components in the granulated material.

In the present invention, it is important to carry out at least one of the above-mentioned various methods or a combination of two or more of them. In the present invention, it is important to substantially remove the metal component in the ceramic material by using the above-described method. 2000pp iron content
m or less, preferably 200 ppm or less.

[0016]

EXAMPLES The present invention will be described below based on actual production examples, but the present invention is not limited to the description of the following examples. Si ₃ N ₄ : 100 parts by weight, Y ₂ O
₃ : 5 parts, Al ₂ O ₃ : 4 parts, AlN: 3 parts, TiO
₂ : 1.5 parts of the raw material ceramic powder were prepared, mixed with a solvent and a binder, and stirred to prepare a raw material slurry.

Next, the slurry was filtered using a screen around which an electromagnet was mounted. Further, the filtrate was granulated by a spray drying method, and the obtained granules were subjected to pressure molding. Thereafter, the added binder was subjected to thermal decomposition and sublimation in an electric furnace, followed by sintering. The obtained sintered product was slightly polished to reduce the iron content to 200.
A ball bearing of 0 ppm or less was obtained.

When the rolling fatigue life of the ball bearing of the present invention and the conventional ball bearing thus obtained was measured, the conventional ball bearing had an average life of 400 hours and a minimum life of 50 hours.
The ball bearing of the present invention has an average of 420 hours and a minimum of 3 hours.
The life was 00 hours. The measurement condition is 400k load
g, the number of revolutions was 1200 rpm, the ball diameter was 10 mm, and the mating material was SUS-2 (disc).

As can be seen from the results of the above-mentioned rolling fatigue life measurement, the ceramic ball bearing of the present invention has a rolling fatigue life as long as 300 hours at the shortest, and the variation in the life is remarkably reduced, so that the quality is greatly increased. It was recognized that it improved.

[0020]

In the ceramic sliding component of the present invention, since the metal component in the ceramic material is substantially eliminated, it is possible to effectively prevent the peeling phenomenon on the surface of the ceramic sliding component, for example, a ball bearing. And have excellent quality stability.

Claims (5)

[Claims] 1. A ceramic sliding component, wherein the content of iron in a ceramic material containing a sintering aid is 2000 ppm or less. 2. The ceramic sliding component according to claim 1, wherein said ceramics contains silicon nitride as a main component. 3. The ceramic sliding component according to claim 1, wherein the iron content is 200 ppm or less. 4. The method according to claim 1, wherein the sintering aid is Y ₂ O ₃ , Al ₂ O ₃ ,
AlN, the ceramic sliding component according to any of claims 1 to 3, characterized in that it comprises at least one TiO _2. 5. The ceramic sliding component according to claim 1, wherein said ceramic sliding component is a ball bearing.