JP2641257B2 - Method for producing ceramic-BN composite material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a ceramic-BN composite material having excellent sliding properties, wear resistance and workability.

[Prior art and problems to be solved] Ceramics have excellent heat resistance and corrosion resistance, and have high hardness and high strength. Therefore, ceramics are widely used as corrosion and wear resistant materials such as slurry transport pipe linings and mechanical seals. However, bearing balls, retainers,
When used as a precision sliding material such as a magnetic head base material or a slider, or as an engine member, it has not been put to practical use because of its large wear coefficient and low machining surface accuracy.

As means for solving this, JP-A-61-281086 discloses a method of impregnating a porous ceramic body with fluorine oil, and JP-A-61-251586 discloses a method of impregnating a porous ceramic body with a resin. Although all are disclosed, they are ceramic-organic composite systems and cannot exhibit excellent heat resistance of ceramics. Further, since the ceramic porous body is simply impregnated with an organic substance, the strength, hardness, and processed surface accuracy are insufficient.

Furthermore, although in JP-A-61-51614 "Method of sintering a mixture of ZrO ₂ and the carbon" is disclosed, for composite component is carbon is insufficient heat resistance.

Japanese Patent Application Laid-Open Nos. 62-56376 and 62-56377 disclose "a method for producing a composite sintered body", which comprises molding and firing a mixture of an aluminum nitride powder and a BN powder. Since the BN powder is used, the types of ceramics are limited, the dispersibility is poor, and the processed surface accuracy of the fired body is low.

On the other hand, at present, various magnetic media devices are commercially available for performing recording and reproduction using a flexible desk, a hard desk or a magnetic tape having a magnetic layer coated on the surface or a magnetic layer formed as a thin film, and further increased in density. Development is under way. These recording / reproducing devices use many components that slide constantly or temporarily relative to a magnetic medium. It is necessary that these components have excellent durability and do not damage the recording medium that slides relatively. In particular, there is a high tendency for high speed and high density, and stricter restrictions are imposed on parts that are in sliding contact with the medium, and there is a demand for a material that can replace conventional ceramics.

[Means for Solving the Problems] The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have excellent sliding characteristics and workability, and have the strength and hardness inherent to the material. A method for producing a ceramic-BN-based composite material that can sufficiently extract the above has been completed.

That is, the present invention is characterized in that a specific BN precursor is used as a BN source in a method for producing a ceramics-BN composite material. The BN precursor used here has a BN (002) plane spacing of 2.15 to 2.40Å and a crystallite size of 50 to 2000Å by X-ray diffraction. After pre-forming the ceramic-BN precursor composition containing 5 to 50 wt%, 10 to 120 MPa,
The present invention relates to a method for producing a ceramic-BN composite material, which is preferably fired under a pressure of 20 to 100 MPa. The (002) plane spacing and crystallite size referred to in the present invention can be calculated from the 2θ value and the half width of the CuKα diffraction peak by X-ray diffraction obtained by the midpoint method of half width at half maximum, respectively, from the black formula and Scherrer's formula. It is calculated from the formula.

Preferably the ceramic particles used in the present _{invention, Al 2 O 3, ZrO 2} , TiO 2, MgO, SrO 2, NiO, oxides such as MnO; SiC, TiC, WC, B 4 C, carbides such as ZrC; Si ₃ N ₄ , AlN, Ti
Nitrides such as N and ZrN; and one or more kinds selected from borides such as ZrB ₂ , CrB and TiB ₂ . Further, solid solutions of these compounds may be used. The purity of these powders is 90% by weight or more for the ceramic component, and the particle size is 0.
It is preferably from 05 to 5.00 μm. If the purity is less than 90 wt%,
The properties of ceramics such as heat resistance and high hardness are not exhibited. When the particle size is below the above range, the powder forms aggregates and does not have a uniform composite structure. When the particle size is above the above range, the sinterability is poor, the strength is low, and the high density is not achieved. The use amount of the ceramic particles is desirably 50 to 95 wt%. If it is less than 50%, it is difficult to exhibit the heat resistance, high strength, and high hardness characteristics of ceramics, and if it is more than 96 wt%, the composite effect of the BN composite is not sufficient.

The BN precursor used in the present invention must have a (002) plane spacing of BN in the range of 2.15 to 2.40 ° by X-ray diffraction and a crystallite size of 50 to 2000 °. Desirably, the BN precursor has a B ₂ O ₃ content contained as an impurity.
It is less than 5 wt%. X-ray diffraction of BN precursor (0
02) If the plane spacing exceeds 2.40 ° or the crystallite size is less than 50 °, crystallization by sintering becomes difficult, and the improvement of properties by composite, for example, the improvement of slidability and workability, cannot be realized. If the (002) spacing is less than 2.15 mm or the crystallite size exceeds 2000 mm, uniform mixing of the BN particles and the ceramic particles becomes difficult, and the types of ceramics to be composited are limited. The strength and precision of the machined surface are inferior. When the B ₂ O ₃ component in the BN precursor is 5 wt% or more, the B ₂ O ₃ component remains in the fired body, and the strength, workability, and sliding characteristics may be poor.

The BN precursor according to the present invention has insufficient development of BN crystal and small crystallites, but therefore has excellent activity, generally has good compatibility and dispersibility with ceramics, and has a firing temperature of ceramics to be used. Easily crystallizes into BN. The method for synthesizing such a BN precursor is, specifically, a conventionally known synthesis method, for example, using boric acid, boron oxide, ammonium borate or the like as a boric acid source, urea, melamine, nitrogen such as dicyandiamide, or the like. Can be obtained by a method of nitriding reduction using an organic substance containing, a method of decomposing diborane, a CVD method, or the like, but a reduction nitriding method is industrially preferable. In these methods, it is necessary to select specific conditions in order to satisfy the above BN precursor conditions.

The amount of the BN precursor used in the present invention is desirably 5 to 50% by weight. If the content is 5 wt% or less, the composite effect of the BN composite may be insufficient as described above, and if the content is 50 wt% or more, the high strength and high hardness characteristics of the ceramic body are not exhibited.

The method for producing a ceramic-BN composite material of the present invention comprises:
After mixing the above-mentioned limited ceramic particles and the BN precursor, they are preformed by die pressing, casting, injection molding or the like. If necessary, after degreasing, insert the preform into a hot die, glass capsule, metal capsule, etc.,
It is obtained by firing in a non-oxidizing atmosphere at a pressure of 10 to 120 MPa, preferably 20 to 100 MPa, at the firing temperature of the ceramic.

Generally, hot pressing is used for hot dies, and HIP (hot isostatic pressing) is used for capsules. As the atmosphere gas, Ar, He, N ₂ , CO, or the like is used alone or in combination of two or more, depending on the type of ceramic.

[Examples] Next, the features of the ceramics-BN composite material obtained by the present invention will be described in detail in Examples.

Examples 1 to 10 and Comparative Examples 1 to 6 Examples 1 to 10 correspond to the ceramic particles and BN shown in Table 1.
The precursor is wet-mixed in ethanol, dried, preformed by a die press, and then hot-pressed at a predetermined atmosphere and temperature at a pressure of 10 to 60 MPa.

Comparative Example 1 was obtained by sintering without pressure at a predetermined temperature. Comparative Examples 2 to 6 were fired under the same conditions as the examples.

Table 1 shows the strength and the like of the composite material. Flexural strength is based on JIS1604R, hardness is 10 kgf load by Vickers hardness tester, friction coefficient and wear amount are 3 kgf load by pin-on-disc method, and the plain ceramic sintered body is selected as the mating material. At 300 rpm. The precision of the machined surface was measured by grinding with a surface grinder to Rmax = 1.20 s, lapping with a polishing machine with 3 μm diamond paste, polishing with 1 μm diamond paste, and measuring with a radar type non-contact surface roughness meter.

When the composite material of Example 1 was applied to a mechanical seal, the sealability was better and the durability for a long time was shown as compared with the conventional material.

When the rolling bearing retainer of the composite material of Example 4 was precision machined and used, it showed no lubrication and long-term durability.

When the composite material of Example 5 was used as a twisted yarn ring, it exhibited a lower coefficient of friction and higher durability than the conventional material.

When the composite material of Example 7 was used as a magnetic head stabilizer, it exhibited no lubrication and long-term durability.

When the composite material of Example 10 was applied to a wire drawing die for a steel wire, there was no seizure of the steel wire and a long-term durability was exhibited.

Further, by using the parts using the present invention in various contact portions that are in sliding contact with the above-described magnetic medium, the sliding characteristics with the medium are improved, the friction coefficient is small, and the recording / reproduction is stable for a long time without damaging the medium. Characteristic was able to be given.

[Effects of the Invention] As described above, in the ceramic-BN composite material prepared according to the present invention, the composite ratio of the ceramic and the BN precursor is limited, and the firing conditions are limited. It is a material that is excellent in sliding characteristics and processed surface accuracy while maintaining the same. Therefore, bearings, mechanical seals,
It is a very suitable material for a non-lubricated sliding member such as a magnetic head slider. The use of the composite material of the present invention significantly improves the durability and reliability of the device, and is industrially useful.

Claims (2)

(57) [Claims] 1. The BN (002) plane spacing by X-ray diffraction is 2.15 to
2.40Å and BN precursor 5 with a crystallite size of 50Å2000Å
A method for producing a ceramic-BN composite material, comprising preforming a mixture of 50 wt% and ceramic particles of 95 to 50 wt%, followed by firing at a pressure of 10 to 120 MPa. 2. The ceramic particles are characterized in that they are composed of one or more particles of oxides, carbides, nitrides or borides, and their content is 50 to 95% by weight. A method for producing a ceramic-BN composite material according to claim 1.