JPS6136173A - High temperature solid lubricating ceramics - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention has excellent hardness, toughness, corrosion resistance, and oxidation resistance, and above all, has a friction coefficient of 0.25 or less, a low wear rate, and is self-lubricating. Regarding excellent ceramic sintered bodies.

[Technical background of the invention and its problems]

Traditionally, materials with self-lubricating properties include C14 and C.
o, Ni, Fe, Sn, Ag + M
MoS z + WS2 + CaFa for metals such as n
Metal-based materials containing a predetermined amount of highly self-lubricating substances such as HLI F2 + graphite are known.

This metal-based material has excellent electrical conductivity and thermal conductivity, but on the other hand, it has 1! : Hardness and poor wear resistance.
Since it softens significantly at high temperatures and has poor corrosion resistance, its use is completely restricted.

In order to solve such problems, the above-mentioned gold base material
Further, cermet materials have been developed which are made by blending transition metals of groups IVa, Va, and Va of the periodic table, or carbides and nitrides of these metals. Certainly, the abrasion resistance of this Ther-Met material is improved compared to the metal-based material. However, its hardness and toughness are still low, and since it contains gold and 4, its corrosion resistance is poor, and it undergoes softening and plastic deformation at high temperatures, so its field of use must be narrowly limited.

[Purpose of the invention]

The present invention eliminates vjAi between conventional lubricating materials, has high hardness and high toughness, and has corrosion resistance and oxidation resistance because it does not contain substantially any metal. The purpose of the present invention is to provide a ceramic sintered body having excellent properties, good thermal conductivity, and self-lubricating properties even at high temperatures.

[Summary of the invention]

In the course of conducting research on iron content to achieve the above objective, the present inventors found that all oxides of metal elements in groups IVa, Va, and Va of the periodic table become solid @ at temperatures up to 1000°C in the atmosphere. It has been found that oxides of Cr exhibit excellent lubricity. Based on all the above findings, even if the sliding surface of a lubricating material is made of carbide or nitride, for example, in the high-temperature atmosphere mentioned above, these carbides and nitrides existing on the sliding surface can be easily removed. The self-lubricating ceramic of the present invention was developed based on the idea that oxidation forms a dense film of carbonates, nitrides, carbonitoxides, and oxides, which improves the lubricity of sliding surfaces. reached.

That is, the high temperature solid @ slippery ceramics of the present invention has C
r carbides, nitrides, oxides, carbonitrides.

At least one selected from carbonates, nitrides, and carbonitoxides, and TiT (Zr + Hf) V t
Nb + Ta, Mo, W, St, B
, a hard phase consisting of at least one selected from carbides, nitrides, oxides of Y, and mutual solid solutions thereof, and unavoidable impurities.゛The essential components of the ceramics of the present invention include the following formula: (Cra.

Mb) (CX + Ny, Oz) ri11! whose composition is indicated by n. 4, which is a qualitative phase, where M n'ri , Zr , Hf , V
, Nb, Ta, Mo.

Represents any one or both of the metal elements of W. a
, bU are the molar ratios of Cr and M, respectively, and are 0 and 2
≦a<1. (1(b≦(], 8. A number that satisfies the relationship of a+b=1^O .4≦X≦1゜0
≦y≦(+, 5, 0≦2≦0.3, so x y y z
-1 relationship 'fr: Satisfied number. If 2 exceeds 0.3, the obtained sintered body will become an oxide living body, and its strength will not only decrease, but also the Cr oxide will have a high vapor pressure, making it difficult to use the sintered body during sintering. Also in Cr
The ingredients evaporate, making it unsuitable for quality control, soil burial, and environmental hygiene. X*'! + Z is 0.4≦X≦, respectively
1, 0≦y≦0.5, 0≦2≦0.3, x10y+
When the number satisfies the relationship z=1, it is preferable because not only the lubricity of the hard phase is excellent but also its high temperature strength is improved.

n is the overall molar ratio of nonmetallic elements (C, N, and O) to metallic elements (Cr and M), and its value is 0.44≦n
<1.33. If n is out of this range, the obtained hard phase is unlikely to be a strong compound mainly having the B1 structure, and a brittle lower compound will be formed, which is disadvantageous.

Furthermore, the hard phase described above may further contain one or more of carbides, nitrides, and oxides of S1+B+Y.

The ceramics of the present invention can be manufactured as follows.

A single powder of each compound belonging to the above group, or a mixed powder of two or more of them suitably mixed together, a powder of a mutual solid solution of these, further a powder of a mutual solid solution and a single powder of each compound, or a chemical powder. This is a method commonly used in powder metallurgy, in which a mixed powder consisting of a combination of various compounds is mixed in a ratio that is inversely specified based on the composition ratio of each component in the desired sintered body. Then, the obtained molded body is sintered under pressure or under pressure in a vacuum or in a non-oxidizing atmosphere such as nitrogen, hydrogen, argon, carbon oxide, etc.

Regarding the starting point, Cr+V, Tt, and other oxides of elements in the fourth period of the periodic table have small free energies of formation, and many lower oxides exist, making them relatively unstable compounds. When producing a sintered body only from these oxides, it is difficult to control the composition, and at the same time, the strength of the obtained sintered body becomes extremely low, which greatly impedes its practical use. Therefore, in the present invention J, the raw materials are not only oxides, but also carbides, nitrides, and carbonitrides.

It is desirable to blend carbonates, nitrides, and carbonitrides.

In the manufacturing process of the sintered body of the present invention, the starting materials are mixed and pulverized using a stainless steel container, a container lined with cemented carbide, or a container lined with urethane rubber as the medium. Hard metal balls or, for example, periodic table 4a.

Mix and grind together with a ball whose surface is coated with a compound of group 5a or 6a metal. In order to improve the grinding effect and make the starting material finer, it is best to mix and grind K with cemented carbide balls in a stainless steel container or a container lined with cemented carbide. It is preferable to add an organic solvent such as hexane, benzene, alcohol, etc. and perform wet mixing and pulverization.

For applications that utilize corrosion resistance and high-temperature abrasion resistance, etc., and when it is necessary to take into account impurities mainly made of metal, use a container lined with urethane rubber and mix with surface-coated balls. Good. Impurities are often mixed in during the mixing and grinding process, and among the cemented carbide used in the mixing and grinding process, the main component of cemented carbide is ■a of the periodic table.
, Va, and Ma group metal compounds are mixed as impurities without any problem in proportion, but the mixing of iron group metals, which are the binder phase of cemented carbide, should be kept at 2 volume or less, preferably 8 t% or less per body. is desirable.

For molding the mixed powder, the mixed and pulverized powder is filled in a graphite mold and hot pressed in a non-oxidizing atmosphere in 1-;
Alternatively, a molding aid such as paraffin or camphor may be added to the mixed and pulverized powder to form fine particles if necessary, and then the mixture is filled into a metal mold and pressure molded, or the mixed powder is surrounded with σ latex rubber, etc. After that, a method of applying external pressure using isostatic pressure to form the material can be applied. The powder compact formed in this way is directly sintered, or the powder compact is pre-sintered at a temperature lower than the sintering temperature, and then processed by cutting, grinding, cutting, etc. Can be sintered.

Regarding the conditions during sintering, for example, when a compound with a substoichiometric composition is used as the starting material, atomic vacancies act as a driving force for sintering, promoting sinterability even at low temperatures and no pressure. In addition, if the Cr content is high, KCr evaporates during sintering and the solid lubricity of the resulting sintered body tends to decrease, so high vacuum and Takagata sintering must be avoided. It is necessary to make an appropriate selection in relation to problems that arise in practice, such as . Therefore, the conditions during sintering cannot be uniquely determined because they vary depending on the composition of the starting materials.

Note that the obtained sintered body is further subjected to hot isostatic sintering (HI
Treatment with P) is effective because it further increases the strength of the sintered body.

In addition, when this sintered body is used as an actual high-temperature sliding member, if the sintered body is treated in advance in an oxidizing atmosphere and an oxide layer with a thickness of 10 μm or less is formed on the surface, the inside will have high strength. It is effective because only the surface exhibits both functions of high lubricity.

[Embodiments of the invention]

Examples 1 to 12 (11 Manufacture of sintered bodies and their characteristics Powders of various compounds shown in Table 1 (average particle size 0.2 to
3 μm) in the indicated ratio, and add 3 to 5 μm to this blended powder.
% of paraffin was added as a molding aid, and the mixture was mixed and ground in an acetone solvent using a WCC cemented carbide ball. After evaporating and drying the solvent from the obtained mixed powder, this mixed powder was molded under pressure of G, )It/d to 5t/crI, ■100
Hot press (H, P) at ~300 to 9/crIt pressure
) t, and the obtained molded body was heated at 10 to 10 mH.
r vacuum or Ar atmosphere, l 35 (1 to 1
'8 (Sintered at a temperature of 10° C. for 30 to 60 minutes.

The properties of each of the obtained sintered bodies are summarized in Table 1.

(2) Measurement of friction coefficient at each temperature Example number] For each sintered body of 2, 9, 10, and 11, a friction and wear simultaneous tester was used to measure the friction coefficient from room temperature to 1000.
A sliding test was conducted in the atmosphere up to ℃. In the test method,
A cylinder with an outer diameter of 26 holes, an inner diameter of 20 reductions, a height of 15 mm, and a 34 hole diameter.
A disk related to XIO was made from each sintered body, and the entire surface of the disk was in contact with a cylinder with the same sample number, and the load was 50 2 and the sliding speed was 20.
Friction and wear tests were conducted under the conditions of 0 tyn/sec, and 1
This method measures the friction coefficient at the time edge.

The results are shown in Table 2.

Table 2 (3) Measurement of friction coefficient and wear rate at various temperatures From each sintered body of Examples 1, 3, 6, 8 and Comparative Examples 2 and 3, outer diameter 26 gates φ inner diameter 20 gates φ height 15 Iol A cylinder with a diameter of 34 mm and a thickness of 10 mm was made of copper nitride (HR).
C55), and the load is 30k when the entire surface is in contact with each other.
A friction and wear test was conducted under the same conditions as (2) by applying f. The results are shown in Table 3. The sintered body of Comparative Example 2 has a higher friction coefficient and wear rate than the sintered body of the present invention, and the sintered body of Comparative Example 3 has low strength, so it cracks when a load is applied, especially at 600°C. , it was impossible to measure the friction coefficient and wear rate at 1000°C.

(4) Measurement of friction coefficient at each temperature A cylinder similar to (2) was manufactured using the sintered bodies of Examples 1, 3, 9. The friction coefficient at each temperature was measured in the same manner as in case (2) except that ester-based synthetic oil was used as a lubricant between the eight IOk cars.The results are shown in Table 4. Indicated.

Table 4 [Effects of the Invention] As is clear from the above explanation, the ceramic sintered body of the present invention has higher hardness than conventional lubricating materials, and has a toughness of 4 to 4 as judged from transverse rupture strength. 8 times higher, it has excellent thermal conductivity, corrosion resistance, and oxidation resistance. Also, because the hard phase has metallic properties, it has excellent electrical conductivity, and has a low friction coefficient and wear rate at high temperatures in the atmosphere. It was also confirmed that a sufficiently low coefficient of friction was maintained even when lubricating oil was present and the temperature was as high as 300°C.

Therefore, the lubricating ceramics of the present invention include journal bearings for turbochargers, thermal nJi rolling rolls,
Continuous six-stroke bearings, air spindle bearings, thrust bearings, etc. are used in the field of bearing parts and seal rings that operate at high temperatures while coming into contact with corrosive liquids such as lubricating oil, organic solvents, and chemicals. It can be used in a wide range of applications, such as friction parts such as J5 cylinders, food hygiene-related parts that require corrosion resistance, and its industrial value is extremely high.

Claims (2)

[Claims] (1) At least one selected from carbides, nitrides, oxides, carbonitrides, carbonates, nitrides, and carbonitrides of Cr, and Ti, Zr, Hf, V, Nb, Ta, Mo,
A high-temperature solid lubrication characterized by comprising a hard phase consisting of at least one selected from carbides, nitrides, oxides, and mutual solid solutions of W, Si, B, and Y, and inevitable impurities. sexual ceramics. (2) The hard phase has the following formula: (Cr_a, M_b) (C_
x, N_y, O_z)_n [However, in the formula, M is Ti, Z
represents a metal element consisting of at least one of r, Hf, V, Nb, Ta, Mo, and W; a and b represent the molar ratio of Cr and the metal element M; (
represents the molar ratio of carbon), N (nitrogen), and O (oxygen), where n
represents the molar ratio of the non-metallic elements that are the sum of C, N, and O to the sum of Cr and the metal element M, and the relationship is a+b
=1, 1>a≧0.2, 0.8≧b>0, x+y+z=
1, 1≧x≧0.4, 0.5≧y≧0, 0.3≧z≧0
, 1.33>n≧0.44. ] The high-temperature solid lubricating ceramic according to claim 1.