JPH1182515A - Sliding member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the corrosion problem of a sliding member which consists by combining a carbite alloy and a ceramics. SOLUTION: In a sliding member which consists by combining a carbite alloy and a ceramics, the carbite alloy is made into a carbite alloy including no metal binding phase. Hard quality particles to compose a hard quality material are made in a carbite mainly of WC, and a part of the WC to compose the hard quality material can be replaced with other carbite, nitride, or oxide, and the sliding member can be made in a sintered body in which the metal binding phase consisting of the iron system metal such as Ni, Co, Cr, and Fe is included less than 1 wt.% to the all amount in the hard quality material. The metal component as a inevitable impurity in the carbite of the metal component is preferable to be as little as possible, but it is allowed until about 1 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member in which a fixed member and a rotating member are made of a combination of different materials.

[0002]

2. Description of the Related Art A sliding member made of a combination of different materials such as a hard material and a ceramic can be started even in a non-lubricated state at the time of starting as a bearing of a vertical axis pump or a diagonal axis pump. Is also known to exhibit a good lubrication state.

As such a combination material, Japanese Patent Publication No. Sho 63-6
No. 7048 discloses a combination of a cemented carbide of 75 to 90% by weight with SiC and Si ₃ N ₄ ceramics, and JP-A-5-87145 discloses a combination of TiC / N cermet and SiC, Si ₃ N 4. Each combination with ₄ ceramics is disclosed.

[0004] In addition to these combinations, WC-based cemented carbides and sliding members in which a WC-based hard alloy is combined with ceramics are known. Excellent in dynamic characteristics and tribological characteristics.

[0005] The device configuration of these sliding members is that a shaft mainly made of stainless steel is combined with a movable sliding member such as a cemented carbide or a hard alloy such as cermet as a sleeve, and the fixed sliding member is made of SiC or SiC. It is made of a ceramic material such as Si ₃ N ₄ and is used in air or water.

[0006] Stainless steel causes a passivation phenomenon in corrosive solutions such as water and seawater, and is noble in terms of potential, and exhibits excellent corrosion resistance. On the other hand, in a cemented carbide containing a metal binder phase such as a WC-Co-based cemented carbide or a WC-Ni-based cemented carbide, particularly, the parts of Co and Ni, which are the binder phase metals, are more electrically potential than stainless steel. It takes a corrosion form in which potential difference corrosion, that is, galvanic corrosion occurs and metal components are preferentially eluted. The same phenomenon occurs when the hard phase is made of another carbide such as TiC instead of WC.

In the case where two sliding members are in contact with each other or form a gap of 1 mm or less as a device configuration, an oxygen concentration cell is formed in the gap, and the pH value is locally reduced. Also, a phenomenon in which the Ni and Ni portions are preferentially dissolved and corroded also occurs.

Further, in the case of a combination of the cemented carbide and the ceramic, in particular, WC-Co based cemented carbide and WC-
A cemented carbide containing a metal binding phase such as a Ni-based cemented carbide has the disadvantage that the intergranular corrosion of hard particles, that is, the dissolution corrosion of the metal binding phase is likely to proceed, and the sliding characteristics are likely to deteriorate.

[0009]

An object of the present invention is to solve the problem of corrosion of a sliding member made of a combination of a cemented carbide and a ceramic.

[0010]

According to the present invention, the intergranular corrosion of a sliding portion composed of a combination of a cemented carbide and a ceramic is achieved by preferentially corroding the metal components of Co and Ni as a binder phase. It was completed based on the finding that it was caused.

That is, the present invention is characterized in that in a sliding member made of a combination of a cemented carbide and a ceramic, the cemented carbide is a cemented carbide containing no metal binding phase.

The hard particles constituting the hard material are made of carbide mainly composed of WC, and a part of the WC constituting the hard material can be replaced by another carbide, nitride or oxide. A sintered body containing 1% by weight or less based on the total amount of a metal binding phase composed of an iron-based metal such as Co, Cr, and Fe can be obtained.

The metal component as an unavoidable impurity in the carbide of the metal component is preferably as small as possible, but is allowed up to about 1% by weight.

According to the present invention, it is possible to obtain a sliding member having excellent wear resistance and corrosion resistance enough to withstand use in seawater.

[0015] As the sliding member, the movable sliding member incorporated in the shaft made of stainless steel has a sleeve made of a sintered material having no metal component mainly composed of WC and a sliding member made of ceramics on the fixed side. Even if the pump incorporating the moving member is used in seawater, it will work perfectly in one year of actual operation.

This is because, in a cemented carbide containing a metal binder phase, particularly the parts of the binder phase metals such as Co and Ni become lower in potential than stainless steel, causing potential difference corrosion, that is, galvanic corrosion, and the metal component is preferentially produced. In the present invention, preferential dissolution corrosion reaction can be prevented by eliminating or extremely reducing the metal components of Co and Ni which cause a corrosion reaction. Further, it is possible to suppress a decrease in sliding characteristics due to corrosion.

Further, instead of the hard phase WC, TiC, TiC
The same effect can be obtained even if the composition is replaced with another carbide such as N or a carbonitride.

It is known that the hardness of a cemented carbide depends on the component ratio between the hard phase WC and the metal binding phase Co or Ni, that is, the hardness decreases as the component ratio of the metal binding phase Co or Ni increases. . The wear resistance of the sliding material largely depends on the hardness of the material. If a high sliding wear resistance is required, it is more advantageous to use a material having a lower component ratio of the metal bonding phase Co or Ni, that is, a material having a higher hardness. .

In the present invention, metal components such as Co and Ni are reduced as much as possible in order to improve the corrosion resistance as described above. Alternatively, an extremely reduced hard sintered alloy has higher hardness than conventional cemented carbides, significantly improves wear resistance, and improves sliding characteristics.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically by way of examples.

Example 1 As a commercially available raw material powder, a powder forming a hard phase was WC,
TiC, TiN, TaC, etc. were mixed by a wet ball mill after predetermined mixing using Co and Ni as binder phase metal components, dried and press-molded. This is 1300-16
Sintered in vacuum at 00 ° C. The composition is shown in Table 1. The physical properties of hardness (HrA) and strength (flexural strength: GPa) of the obtained sintered body were examined. The corrosion resistance was evaluated using seawater, 10% sulfuric acid solution, 10%
A nitric acid solution was used. The corrosion test was performed on each sample (4 × 8 × 2) which had been front ground and finished in a beaker containing a 500 cc solution.
5) was immersed for 48 hours, the weight loss was measured, and the corrosion rate was calculated and displayed by (g / m ² × day) from the surface area and time.

[0022]

[Table 1] In all the alloys 1 to 16 shown in Table 1, the hardness decreases as the amount of iron-based metal increases. The wear resistance of the sliding material largely depends on the hardness of the material. If high sliding wear resistance is required, the component ratio of the metal bonding phase Co or Ni is lower, that is, the iron-based metal component is small, It is more advantageous to use a hardened material. On the contrary, the strength has been decreasing due to the decrease in the amount of iron-based metal, but the practical strength is 1 GP.
About a is practically sufficient, and it has been confirmed that the alloy of the present invention is in a sufficiently usable range.

FIG. 1 shows a graph in which the corrosion rates of the alloys 1 to 16 shown in Table 1 in the corrosion solution, seawater, 10% sulfuric acid solution, and 10% nitric acid solution are plotted against the amount of iron-based metal. It can be seen that the corrosion rate increased with an increase in the amount of iron-based metal.
% Or more, the corrosion rate increases linearly, but when it is less than 2%, it shows a sharp decrease. At about 1% or less, the corrosion rate is reduced by one to two digits and the corrosion resistance is improved. You can see that. In other words, it can be seen that those with the amount of iron-based metal suppressed to about 1% or less have significantly improved corrosion resistance in addition to wear resistance, and exhibit excellent characteristics as a sliding material.

Example 2 In this example, the results found by the basic experiment of Example 1 were subjected to an actual machine test to evaluate the characteristics.

FIG. 2 is a sectional structural view of a pump used in the actual machine test. FIG. 3 shows a sectional structural view of a bearing portion of the pump.

First, a bearing provided with the sliding member of the present invention will be described with reference to FIGS. In FIG. 2, reference numeral 1 denotes a bearing portion to which the sliding member of the present invention is provided, 2 denotes a shaft shaft, and 3 denotes a casing.
3 in the sectional structural view of the bearing portion of the pump 2 is a shaft shaft,
Reference numeral 4 denotes a movable sliding portion in which the hard sintered alloy of the present invention fitted to a shaft is provided in a sleeve shape, and 5 denotes SiC or Si _3.
Stationary sliding portion composed of a ceramic material such as N _4, 6
Denotes a rubber portion for absorbing vibration of the ceramic fixed sliding portion, and 7 denotes a bearing case.

An operation test of an actual pump was performed in such a configuration. The test conditions were seawater + sand concentration 20
The pressure was set to 00 ppm, and a surface pressure of 1 kg / cm ² was forcibly applied to the sliding portion during an operation time of 240 hours. As an evaluation, the test piece was disassembled after completion of the test, and the amount of wear (abrasion depth: mm) in the radial direction of the sliding portion on the movable side where the invention alloy was provided in the form of a sleeve and the presence or absence of corrosion were confirmed by surface and cross-sectional observation.

Table 2 shows the composition of the sample subjected to the actual pump operation test, the amount of radial wear (abrasion depth: mm) of the sliding part on the movable side, and the presence or absence of corrosion as determined by observing the surface and cross section. The results are shown.

[0029]

[Table 2] In the product of the present invention in which the iron-based metal component is suppressed to 1% or less,
The amount of wear was very small at 0.1 mm or less, and no corrosion was observed. The clearance between the movable side and the fixed side of the sliding portion is 0.5 mm by default, and if the amount of wear exceeds 0.1 mm, it is not preferable in terms of sliding characteristics. In the comparative products, those having a 2% iron-based metal component had an abrasion amount of 0.1 mm, and some corrosion was observed. 5%
As described above, those having an iron-based metal component were greatly corroded, and were observed to be greatly worn due to a decrease in strength due to the corrosion and a low hardness of the iron itself.

[0030]

The sliding member according to the present invention has the following effects.

(1) Corrosion resistance to seawater is greatly improved.

(2) Corrosion resistance to an acidic solution is greatly improved.

(3) Abrasion resistance is improved due to high hardness.

(4) The characteristics as a sliding member are greatly improved by improving both the corrosion resistance and the wear resistance.

[Brief description of the drawings]

Fig. 1 Relationship between ferrous metal content and corrosion rate

FIG. 2 is a sectional structural view of a pump used in an actual machine test.

FIG. 3 is a cross-sectional structural view of a pump bearing used in an actual machine test.

[Explanation of symbols]

1: Bearing part to which the sliding member of the present invention is provided 2: Shaft shaft 3: Casing 4: Sleeve-shaped movable sliding part fitted to the shaft shaft 5: Ceramic material such as SiC or Si ₃ N ₄ Fixed side sliding part 6: Rubber part that absorbs vibration of ceramic fixed sliding part 7: Bearing case

Claims (4)

[Claims] 1. A sliding member in which a fixed member and a rotating member are made of a combination of a hard material and a ceramic, wherein the hard material is made of a sintered body of hard particles containing no metal binding phase. Element. 2. A sliding member in which a fixed member and a rotating member are made of a combination of a hard material and a ceramic, wherein the hard material contains 1% by weight or less of the total amount of a metal binding phase. Element. 3. The sliding member according to claim 1, wherein the hard particles constituting the hard material are made of carbide mainly composed of WC. 4. A sliding element according to claim 1, wherein a part of carbide mainly composed of WC constituting the hard material is replaced by another carbide, nitride or oxide. Element.