JPWO2010001762A1 - Sliding member and mechanical seal - Google Patents

Abstract

To provide a sliding member having improved adhesion between a substrate and a coating film and having excellent corrosion resistance and wear resistance, and a mechanical seal using the sliding member. A base material 50 including a composite material of silicon carbide 52 having high thermal conductivity and carbon 51 softer than silicon carbide; and a coating film 54 formed on the surface of the base material 50 and including a synthetic resin. A sliding member.

Description

  The present invention relates to a sliding member suitable for use in a mechanical seal and the like, and a mechanical seal using the same. More specifically, the present invention relates to a sliding member that improves the adhesion between a substrate and a coating film and has excellent wear resistance. The present invention relates to a moving member and a mechanical seal using the same.

  The mechanical seal is a typical sealing device used for a shaft seal portion of various rotating machines. Specifically, the sliding member that rotates together with the rotating shaft and the sliding member provided on the fixed side that does not rotate slide closely against each other at the facing end faces, thereby preventing leakage of the sealed fluid. .

For example, in the case of a mechanical seal in which an atmosphere such as gas or mist is used under dry or semi-dry conditions, the lubricity of the seal liquid cannot be expected. Therefore, of the two materials facing each other (rotating side sliding member and fixed side sliding member), the soft side material is made of carbon material, graphite, glass fiber, carbon, etc. due to its characteristics such as self-lubrication and wear resistance. A tetrafluoroethylene resin (PTFE resin) -based material in which aggregates such as fibers are blended is generally used. On the other hand, silicon carbide (SiC), alumina (Al ₂ O ₃ ), cemented carbide (tungsten carbide), or the like is used as the material of the hard side member.

  However, the wear of the soft side member progresses with time and often reaches the end of its life in a short time, and there are cases where the wear powder generated at the time of wear contaminates the sealing atmosphere. For this reason, there is a problem that its use is restricted when it is necessary to prevent contamination of foreign substances such as in the production process of foods and pharmaceuticals.

  In order to solve this problem, for the purpose of improving wear resistance, a sliding material in which a synthetic resin is coated on a metal material is also considered, but in this case, galling occurs when the coating is peeled off, There were problems such as greatly affecting the slidability.

  Patent Document 1 discloses that a coating containing a solid lubricating material is performed on the surface of a base material as a sliding material. However, such a coating has a problem in adhesion to the substrate, and it is considered that the coating film can be peeled off.

  Patent Document 2 discloses a sliding member in which a surface of a metal base material is coated with a resin layer containing a fluororesin or the like. However, when a metal is used as the base material, there is a problem that abnormal noise is generated during sliding.

JP 2001-26792 A JP 2006-275280 A

  This invention is made | formed in view of such an actual condition, The objective is to provide the sliding member in which a base material and a coating film have favorable adhesiveness, and a mechanical seal using the same.

  As a result of intensive studies to achieve the above object, the inventors of the present invention have used a composite material of silicon carbide and carbon as the base material of the sliding member, thereby forming the base material surface and the surface thereof. As a result, it was found that the adhesion with the coating film containing a synthetic resin can be improved, and the present invention has been completed.

That is, the sliding member according to the present invention is
A substrate comprising a composite material of silicon carbide and carbon;
And a coating film formed on the surface of the base material and containing a synthetic resin.

  In the present invention, the base material includes a composite material of silicon carbide (SiC) and a carbon material softer than silicon carbide. On the surface of such a base material, convex portions made of silicon carbide and concave portions made of carbon are appropriately formed, and the surface of the base material can be made into a complex network surface. it can. And the convex part comprised from a silicon carbide bites into a coating film by forming the coating film containing a synthetic resin on this surface. As a result, it is possible to improve the adhesion between the substrate and the coating film that are usually difficult to adhere.

  Synthetic resins generally have thermal characteristics such as low thermal conductivity and high thermal expansion coefficient specific to the resin, and are not inherently suitable for the sliding surface. However, since the above silicon carbide has high thermal conductivity, even if heat is generated by friction on the sliding surface (coating film), heat is easily radiated through the silicon carbide that has bitten into the coating film. Therefore, the thermal characteristics such as low thermal conductivity and high thermal expansion coefficient of the synthetic resin are not particularly problematic.

  Preferably, the coating film includes a polyether ether ketone resin (PEEK resin).

  By using the PEEK resin as the synthetic resin contained in the coating film, the coating film can be made excellent in wear resistance and corrosion resistance. Therefore, for example, by using a coating film containing PEEK resin as a sliding surface even in an atmosphere of acid, alkali, etc., the sliding member according to the present invention has excellent corrosion resistance and without peeling of the coating film. Abrasion resistance can be shown.

  Preferably, the surface roughness Ra of the surface of the base material on which the coating film is to be formed is 0.25 μm or more.

  By setting the surface roughness Ra of the substrate surface to a specific range, the adhesion between the substrate and the coating film can be further improved, and peeling of the coating film can be effectively prevented.

  Preferably, the ratio of the area occupied by the silicon carbide is 10 to 70% with respect to the area of the surface of the base material on which the coating film is to be formed. Preferably, the average thickness of the coating film is 0.01 to 0.35 mm.

  By adjusting the ratio of the area occupied by silicon carbide to the surface area of the base material and the average thickness of the coating film within the above range, the adhesion between the base material and the coating film is maintained while maintaining good wear resistance. Can be improved.

  Preferably, the coating film further contains a tetrafluoroethylene resin. Since the tetrafluoroethylene resin (PTFE resin) functions as a lubricant, it can improve the slipping property on the coating film, that is, the sliding surface, and can further improve the wear resistance.

  The mechanical seal which concerns on this invention has the sliding member in any one of said as a sealing ring for fixation and a sealing ring for rotation. As described above, the sliding member of the present invention has good adhesion between the coating film and the substrate, and is excellent in corrosion resistance and wear resistance. Therefore, the sliding member is suitable as a sealing ring in a mechanical seal. Therefore, the mechanical seal according to the present invention can effectively prevent foreign substances such as wear powder from being mixed even in an atmosphere where corrosion resistance such as acid and alkali is required. In the mechanical seal according to the present invention, the sliding member of the present invention may be used as both a sealing ring and a sealing ring for rotation. Or you may use as a sealing ring for fixation, and may be used as a sealing ring for rotation.

  In the present invention, the base material includes a composite material of silicon carbide and carbon having high thermal conductivity, and the complex surface having a mesh shape in which convex portions (silicon carbide) and concave portions (carbon) are appropriately formed. Have a state. Therefore, even when a coating film containing a synthetic resin is formed on the surface of the base material, it is possible to obtain a sliding member in which the convex portions on the surface of the base material bite into the coating film and the adhesion with the coating film is improved. it can.

  In particular, when the coating film contains a PEEK resin as a synthetic resin, a sliding member having excellent corrosion resistance and wear resistance can be obtained even in an atmosphere of acid, alkali, or the like. Furthermore, by making the surface roughness Ra of the substrate surface, the ratio of the area occupied by silicon carbide in the area of the substrate surface, the average thickness of the coating film, and the like within the above preferable ranges, the adhesion between the substrate and the coating film is achieved. It is possible to further improve the performance and wear resistance.

  Moreover, according to this invention, the mechanical seal which has said sliding member as a sealing ring is obtained. The mechanical seal of the present invention exhibits good sealing properties because the coating film does not peel off and is excellent in wear resistance even in an atmosphere where corrosion resistance is required.

FIG. 1 is a schematic view showing a process of forming a coating film on the surface of a base material of a sliding member according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a mechanical seal using a sliding member according to an embodiment of the present invention and a test apparatus therefor. FIG. 3 shows measurement data of the surface roughness Ra of the sample according to the example of the present invention.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

Sliding member The sliding member of the present invention includes a base material and a coating film formed on the surface of the base material.

Base Material The base material constituting the sliding member of the present invention includes a composite material of silicon carbide (SiC) having high thermal conductivity and extremely hard silicon carbide and silicon carbide.

  As such a composite material of silicon carbide (SiC) and carbon, a reactive sintering type in which metal silicon is melt-impregnated and reacted in pores having a complicated shape of carbon in an inert atmosphere at about 1500 ° C. It is particularly preferable to use a SiC / carbon composite as a base material.

  When a reaction sintered SiC / carbon composite material is used as a base material, as will be described later, a convex portion made of extremely hard SiC and a concave portion made of carbon are formed on the surface of the base material. be able to. Due to the presence of such concavo-convex portions, the surface of the substrate has a complicated network shape. As a result, when the coating film is formed on the surface of the base material, the convex portion bites into the coating film, and the adhesion between the base material and the coating film can be improved.

Coating film The coating film which comprises the sliding member of this invention has a synthetic resin at least. Synthetic resins have thermal properties such as low thermal conductivity and a high coefficient of thermal expansion, and therefore have a problem of poor sliding properties when used on sliding surfaces where heat is generated by sliding. .

  However, in the present invention, by forming a coating film containing a synthetic resin on the surface of the base material having the above-described uneven portion, the frictional heat generated on the coating film (sliding surface) by sliding is applied to the coating film. The protrusions (SiC) on the surface of the base material that have penetrated into the substrate effectively radiate heat. Therefore, the deformation of the coating film due to heat becomes almost negligible, and the thermal characteristics of the synthetic resin do not become a problem. Furthermore, the slipperiness in the adhesion state accompanying the softening of the coating film by heat is improved, and the discharge of wear powder is also improved.

  In the present embodiment, polyether ether ketone resin (PEEK resin) is used as the synthetic resin. This is because the PEEK resin is excellent in corrosion resistance and wear resistance. By using the PEEK resin, a sliding member having good corrosion resistance and wear resistance can be obtained even in an atmosphere of acid, alkali or the like.

In the present embodiment, the coating film may further contain a tetrafluoroethylene resin (PTFE resin). PTFE resin is a solid lubricant, and by being contained in the coating film, it can improve the slipperiness on the sliding surface and improve the wear resistance. As the solid lubricant, in addition to PTFE resin, MoS ₂ (molybdenum disulfide), graphite powder, or the like may be used.

  The content of the PTFE resin is preferably 5 to 25% by weight and more preferably 10 to 15% by weight with respect to 100% by weight of the synthetic resin contained in the coating film. If the content is too small, the effect of improving the slipperiness tends not to be obtained. If the content is too large, the hardness of the coating film is lowered and scratches due to foreign matters tend to occur.

  The process of forming this coating film on the surface of the substrate (SiC / carbon composite material) will be described with reference to FIG. FIG. 1A is a schematic cross-sectional view of the substrate 50. As shown in FIG. 1A, in the base material 50, SiC 52 having a complicated shape is dispersed in carbon 51. Next, in this base material 50, the surface roughness Ra of the surface on which the coating film is to be formed is adjusted.

The method for adjusting the surface roughness Ra is not particularly limited. For example, a method of lapping with a polishing liquid in which SiC particles or alumina (Al ₂ O ₃ ) particles are dispersed in oil or water, or ceramic particles is used. A method of performing shot blasting can be mentioned. In this case, the abrasive particles are preferably softer than silicon carbide and harder than carbon.

  In this embodiment, as shown to FIG. 1 (A), the base material 50 is wrapped with a polishing liquid to a dotted line part. Then, as shown in FIG. 1B, the relatively soft carbon 51 is polished and removed to form a recess. On the other hand, the hard SiC 52 is not so much polished and remains so as to form a ridge-like convex portion on the lapping surface. In this way, the surface of the base material can be formed into a complicated mesh shape, and the surface roughness Ra can be calculated from the sizes of the concave portions and the convex portions.

  The surface roughness Ra is preferably 0.25 μm or more, more preferably 0.50 μm or more. Moreover, as an upper limit of Ra, it is preferable that it is 5 micrometers or less. If the value of Ra is too small, the adhesion between the substrate and the coating film tends not to be improved. On the other hand, if Ra is too large, the SiC convex portion tends to drop off from the carbon portion, and conversely, the adhesion tends to be inferior.

  Next, a coating film 54 having a PEEK resin is formed on the surface having the surface roughness Ra. The forming method is not particularly limited, and examples thereof include a powder method and a solution dispersion type (dispersion) method. As shown in FIG. 1C, the hook-shaped SiC 52 (convex portion) bites into the coating film 54 formed. Therefore, the base material 50 and the coating film 54 are engaged with each other in a complicated manner, and the adhesion between the base material 50 and the coating film 54 can be improved.

  In particular, when the above-described reaction sintered type SiC / carbon composite is used as the base material, the convex SiC formed on the surface can be made more complex, and the uneven portions are dispersed. It exists and a very complex mesh surface is obtained. As a result, the improvement in adhesion becomes remarkable. Furthermore, since the contact area between SiC and the coating film increases, the heat dissipation effect is also enhanced.

  The average thickness of the coating film is preferably 0.01 to 0.35 mm, more preferably 0.02 to 0.25 mm. When the value of the average thickness is too small, silicon carbide which is a convex portion tends to be undesirably exposed on the surface of the coating film. On the other hand, if the value of the average thickness is too large, heat dissipation through silicon carbide is hindered, and wear powder discharge becomes worse, with the result that wear resistance tends to deteriorate.

Mechanical seal Next, the mechanical seal according to the present invention will be described in detail with reference to the drawings. FIG. 2 is a cross-sectional view of a mechanical seal and its test apparatus according to this embodiment using the sliding member of the present invention.

  In FIG. 2, the mechanical seal 1 is held via an O-ring 31 on the inner periphery of a housing 30 that surrounds the outer peripheral side of the rotary shaft 20. The seal portion of the mechanical seal 1 includes a rotation seal ring 2 and a fixing seal ring 3. In this embodiment, the sealing ring 2 for rotation and the sealing ring 3 for fixation which this mechanical seal 1 has are comprised by the sliding member of this invention. However, one sealing ring for rotation or fixing may be constituted by the sliding member of the present invention.

  The rotation sealing ring 2 is formed on a fitting surface whose inner peripheral surface is slidably fitted to the rotation shaft 20. An O-ring step is formed on one end of the fitting surface. An O-ring 24 is attached to the O-ring step so as to seal between the fitting surfaces of the rotary seal ring 2 and the rotary shaft 20.

  Further, an intermediate ring 21 having an L-shaped cross-section that holds an O-ring 24 provided on the O-ring step of the sealing ring 2 for rotation from one side is arranged in a state of being slidably fitted to the rotary shaft 20. Yes. The intermediate ring 21 is engaged with a guide pin fixed to the O-ring 24 in an axial direction and is engaged in a locked state in the circumferential direction. Further, the intermediate ring 21 is pressed by a plurality of springs 22 arranged at equal intervals in the circumferential direction of the rotating shaft 20. The plurality of springs 22 are seated in respective spring mounting holes provided in the O-ring 24, and the other ends elastically press the rotation sealing ring 2 via the intermediate ring 21. As a result, the rotation-side sliding surface 2a and the fixed-side sliding surface 3a are in contact with each other so as to be slidable. The O-ring 24 is fixed to the rotary shaft 20 by a set screw, and is held via a guide pin and a rotation stop pin so that the intermediate ring 21 and the rotation sealing ring 2 do not rotate.

  The fixing seal ring 3 is provided with an inner peripheral surface that is fitted to the rotary shaft 20, and a convex portion that is provided with a fixed-side sliding surface 3 a at the tip thereof. The fixing sealing ring 3 is provided with a fitting surface that is attached to the mounting step portion of the housing 30 in a fitted state. Further, the fixed sealing ring 3 is in contact with the support surface provided at the mounting step portion and is fixed in sliding contact with the rotating side sliding surface 2a of the rotating sealing ring 2 so as to be slidable. A back surface for supporting 3a is provided. In addition, an O-ring groove is provided in the mounting step portion of the housing 30, and an O-ring 31 is attached to the O-ring groove to seal between the two fittings.

  The mechanical seal 1 of the present invention has an atmosphere in which corrosion resistance such as an acid or alkali atmosphere is required because both or one of the sealing ring 2 for rotation and the sealing ring 3 for fixing is constituted by the sliding member of the present invention. In this case, good wear resistance can be exhibited.

  In particular, the mechanical seal 1 in which both the rotation sealing ring 2 and the fixing sealing ring 3 are constituted by the sliding member of the present invention has the following advantages. That is, by configuring both the rotating and stationary sealing rings with the sliding member of the present invention, it is difficult for only one of them to wear out. Furthermore, since the components of the coating film are the same, the coating film slides in a state in which the unevenness of the sliding trace generated by the sliding of the coating films (the rotating side sliding surface 2a and the fixed side sliding surface 3a) is engaged. Therefore, the sealing performance is improved as compared with the case where the smooth surfaces slide. Further, in a non-sliding state, the meshed surfaces are more closely adhered to each other due to the elastic deformation and slight repulsion of the coating film on the meshed surfaces.

  Hereinafter, the present invention will be described based on further detailed examples, but the present invention is not limited to these examples.

Example 1
As a base material, a SiC / carbon composite, a carbon simple substance, a SiC simple substance, and SUS304 were prepared. The SiC / carbon composite is a reaction sintered type in which carbon is impregnated with carbon in a vacuum atmosphere at 1500 ° C., and the area occupied by SiC and carbon on the polished surface (before coating) is shown in Table 1. It adjusted so that it might become a value. As the carbon, carbon graphite having a hardness of 105 was used. As the SiC, one sintered at normal pressure was used.

  Subsequently, the surface of the SiC / carbon composite, carbon simple substance, and SiC simple substance was polished with an oil slurry containing SiC particles of GC1000, the surface roughness Ra was adjusted, and after degreasing, it was dried. For the SUS304 material, the surface roughness Ra was adjusted by shot blasting. Table 1 shows the surface roughness Ra of the substrate surface before coating. FIG. 3 shows Ra measurement data for Sample No. 3. From FIG. 3, it can be confirmed that many convex portions are formed.

  Subsequently, the surface on which the surface roughness Ra was adjusted was spray-coated using a dispersion containing PEEK resin to form a coating film (sliding surface) and subjected to heat treatment. Thereafter, the coating film was lapped with a diamond slurry having an average particle size of 6 μm and finished smooth to produce a sliding member (sealing ring for rotation and sealing ring for fixing). The average thickness of the coating film was set to 0.06 mm.

  The obtained sliding member was mounted on a mechanical seal test apparatus shown in FIG. 2 and evaluated as follows. The rotation sealing ring was concentric with a size of φ56.5 × φ77 × 26.5 mm and a rotation-side sliding surface of φ56.5 × φ75 mm. The fixing sealing ring has a concentric shape with a size of φ56 × φ80 × 27 mm and a fixed sliding surface of φ58.6 × φ66.1 mm.

Sliding test A rotating sliding test was performed by a mechanical seal test apparatus shown in FIG. The test conditions were: rotation speed: 300 rpm, seal portion atmosphere: nitrogen atmosphere, seal portion pressure: 0.2 MPa, test time: 100 hours. The evaluation was performed for the amount of wear on the rotating side sliding surface and the stationary side sliding surface after 100 hours, the temperature of 1 mm immediately below the stationary side sliding surface, and the presence or absence of abnormal noise during the sliding test. The results are shown in Table 1.

Peeling test The sealing ring for rotation after the sliding test was immersed in hot water of 0.2 MPa-120 ° C for 1 hour. Then, after cooling to 40 ° C. or lower and drying, the presence or absence of peeling of the coating film was visually evaluated. The results are shown in Table 1.

  From Table 1, peeling occurred in the peel test in the sample (sample number 1) in which the base material is a simple carbon material and in the sample (sample number 5) in which the base material is a simple SiC material. In addition, the sample (sample No. 6) having the base material made of SUS304 did not cause peeling, but a sliding sound (abnormal noise) called a key was generated during the sliding test, and good results were obtained. There wasn't. Further, when the surface roughness Ra before coating was outside the preferred range of the present invention (Sample Nos. 7 and 8), peeling occurred in the peeling test.

Example 2
Except that the average thickness of the coating film was changed to the value shown in Table 2, a sealing ring for rotation and a sealing ring for fixing were prepared in the same manner as in Sample No. 3, and the same evaluation as in Example 1 was performed (Sample No. 11-16).

  Further, a dispersion was prepared by blending PEEK resin with an amount of tetrafluoroethylene resin (PTFE resin) having an average particle diameter of 20 μm shown in Table 2. And except having formed the coating film using this, it carried out similarly to sample number 3, and produced the sealing ring for rotation and the sealing ring for fixation, and performed evaluation similar to Example 1 (sample numbers 17- 19).

  Furthermore, instead of PEEK resin, PAI (polyamideimide) or epoxy resin was used and 10% of PTFE resin was blended to prepare a dispersion. Then, a rotating seal ring and a fixing seal ring were produced in the same manner as in sample number 3 except that a coating film was formed using this, and the same evaluation as in Example 1 was performed (sample number 20 and 21). The results are shown in Table 2. Sample number 13 in Table 2 is the same as sample number 3 in Table 1.

  Moreover, about the sample numbers 18, 20, and 21 of Table 2, the peeling test with respect to the corrosion resistance (acidity and alkalinity) shown below was done.

Peeling test The sealing ring for rotation after the sliding test of sample numbers 18, 20, and 21 was immersed in sodium hydroxide (NaOH) at 1 N-60C for 200 hours. Similarly, the rotary seal ring after the sliding test was immersed in hydrochloric acid (HCl) at 1N-60 ° C. for 200 hours. Then, after cooling to 40 ° C. or lower and drying, the presence or absence of peeling of the coating film was visually evaluated. The results are shown in Table 2.

  From Table 2, when the average thickness of the coating film is within the preferred range of the present invention (Sample Nos. 11 to 16), it is excellent in abrasion resistance and peeled off in a peeling test against 120 ° C. hot water. Did not occur.

  In addition, by including PTFE resin that enhances lubricity in the coating film, it is possible to improve wear resistance while maintaining good adhesion. However, since the hardness of the coating film tends to be low, streak-like marks were observed on the sliding surface after the test. Therefore, it was confirmed that the addition amount of PTFE resin is preferably small (sample numbers 17 to 19).

  Further, when PAI and epoxy resin were used as the coating film resin instead of PEEK resin, the wear amount, sliding temperature, and corrosion resistance tended to be inferior (Sample Nos. 18, 20 and 21). Therefore, it was confirmed that PEEK resin is preferable as the synthetic resin contained in the coating film.

Example 3
A sliding member was produced in the same manner as in Example 1 except that the fixing sealing ring and the rotating sealing ring were constituted by the sliding members shown in Table 3, and the same evaluation as in Example 1 was performed. The results are shown in Table 3.

  From Table 3, when the sealing ring for fixing and the sealing ring for rotation were not constituted by the sliding member of the present invention, the wear resistance deteriorated. In addition, Samples 23 and 24 generated abnormal noise during the sliding test.

50 ... Substrate 51 ... Carbon 52 ... SiC
54 ... Coating film

Claims (7)

A substrate comprising a composite material of silicon carbide and carbon;
A sliding member having a coating film formed on the surface of the base material and containing a synthetic resin.   The sliding member according to claim 1, wherein the coating film includes a polyether ether ketone resin.   The sliding member according to claim 1 or 2, wherein the surface roughness Ra of the surface of the base material on which the coating film is to be formed is 0.25 µm or more.   The sliding member according to any one of claims 1 to 3, wherein a ratio of an area occupied by the silicon carbide is 10 to 70% with respect to an area of a surface of the base material on which the coating film is formed. .   The sliding member according to any one of claims 1 to 4, wherein an average thickness of the coating film is 0.01 to 0.35 mm.   The sliding member according to claim 1, wherein the coating film further contains a tetrafluoroethylene resin.   A mechanical seal having the sliding member according to claim 1 as both or one of a sealing ring for fixation and a sealing ring for rotation.

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