JP2016033418A - Internal combustion engine piston ring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine piston ring capable of preventing aluminum adhesion for a long period of time even under a high temperature, high load condition, and suppressing the self abrasion of a coat and the abrasion of a piston material.SOLUTION: An internal combustion engine piston ring 1 in which a piston ring base material 11 is coated with an aluminum adhesion resistant coat 12, is configured so that the aluminum adhesion resistant coat 12 is a composite coat consisting only of ceramics that contains second ceramics harder than first ceramics constituting a matrix with the first ceramics coating at least one of upper and lower side surfaces 11a and 11b of the piston ring base material 11 as the matrix.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a piston ring for an internal combustion engine, and more particularly to a piston ring for an internal combustion engine that can prevent aluminum adhesion over a long period of time even under high temperature and high load conditions, and can suppress self-wearing of the coating and wear of the piston material. It is.

  The three piston rings used in an internal combustion engine, the top ring, the second ring, and the oil ring, are arranged to engage with piston ring grooves provided on the surface of the piston, respectively, and combustion gas leaks from the combustion chamber to the outside. A gas seal function that prevents the piston from moving, a heat conduction function that transmits the piston heat to the cooled cylinder wall and cools the piston, and a function that applies engine oil as lubricating oil to the cylinder wall to scrape excess oil. have.

These three piston rings repeatedly collide with the groove inner surface in the piston ring groove of the piston when the piston reciprocates due to the explosion of fuel in the combustion chamber during the operation of the internal combustion engine. Further, since the piston ring is slidable in the circumferential direction in the piston ring groove, the piston ring slides in the piston ring groove. By the way, on the surface of the piston ring groove, a protrusion having a height of about 1 μm is formed by a lathe process for forming the groove, and the protrusion is fatigued and destroyed by the collision and sliding with the piston ring. The active aluminum alloy surface is exposed on the surface of the piston ring groove.
This exposed aluminum alloy surface comes into contact with the side surface of the piston ring due to a collision, and when it repeatedly slides, the aluminum alloy adheres to the side surface of the piston ring. Occurs). This is particularly noticeable in the top ring located closest to the combustion chamber and placed under high temperature conditions.

  As this aluminum adhesion further progresses, the piston groove wears rapidly, the gas seal function of the piston ring decreases, and a phenomenon called so-called blow-by occurs in which high-pressure combustion gas flows out from the combustion chamber to the crank chamber. This causes a problem that causes a reduction in engine output.

  In response to this situation, various techniques for preventing aluminum adhesion of piston rings have been proposed. For example, Patent Document 1 discloses a technique for improving conformability and preventing aluminum adhesion by providing a resin-based film containing carbon black particles on the side surface of a piston ring that collides with and slides on a piston ring groove. Is described.

  Patent Document 2 discloses that one or two or more powders selected from the group consisting of nickel-based powder, lead-based powder, zinc-based powder, tin-based powder, and silicon-based powder are 10 to 80 with respect to the entire surface coating. It describes a technique for effectively preventing aluminum adhesion to the piston ring by providing a heat-resistant resin containing mass% on at least one of the upper and lower side surfaces of the piston ring.

  However, in the case of the coatings described in Patent Documents 1 and 2, there is a problem that the aluminum adhesion resistance decreases when the temperature in the engine rises. Therefore, in Patent Document 3, a polyimide coating containing hard particles and having a solid lubricating function is provided on at least one of the upper and lower side surfaces of the piston ring, so that even under high temperature conditions exceeding 230 ° C., for a long period of time. A technique for maintaining high aluminum adhesion resistance is described.

Further, Patent Document 4 discloses a first diamond-like carbon (DLC) film containing at least silicon instead of a resin-based film, and at least W or W formed under the first DLC film. A technique for providing a piston ring having excellent aluminum adhesion resistance, scuff resistance and wear resistance by providing a second DLC film containing Ni on the upper and lower side surfaces of the piston ring is described.
Furthermore, Patent Document 5 describes a film obtained by vitrifying polysilazane containing hard nanoparticles.

JP 2007-278495 A JP 2008-248986 A International Publication No. 2011/071049 Pamphlet JP 2003-014122 A International Publication No. 2012/111826 Pamphlet

By the way, in recent years, downsizing of vehicles has progressed, and the amount of exhaust gas has been reduced in order to improve fuel efficiency. As a result, the temperature and pressure in the engine have been increasing. However, in the resin-based coating as in Patent Document 3, aluminum adhesion resistance is maintained over a long period of time under a high temperature condition exceeding 260 ° C. and a high load condition where the pressure in the engine exceeds 10 MPa. It is difficult.
In addition, the DLC film described in Patent Document 4 is graphitized under a high temperature condition exceeding 260 ° C., and oxidation proceeds in an oxidizing atmosphere, and the original characteristics of the DLC film are exhibited and the aluminum adhesion resistance is maintained. It is difficult to do.
Furthermore, the coating described in Patent Document 5 is sufficiently deteriorated under a high temperature condition exceeding 260 ° C. due to a chemical reaction such as oxidation of organic substances remaining in the coating upon conversion to silica or resin-based particles. May not be able to maintain high aluminum adhesion resistance, and may not be able to maintain aluminum adhesion resistance over a long period of time under high temperature conditions exceeding 260 ° C. and under high load conditions where the internal pressure of the engine exceeds 10 MPa. There is.

  Furthermore, in addition to the long-term prevention of aluminum adhesion under high-temperature and high-load conditions, the aluminum adhesion-resistant coating suppresses self-abrasion of the aluminum adhesion-resistant coating and attacks the piston material that is the counterpart material. It is also important to reduce the amount of wear of the piston material by reducing

  Accordingly, an object of the present invention is to provide a piston ring for an internal combustion engine that can prevent adhesion of aluminum over a long period of time even under high temperature and high load conditions, and can suppress self-wearing of the coating and wear of the piston material. is there.

  The inventors diligently studied how to solve the above problems. As a result, it has been found that it is extremely effective to make the aluminum anti-adhesion coating into a composite coating composed of ceramics in which two or more ceramics having different hardnesses are combined, and the present invention has been completed. .

That is, the gist of the present invention is as follows.
(1) A piston ring for an internal combustion engine in which a base material for piston ring is coated with an aluminum anti-adhesion coating, wherein the aluminum anti-adhesion coating covers at least one of the upper and lower side surfaces of the piston ring base material. A piston ring for an internal combustion engine, characterized in that it is a composite coating made of only ceramics, the second ceramics being harder than the first ceramics constituting the matrix.

(2) The Vickers hardness HV of the aluminum adhesion-resistant coating and the arithmetic average roughness Ra (μm) of the surface of the aluminum adhesion-resistant coating satisfy the following formula (A): Piston ring for internal combustion engines.
Ra <−8.7 × 10 ⁻⁵ HV + 0.39 (A)

(3) The internal combustion according to (1) or (2), wherein the Vickers hardness HV of the aluminum adhesion-resistant coating and the thickness h (μm) of the aluminum adhesion-resistant coating satisfy the following formula (B): Piston ring for engine.
H> -2.9 × 10 ⁻⁴ HV + 0.89 (B)

(4) The aluminum adhesive coating has the structure in which the layer made of the first ceramic and the layer made of the second ceramic overlap each other in a cross section in the thickness direction. The piston ring for internal combustion engines as described in any one of these.

(5) The piston for an internal combustion engine according to any one of (1) to (4), wherein the first ceramic constituting the matrix has a Vickers hardness HV of 500 to 1300. ring.

(6) The piston ring for an internal combustion engine according to any one of (1) to (5), wherein the second ceramic has a Vickers hardness HV of 1000 or more and 2500 or less.

(7) The piston ring for an internal combustion engine according to any one of (1) to (6), wherein the content of the second ceramic is 5% by weight or more and 40% by weight or less with respect to the entire coating film.

(8) The piston ring for an internal combustion engine according to any one of (1) to (7), wherein an arithmetic average roughness of a surface of the aluminum adhesion-resistant coating is 0.3 μm or less.

(9) The piston ring for an internal combustion engine according to any one of (1) to (8), wherein the thickness of the aluminum adhesion-resistant coating is 1 μm or more and 20 μm or less.

(10) The first ceramic constituting the matrix is at least one selected from the group consisting of titania, yttria, magnesia and alumina, and the second ceramic is alumina, zirconia, silica, chromia, aluminum nitride, The piston ring for internal combustion engines according to any one of (1) to (9), which is made of at least one selected from the group consisting of silicon nitride and silicon carbide.

  According to the present invention, the aluminum anti-adhesion coating is a composite coating composed of two or more ceramics having different hardnesses, and the matrix of the aluminum anti-adhesion coating is composed of the first ceramic having a relatively low hardness. Since the first ceramics contains a second ceramic that is harder than the first ceramic of the matrix, the coating is made more durable by reducing the attack of the coating against the other party. Even under conditions, aluminum adhesion can be prevented over a long period of time, and self-wearing of the coating and wear of the piston material can be suppressed.

1 is a schematic cross-sectional view of a piston ring for an internal combustion engine according to the present invention in a state of being engaged with a piston ring groove. It is a schematic diagram of the engine simulation test apparatus used for the Example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a piston ring for an internal combustion engine according to the present invention in a state engaged with a piston ring groove. The piston ring 1 for an internal combustion engine shown in this figure is a piston ring for an internal combustion engine in which a piston ring base material 11 is coated with an aluminum adhesion coating 12. Here, the aluminum anti-adhesion coating 12 is a first that constitutes a matrix using the first ceramic with relatively low hardness coated on at least one of the upper and lower side surfaces 11a and 11b of the piston ring base material 11 as a matrix. It is important to be composed of a composite coating made only of ceramics, containing a second ceramic that is harder than this ceramic.

  As shown in FIG. 1, the piston ring 1 closes the gap between the side wall of the cylinder 24 and the piston 20 while being engaged in the piston ring groove 21, and seals combustion gas and oil. The piston ring 1 follows the reciprocating motion of the piston 20 (the motion in the direction of the arrow in the figure), and the vertical motion occurs in the piston ring groove 21, and the upper surface of the piston ring 1 and the piston ring groove 21. The collision is repeated between 22 and the lower surface 23. Further, since the piston ring 1 is slidable in the circumferential direction in the piston ring groove 21, the piston ring 1 repeats sliding while being in contact with the upper surface 22 and the lower surface 23 of the piston ring groove 21.

  Projections (not shown) formed on the upper surface 22 and the lower surface 23 of the piston ring groove 21 due to repeated collision and sliding between the piston ring 1 and the upper surface 22 and the lower surface 23 of the piston ring groove 21. The active aluminum alloy surface centering on the protrusion trace is generated by cutting. Here, in the present invention, the aluminum adhesion-resistant coating 12 is mainly composed of ceramics having excellent heat resistance and oxidation resistance, and the matrix of the aluminum adhesion-resistant coating is made of ceramics having relatively low hardness. The surface of the aluminum ring is scraped between the upper surface 22 and the lower surface 23 of the piston ring groove 21 to form a surface in which the primary crystal silicon protrudes from the surface. The primary silicon that protrudes on the surface and the ceramics harder than the matrix ceramics contained in the aluminum anti-adhesion coating slide to prevent self-wearing of the coating and piston material even under high temperature and high load conditions. It is possible to prevent aluminum adhesion over a long period of time. Hereinafter, each structure of the piston ring 1 for internal combustion engines is demonstrated.

  The material of the piston ring base material 11 is not particularly limited as long as it has strength to withstand a collision with the piston ring groove. Steel, martensitic stainless steel, austenitic stainless steel, high-grade cast iron and the like are preferable. Moreover, in order to improve wear resistance, the side surface may be a base material subjected to nitriding treatment for stainless steel and hard Cr plating or electroless nickel plating treatment for cast iron.

  The Vickers hardness HV of the first ceramic constituting the matrix of the aluminum adhesion-resistant coating 12 is preferably 500 or more and 1300 or less. Here, by setting the Vickers hardness to 500 or more, the tip of the convex portion on the surface of the piston material can be worn. Further, by setting the Vickers hardness to 1300 or less, it is possible to hardly cause wear on the flat portion of the piston material surface. That is, by setting the Vickers hardness to 500 or more and 1300 or less, only the local convex portions can be selectively worn and flattened on the surface of the piston material. More preferably, it is 500 or more and 700 or less.

  In the present invention, the above-mentioned “composite coating” means a coating in which the fine particle-like second ceramic is uniformly dispersed in the first ceramic as a matrix, and the layered matrix is formed on the layered matrix. The structure in which the second ceramic is laminated is not included. However, a state in which the second ceramic in the form of fine particles is present on the surface of the matrix is not excluded.

  The Vickers hardness HV of the second ceramic harder than the first ceramic is preferably 1000 or more and 2500 or less. Here, by setting the Vickers hardness to 1000 or more, the aluminum adhesion coating 12 is prevented from being significantly worn by the primary crystal silicon (Vickers hardness of about 1000) formed on the surface of the piston ring groove 21. be able to. Further, by setting the Vickers hardness to 2500 or less, it is possible to suppress the ratio of breaking the primary crystal silicon and prevent the piston material from being significantly worn. More preferably, it is 1000 or more and 1500 or less.

  It is preferable that the content of the second ceramic harder than the first ceramic is 5 wt% or more and 40 wt% or less with respect to the entire coating film. Here, by setting the content to 5% by weight or more, it is possible to prevent the aluminum adhesive coating 12 from being significantly worn. Moreover, it can prevent that piston material wears significantly by setting it as 40 weight% or less.

  Such a second ceramic is specifically a ceramic having a fine particle form, and is uniformly dispersed in the aluminum adhesion-resistant coating. When a film thickness of 1 μm or more is applied, it is preferable that the abundance ratio of fine particles on the piston ring base material side and the coating surface side is gradually changed in the film thickness direction to about 1:20. As a result, it becomes possible to remove protrusions on the piston surface at an early stage, and in addition, local adhesion due to the presence of the second ceramic particles partially concentrated near the boundary with the piston ring base material. Deterioration can be suppressed.

  The dimension (particle diameter) of the second ceramic is preferably 10 nm or more and 900 nm or less. Here, by setting the particle size to 10 nm or more, it is possible to prevent the second ceramic from being swept away from the matrix made of the first ceramic by the protrusions on the piston surface, thereby effectively increasing the hardness of the second ceramic. It is possible to suppress the consumption of the coating. On the other hand, if the particle size exceeds 900 nm, an extra thickness (specifically, 5 μm or more) more than the film thickness necessary to maintain the performance of the aluminum adhesive film is required to cover the second ceramic. However, by setting the particle size to 900 nm or less, such extra thickness can be eliminated.

  The surface roughness of the aluminum adhesion-resistant coating 12 is preferably 0.3 μm or less. The aluminum anti-adhesion coating 12 having such a surface roughness suppresses the attack of the piston material by suppressing the surface pressure even when contacting the piston ring groove, and suppresses an increase in the wear amount of the piston material. Can do. In the present invention, the surface roughness of the ceramic means an arithmetic average roughness Ra based on JIS B0601 (1994), and is measured using a surface roughness measuring device.

Here, it is preferable that the Vickers hardness HV and the surface arithmetic average roughness Ra (μm) of the aluminum adhesion-resistant coating 12 satisfy the following formula (A).
Ra <−8.7 × 10 ⁻⁵ HV + 0.39 (A)
The inventors formed an aluminum-resistant adhesive coating 12 having various materials, Vickers hardness, surface roughness, and film thickness on the base material 11 for piston ring, and the aluminum-resistant adhesive of the piston ring 1 thus obtained. The performance and the wear amount of the piston material were evaluated. As a result, when the Vickers hardness HV and the arithmetic average roughness Ra of the surface of the aluminum adhesion-resistant coating 12 satisfy the above formula (A), the aluminum material has high aluminum adhesion resistance while suppressing the wear of the piston material. I found out. This is because the piston ring 1 and the upper surface 22 and the lower surface 23 of the ring groove 21 come into contact with each other by setting the arithmetic average roughness Ra of the surface to an appropriate value corresponding to the hardness of the aluminum adhesion-resistant coating 12. It is considered that the surface pressure between them can be reduced.

  In the present invention, the Vickers hardness HV of the aluminum adhesion-resistant coating 12 (composite coating) is determined from the Vickers hardness of the first ceramic, the Vickers hardness of the second ceramic, the average particle diameter, the content, and the like. Specifically, the aluminum adhesion-resistant coating 12 was formed on a measurement substrate prepared in advance, and measured and obtained based on JIS Z2244 (2009).

  The thickness of the aluminum adhesion-resistant coating 12 is preferably 1 μm or more and 20 μm or less. Here, by setting the thickness to 1 μm or more, the thickness of the coating becomes sufficient with respect to the surface roughness of the ceramic, and the self-abrasion can be suppressed by making the aluminum adhesion-resistant coating a homogeneous film. Moreover, by setting it as 20 micrometers or less, sufficient clearance in a piston ring groove | channel is ensured and the function of said piston ring can be performed.

Here, it is preferable that the Vickers hardness HV and the film thickness h (μm) of the aluminum adhesion-resistant coating 12 satisfy the following formula (B).
h> -2.9 × 10 ⁻⁴ HV + 0.89 (B)
As in the case of the above formula (A), the inventors suppress the wear of the piston material even when the Vickers hardness HV and the film thickness h of the aluminum adhesion resistant coating 12 satisfy the above formula (B). However, it has been found that it has high aluminum adhesion resistance. This is presumably because the wear of the piston material can be suppressed without wear of the aluminum-resistant adhesive coating 12 by setting the film thickness h to an appropriate value according to the hardness of the aluminum-resistant adhesive coating 12.

  The first ceramic constituting the matrix can be at least one selected from the group consisting of titania, yttria, magnesia, and alumina. Among these, titania and magnesia are particularly preferable because it is easy to obtain a uniform powder material.

  The ceramic harder than the matrix ceramic can be at least one selected from the group consisting of alumina, zirconia, silica, chromia, aluminum nitride, silicon nitride, and silicon carbide. Among these, alumina, zirconia, silica, and chromia are particularly preferable because of high recombination between particles and easy formation of a uniform film.

  Such an aluminum adhesion-resistant coating 12 can be formed by various known methods in which ceramic fine particles or vaporized ceramic fine particles are directly laminated on the surface. Specifically, deposition is performed under appropriate deposition conditions using thermal spraying, chemical vapor deposition (CVD), physical vapor deposition (PVD), cold spraying, or the like. By performing the above, the piston ring according to the present invention can be manufactured.

  When the aluminum adhesion-resistant coating 12 is formed by thermal spraying, the powder composition is heated in the thermal spraying apparatus and sprayed at a high speed toward the side surface of the piston ring base material 11. Examples of the method of spraying the powder composition on the side surface of the piston ring base material 11 include a gas flame spraying method, a plasma spraying method, and a high-speed flame spraying method (HVOF), and the plasma spraying method is preferable.

  In the plasma spraying method, the gas between the anode and the cathode is turned into plasma by applying a high voltage between the anode and the cathode of the thermal spraying apparatus. Since the gas converted into plasma is heated and further expanded, it is ejected from the thermal spraying apparatus at a high temperature and at a high speed, and becomes a plasma jet flow. The powder composition supplied to the thermal spraying apparatus is heated and accelerated in the plasma jet stream, and sprayed toward the piston ring base material 11. Since the heated and accelerated particles are partially melted, they are flattened when they collide with the piston ring base material 11 and are layered on the side surfaces of the piston ring base material 11. To do. The particles deposited in layers are rapidly cooled by the piston ring base material 11 to form a sprayed coating.

  In the plasma spraying method, particles in the supplied powder composition can be heated to a higher temperature than other spraying methods, and the melting of each particle in the powder composition tends to be promoted. For this reason, in the cross section perpendicular to the sliding surface of the thermal spray coating obtained by plasma spraying (the cross section parallel to the thickness direction of the coating), the layer made of the first ceramic and the layer made of the second ceramic are waved. There is a tendency that tissues that overlap (fold) and entangle with each other while undulating are formed. And, by forming the above structure in the cross section of the thermal spray coating, the second ceramic is held in the aluminum anti-adhesion coating even after sliding, and the surface of the thermal spray coating after sliding tends to be smooth. is there. Therefore, the aluminum adhesive coating obtained by the above plasma spraying is excellent in wear resistance and suppresses aluminum adhesion.

  In order to give the aluminum adhesive coating 12 a lubricating function, a small amount of a solid lubricant such as graphite or molybdenum disulfide can be added.

  Thus, the piston ring according to the present invention can prevent adhesion of aluminum over a long period of time even under high temperature and high load conditions, and can suppress self-wearing of the coating and wear of the piston material.

<Production of piston ring>
Examples of the present invention will be described below.
A film having the materials shown in Table 1, the hardness of the material, the content of the hard material, the surface roughness of the film, and the film thickness was formed on the upper and lower sides of the piston ring base material made of low chromium steel. Inventive Examples 33 and 34 in Table 2 are the same as Inventive Examples 19 and 20 in Table 1, respectively, and Inventive Example 42 in Table 3 is the same as Inventive Example 24 in Table 1.
For Invention Examples 1 to 46 and Comparative Example 5, piston rings were produced by forming coatings by various known methods of directly laminating ceramic fine particles or vaporized ceramic fine particles on the surface. In Invention Examples 1 to 46, the hard material, which is the second ceramic contained in the matrix made of the first ceramic, is in the form of fine particles, and the particle size is as shown in Table 1. On the other hand, in Comparative Examples 1, 2, and 6, a piston ring was produced by forming a film by spray coating a paint adjusted to each composition described later. Moreover, about the comparative example 3, the film was formed by the electroless-plating method and the piston ring was produced. Furthermore, about the comparative example 4, the film was formed by PVD method and the piston ring was produced. Regarding Comparative Example 6, polysilazane-derived silica is used as the first ceramic by the same method as that of Invention Example 1 of Patent Document 5 using the same material as Invention Example 28 as the hard nanoparticles (second ceramic). Except for this, a piston ring similar to that of Invention Example 28 was produced.
The resin coating A of Comparative Example 1 is a polyimide resin coating containing 5% by mass of MoS ₂ powder (average particle size 2 μm) and 5% by mass of graphite powder (average particle size 2 μm). Furthermore, the resin coating B of Comparative Example 2 is a polyimide resin coating containing 10% by mass of Al ₂ O ₃ powder (average particle size 0.5 μm).

Aluminum adhesion resistance of the piston rings of Invention Examples 1 to 46 and Comparative Examples 1 to 6 was evaluated. For this purpose, the engine simulation test apparatus shown in FIG. 2 was used. The engine simulation test apparatus 30 shown in FIG. 2 has a mechanism in which the piston material 32 reciprocates up and down and the piston ring 33 rotates. The test is performed using the heater 31, the temperature controller 34, and the thermocouple. 35, the piston material 32 was heated and controlled. The test conditions were a surface pressure of 13 MPa, a ring rotation speed of 3 mm / s, a control temperature of 270 ° C., a test time of 5 hours, and nitrogen gas and a fixed amount of oil were injected at predetermined intervals. After the test, the remaining amount of coating on the piston ring and the presence or absence of aluminum adhesion were examined. The obtained results are shown in Table 1. In addition, the evaluation criteria of the film remaining amount are as follows.
◎: 80% or more remains with respect to the initial film thickness ○: 40% or more but less than 80% remains with respect to the initial film thickness △: Less than 40% remains with respect to the initial film thickness ×: No film

The evaluation of the aluminum adhesion resistance was confirmed visually. The obtained results are shown in Table 1. The evaluation criteria for the aluminum adhesion resistance are as follows.
◎: Aluminum adhesion not occurred ○: Aluminum adhesion occurred but very slight ×: Aluminum adhesion occurred

The amount of wear of the piston material was calculated by measuring the shape of the surface of the piston material after the test and calculating the depth from the reference surface. The obtained results are shown in Table 1. The evaluation criteria for the amount of wear are as follows.
A: Less than 0.5 μm O: 0.5 μm or more and less than 1.0 μm Δ: 1.0 μm or more and less than 3.0 μm ×: 3.0 μm or more

The performance of the piston ring was comprehensively evaluated from the evaluation results of the aluminum ring anti-adhesion performance of the piston ring and the wear amount of the piston material. The obtained results are shown in Table 1. The criteria for comprehensive evaluation are as follows.
◎: Excellent ○: Good △: Relatively good ×: Bad Here, the overall evaluation is ◎ when all the evaluations of the film residual amount, the aluminum adhesion resistance performance and the wear amount of the piston material are ◎. When any one of the evaluation of the amount, the aluminum adhesion resistance performance and the wear amount of the piston material was Δ or ○, it was evaluated as ◯, and when any one of the evaluations was evaluated as ×, it was evaluated as △.

<Evaluation of residual coating amount and aluminum adhesion resistance>
As shown in Table 1, aluminum adhesion did not occur in all of the piston rings of Invention Examples 1 to 46. Further, in the inventive examples except the inventive examples 10, 23, 37 and 41, the remaining amount of the film was very large as 80% or more with respect to the initial film thickness. On the other hand, in Comparative Examples 1 and 2, no film remained after the test, and aluminum adhesion occurred. In Comparative Examples 3 and 6, as in Comparative Examples 1 and 2, no coating remained after the test and aluminum adhesion occurred, but it was very slight. Furthermore, in Comparative Example 4, the remaining amount of the film was large, and aluminum adhesion did not occur. Furthermore, in Comparative Example 5, there was a coating film remaining amount, but not as much as Invention Examples 1 to 9 and the like, and aluminum adhesion did not occur.

<Evaluation of piston material wear>
As shown in Table 1, with respect to the inventive examples except the inventive examples 16, 22, 23, 28, 32, 36, 37 and 41, the piston wear amount was very small at less than 0.5 μm. With respect to Invention Example 16 in which the content of the hard material is relatively large, the wear amount was somewhat high, 1.0 μm or more and less than 3.0 μm. In addition, in the inventive examples 22, 32, and 36 in which the surface roughness was large with respect to the Vickers hardness of the aluminum adhesion-resistant coating (composite coating), the abrasion amount was slightly higher than 1.0 μm and less than 3.0 μm. Similarly, in the inventive examples 23, 37 and 41 in which the film thickness of the aluminum adhesive film was small, the wear amount was slightly higher than 1.0 μm and less than 3.0 μm.
On the other hand, in Comparative Examples 1 and 2, the wear amount was as large as 3 μm or more. In Comparative Example 3, the amount of wear was slightly small, but in Comparative Example 4, the amount of wear was large. Furthermore, in Comparative Examples 5 and 6, although the wear amount of the piston material was small, it was not as high as Invention Examples 1 to 15 and the like.

<Comprehensive evaluation>
Excellent or relatively good evaluation was given to all of Invention Examples 1 to 46. In particular, a ceramic coating made of at least one selected from the group consisting of titania, yttria, magnesia and alumina is used as the matrix of the aluminum adhesion-resistant coating, and alumina, zirconia, silica, chromia, aluminum nitride, which are ceramics harder than the matrix, Excellent evaluation is given for all coatings containing 5% by weight or more and 40% by weight of at least one selected from the group consisting of silicon nitride and silicon carbide and satisfying the formula (A) or the formula (B). It can be seen that a piston ring having a high aluminum adhesion resistance performance was obtained while suppressing self-wearing of the coating and wear of the piston material.
On the other hand, Comparative Examples 1 and 2 provided with the resin film were inferior in both aluminum adhesion resistance and piston material wear. In Comparative Example 3 provided with the nickel coating and Comparative Example 4 provided with the DLC coating, the aluminum adhesion resistance was good or excellent, but the piston material wear characteristics were slightly inferior. Further, Comparative Example 5 showed high aluminum adhesion resistance. Moreover, although the abrasion amount of the piston material was small, it was not as much as Invention Examples 1-9.
Moreover, when the same evaluation was performed about the invention example 28 and the comparative example 6 which were exposed to 700 degreeC for 5 days as an acceleration test, the comparative example 6 confirmed lack of the film | membrane partially with the deterioration of the aluminum adhesion resistance performance. However, Invention Example 28 gave good results. When the porosity of each coating was accurately examined by the Archimedes method, Comparative Example 6 was 5 to 14% (average 10% of 10 points measurement), and Invention Example 28 was 0.1 to 6% (10 points). The average of the measurement was 0.6%). The porosity of the other inventive examples was 0 to 6% (average of 0.4% for each invention example 10 point measurement), and no missing film was confirmed even in the acceleration test. Thus, it was found that the loss of the coating film over a long period of time can be suppressed by setting the porosity to 6% or less.

  According to the present invention, an aluminum adhesion coating composed of two or more kinds of ceramics having different hardnesses is coated on at least one of the upper and lower side surfaces of the piston ring base material, so that the aluminum adhesion over a long period of time even at high temperatures. Can be prevented, and the self-wearing of the coating and the wear of the piston material can be suppressed, which is useful for the automobile parts manufacturing industry.

1,33 Piston ring 11 Piston ring base material 11a Upper side surface 11b of piston ring base material Lower side surface of piston ring base material 12 Aluminum adhesion coating 20 Piston 21 Piston ring groove 22 Upper surface 23 of piston ring groove Piston Lower surface of ring groove 24 Cylinder 30 Engine simulation test device 31 Heater 32 Piston material 34 Temperature controller 35 Thermocouple

That is, the gist of the present invention is as follows.
(1) A piston ring for an internal combustion engine in which a base material for piston ring is coated with an aluminum anti-adhesion coating, wherein the aluminum anti-adhesion coating covers at least one of the upper and lower side surfaces of the piston ring base material. as a first ceramic matrix which is contained a first rigid second ceramic than ceramic constituting the matrix, Ri composite coating der made of ceramics alone, Vickers hardness of the anti-aluminum adhesion coating A piston ring for an internal combustion engine, characterized in that HV and arithmetic average roughness Ra (μm) of the surface of the aluminum adhesion-resistant coating satisfy the following formula (A):
Record
Ra <−8.7 × 10 ⁻⁵ HV + 0.39 (A)

(2) The piston ring for an internal combustion engine according to (1 ) , wherein the Vickers hardness HV of the aluminum adhesion-resistant coating and the thickness h (μm) of the aluminum adhesion-resistant coating satisfy the following formula (B): .
H> -2.9 × 10 ⁻⁴ HV + 0.89 (B)

(3) the aluminum adhesion coating in its thickness direction cross-section, has a layer have a mutually overlapping structure consisting wherein the first made of a ceramic layer a second ceramic, the (1) or (2) 2. A piston ring for an internal combustion engine according to 1.

(4) The piston for an internal combustion engine according to any one of (1) to (3) , wherein the first ceramic constituting the matrix has a Vickers hardness HV of 500 to 1300. ring.

(5) The piston ring for an internal combustion engine according to any one of (1) to (4) , wherein the second ceramic has a Vickers hardness HV of 1000 or more and 2500 or less.

(6) The piston ring for an internal combustion engine according to any one of (1) to (5) , wherein the content of the second ceramic is 5% by weight or more and 40% by weight or less with respect to the entire coating film.

(7) The piston ring for an internal combustion engine according to any one of (1) to (6) , wherein an arithmetic average roughness of a surface of the aluminum adhesion-resistant coating is 0.3 μm or less.

(8) The piston ring for an internal combustion engine according to any one of (1) to (7) , wherein the aluminum adhesion-resistant coating has a thickness of 1 μm to 20 μm.

(9) The first ceramic constituting the matrix is at least one selected from the group consisting of titania, yttria, magnesia, and alumina, and the second ceramic is alumina, zirconia, silica, chromia, aluminum nitride, The piston ring for an internal combustion engine according to any one of (1) to (8) , which is made of at least one selected from the group consisting of silicon nitride and silicon carbide.

Claims (10)

  A piston ring for an internal combustion engine in which a piston ring base material is coated with an aluminum anti-adhesion coating, wherein the aluminum anti-adhesion coating is coated on at least one of the upper and lower side surfaces of the piston ring base material. A piston ring for an internal combustion engine, comprising: a ceramic coating comprising a ceramic as a matrix and a second ceramic harder than the first ceramic constituting the matrix. 2. The piston for an internal combustion engine according to claim 1, wherein the Vickers hardness HV of the aluminum adhesion-resistant coating and the arithmetic average roughness Ra (μm) of the surface of the aluminum adhesion-resistant coating satisfy the following formula (A): ring.
Ra <−8.7 × 10 ⁻⁵ HV + 0.39 (A) The piston ring for an internal combustion engine according to claim 1 or 2, wherein a Vickers hardness HV of the aluminum adhesion-resistant coating and a thickness h (µm) of the aluminum adhesion-resistant coating satisfy the following formula (B).
H> -2.9 × 10 ⁻⁴ HV + 0.89 (B)   The aluminum adhesive coating according to any one of claims 1 to 3, wherein the first ceramic layer and the second ceramic layer overlap each other in a cross section in the thickness direction thereof. The piston ring for internal combustion engines as described.   The piston ring for an internal combustion engine according to any one of claims 1 to 4, wherein the first ceramic has a Vickers hardness HV of 500 or more and 1300 or less.   The piston ring for an internal combustion engine according to any one of claims 1 to 5, wherein the second ceramic has a Vickers hardness HV of 1000 or more and 2500 or less.   The piston ring for an internal combustion engine according to any one of claims 1 to 6, wherein the content of the second ceramic is 5 wt% or more and 40 wt% or less with respect to the entire coating film.   The piston ring for an internal combustion engine according to any one of claims 1 to 7, wherein an arithmetic average roughness of the surface of the aluminum adhesion-resistant coating is 0.3 µm or less.   The piston ring for internal combustion engines according to any one of claims 1 to 8, wherein the aluminum adhesion-resistant coating has a thickness of 1 µm to 20 µm.   The first ceramic is made of at least one selected from the group consisting of titania, yttria, magnesia, and alumina, and the second ceramic is made of alumina, zirconia, silica, chromia, aluminum nitride, silicon nitride, and silicon carbide. The piston ring for internal combustion engines according to any one of claims 1 to 9, comprising at least one selected from the group.

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