KR100501985B1 - An abrasion-resistant thermal-sprayed coating for a sliding member - Google Patents

Abstract

According to one aspect of the present invention, a mixture of a hard material (hard material particle) (5) powder, a metal powder forming the matrix 6, and a solid lubricant powder is formed by thermal spraying on a sliding surface of the sliding member 1. A wear resistant thermal spray coating 3 for a sliding member is provided. The mixture comprises less than 0.1 to 10% by mass of metallized solid lubricant particles of the mixture, wherein the metallized solid lubricant particles may be copperlized graphite particles (4). Alternatively, the coating metal of the metallized solid lubricant particles is preferably one material selected from the group consisting of copper, nickel, silver, cobalt, and molybdenum, and the solid lubricant particles are graphite, manganese sulfide, graphite fluorinated graphite, fluorine. It is preferably one material selected from the group consisting of calcium sulfide, boron nitride, molybdenum disulfide, and tungsten disulfide. According to another aspect of the present invention, the metallized solid lubricant particles preferably contain 10 to 50% by mass of the solid lubricant of the copperlized solid lubricant particles. According to another aspect of the present invention, the thermal sprayed coating may be formed by plasma spraying to have a porosity of 5 to 15% by volume of the mixture.

According to the thermal spray coating described above, a mixture composed of ceramic powder as a hard material, metal powder forming a matrix, and metal-coated solid lubricant particles as a solid lubricant powder is formed on the sliding surface of a sliding member such as a piston ring and a cylinder liner of an internal combustion engine. It is advantageous to obtain a wear-resistant thermal spray coating which is formed by thermal spraying at, and which is not sensitive to brittleness and has poor retention.

Description

Abrasion resistant thermal spray coating for sliding members {AN ABRASION-RESISTANT THERMAL-SPRAYED COATING FOR A SLIDING MEMBER}

The present invention relates to a wear-resistant thermal spray coating for sliding members such as piston rings and cylinder liners of an internal combustion engine.

As is well known, the wear-resistant thermal spray coating covering the sliding surface of the sliding member for an internal combustion engine comprises a mixture containing a hard material powder such as ceramic, a metal powder forming a matrix such as molybdenum, and a solid lubricant powder such as calcium fluoride. It is formed by thermal spraying on the sliding surface of the sliding member.

A thermal spray coating is known from Japanese Patent Application Laid-Open No. 08-253877, wherein the coating uses 10 to 20% by mass of metal-coated graphite particles as a solid lubricant. The known thermal spray coatings have graphite particles having a size distribution characterized by a particle size analysis of -88 + 44 μm, wherein the coating mixture contains about 75 mass% of nickel as a coating metal and about 25 mass% of graphite as a solid lubricant. It contains.

If metal-coated graphite particles are used in place of uncoated graphite particles, the problem of oxidation and decomposition of graphite in the thermal spraying process will be solved. Compared to the above, the thermal spray coating has a significant decrease in the strength of the spray coating. Moreover, when using a high-speed oxygen flame (HVOF) spray, there is another drawback that the film has a porosity of less than 5% by volume, resulting in poor retention.

The present invention has been made to solve these problems. Accordingly, an object of the present invention is to provide a mixture composed of ceramic powder as a hard material, metal powder to form a matrix, and metal-coated solid lubricant particles as a solid lubricant powder, on a sliding surface of a sliding member such as a piston ring and a cylinder liner of an internal combustion engine. It is a wear-resistant thermal spray coating formed by thermal spraying on a non-sensitive brittle and poor retention.

In order to achieve the above object, the present invention provides a wear-resistant spray coating for a sliding member formed by spraying a mixture composed of a hard material powder, a metal powder forming a matrix, and a powder of a metal-coated solid lubricant on a sliding surface of the sliding member. Provided, wherein the coating mixture comprises less than 0.1 to less than 10% by mass of metallized solid lubricant particles.

The reason for limiting the content of the metal-coated solid lubricant particles as described above is that when less than 0.1% by mass, the lubricating effect is insufficient, and when it is 10% by mass or more, the coating is weak and the effect of improving the coefficient of friction is small. In order to improve a lubricating effect, it is preferable to adjust to 1 mass% or more. Moreover, it is preferable to adjust to 8 mass% or less from a viewpoint of film strength.

Further, according to the present invention, the metallized solid lubricant particles contain a solid lubricant within a limited range of 10 to 50% by mass of the metallized graphite particles. The reason is that when less than 10% by mass, the lubricating effect is not sufficient, and when it exceeds 50% by mass, the residual amount of solid lubricant particles when sprayed is reduced, resulting in a counterpart of the sliding member. This is because the wear amount of the is increased.

The solid lubricant particles used in the coating mixture according to the present invention are graphite (C), manganese sulfide (MnS), graphite fluoride, calcium fluoride (CaF ₂ ), boron nitride (BN), molybdenum disulfide (MoS ₂ ), and It may be one material selected from the group consisting of tungsten disulfide, of which graphite is preferably used in view of workability.

The method of coating the solid lubricant particles with metal may include chemical, electrochemical, and mechanical plating methods, gas reduction methods, and mechanical fusion methods. The metal used to coat the solid lubricant particles according to the present invention may be one material selected from the group consisting of copper, nickel, silver, cobalt, and molybdenum, of which copper (Cu) is used in view of metal plating ability. It is desirable to be.

The hard material used in the coating mixture may be selected from the group consisting of carbides, oxides, nitrides, and carbonitrides of chromium, tungsten, molybdenum, and vanadium, among which, according to the present invention, the relative non-attack (i.e., spraying) In view of the non-aggression property of the sliding member having the film and the counterpart of the sliding member, it is preferable to use chromium oxide (Cr ₂ O ₃ ) or chromium carbide (CrC).

The metal used in the coating mixture forming the matrix may be selected from the group consisting of molybdenum, nickel-chromium alloy, cobalt, cobalt-chromium alloy, nickel-molybdenum alloy, and cobalt-nickel alloy, among which, according to the present invention From the viewpoint of wear resistance and scuffing resistance, it is preferable to use molybdenum (Mo) and nickel-chromium (Ni-Cr) alloys together.

In addition, it is preferable that the porosity of the thermal sprayed coating is limited to the range of 5-15 volume% by plasma spraying. This is because if the porosity is less than 5% by volume, the retention is poor, and if the porosity is more than 15% by volume, the thermal spray coating is brittle and the film strength is extremely reduced.

As described above, according to the thermal spray coating according to the present invention, there is no decrease in film strength that causes brittleness and no poor film retention. In addition, the thermal spray coating according to the present invention has not only an improved low coefficient of friction but also excellent wear resistance, scuffing resistance, and counterattack resistance.

With reference to FIG. 1, the thermal spray coating which concerns on this invention is demonstrated below with respect to a piston ring.

The piston ring 1 shown in FIG. 1 has a thermal sprayed coating 3 formed on the outer circumferential sliding surface of the base material 2. The thermal spray coating (3) comprises 40 to 80 mass% molybdenum powder, 10 to 50 mass% nickel-chromium alloy powder, 1 to 20 mass% chromium oxide or chromium carbide, and 0.1 to 10 mass% copper clad graphite. A mixture of particles is formed by plasma-spraying.

The copper coated graphite particles have a copper coating having 10 to 50% by mass of graphite, and have a size distribution of 10 to 106 μm.

As can be seen through the cross section of the thermal sprayed coating 3, the coating mixture comprises 0.1 to 10% by mass of copper coated graphite particles 4, which copper coated graphite particles are almost evenly dispersed throughout the coating mixture. Therefore, there is almost no decrease in strength of the thermal sprayed coating 3 generated by the copper-coated graphite particles 4. Furthermore, the hard material particles 5 of chromium oxide or chromium carbide of the thermal sprayed coating 3 are evenly dispersed in the matrix 6 formed of molybdenum and nickel-chromium alloys, so that the relative aggressiveness of the thermal sprayed coating 3 is prevented. Is low. Moreover, since the porosity of the thermal sprayed coating 3 formed by plasma-spray is 5 to 15% by volume, the thermal sprayed coating 3 has a low frictional resistance and abrasion resistance due to the synergistic effect of the porosity and the graphite phase. And scuffing resistance is excellent.

(Example of a thermal spray coating and explanation of the test)

The thermal spray coating of the present invention will be described in more detail below in connection with some tests performed on Examples, Comparative Examples and Conventional Examples.

As shown in Table 1 below, Specimens No. 1 and No. 2 are conventional examples having a film formed by HVOF (No. 1) or plasma (No. 2) spraying, which do not contain a metal-coated solid lubricant. . Specimens No. 3 to No. 15 are examples of plasma-spray coatings containing metallized solid lubricant particles, according to embodiments of the present invention. Finally, Specimens No. 16 to No. 19 are comparative examples of plasma sprayed coatings containing metal-coated solid lubricants, and the comparative examples and examples contained the content ratio of the metal-coated solid lubricants in the coating mixture or the metal-coated solid lubricants The content ratio of the solid lubricants is different.

Type and content ratio (mass%) of the hard materials in the coating mixture, type and content ratio (mass%) of the matrix of the coating mixture, type and content ratio (mass%) of the metal coating solid lubricant in the coating mixture, metal coating solid lubricant The content ratio (mass%) of the solid lubricant in the inside, the porosity of the film, and the spraying method are shown in Table 1. The graphite of the copper-coated graphite particles used to form the thermal spray coating was granular.

In Table 1, in the heat of the hard material,% means the mass% of the hard material contained in the coating mixture. In the matrix row, the Mo and Ni—Cr alloy values represent the metal forming the matrix and the composition of the metal within the matrix. Metallized Solid Lubricant In the thermal class, the front part represents the metal being covered and the back part is the coated solid lubricant (e.g. Cu-C means Cu coated C (graphite) as the metallized solid lubricant), % Means mass% of the metal-coated solid lubricant contained in the coating mixture, and SL% means mass% of the solid lubricant contained in the metal-coated solid lubricant. In the thermal spraying method, HV means HVOF method and Plas means plasma method. In the remarks column, Cnv, Emb, and Cmp mean a conventional example, an example, and a comparative example, respectively.

Conditions for plasma spraying are as follows.

Spray gun used: 9MB plasma gun manufactured by Sulzer Metco,

Voltage: 60-70 V,

Current: 500 A.

The conditions for HVOF spraying are as follows.

Spray gun used: Diamond Jet Gun (trade name) manufactured by Sulzer Metco,

Fuel gas: propane-oxygen (1: 7).

Each specimen was subjected to a scuffing test, abrasion test, and counter-attack test.

(Scuffing test)

As shown in FIG. 2, the scuffing critical area pressure of each specimen was measured using a rotary tester for planar sliding frictional wear. Each specimen 11 was kept in contact with the rotating surface of the counterpart 12 rotating at a constant speed under a predetermined surface pressure P for a predetermined time, and the surface pressure at the time of scuffing was set as the critical surface pressure. The pressure operation was performed by setting the initial pressure to 2.45 MPa, increasing the pressure to 4.9 MPa after the first 30 minute period, and then gradually increasing the pressure by 0.98 MPa every 5 minutes.

The test conditions were as follows.

Sliding speed: 5 m / sec,

Lubricant: SAE30 + White Kerosene (1: 1),

The amount of lubricant supplied: no oil other than initial

Object: tarkalloy (boron cast iron known under the trade name of Piston Ring Co., Ltd., Japan).

(Wear test and object-attack test)

As shown in FIG. 2, the wear depth of each specimen and the wear depth of the object were measured using a rotary tester for flat sliding frictional wear. Each specimen 11 was kept in contact with the rotating surface of the counterpart 12 rotating at a constant speed under a predetermined surface pressure P for a predetermined time. Lubricating oil was dropped on the rotating counterpart 12.

The test conditions were as follows.

Sliding speed: 6 m / sec,

Surface pressure: 6 MPa,

Lubricant: Spinox-2 bearing oil (a bearing oil known under the trade name of Mitsubishi Oil Corporation in Japan),

Oil temperature: 60 ± 10 ℃

Amount of lubricant supplied: 10 ^-4 m ³ / min,

Exam time: 80 hours

Object: tarkalloy (boron cast iron known under the trade name of Piston Ring Co., Ltd., Japan).

Table 1 shows the measurement results for each specimen when the measured values of the scuffing critical surface pressure of specimen No. 1, the wear amount of the specimen, and the wear amount of the object were set to 100, respectively.

From the above results, it can be confirmed that the Examples are superior to the conventional and comparative examples in scuffing resistance, abrasion resistance, and counterattack resistance.

As described above, the wear-resistant sprayed coating according to the present invention is formed by plasma-spraying a mixture of a hard material powder, a metal powder forming a matrix, and a metal-coated solid lubricant powder, but the metal-coated solid lubricant is 10% by mass or more of metal. Unlike the conventional thermal spray coating with coated graphite, the content ratio of the metal-coated solid lubricant in the thermal spray coating is less than 10 mass%.

Therefore, the thermal spray coating according to the present invention has a clear and excellent advantage in that the coating is not fragile. Moreover, the thermal spray coating according to the present invention has a small frictional resistance due to the synergistic effect between the porosity and the solid lubricant phase, and has excellent advantages in scuffing resistance, wear resistance, and counterattack resistance.

While the above-described novel features of the present invention have been described and illustrated by applying them to preferred embodiments, those skilled in the art will understand that various modifications or changes can be made to such embodiments without departing from the scope of the present invention. Accordingly, the invention is not limited to only the claims appended hereto.

1 is a partially enlarged cross-sectional view of a piston ring having a thermal spray coating formed according to an embodiment of the present invention.

2 is a schematic view of a rotary tester used in the testing of planar sliding frictional wear.

Explanation of reference numerals

1: piston ring 2: base material

3: thermal sprayed coating 4: copper coated graphite particles

5: hard material particle 6: matrix

11: psalm 12: counterpart

P: surface pressure

Claims (8)

As a thermal spray coating formed by plasma-spraying the mixture which consists of a hard material powder, the metal powder which forms a matrix, and a solid lubricant powder on the sliding surface of a sliding member, The hard material contains 1 to 20% by mass of chromium oxide or chromium carbide, and the metal forming the matrix contains 40 to 80% by mass of molybdenum and 10 to 50% by mass of a nickel-chromium alloy. The solid lubricant contains less than 0.1 to 10% by mass of the metal-coated solid lubricant particles, The coating metal of the metal-coated solid lubricant particles is one selected from copper, nickel, silver, cobalt and molybdenum, The solid lubricant particles of the metal-coated solid lubricant particles are at least one selected from graphite, manganese sulfide, graphite fluoride, calcium fluoride, boron nitride, molybdenum disulfide, and tungsten disulfide. The wear-resistant thermal sprayed coating of the sliding member according to claim 1, wherein the coating metal of the metal-coated solid lubricant particles is formed by a plating method. The wear-resistant sprayed coating of the sliding member according to claim 1 or 2, wherein the metal-coated solid lubricant particles are metal-coated graphite particles having 10 to 50 mass% of graphite. The wear-resistant thermal sprayed coating of the sliding member according to claim 1 or 2, wherein the metal-coated solid lubricant particles are copper-coated solid lubricant particles. The wear-resistant thermal sprayed coating of the sliding member according to claim 4, wherein the copper-coated solid lubricant particles have 10 to 50 mass% of solid lubricant particles. delete delete delete