DK180330B1

DK180330B1 - STAMP RING AND METHOD OF MANUFACTURE THEREOF

Info

Publication number: DK180330B1
Application number: DKPA201870188A
Authority: DK
Inventors: Aizawa Takeshi
Original assignee: Nippon Piston Ring Co Ltd
Priority date: 2017-03-28
Filing date: 2018-03-27
Publication date: 2020-11-25
Also published as: JP6985961B2; DK201870188A1; JP2018165402A; KR20180109732A; KR102080540B1; CN108660408A

Abstract

To provide a piston ring having a thermal spray coating formed thereon with favorable adhesion, the thermal spray coating being excellent in wear resistance, scuffing resistance, and initial running-in property, and having low aggressiveness against a mating material, and a manufacturing method therefor. A piston ring is provided with a thermal spray coating comprising Mo particles, Ni-based self-fluxing alloy particles, and Co alloy particles and/or Cr3C2 particles on at least a sliding surface of a piston ring base material 2. Given 100 mass% as a content ratio of the Mo particles, the Ni-based self-fluxing alloy particles, and the Co alloy particles and the Cr3C2 particles combined, the Ni-based self-fluxing alloy particles are within a range of 20 to 40 mass%, inclusive, the Co alloy particles and the Cr3C2 particles, combined, are within a range of 15 to 30 mass%, inclusive, and the remainder is Mo particles. The thermal spray coating may further include NiCr particles.

Description

, DK 180330 B1

SPECIFICATION

PISTON RING AND MANUFACTURING METHOD THEREFOR Field of the Invention

[0001] The present invention relates to a piston ring and a manufacturing method therefor. More specifically, the present invention relates to a piston ring having a thermal spray coating formed thereon with favorable adhesion, the thermal spray coating being excellent in wear resistance, scuffing resistance, and initial running-in property, and having low aggressiveness against a mating material, and a manufacturing method therefor.

BACKGROUND ART

[0002] In recent years, internal combustion engines have increased in output as well as — performance, making the usage environment of a sliding member such as a piston ring increasingly severe, and resulting in a demand for sliding members having favorable wear resistance and scuffing resistance. The piston ring is configured so that an outer peripheral surface thereof slides with a cylinder liner, and thus requires high wear resistance, scuffing resistance, and the like particularly on the outer peripheral sliding surface. In response to such demands, Patent Documents 1 to 3 propose technologies that provide a thermal spray coating on the outer peripheral sliding surface of the piston ring.

[0003] Patent Document 1 proposes a piston ring with a thermal spray underlayer and a thermal spray surface layer formed on the sliding surface, in that order. The thermal spray underlayer is obtained by spraying a mixed powder including at least Mo powder, Ni-based self-fluxing alloy powder, and Cu or Cu alloy powder, and the thermal spray surface layer contains Cu. The thermal spray underlayer contains at least 50 to 80 mass% of Mo, 1 to 12 mass% of Cu or Cu alloy, and the remaining portion being the Ni-based self-fluxing alloy.

[0004] Patent Document 2 proposes a thermal spray coating for a piston ring obtained by spraying a powder composition onto the outer peripheral sliding surface of a piston ring base material using a plasma spraying method. The powder composition includes molybdenum particles, nickel chrome alloy particles, and chromium carbide particles, with the chromium carbide particles having a median diameter within a specific range.

[0005] Patent Document 3 proposes a thermal spray coating that includes a molybdenum phase, a chromium carbide phase, and a nickel chrome alloy phase. The molybdenum phase, the chromium carbide phase, and the nickel chrome alloy phase are deposited on the sliding surface of the base material, and a ratio of an average value of a thickness of the chromium 40 carbide phase in a direction orthogonal to the sliding surface of the base material and that of the molybdenum phase is specified.

[0006] Patent Document 4 proposes a piston ring that comprises a thermal spray coating obtained by spraying a raw material powder including at least Mo powder and a mixed

, DK 180330 B1 powder of Cr3C> powder and a NiCr powder. An average particle size of the mixed powder is 50 um or greater, and an average particle size of the Mo powder is less than that of the mixed powder. Patent Documents

[0007] Patent Document 1: Japanese Laid-Open Patent Application No. 2012-46821 Patent Document 2: WO2014/091831 Patent Document 3: Japanese Laid-Open Patent Application No. 2015-214719 Patent Document 4: Japanese Laid-Open Patent Application No. 2016-102233

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

[0008] It is therefore an object of the present invention to provide a piston ring having a thermal spray coating formed thereon with favorable adhesion, the thermal spray coating being excellent in wear resistance, scuffing resistance, and initial running-in property, and having low aggressiveness against a mating material, and a manufacturing method therefor.

Means for Solving the Problems

[0009] (1) A piston ring according to the present invention is provided with a thermal spray coating comprising Mo particles, Ni-based self-fluxing alloy particles, Cr;C; particles and NiCr particles on at least a sliding surface of a piston ring base material.

[0010] According to this invention, Ni-based self-fluxing alloy particles and Cr3C» particles are included, making it possible to achieve a thermal spray coating that has particularly favorable adhesion and low aggressiveness against a mating material.

[0011] In the piston ring according to the present invention, given 100 mass% as a content ratio of the Mo particles, the Ni-based self-fluxing alloy particles, and the Cr3C2 particles and the NiCr particles combined, the Ni-based self-fluxing alloy particles are within a range of 20 to 40 mass%, inclusive, the Cr3C2 particles, are within a range of 15 to 30 mass%, inclusive, — the NiCr particles are within a range of 0.01 to 10 mass%, inclusive, and the remainder is Mo particles.

[0012] In the piston ring according to the present invention, a ratio (A/B) of a content A of 40 the Ni-based self-fluxing alloy particles to a content B of the NiCr particles is preferably 1.5 or greater by mass.

2 DK 180330 B1

[0013] In the piston ring according to the present invention, the thermal spray coating may include a granulated structure of the NiCr particles and the Cr3C particles when the NiCr particles are included.

[0014] (2) A method for manufacturing a piston ring according to the present invention comprises the steps of plasma-spraying a mixed powder composition of Mo powder, Ni-based self-fluxing alloy powder, Cr3C> powder and NiCr powder, and forming the thermal spray coating on an outer peripheral sliding surface of a piston ring base material.

Effect of the Invention

[0015] According to the present invention, it is possible to provide a piston ring having a thermal spray coating formed thereon with favorable adhesion, the thermal spray coating — being excellent in wear resistance and scuffing resistance, and having low aggressiveness against a mating material, and a manufacturing method therefor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Fig. 1 is a cross-sectional view illustrating an example of a piston ring according to the present invention. Figs. 2A to 2D are cross-sectional images of thermal spray coatings obtained in Examples 1 and 2 and Comparative Examples 1 and 2. Fig. 3 is a configuration principle view of a high-load type abrasion tester used for wear measurement. Embodiments of the Invention

[0017] The following describes in detail a piston ring and a manufacturing method therefor according to the present invention. It should be noted that the present invention is not limited to the embodiments below and may be carried out in various forms within a scope that does not deviate from the gist thereof.

[0018] [Piston Ring] A piston ring 1 according to the present invention, as illustrated in Fig. 1, is provided with a characteristic thermal spray coating 3 on at least a sliding surface of a piston ring base material 2. The thermal spray coating 3 comprises Mo particles, Ni-based self- fluxing alloy particles, and Co alloy particles and/or Cr3C; particles. Such a piston ring 1 is manufactured by plasma spraying a mixed powder composition of Mo powder, Ni-based self- 40 — fluxing alloy powder, and Co alloy powder and/or Cr3C> powder, and forming the thermal spray coating 3 on the outer peripheral sliding surface of the piston ring base material 2. The piston ring 1 with the thermal spray coating 3 formed thereon makes it possible to achieve a thermal spray coating that has particularly favorable adhesion and low aggressiveness against a mating material.

2 DK 180330 B1

[0019] Fach component of the piston ring 1 according to the present invention will now be described.

[0020] — <Piston Ring Base Material> Fxamples of the materials used as the piston ring base material 2 of the piston ring 1 on which the thermal spray coating 3 is formed are various and not particularly limited. For example, materials such as various steel materials, stainless steel materials, casting materials, and cast steel materials can be applied. Among these, preferable examples include a — martensitic stainless steel, a chromium manganese steel (SUP9), a chrome vanadium steel (SUP10), a silicon chromium steel (SWOSC-V), and the like. Further, preferable examples of the casting materials include a boron cast iron, a flake graphite cast iron, a nodular graphite cast iron, a CV cast iron, and the like. The piston ring base material 2 is fabricated by means for manufacturing a general piston ring.

[0021] The piston ring base material 2 may be pretreated as necessary. Examples of the pretreatment include processing that polishes the surface to adjust the surface roughness. This adjustment of the surface roughness is performed by, for example, methods such as lapping and polishing the surface of the piston ring base material 2 using diamond abrasive grains.

[0022] <Thermal Spray Coating> The thermal spray coating 3 is provided to at least the sliding surface of the piston ring base material 2. This thermal spray coating 3 comprises Mo particles, Ni-based sel f- fluxing alloy particles, and Co alloy particles and/or Cr3C> particles, and is formed by spraying a raw material powder comprising Mo powder, Ni-based self-fluxing alloy powder, and Co alloy powder and/or Cr3C; powder.

[0023] The component composition of the thermal spray coating 3 is configured so that, given 100 mass% as a content ratio of the Mo particles, the Ni-based self-fluxing alloy particles, and the Co alloy particles and the Cr3C> particles combined, the Ni-based self- fluxing alloy particles are within a range of 20 to 40 mass%, inclusive, the Co alloy particles and the Cr3C; particles, combined, are within a range of 15 to 30 mass%, inclusive, and the remainder is Mo particles. The content ratio is by mass, and each mass is calculated given 100 mass% as the content of the Mo particles, the Ni-based self-fluxing alloy particles, and the Co alloy particles and the Cr3C» particles combined. When particles other than these are included, each mass is calculated using the 100 mass% as the total excluding such particles.

[0024] The raw material powder may contain, as desired, Co, B, Si, Cu, Al, Fe, or the like, for example, within a range that does not hinder the effects exhibited by the present invention.

40 — It should be noted that, because the content of each particle component constituting the thermal spray coating 3 is normally the same as the composition ratio in the raw material powder, the content of each component of the thermal spray coating 3 can be regarded as the component ratio in the raw material powder. Accordingly, the mixture ratio of each powder that constitutes the raw material powder can be regulated to attain a desired component ratio

. DK 180330 B1 of the thermal spray coating 3. It should be noted that the content of each of the particles included in the thermal spray coating 3 can be measured using a backscattering measuring device. Further, because the content of each of the particles constituting the thermal spray coating 3 normally matches the mixture amounts of each of the raw material powders included in the thermal spray raw material, the mixture ratio of each powder constituting the raw material powder can also be specified by measuring the content of each of the particles of the thermal spray coating 3.

[0025] (Mo particles) The Mo particles are a main element constituting the thermal spray coating 3, are included based on a content separate from the content of the NiCr self-fluxing alloy particles, and the Co alloy particles and the Cr3C; particles combined, and are included within a range of, for example, 40 to 60 mass%, inclusive. The Mo particles, which are particles of a high melting point metal, are included in the above-described range, making it possible to obtain a thermal spray coating excellent in wear resistance and scuffing resistance as well as adhesion with the piston ring base material. A content of less than 40 mass% results in inferior wear resistance and scuffing resistance in the thermal spray coating 3 obtained. On the other hand, a content of more than 60 mass% leads to high cost.

[0026] An average particle size of the Mo particles may be about the same as that of a general thermal spray raw material powder and is, for example, preferably within a range of 10 um to 50 um, inclusive, and more preferably within a range of 20 um to 40 um, inclusive, from the viewpoint of adhesion. In this application, the average particle sizes of the Mo and other particles are expressed as a value of Dsp measured using a particle size distribution measuring device (Microtrac HRA manufactured by Nikkiso Co., Ltd., for example). It should be noted that the shape and the like of the Mo particles are not particularly limited, and the particles may be granulated-sintered particles. Mo granulated-sintered particles are obtained by granulating and then heating and sintering small-sized Mo particles. The average particle size of the Mo particles used in granulating is I to 10 um, for example. The Vickers hardness of the Mo particles is within a range of 320HV to 420HV. It should be noted that Vickers hardness in this application was measured using a micro Vickers hardness meter (manufactured by Akashi), and was expressed as an average value of the measurement results of five locations randomly selected at a load of 0.05 kgf.

[0027] (NiCr self-fluxing alloy particles) The Ni-based self-fluxing alloy particles are main elements constituting the thermal spray coating 3, and are obtained by spraying Ni-based self-fluxing alloy powder. These Ni- based self-fluxing alloy particles are alloy particles in which a nickel-based alloy contains a flux component such as boron or silicon, and is used as a raw material powder that, upon 40 spraying and subsequently performing a fusing process or the like, has an effect of making it possible to obtain a thermal spray coating having minimal pores and high adhesive strength. According to the present invention, Ni-based self-fluxing alloy particles containing Cr are used as the powder raw material. These Ni-based self-fluxing alloy particles contain 14 to 18 mass% of Cr, 2 to 4 mass% of boron, 3 to 4.5 mass% of silicon, 2 to 5 mass% of iron, and a

6 DK 180330 B1 slight amount of unavoidable impurities. Further, one or both of 1 to 3 mass% of molybdenum and 1 to 4 mass% of copper may be contained. Such a Ni-based self-fluxing alloy acts as a binder of Mo, which is a base metal. Furthermore, a favorable wear resistance can be advantageously obtained by virtue of the fact that this Ni-based self-fluxing alloy is self- fluxing. Well-known Ni-based self-fluxing alloys include a NiCr self-fluxing alloy and a NiCo self-fluxing alloy, and a NiCr self-fluxing alloy is used in the present invention. In particular, according to the present invention, NiCr self-fluxing alloy particles included in the thermal spray coating 3 were newly discovered to act so as to decrease differences in hardness between the Mo particles, and the Co alloy particles and the Cr3C, particles, and exhibit the — effect of making it possible to prevent the shedding of Co alloy particles and Cr3C, particles caused by differences in hardness. As a result, the capability of suppressing aggressiveness against a mating material is advantageously obtained. The Vickers hardness of the NiCr self- fluxing alloy particles is within a range of 700HV to 850HV.

[0028] The NiCr self-fluxing alloy particles are preferably included within a range of 20 to 40 mass%, inclusive, given 100 mass% as the content ratio of the Mo particles, the Ni-based self-fluxing alloy particles, and the Co alloy particles and the CrsC; particles combined. With this range, it is possible to better exhibit the above-described effects. When the content is less than 20 mass%, the effect of acting as a Mo binder fades, possibly resulting in a decrease in adhesive strength between the Mo particles. On the other hand, when the content is more than 40 mass%, scuffing resistance may decrease. The more preferred content is within a range of to 35 mass%, inclusive, which has the advantage of improving adhesion and scuffing resistance.

[0029] 25 An average particle size of the NiCr self-fluxing alloy particles may be about the same as that of a general thermal spray raw material powder and is, for example, preferably within a range of 15 to 53 um, inclusive, and more preferably within a range of 15 to 30 um, inclusive, from the viewpoint of wear resistance. The average particle size of the NiCr self- fluxing alloy particles is also expressed as a value measured using a particle size distribution measuring device (Microtrac HRA manufactured by Nikkiso Co., Ltd., for example). It should be noted that the shape and the like of the NiCr self-fluxing alloy particles are also not particularly limited, and the particles may be granulated-sintered particles. NiCr self-fluxing alloy granulated-sintered particles are obtained by granulating and then heating and sintering small-sized NiCr self-fluxing alloy particles. The average particle size of the NiCr self-fluxing alloy particles used in granulating is 1 to 10 um, for example.

[0030] (Co alloy particles, Cr3C> particles) The Co alloy particles and the Cr3C; particles are main elements constituting the thermal spray coating 3, and are obtained by spraying a raw material powder that includes one 40 or both. The Co alloy particles have favorable wear resistance and, by inclusion in the thermal spray coating 3, make it possible to impart a high wear resistance effect. On the other hand, the Cr3C; particles are hard particles and, by inclusion in the thermal spray coating 3, make it possible to impart favorable wear resistance and adhesion to the thermal spray coating 3. According to the present invention, the above-described effects can be exhibited by making the

, DK 180330 B1 thermal spray coating 3 include one or both of the Co alloy particles and the Cr3C; particles. It should be noted that the Co alloy particles are Co-based alloy particles including 16 to 20 mass% of Cr.

[0031] The Co alloy particles and the Cr3C, particles are preferably included within a range of 15 to 30 mass%, inclusive, given 100 mass% as the content ratio of the Mo particles, Ni- based self-fluxing alloy particles, and Co alloy particles and Cr3C; particles combined. With this range, it is possible to better exhibit the above-described effects. A content of less than 15 mass% results in inferior wear resistance and adhesion in the thermal spray coating 3 obtained. On the other hand, when the content is more than 30 mass%, the CrsC; particles, for example, may shed from the surface of the thermal spray coating, possibly increasing aggressiveness against a mating material. The more preferred content is within a range of 15 to 25 mass%, inclusive, which has the advantage of improving wear resistance and suppressing aggressiveness against a mating material.

[0032] Whether both or one of the Co alloy particles and the Cr3C; particles are to be included in the mixed powder is selected taking into consideration the characteristics of the thermal spray coating 3 to be obtained. For example, the Co alloy particles may be selected when the thermal spray coating 3 emphasizing corrosion resistance is to be obtained, the Cr3Cy particles may be selected when the thermal spray coating 3 emphasizing wear resistance and adhesion is to be obtained, and both the Co alloy particles and the Cr3C; particles may be selected when the thermal spray coating 3 having both effects is to be obtained. It should be noted that, with the thermal spray coating 3 that includes the Co alloy particles only, the above-described content is preferably within a range of 17 to 23 mass%; with the thermal — spray coating 3 that includes the Cr3C» particles only, the above-described content is preferably within a range of 18 to 28 mass%; and with the thermal spray coating 3 that includes both, the combined content is preferably within a range of 35 to 55 mass%, the content of the Co alloy particles is within a range of 20 to 30 mass%, and the content of Cr3C> particles is within a range of 15 to 25 mass%.

[0033] An average particle size of the Co alloy particles and the Cr3C; particles may be about the same as that of a general thermal spray raw material powder and is, for example, preferably within a range of 10 to 45 um, inclusive, and more preferably within a range of 10 to 30 um, inclusive, from the viewpoint of wear resistance. The average particle size of these particles is also expressed as a value measured using a particle size distribution measuring device (Microtrac HRA manufactured by Nikkiso Co., Ltd., for example). It should be noted that the shape and the like of the Co alloy particles and the Cr3C; particles are also not particularly limited, and the particles may be granulated-sintered particles. The Co alloy granulated-sintered particles and the Cr3C> granulated-sintered particles are obtained by 40 granulizing and then heating and sintering small-sized particles. The average particle size of the particles used in granulating is 1 to 10 um, for example. The Vickers hardness of the Cr3C> particles is within a range of 1600HV to 1800HV.

[0034] (NiCr particles)

2 DK 180330 B1 The thermal spray coating 3 may further include NiCr particles as necessary. Generally, NiCr particles may be included as an element that imparts favorable wear resistance and adhesion to the thermal spray coating 3. According to the present invention, however, the effects of wear resistance and adhesion are satisfied by inclusion of one or both of the Co alloy particles and the Cr3C, particles in predetermined amounts. Furthermore, as described above, with inclusion of the NiCr self-fluxing alloy particles, the thermal spray coating 3 acts so as to improve adhesion with the piston ring base material 2 and reduces the differences in hardness between the Mo particles, and the Co alloy particles and Cr3C» particles. Thus, according to the present invention, the NiCr particles are mixed as an optional component and are not required. It should be noted that the difference between the NiCr self- fluxing alloy particles and the NiCr particles is that the NiCr self-fluxing alloy particles contain boron and silicon at a predetermined ratio, and thus the two can be differentiated and sorted by X-ray fluorescence analysis.

[0035] When the NiCr particles are included in the thermal spray coating 3, a ratio (A/B) of a content (A) of the Ni-based self-fluxing alloy particles to a content (B) of the NiCr particles is preferably 1.5 or greater by mass. With this range, it is possible to realize the effects of the NiCr self-fluxing alloy particles. When the ratio (A/B) is less than 1.5, the impact of the NiCr particles relatively increases, making the adhesion improving effect and hardness difference reducing effect of the NiCr self-fluxing alloy particles no longer adequate. It should be noted that the NiCr particles may not be included in the thermal spray coating 3 as well. When NiCr powder is included, the upper limit of the ratio is not particularly limited, but may be 20, for example. When NiCr particles are included, the content may be within a range of 0.01 to 10 mass%, inclusive.

[0036] When NiCr particles are included in the thermal spray raw material, an average particle size of the NiCr particles may be about the same as that of a general thermal spray raw material powder, and is preferably within a range of 5 to 45 um, inclusive, for example. The average particle size of the NiCr particles can also be expressed as a value measured using a particle size distribution measuring device (Microtrac HRA manufactured by Nikkiso Co., Ltd., for example). It should be noted that the shape and the like of the NiCr particles are also not particularly limited, and the particles may be granulated-sintered particles. The Vickers hardness of the NiCr particles is within a range of 400HV to 550HV. It should be noted that the Vickers hardness of the particles obtained by granulating these NiCr particles and the CrsC» particles described above (expressed as "Cr3C>/NiCr granulated particles") is within a range of 1000HV to 1200HV.

[0037] (Other chemical elements) Chemical elements other than the above may be contained in the mixed powder 40 serving as the thermal spray raw material. Examples of such other components include Fe, C, Mn, S, and the like. These components may be unavoidably contained as impurities. The content of the above-described impurities may be low enough so as to not hinder the effects of the present invention.

[0038]

2 DK 180330 B1 (Means for forming thermal spray coating) The thermal spray coating 3 is formed on the sliding surface of the piston ring 1 by plasma spraying. In plasma spraying, by using a plasma jet generated by a plasma spray gun, the raw material powder described above is heated and accelerated to melt or almost melt the powder, and the molten or almost molten material is sprayed on the base material. The principle is well known. When voltage is applied between the cathode and the anode, a DC arc is generated, which causes ionization of the working gas (such as an argon gas) fed from the backside to generate plasma. The raw material powder is carried by an argon gas or the like in the plasma flame and sprayed on the piston ring base material 2, thereby forming the thermal — spray coating 3 on the piston ring base material 2. The thermal spray coating 3 according to the present invention is formed by such plasma spraying, and the raw material powder is sprayed at or near a melting temperature in comparison to a high velocity oxygen fuel (HVOF) spraying described below, making it possible to exhibit the effects particular to the present invention. While examples of the sliding surface include the outer peripheral sliding surface of the piston ring 1 which slides upon contact with a cylinder liner (not illustrated), the thermal spray coating may be provided to other surfaces.

[0039] It should be noted that, HVOF spraying, although not the means for forming the thermal spray coating 3 of the present invention, is a thermal spraying that uses a high-speed jet flame using oxygen and fuel. Specifically, a mixed gas of high-pressure oxygen and fuel is combusted in a combustion chamber to generate a combustion flame. The combustion flame is narrowed through a nozzle and, upon release into the atmosphere, undergoes rapid gas expansion, producing a supersonic jet stream. The raw material powder accelerated by high acceleration energy does not substantially oxidize or change in composition, and thus forms — the high-density thermal spray coating 3 on the piston ring base material 2. This HVOF spraying forms a coating at high speed without an increase in temperature, and therefore the raw material powder is sprayed substantially without melting. As a result, small fine grains are used as the raw material powder.

[0040] While not particularly limited, a thickness of the thermal spray coating 3 is, for example, preferably within a range of 200 to 600 um, inclusive. With this thickness range, the effects specific to the present invention can be exhibited.

[0041] A porosity of the thermal spray coating 3 is also not particularly limited, but is preferably 5% or less by surface area, for example. It should be noted that, from the viewpoint of wear resistance based on the fineness and oil retention performance of the thermal spray coating 3, the porosity is more preferably 4% or less. Further, while not particularly limited, a lower limit of the porosity may be 0.5%, for example. The porosity can be measured by analysis using image analysis software, for example.

40 — [0042] (Application examples) As an application example, a thermal spray surface layer (not illustrated) may be provided as desired on the thermal spray coating 3. Examples of thermal spray surface layers, while not particularly limited, include a layer containing Al, Fe, Cu, and the like. The thermal

DK 180330 B1 10 spray surface layer may be provided for the purpose of further reducing aggressiveness against a mating material, improving the initial running-in property, or the like. Such a thermal spray surface layer can also be formed on the thermal spray coating 3 by plasma spraying, arc spraying, gas spraying, or the like, similar to the thermal spray coating 3.

[0043] [Manufacturing Method] A manufacturing method of the piston ring 1 according to the present invention is a method for manufacturing a piston ring comprising the characteristic thermal spray coating 3 on at least the sliding surface of the piston ring base material 2, and includes the steps of plasma-spraying a mixed powder composition of Mo powder, Ni-based self-fluxing alloy powder, and Co alloy powder and/or Cr3C; powder, and forming the thermal spray coating 3 on the outer peripheral sliding surface of the piston ring base material 2. This manufacturing method is described in detail in the above description area of the piston ring, particularly in the description area of the formation of the thermal spray coating 3, and thus a description thereof is omitted here. The granulated-sintered powder described above may be applied as desired to the raw material powder. It should be noted that, in this application, material constituting the raw material powder is referred to as "powder" and material constituting the thermal spray coating is referred to as "particles." Examples

[0044] The present invention will be described in further detail with reference to examples and comparative examples.

[0045] [Example 1] Mo powder (45 mass%), NiCr self-fluxing alloy powder (25 mass%), and Cr3Cy/NiCr granulated-sintered powder obtained by granulating Cr3C> powder (22.5 mass%) and NiCr powder (7.5 mass%), with average particle sizes of 31 um, 43 um, and 36 um, respectively, were mixed to prepare a raw material powder. Table 1 shows the mixed amounts of the raw material powder. At this time, given 100 mass% as the content ratio of the Mo powder, the NiCr self-fluxing alloy powder, the Cr3C>/NiCr granulated-sintered powder, the NiCr self-fluxing alloy powder is 25 mass%, the Cr3C>/NiCr granulated-sintered powder is 30 mass% (Cr3C> powder: 22.5 mass%, NiCr powder: 7.5 mass%), and the remaining 45 mass% is Mo powder. It should be noted that the component composition of the NiCr self-fluxing alloy powder was Ni: 70 mass%, Cr: 17 mass%, B: 3.5 mass%, Si: 4 mass%, Fe: 4 mass%, and the remainder: unavoidable impurities. Further, the component configuration of the Cr3C> powder was Cr: 86 mass%, C: 13 mass%, and the remainder: unavoidable impurities. Furthermore, the component composition of the NiCr powder was Ni: 78 mass%, Cr: 20 mass%, and the remainder: unavoidable impurities. The component composition was 40 quantified with a backscattering measuring device (manufactured by NHV Corporation), and the average particle size is expressed as a value of Dso measured using a particle size distribution measuring device (Microtrac HRA manufactured by Nikkiso Co., Ltd.).

[0046]

DK 180330 B1 11 This raw material powder was plasma-sprayed under the conditions described below to form the thermal spray coating 3 having a thickness of 300 um on the sliding surface of the piston ring base material 2 made from boron cast iron. The plasma spraying was carried out using a 9MB plasma spray gun manufactured by Sulzer Metco, Inc. at a voltage of 60 to 70 V and a current of 500 A.

[0047] The component composition of the obtained thermal spray coating 3 was quantified using a backscattering measuring device (manufactured by NHV Corporation) as described above, and was the same as that of the raw material powder serving as the raw material, that is, Mo: 45 mass%, NiCr self-fluxing alloy: 25 mass%, Cr3C: 22.5 mass%, and NiCr: 7.5 mass%. Further, the ratio (A/B) of the content A of the NiCr self-fluxing alloy and the content B of the NiCr was 3.3 by mass.

[0048] [Example 2] The thermal spray coating 3 in Example 2 was formed in the same manner as in Example 1, only the raw material powder was changed. The component composition of the thermal spray coating 3 was also the same as that of the raw material powder below, that is, Mo: 50 mass%, NiCr self-fluxing alloy: 30 mass%, and Co alloy: 20 mass%.

[0049] The raw material powder was a mixture of Mo powder (50 mass%), NiCr self- fluxing alloy powder (30 mass%), and Co alloy powder (20 mass%) having average particle sizes of 31 um, 43 um, and 31 um, respectively, and is shown in Table 1. At this time, the content ratio of each powder, given 100 mass% as the content ratio of the Mo powder, the NiCr self-fluxing alloy powder, and the Co alloy powder, is the same as that of the above- — described powder composition. It should be noted that the component composition of the NiCr self-fluxing alloy powder was the same as in Example 1, and that of the Co alloy powder was Co: 49.8 mass%, Mo: 28 mass%, Cr: 18 mass%, Si: 3.4 mass%, and the remainder: unavoidable im purities.

[0050] [Example 3] The thermal spray coating 3 in Example 3 was formed in the same manner as in Example 1, only the raw material powder was changed as shown in Table 1. The component composition of the thermal spray coating 3 was also the same as that of the raw material powder in Table 1. It should be noted that, in this Example 3, the NiCr self-fluxing alloy powder used, unlike in Example 1, had an average particle size of 43 um and a component composition of Ni: 70 mass%, Cr: 17 mass%, B: 3 mass%, Si: 4 mass%, Mo: 2 mass%, Cu: 3 mass%, and the remainder: unavoidable impurities. All other components were the same.

[0051] [Examples 4 to 6] 40 The thermal spray coatings 3 in Examples 4 to 6 were formed in the same manner as in Example 1, only the raw material powder was changed as shown in Table 1. The component composition of the thermal spray coatings 3 was also the same as that of the raw material powder in Table 1. It should be noted that the NiCr self-fluxing alloy powders in Examples 4 to 6 were the same as in Example 1.

DK 180330 B1 12

[0052] [Comparative Example 1] The thermal spray coating 3 in Comparative Example 1 was formed in the same manner as in Example 1, only the raw material powder was changed. The component composition of the thermal spray coating 3 was also the same as that of the raw material powder below, that is, Mo: 33 mass%, NiCr alloy: 17 mass%, and Cr3C: 50 mass%.

[0053] The raw material powder was a mixed powder of Mo powder (33 mass%), NiCr powder (17 mass%), and Cr3C» powder (50 mass%) having average particle sizes of 31 um, 21 um, and 21 um, respectively, and is shown in Table 1. It should be noted that the component compositions of the NiCr powder and the Cr3C> powder were the same as in Example 1.

[0054] [Comparative Example 2] The thermal spray coating 3 in Comparative Example 2 was formed in the same manner as in Example 1, only the raw material powder was changed. The component composition of the thermal spray coating 3 was also the same as that of the raw material powder below, that is, Mo: 50 mass%, NiCr alloy: 15 mass%, and Cr3C»: 35 mass%.

[0055] The raw material powder was a mixed powder of Mo powder (50 mass%), NiCr powder (15 mass%), and Cr3C> powder (35 mass%) having average particle sizes of 31 um, 22 um, and 13 um, respectively, and is shown in Table 1. It should be noted that the component compositions of the NiCr powder and the Cr3C> powder were the same as in Example 1.

[0056] [Comparative Fxamples 3 and 4] The thermal spray coatings 3 in Comparative Fxamples 3 and 4 were formed in the same manner as in Example 1, only the raw material powder was changed as shown in Table

1. The component composition of the thermal spray coatings 3 was also the same as that of the raw material powder in Table 1. It should be noted that the NiCr self-fluxing alloy powder in Comparative Examples 3 and 4 was the same as in Example 1.

[0057] [Table 1] Table 1 ee ms oa mas (mass%) (mass%) (mass%) | (mass%) | (mass%) | Exampler | 45 | 25 | 25 | 75 [ - | Example2 | so | 30 | - | - | 20 | | Example3 | so | 25 | 188 | 62 | - | | Example4 | 40 | 03 | 19 | 6 | - | | Examples | 58 | 24 | 16 | 5 [ - | Example6 | 45 | 20 | 28 | 7 | - | | Comparative Example 1| 33 | ~~ - | 50 | 17 [ - | Comparative Example2| 50 | ~~ - 13% | 15 | - | | Comparative Example3| 50 | ~~ - | 2 | 30 [ - | Comparative Example 4| 70 | ~~ - ~~] 20 | 10 | - |

DK 180330 B1 13

[0058] [Measurement Method and Measurement Results] (Wear resistance index and wear resistance index of mating material) The wear resistance index and the wear resistance index of the mating material were measured by an abrasion test. The abrasion test was carried out using a high-load type abrasion tester 6 illustrated in Fig. 3. Samples 7 obtained under the same conditions as the piston rings obtained in the above-described Examples 1 to 6 and Comparative Examples 1 to 4 were used as fixed pieces in this test. The sample 7 (fixed piece) was brought into contact with a mating material 8, which was a rotating piece, and a load P was applied thereto. Sample 7 used herein was obtained by integrating three pins made from flake graphite cast iron (5 mm, 58.9 mm?) and a disk with an outer diameter of 40 mm, and the disk had an outer diameter of 40 mm and a thickness of 12 mm, including the pins. Further, the mating material 8 (rotating piece) was a boron cast iron having an outer diameter of 40 mm and a thickness of 12 mm. The abrasion test was carried out under the conditions of an oil product equivalent to spindle oil as the lubricating oil, an oil temperature of 125°C, a peripheral speed of 1.65 m/sec (1050 rpm), a contact pressure of 76.4 MPa, and a test time of 8 hours.

[0059] As for the wear resistance and the wear resistance of the mating material, the abrasion losses of each sample corresponding to Examples 1 to 6 and Comparative Examples 2to 4 were compared with the abrasion loss of the sample corresponding to Comparative Example 1, respectively, to obtain the relative ratio, which was defined as the wear resistance index. Accordingly, the sample having a smaller wear resistance index below 100 is considered to have a smaller abrasion loss compared to Comparative Example 1. The results are shown in Table 2.

[0060] (Adhesive strength) Adhesive strength was measured by integrating two end surfaces of cylindrical test pieces, one with and one without the thermal spray coating 3 formed thereon, by adhesion using a thermosetting resin, fixing both ends of the cylinder using a vertical chuck of a tensile tester, and conducting a tensile test, in compliance with JIS H 8667. In the tensile test, the load when the thermal spray coating 3 separated from the interface of the boron cast iron or when the layers separated within the thermal spray coating 3, given a tensile speed of 1 mm/minute, was measured, and that load was then divided by the surface area of the cylindrical end surface to find the value. Given the value of the thermal spray coating 3 in Comparative Example 1 as 100 (standard), the adhesive strength of each sample corresponding to Examples 1 to 6 and Comparative Examples 2 to 4 were relatively evaluated and expressed as the adhesive strength index. The greater the adhesive strength index, the more superior the adhesive strength. It should be noted that separation at the interface with the curing resin and delamination within the curing resin layer were excluded from evaluation. The results are 40 shown in Table 2.

[0061] (Evaluation)

DK 180330 B1 14 As shown in Table 2, the thermal spray coatings in Fxamples 1 to 6 were confirmed as having a wear resistance index, a wear resistance index of the mating material, and an adhesive strength superior to those in Comparative Example 1.

[0062] [Table 2] Table 2 imi mgt Strength Index | Example | 60 | 15 | vv | Comparative Example 2] 110 | 60 | 101

[0063] Use of the Ni-based self-fluxing alloy having a higher hardness than that of the NiCr alloy is found to facilitate a reduction in the differences in hardness between the Mo particles — and the Cr3C; particles, and use of the Cr3C>/NiCr granulated-sintered powder in addition to the Ni-based self-fluxing alloy is considered to prevent the shedding of the Cr3C; particles caused by these differences in hardness, making it possible to suppress aggressiveness against the cylinder liner. Descriptions of Reference Numerals

[0064] 1 Piston ring 2 Piston ring base material 3 Thermal spray coating 4 Thermal spray surface layer 6 High-load type abrasion tester 7 Sample 8 Rotating piece P Load

Claims

DK 180330 B1 1 STAMP RING AND METHOD OF MANUFACTURE THEREOF

Piston ring provided with a thermal spray coating comprising Mo particles, Ni-based self-flux alloy particles, CraC2 particles and NiCr particles, on at least one sliding surface of a base material of the piston ring.

Piston ring according to claim 1, wherein the Ni-based self-flux alloy particles - given 100% by mass as a content ratio of the Mo particles, the Ni-based self-fluff alloy particles, the CraC2z particles and NiCr particle - the clays together - are in a range from and including 20 to 40% by mass, the Cr3C2 particles are in a range from and including 15 to and including 30% by mass, the NiCr particles are in a range from and with 0.01 to 10% by mass and the remainder are Mo particles.

Piston ring according to claim 1 or 2, wherein a ratio (A / B) of a content A of the Ni-based self-flux alloy particles and a content B of the NiCr particles is 1.5 or larger in mass.

A piston ring according to any one of claims 1 to 3, wherein the thermal spray coating comprises a granular structure of the NiCr particles and the CraC2 particles.

A method of making a piston ring comprising the steps of plasma spraying a mixed powder composition of Mo powder, Ni-based self-fluffing alloy powder, CraC2 powder and NiCr powder, and forming the thermal spray coating on an outer peripheral sliding surface. of a base material of the piston ring.