SE526708C2 - Methods of making a abrasion resistant hot-sprayed coating for a slider - Google Patents

Abstract

PURPOSE: Provided is a wear-resistant sprayed coating film having no possibility of causing embrittlement and reduction in oil retentivity and formed on the sliding surface of a sliding member, such as piston ring and cylinder. CONSTITUTION: A sprayed coating film(3) is obtained by using a powder mixture consisting of powder of a hard material(5), powder of a metal constituting a matrix(6), and particles of a metal-coated solid lubricant and plasma spraying it onto the sliding surface of the sliding member. In the sprayed coating film(3), copper-coated graphite particles(4) are used as the powder of the metal-coated solid lubricant and the content of the copper-coated graphite particles(4) is made to 0.1 to 10 mass%.

Description

"This invention has been made to solve these problems."

An object of the invention is thus to provide an abrasion-resistant hot-spray coating which is produced by thermal spraying of a mixture consisting of ceramic powder as hard material, powder of metals to form a matrix, and metal-coated solid lubricant particles such as solid lubricant powder. on the sliding surface of a sliding member, such as a piston ring and a cylinder liner in an internal combustion engine, the coating being neither sensitive to brittleness nor having a poor ability to retain oil therein.

SUMMARY OF THE INVENTION In order to achieve the above-described object, the invention provides a method of producing an abrasion resistant hot spray coating for a slider, which method is characterized in that said coating is formed by hot spraying a mixture of particles of hard material, powder of metals for forming a matrix, and powder of solid lubricant, on the sliding surface of the slider, said hard materials being selected from the group of carbides, oxides, nitrides and carbide nitrides of chromium, tungsten, molybdenum and vanadium and said metals to form a matrix being selected from the group of molybdenum , nickel-chromium alloy, cobalt, cobalt-chromium alloy, nickel-molybdenum alloy and cobalt-nickel alloy. The mixture comprises metal-coated solid lubricant particles such as said solid lubricant with 0.1 to less than 10 percent of the mass of the mixture.

The limited range is specified as above because if the percentage in the mass is less than 0.1%, the lubricating effect will not be sufficient while if the percentage in the mass is 10% or more, the coating becomes brittle and the coefficient of friction does not improve sufficiently. However, in order to increase the lubricating effect, the percentage mass can preferably be adjusted so that it becomes 1% or greater. Furthermore, the percentage mass can be suitably adjusted so that it becomes 8% or less, this taking into account the strength of the coating.

According to the invention, the metal-coated lubricant particles further contain solid lubricant within the limited range of 10 to 50 percent of the entire mass of the metal-coated graphite particles. This limited range is indicated in this way because if the percentage mass is less than 10%, the lubricating effect will not be sufficient while if the percentage mass is greater than 50% or more, the amount of solid lubricant particles remaining when thermal spraying occurs, resulting in that the amount of abrasive is increased on the counterpart of the sliding intervention.

Solid lubricant particles to be used in the coating composition of the invention may consist of a material selected from the group of graphite (C), manganese sulfide (MnS), graphite fluoride, calcium fluoride (CaF2), boron nitride (BN), molybdenum disulfide (MoS2) and tungsten disulfide. , among which graphite can preferably be used with respect to machinability.

The methods of coating the solid lubricant particles with metal may include chemical, electrochemical and mechanical coating methods, the gas reduction method and the mechanical melting method. The metal to be used for coating the solid lubricant particles of the invention may consist of a material which. is selected from the group of copper, nickel, silver, cobalt and molybdenum, among which copper (Cu) can be used preferably with regard to metal plating ability.

The hard. the material to be used in the coating mixture * may be selected from the group of carbides, oxides, nitrides and carbide nitrides of chromium, tungsten, molybdenum and vanadium, among which chromium oxide (Cr 2 O 3) or chromium carbide (CrC) may preferably be used aggressive towards the counterpart (ie not aggressive towards the counterpart in the sliding grip with the sliding member on which the hot spray coating is applied) according to the invention.

The metals to be used in the coating mixture to form the matrix can be selected from the group of molybdenum, nickel-chromium alloy, cobalt, cobalt-chromium alloy, nickel-molybdenum alloy and cobalt-nickel alloy, among which molybdenum (Mo) and nickel-chromium alloy (Ni-Cr ) together can preferably be used with respect to abrasion resistance and scratch resistance 526 708 according to the invention.

Furthermore, the porosity of the thermally applied coating can preferably be limited to the range of 5 to 15% by volume by means of the plasma-sprayed coating. This limited range is specified in this way because a coating with a porosity in volume percentage less than 5% can result in poor ability to retain oil therein, while a coating with a porosity with a volume percentage above 15% can result in a brittle , hot spray coating, thereby causing an extremely steep decrease in the strength of the coating.

With a thermally applied coating implemented. in the manner described above, according to the invention, an advantage is obtained in that a steep decrease in strength, causing brittleness, is unlikely to occur and that it is also not likely that the result will be poor ability to retain oil in the coating. In addition, the thermally applied coating according to the invention has excellent abrasion resistance, scratch resistance and is not aggressive to the substrate and has improved low sliding friction.

Brief Description of the Drawings Fig. 1 is an enlarged partial cross-sectional view of a piston ring with a hot-sprayed coating formed thereon according to an embodiment of the invention, and Fig. 2 is a schematic drawing showing a rotary type test device used in plane tests. sliding friction grinding.

Detailed Description of the Invention Referring to Fig. 1, an exemplary hot spray coating of the invention is described below along with a piston ring.

The piston ring 1 shown in Fig. 1 is provided with a hot-sprayed coating 3 formed on the outer peripheral sliding surface of a base material 2. The hot-sprayed coating 3 is prepared by plasma-spraying a mixture consisting of molybdenum powder with 40 to 80 percent of the whole mass, nickel-chromium alloy powder with 10 to 50 percent of oo ooo oo 'oo: z 0 ooooooo. In the whole mass, either chromium oxide or chromium carbide powder with 1 to 20 per cent of the whole mass, and copper-plated graphite particles with 0.1 to 10 per cent of the whole mass.

The copper-coated graphite particles have a copper coating with graphite of 10 to 50 percent of the entire mass and a size distribution between 10 and 106 μm.

As can be seen from the cross section of the hot-sprayed coating 3, the coating mixture has copper-coated graphite particles 4 with 0.1 to 10 percent of the whole mass and almost evenly distributed over the whole coating mixture. A decrease in the strength of the hot-sprayed coating 3 and which is caused by the copper-coated graphite particles 4 thus becomes very small. Furthermore, the hard material particles E1 of either chromium oxide or chromium carbide of the hot-sprayed coating 3 are evenly distributed in a matrix 6 formed by an alloy of molybdenum and nickel-chromium. The aggressiveness of the hot-spray coating 3 against the substrate is thus small. The porosity of the hot spray coating 3 formed by plasma spraying amounts to 5 to 15 percent of the whole mass. The synergistic effect of the porosity and the graphite phase therefore makes it possible for the hot-sprayed coating 3 to have low frictional resistance and to be excellent in terms of abrasion resistance and scratch resistance.

Description of examples of the hot spray coating and examination thereof.

The hot spray coating according to the invention will be further discussed below in connection with several tests which have been carried out on samples of working examples, comparative tests and conventional tests.

As shown in the following Table 1, Samples 1 and 2 are conventional samples with a coating prepared either by HVOF (No. 1) or plasma (No. 2) spray processes which do not contain a metal-coated solid lubricant. Samples No. 3 through No. 15 are samples of embodiments of plasma spray coatings according to the invention, which contain metal-coated solid lubricant particles. Finally, samples Nos. 16 to 19 526 708 are comparative tests on plasma-sprayed coatings containing metal-coated solid lubricants, the test specimens being separated and the the amount ratio of the metal-coated solid lubricant in the coating mixture or the ratio of the solid lubricant to the metal-coated solid lubricant.

The varieties and the proportions (percent of the whole mass) of the hard materials in the coating mixture, of the whole pulp) of the matrix in the varieties and the proportions of the coating mixture, the varieties and proportions of the metal-coated solid lubricant in the coating mixture, the proportions of the whole in the metal-coated solid lubricant, the porosities of the coatings and the spray graphite of those with (percent (percent of the whole mass) (percent of the methods used are shown in Table 1. granular.

In Table 1,% in the column refers to hard material contained with the percentage of the whole mass in In the matrix columns, the values Mo- and "Hard material" show the coating mixture.

Ni-Cr alloy the matrix-forming metals and their aggregate. (percent of the whole settlement in the matrix, i identifies the coating material in the part. metal coated solid lubricant), the mass) means the net-coated solid lubricant contained at the percentage of the whole mass in the coating mixture, while SL% means the solid lubricant contained at that percentage of the whole mass in the metal-coated column, the column HV and the% solid lubricant. In the column "Spray method" the HVOF method while Plas means the plasma method. means Cnv, Emb and Cmp conventional test, embodiment test In the column "Test" (respectively comparative test. 7 '53 'å * å> g MW a 0 H m M 1-4 Sl Hart Matrix With metal ï b>, _, ä w Q. w q.

N - 1 belagt fast a, 'Q o u ... 1 g>:> _ s-1 r materla ... U E u M 5 .... q, 111.0 lubricant _ .. o. O 31 w g g s * H o L. H.

S1 Ni-cf sL ä šfå fi-fifl fñ ag% M ° lege. stroke%% ° * M5? ä a 1 CrzOa 5 60 35 3 HV Cnv 100 1 00 100 2 CrzOa 5 60 35 8 Pias Cnv 103 98 97 3 CrzOa 7 60 30 Cu-C 3 50 7 Plas Emb 116 83 85 4 C110; 5 so so. cu-c 5 so s Plss Emb 124 so '82 5 CrC 5 60 30 Cu-C 5 50 8 Plas Emb 121 82 85 6 CrzOa 7 55 30 Cu-C 8 50 8 Plas Emb 123 84 82 7 CrzOa 5 60 30 Cu -C 5 10 7 Plas Ernb 113 90 92 8 C210: 5 60 30 Cu-C 5 20 8 Plas Emb 116 84 88 9 CrC s so so cu-c s so s 91115 smb 113 ss ss 10 CrzOa 5 60 30 Cu- C 5 40 8 Plas Emb 120 82 84 11 01-10; 5 60 30 N1-C 5 so s Plas Emb 123 81 82 12 cmos s so so C * s so s P11; sms 1-zs s1 ss MnS 13 Cmos s so so C * s so s 91115 sms 124 sz ss CaFz 14 Cmos s so so s so s Pm smb 123 sz sz 15 Cmos s so so s so s mas sms 123 s1 ss 16 CrzOs 4.95 60 35 Cu-C 0.05 30 6 Plas Cmp 103 97 103 17 CrzOa 3 55 30 Cu-C 12 30 12 Plas Cmp 122 103 83 18 CrzOs 5 60 30 Cu-C 5 5 10 Plas Cmp 105 95 102 19 CrzOs 5 60 30 Cu-C 5 60 10 Plas Cmp 123 83 103 Table 1 526 708 0000 s ola I 0000 un Q 0 I 0 n 0 oøonoo u 0 o 0 nu onnooo 0 0 0 0 once un anno o 0 0 0 nano 0 nu n Q The conditions for plasma spraying were as follows: Use spray gun: 9 MB Plasma Gun from Sulzer Metco Voltage: 60-7OV Current: 500 A The conditions for HVOF spraying were as follows: Use spray gun: Diamond Jet Gun (trade name) from Sulzer Metco Fuel gas: propane - oxygen (1: 7) Tests on scratches, abrasion tests and tests for aggression against the substrate were performed on each test piece.

Scratch Samples Critical surface pressures for scratches were measured on each specimen using a rotary friction grinding type test device as shown in Fig. 2. Each specimen ll was kept in contact with a specified surface pressure (P) for a specified time and: note a rotating surface of a substrate material l2 which rotated at a constant speed, and the surface pressure when scratches occurred was measured as a critical surface pressure.

The pressure was applied in such a way that an initial pressure was set to 2.45 MPa, and the pressure was increased to 4.9 MPa after an initial time period of 30 minutes and then increased successively by 0.98 MPa every 5 minutes thereafter.

The test conditions were as follows: Sliding speed: 5 m / s Lubricating oil: SAE30 + heavy petrol (lzl) Amount of lubricating oil added: no lubrication except in the initial application.

Substrate material: Tarkalloy (known as a trade name owned by Nippon Piston Ring Co., Ltd. for a boron-containing cast iron).

Abrasion tests and tests on aggression against the substrate The abrasion depth of each sample and the abrasion depth of the underlying material were measured using the rotary type test device for planar slip friction grinding as shown in Fig. 2. Each specimen 11 was kept in contact with a specified NJ surface pressure ( P) for a specified time with and against the rotating substrate material 2 with constant Lubricating Oil was allowed to drip down on the rotating substrate 1 -v 1 which rotated the surface of velocity. the team material 12.

The test conditions were as follows: Sliding speed: 6 m / s Surface pressure: 6 MPa Lubricating oil: Spinox 2 bearing oil from Nippon Mitsubishi Oil Corporation for a bearing oil) Oil temperature: 60 10 degrees C Amount of lubricating oil added: 1O'4 m3 / min 80 hours (known as trade name owned + Duration of the test: Substrate material: Tarkalloy (known as a trade name owned by Nippon Piston Ring Co., Ltd. for a boron-containing cast iron).

The measurement results on each sample are shown in Table 1 expressed in terms of measurements of critical surface pressure for scratches, the extent of grinding on the test pieces and the material as a basis for test piece no. 1 each set to the nominal value 100.

From the results, it has been confirmed that the embodiment tests are superior to the conventional tests and the comparative tests in terms of scratch resistance, abrasion resistance and non-aggression against the substrate.

As described above, the abrasion resistant heat spray coating of the invention is prepared by plasma spraying a mixture of powder of hard material, powder of the metal to form a matrix and powder of metal coated solid lubricant, where the amount ratio in the heat spray coating of the metal-coated solid lubricant is less than 10 percent of the entire Amassan and differs from conventional heat-sprayed coatings that have metal-coated graphite as the metal-coated solid lubricant with 10 percent of the entire mass or greater.

The heat-sprayed coating according to the invention thus has a clear and extraordinary advantage in that it is due to the fragility. The synergistic effect of the porosity and the solid lubricant phase has the advantage of the fact that the coating according to the invention also has the advantage excellent in terms of scratch resistance and abrasion resistance and is not aggressive to the surface.

Although fundamental new features of the invention applied to preferred embodiments have been shown and described, it is to be understood that various modifications and alterations to these embodiments may be made by those skilled in the art within the scope of the invention.

It is thus our intention that limitation should be performed only as indicated by the scope of the appended claims.

Claims (8)

526 708 ll PATENT REQUIREMENTS A method of producing an abrasion-resistant hot-sprayed coating for a slider (1), characterized in that said coating is formed by hot-spraying a mixture consisting of particles of hard material (5), powder of metals to form a matrix (6 ), and powder of solid lubricant, on the sliding surface of the slider (1), the hard material being selected from the group of carbides, oxides, nitrides and carbide nitrides of chromium, tungsten, molybdenum and vanadium and the metals to form a matrix being selected from the group of molybdenum, nickel-chromium alloy, cobalt, cobalt-chromium alloy, nickel-molybdenum alloy and cobalt-nickel alloy, the mixture comprising metal-coated solid lubricant particles such as. the solid lubricant with 0.1 to less than 10 percent of the mass of the mixture. 2. A method according to claim 1, characterized in that the metal-coated solid lubricant particles are net-coated graphite particles applied by a plating method and that a material from the group of copper, nickel, silver, cobalt and molybdenum is selected as the coating metal. 3. A method according to claim 2, characterized in that the metal-coated graphite particles contain graphite with 10 to 50 percent of the mass of the metal-coated graphite particles. 4. A method according to claim 1, characterized in that the metal-coated solid lubricant particles are copper-coated solid lubricant particles and that the solid lubricant particles consist of a material selected from the group of graphite, manganese sulphide, graphite fluoride, calcium fluoride and boron nitride sulphide; 5. A method according to claim 4, characterized in that the copper-coated solid lubricant particles contain solid lubricant with 10 to 50 percent of the mass of the copper-coated solid lubricant particles. 6. A method according to any one of claims 1-5, characterized in that the hot-sprayed coating is formed so that it has a porosity of 5 to 15% by volume of the mixture by plasma spraying. 7. A method according to any one of claims 1-5, characterized in that the hard material is either chromium oxide or chromium carbide and that the metals to form the matrix are both molybdenum and nickel-chromium alloy. 8. A method according to claim 6, characterized in that the hard material is either chromium oxide or chromium carbide and that the metals to form the matrix are both molybdenum and nickel-chromium alloy.