JPS5893867A - Sliding member - Google Patents

Abstract

PURPOSE:To improve the service performance of a sliding member and to reduce the abrasion of the mating member, by plasma melt-spraying ground powder of high chromium cast iron contg. C, Cr and further contg. Si or Mo, and forming a heat resistance and abrasion resistant layer on the slideways. CONSTITUTION:This sliding member is produced by forming a heat resistant and abrasion resistant layer on slideways by plasma melt-spraying of ground powder of high chromium cast iron having the following compsn. and grain sizes: the ground powder of high chromium cast iron which contains, by wt%, 1-6% C, and 20-35% Cr, and further contains >=1 kind among 0.5-6% Si and 0.5-3% Mo and has grain sizes not coarser than 200 meshes is used. If necessary, 55-90% the ground powder of the above-mentioned high chromium cast iron and 10-45% a self-fluxing alloy consisting of atomized powder not coarser than 250 meshes are plasma melt-sprayed.

Description

Detailed Description of the Invention The present invention relates to a sliding member of an internal combustion engine, etc., and more specifically, it is a sliding member that is compatible with a cylinder as a mating material (including a cylinder sleeve and a cylinder liner, the same applies hereinafter). This relates to piston rings for internal combustion engines.

Conventionally, for sliding members such as piston rings of internal combustion engines, various surface treatments have been applied to the base material, such as cast iron, to improve initial sliding performance (compatibility) and long-term sliding performance. Improves durability. Hard chrome plating and M are representative examples.

There are piston rings coated with thermal spray coating, but they all have their advantages and disadvantages, and they do not meet the advanced requirements of internal combustion engines in recent years.In other words, hard chrome plating has excellent wear resistance. Although it has the advantage of reducing the amount of wear on the piston rings, it has the disadvantage that it has poor seizure resistance, so when the internal combustion engine load increases, it will seize, resulting in an abnormally large amount of wear. Furthermore, the high hardness f of hard chromium plating is due to its unique electrodeposited structure, and under high temperature and high load internal combustion engine operating conditions, the hardness decreases significantly and its wear resistance deteriorates. Furthermore, in engines using high lead gasoline, diesel engines, etc., abrasive combustion products also accelerate the wear of hard chromium-plated piston rings, making it impossible to expect a stable service life. On the other hand, Mo spray coating is superior to hard chromium plating in terms of seizure resistance, but inferior in abrasive wear resistance.

Furthermore, as a measure to improve the wear resistance and seizure resistance of piston rings, etc., it has been known to perform surface treatment on piston rings, etc. by spraying a mixture of hard substances such as various carbides and oxides. However, although these methods improve the wear resistance and seizure resistance of the piston ring itself, the cylinder, which is the mating member, suffers from large wear, and there are defects in the overall performance of the internal combustion engine sliding member as a whole.

An object of the present invention is to provide a sliding member that has excellent performance that can cope with the severe operating conditions of modern internal combustion engines, and that also reduces wear on mating materials (for example, cylinders). The object of the present invention is to provide a piston ring that has superior overall performance to either conventional hard chrome plating or Mo spray coating piston rings.

The first feature of the present invention is that in terms of weight ratio, C1 to 61j6
and Cr 20 to 35-, and further contains at least one of 0.5 to 696 81 and 0.5 to 3 Mo, and has a grain size of 200 mesh and is not coarse. The sliding member has a heat-resistant and wear-resistant layer formed on the sliding surface by plasma spraying crushed powder.

A second feature of the present invention is that the present invention contains, in a weight ratio, CI to 6 and Cr 2 G to 35, and further contains Ol, 5
Contains at least one lumber of 0.5 to 6 liters of St and 0.5 to 3 liters of MO. A self-fluxing alloy consisting of a non-coarse high chromium cast iron ground powder having a particle size of 200 mesh or more and a non-coarse atomized powder having a particle size of 250 mesh or more, and a self-fluxing alloy of 10 to 45 milligrams, which is not coarse, are heated in plasma. This is a sliding member that is thermally sprayed to form a heat-resistant and wear-resistant layer on the sliding surface.

The feature of Kame 3 of the present invention is that it contains 1 to 6 Ls of CI and 20 to 35 Ls of Cr, and further contains at least one of 0.5 to 6 Ls of 81 and 0.5 to 3 Ls of Me. Contains particle size of 200m.

70 to 95% by weight of crushed high chromium cast iron powder, which is not very coarse, and 5 to 30% by weight of Mo, which is a granulated powder with a particle size of 350 mm and which is not very coarse, were plasma sprayed to prepare the sliding surface. The sliding member has a heat-resistant and wear-resistant layer formed thereon.

The fourth feature of the present invention is that it contains 1 to 6 Cr and 20 to 35 Cr, and further contains at least one of 0.5 to 696 81 and 0.5 to 3 Mo of Mo. The particle size is 200 mm, 70 to 85% by weight of crushed high chromium cast iron powder that is not coarsely ground, and
Plasma spraying of Mo5 to 15% by weight of granulated powder with a particle size of 50 mesh, which is not coarser, and 10 to 25 weight% of Mo2 alloy, which is an atomized powder with a particle size of 250 mesh, which is not coarser than Mo, is plasma sprayed, and then rubbed. The sliding member has a heat-resistant and wear-resistant layer formed on its moving surface.

The common feature of the present invention is that high chromium cast iron ground powder is plasma sprayed.The significance of this is that high chromium cast iron has excellent heat resistance due to its high Cr content, and Cr is cast as a carbide. This is because since it already exists in the material, it is finely dispersed in the sprayed layer in the form of stable carbides and exhibits excellent wear resistance. t7
The significance of the above common features is that the heat-resistant and wear-resistant (sliding) layer is compatible with the mating material. In other words, the current material for internal combustion engine cylinders is a material equivalent to FC25 in the case of linerless engines, and high-grade alloy cast iron materials are used in diesel engines fitted with cylinder liners, but none of these materials are used. It has good compatibility with both materials and will not cause excessive wear on the other material.

In addition, the chromium carbide itself in high chromium cast iron has high hardness I.
f, which is not preferable from the viewpoint of compatibility, but in the present invention, chromium carbide is not sprayed alone, but chromium carbide is sprayed evenly dispersed in the cast iron base, so good results can be achieved. It is possible to obtain it. Furthermore, since high chromium cast iron has good corrosion resistance, particularly against dilute sulfuric acid corrosion, there are fewer problems with corrosive acids produced from SO5 as a combustion product of internal combustion engines. In addition, high chromium cast iron has a white cast iron structure in the cast state, which has a positive effect on the crushability of castings (ingots, etc.), and as a result makes it easier to produce powder. First, it is thought that the powder shape also increases the amount of bonding between powder particles.

Furthermore, high chromium cast iron has many advantages in that it can be obtained at low cost and by known methods compared to carbides and the like. Note that in the present invention, atomized iron powder can be used instead of ground cast iron powder.

Next, we will discuss the reasons for limiting the composition of high chromium cast iron.

Cr, the main component, is an element that has a strong effect on the formation of carbonized metal, and most of this contained in cast iron is Cr7C3.
*Fixed as a carbide such as Cr23C6. These carbides are dispersed in fine form in the matrix and are also included as an intervening phase in the thermally sprayed cast iron particles, and play an important role in imparting wear resistance and seizure resistance to sliding members. . Therefore, the Cr content is determined keeping in mind the relative wear with the cast iron cylinder as a mating material, and if it is less than 20%, the amount of carbide crystallized will be insufficient and the wear resistance and durability of the piston ring itself will be affected. The seizure resistance decreases, and if the piston ring exceeds 35 mm, the wear resistance of the piston ring improves, but on the other hand, it accelerates the wear of the mating material. Therefore, the cr content is between 20 and 35 tE), preferably between 25 and 35 tE.

The C content should be kept within a range that combines with Cr to form the carbide, and for this purpose the appropriate range is 1 to 6, preferably 2 to 5. That is, if the C content is less than 1, the absolute amount of carbides produced is insufficient, resulting in unsatisfactory wear resistance, and if it exceeds 6, free carbon ( Since there is a risk that graphite (graphite) may be generated in cast iron, it is desirable to keep the carbon content to 61 or less so that free carbon does not coexist.

Sl provides oxidation resistance to cast iron, improves the grindability of high chromium cast iron as a source material for thermal spray powder, and facilitates adjustment of the particle size of high chromium cast iron powder. It is well known that in general cast iron, St promotes graphitization, and in the present invention, since it contains a large amount of CF, which has a strong tendency to form carbides, it is significant in improving grindability rather than graphitization. s
If the l content is less than 0.5, the effect cannot be expected, and 6
If it exceeds -, the thermal spray coating layer's resistance to heat shrinkage and corrosion will deteriorate, so it should be in the range of 0.5 to 6. The preferred content of 81 is 2 to 6.

Mo is added together with or in place of St, is almost solidly dissolved in the matrix of high chromium cast iron, improves its high-temperature strength and heat resistance, and contributes to increasing the seizure resistance of the thermally sprayed coating layer. Works to improve the crushability of high chromium cast iron. If the Mo content is less than 0.5, the above effect cannot be expected, and 3Is
If it exceeds 0.5 to 3, the cost will increase and become disadvantageous, so it should be in the range of 0.5 to 3. The preferred Mo content is 0.5-2.

In addition, in addition to the above-mentioned C+ St y Mo and Cr, other components as a cast iron material, such as Mn T P e S r
A small amount of NL etc. may be contained within a range that does not impair the properties of the compound.

Furthermore, it is sufficient that either 81 or Mo is contained, but if the intention is to facilitate particle size adjustment of high chromium cast iron crushed powder, stabilize thermal spraying conditions, or improve the quality of the thermal spray coating layer, both may be used. It may be included.

Next, as a grinding method for high chromium cast iron, the casting or molten metal is solidified into an appropriate shape, the resulting material is ground using a stamp mill, a gale mill, etc., and the particles are sized using a sieve, etc., to achieve the desired particle size. .

The reason for limiting the particle size of the ground chromium cast iron powder to no more than 200 mm will be described below. Generally, thermal sprayed layers have pores, which act as oil pockets and contribute to seizure resistance.
- When the male pores become coarse, the self-bonding force between the sprayed particles is insufficient, causing not only the sprayed particles to fall off the piston ring surface during sliding and wear, but also the fallen particles to be interposed between the sliding members. This results in wear of the mating material as well. Therefore, the porosity, pore size, and distribution state should be appropriately controlled from the viewpoint of lubricant retention and wear resistance of the piston ring or mating material. It is mainly influenced by the particle size of the thermal spraying material, especially the thermal spraying powder. Considering this aspect, the particle size was limited to not exceed 200 mesh. Furthermore, the workability of thermal spraying and the properties of the sprayed layer are also affected by the particle size of the sprayed powder.If the powder becomes too fine, the fluidity will be impaired, making it difficult to stably supply the powder to the thermal spray nozzle, and the powder will be crushed to an unfavorable e*. In the case of powder, the particle shape becomes irregular and fluidization is inhibited.

From this point of view, coarse particles of 20 microns or more are preferable.

When the particle size is 20 microns or more and does not exceed 200 mesh, the pore ratio and pore distribution are stable.
The pore size is controlled to 3 microns or less, and pores are evenly distributed.

The base body can be made of cast iron, which is commonly used for piston rings, or other steel materials.

According to the present invention, Mo0l! Compared to acetylene gas spraying, etc., the material can be improved by 9 times.
A second feature of the invention (hereinafter referred to as the second invention) is provided, in which a self-fluxing alloy such as a Ni-Cr base or an Fe base is mixed with ground high chromium cast iron powder at a certain ratio.

This self-fluxing alloy has a common self-fluxing component, for example 2~
396 and/or F1811r3 to 4.5, and the remainder contains at least one strain of Ni, Co, Fe, and Nt-Cr as main components. The above Ni, Co
, Cr etc. generally have good heat resistance and oxidation resistance,
The same effect can be achieved even when thermally sprayed on piston rings, and since it is assumed that Ni, etc. will solidify into particles after entering a liquid phase due to the presence of self-soluble components, high chromium cast iron particles will be firmly dispersed and retained. However, as a result, the strength of the sprayed coating layer is also significantly increased. Additionally, thermal spraying without a self-fluxing alloy generally tends to increase the porosity, but the use of a self-fluxing alloy also adjusts the porosity. Furthermore, when a self-fluxing alloy is used, an extremely smooth surface can be obtained when the finger surface is processed and finished after thermal spraying, resulting in excellent compatibility with the mating material at the initial stage of sliding.

As mentioned above, self-fluxing alloys have high oxidation resistance and also increase the strength of the thermally sprayed coating layer, thereby improving the performance of the piston ring system under internal combustion engine operating conditions with high heat loads and severe oxidation.

In addition to the above requirements, the amount of self-fluxing alloy is determined by considering the relative proportion with other powders, and is determined in particular so as not to impede the wear resistance provided by the ground high chromium cast iron powder.
A weight of 96 is considered good. If the amount of self-fluxing alloy powder mixed is less than 10%, the above effect will not be sufficient, and if it exceeds 45%, the amount of ground high chromium cast iron powder, that is, the amount of chromium carbide produced will inevitably be insufficient, and the piston The wear resistance of rings, etc. decreases. On the other hand, the mixing amount of the ground high chromium cast iron powder in the second invention naturally falls within the range of 55 to 90% by weight. The preferred amount of high chromium cast iron ground powder mixed is 60-85% by weight.

The particle size of the self-fluxing alloy powder is 250 mm, and if it becomes coarse, particle melting during thermal spraying will be insufficient, resulting in an increase or coarsening of pores, deterioration of interparticle bonding force, and damage to each component in the thermal spray coating layer. This leads to disadvantageous results such as non-uniform dispersion. Preferably, the particle size is 10 tons or more; if the particle size is smaller than this, the self-fluxing alloy will over-dissolve during thermal spraying, and the physical properties of the thermal sprayed layer will deteriorate. As for the type of powder, atomized powder was used because of its good fluidity and marketability. Therefore, if the fine particles do not exceed 250 mesh, and the fine particles do not exceed 350 mesh, and the number of fine particles does not exceed 50 mesh, the fluidity of the thermal spray material during thermal spraying will improve,
As the meltability of the particles increases, high chromium cast iron particles and self-fluxing alloy particles are deposited in a flat layer, and even fine powders do not undergo oxidative deterioration and have excellent resistance to thermal oxidation from the surface. In order to demonstrate the properties of the sliding surface, the coating layer is not sticky, which helps to form a more stable coating layer, and its density and workability are improved, and the shedding of sprayed particles during finishing of the sliding surface is reduced. A more stable finished surface can be obtained in terms of dynamic characteristics. The porosity when sprayed with a mixture of self-fluxing alloys is 3 to 15.
%, the pore size is adjusted to less than 5 microns, and the pores are evenly distributed.

Next, the molybdenum granulated powder of the invention of the third feature (third invention) and the invention of the fourth feature (fourth invention) will be described. When molybdenum granulated powder is mixed and sprayed with high chromium cast iron ground powder and, in some cases, self-fluxing alloy powder, the powder particles are fused and bonded to each other, improving the adhesion of the sprayed layer to the base material (iron, steel, etc.). The particle bonding force inside the thermal spray coating layer can be improved.

On the other hand, when Mo alone is sprayed, which is currently widely used as a surface treatment for piston rings, etc., the bonding force of Mo particles in the layer is weak, and the Mo particles on the surface fall off relatively easily due to sliding with the cylinder, resulting in a large number of At present, several improvement proposals have been made. The cause of this is the low oxidation resistance of MO, and the fact that M is exposed to combustion gas from an internal combustion engine.

It is presumed that the cause is that the particles are oxidized and their mutual bonding strength decreases. In the present invention, Mo particles are mixed and sprayed with high chromium cast iron granulated powder, so they exist in a kind of alloyed state with Cr, which has excellent oxidation resistance, and the low oxidation resistance of itself is alleviated. As a drastic improvement measure, the present invention focuses on the powder structure of Mo. As a result, we decided to use Mo granulated powder. Mo granulated powder is made by binding Mo fine particles with an organic or other binder. Mo particles are finely dispersed by gold plasma spraying. A thermally sprayed coating layer is obtained, and an improvement in particle bonding strength is expected due to the fine dispersion of Mo fine particles.

Moreover, since metallic molybdenum has sublimation properties, if it becomes fine particles, it disappears during thermal spraying. However, by adopting a granulated powder structure, this drawback is eliminated and molybdenum in a uniformly dispersed state can be obtained.

Furthermore, in the third invention and the fourth invention, M.

The reason why the particle size of the granulated powder is fine, not exceeding 350 mm, is because the thickness of the sprayed layer increases with the powder particle size, and if the particle size is coarse, the thickness of the layer becomes large. This is because uniform distribution of Mo particles cannot be ensured. In this particle size range, ultrafine powder of about 3 microns, which cannot be used alone due to the sublimation property of Mo, can be used for granulation as a raw material for thermal spraying. Furthermore, when ultrafine powder of Mo alone is used for thermal spraying, segregation of Mo in the raw material powder is unavoidable, but this drawback is also eliminated. Preferably, the particle size of the Mo granulated powder is 5 microns or more.

If the apparent density 1 of Mo granulated powder is set to 2.5 t/c♂ or less, preferably e'12.0 to 25 to 15 or less, uniform distribution of each powder and Mo powder is good at the thermal spraying stage. Even if a granulated powder of pear or fine powder is used, it is possible to solve thermal spraying operation troubles due to poor fluidity during thermal spraying.

Next, the reason for limiting the amount of unused Mo granulated powder in the third invention will be described. As mentioned above, MO has the effect of increasing the bonding strength f of each particle in the thermal spray coating layer, and also has the effect of increasing the bonding strength f of each particle in the thermal spray coating layer.
It has the effect of preventing high chromium cast iron particles from falling off during the machining of pins, etc., so it prevents microscopic wear of the mating material at the initial stage of sliding, and also prevents sliding caused by high chromium cast iron particles falling off during engine operation. Significantly reduces abrasive wear between the component and the mating material. Furthermore, it exhibits scuffing resistance unique to molybdenum. Then, M.

If the amount of granulated powder mixed is less than 5 liters, the above effects will not be exhibited, and if it exceeds 3 liters, the oxidation resistance of the sprayed coating layer will deteriorate and the interparticle bonding force will rapidly decrease during engine operation. As a result, abrasive wear also occurs.Therefore, M
o The amount of granulated powder mixed is in the range of 5 to 30 parts by weight, preferably in the range of 5 to 25 parts by weight. On the other hand, the amount of high chromium cast iron crushed powder is limited for the same reason as in the case of the first invention. be.

Next, the fourth invention is high chromium cast iron crushed powder, M.

It features a combination of granulated powder and self-fluxing alloy powder. This is a combination of the characteristics of each powder, and in particular, the heat resistance, seizure resistance, wear resistance, and compatibility with the mating material of high chromium cast iron particles are improved by coexisting with other particles. It turns out that it will also be revised. The mixing amount of each powder is limited for the same reason as the second to wJ3 inventions, but in relation to the other powder mixing amounts, high chromium cast iron ground powder is 70 to 85 weight, Mo granulated powder is 5-151, and self-fluxing alloy powder is 10-25'16. It is.

The following is a detailed explanation of the present invention based on actual machine tests. The test engine and test conditions were as follows. (1) Inner diameter (77φ) x stroke (86 cranes) x 4 cylinders
2) Total displacement 770CC (3) Cylinder FC25 equivalent material (4) Fuel used: Leaded gasoline (Pb 3.2 i/us gallon) (5)
Operating conditions: 5000 rpm x full load x 200 hours The surface treatment of the piston ring (base material - cast iron) was as follows.

(c) Mo wire thermal spraying 99.9% Mo1kl [base-acetylene thermal spraying to a thickness of 1
A 5 micron thermal spray coating layer was applied.

(b) Fist with hard chromium plating with a 15-micron-thick plating layer High chromium cast iron crushed powder 31.8796Cr, 2.43%C-1,1996S
t, 1.511M0% 0.261! +Mn% balance iron and impure iron 1 to 200 mesh, fine particles not exceeding 20 microns and 20 microns or more? - Grind with Lumil, METCo
It was sprayed to a thickness of 15 microns using a 7M plasma spray machine.

) High chromium cast iron crushed powder + N1 self-fluxing alloy (30%) 1
4.7 Cr, 3.24 B, 4.261681
The other wire was the same as e1 above, using a self-fluxing alloy equivalent to JIS M8FNi3 of 10.651C, 2.75% F, and the remainder mainly N1, which was atomized to fine particles of 10 microns or more and not exceeding 250 mesh 1.

- High chromium cast iron crushed powder (85%) + Mo granulated powder (1
5.) Molybdenum fine powder of 3 to 5 microns is granulated to form fine particles of 5 microns or more and not exceeding 350 mesh, and the apparent density is 112.0 to 2.5 t/cx. was bound in the same way as Ie→ above.

(f) High chromium cast iron crushed powder (7' on) + Mo granulated powder (10 on) + 0 molten alloy powder (20 on) A predetermined amount of each of the above powders was mixed and thermal sprayed in the same manner as eJ.

All percentages in the examples are by weight.

The test results are shown in the table below.

According to the above explanation, the piston ring of the present invention has excellent usability in internal combustion engines and does not wear out the mating cylinder, so it can be used for sliding members such as piston rings at high speeds and under high loads and with a reduction in the amount of lubricant used. It will be understood that it is possible to provide a sliding member that has comprehensive performance that is resistant to brittleness under severe conditions.

Claims (1)

[Claims] 1. CI to 6 cm and Cr 20 to 3 in weight ratio
5% and further contains 0.5 to 6 degrees of 81 and 0.5%.
A sliding member in which a heat-resistant and wear-resistant layer is formed on a sliding surface by plasma spraying high chromium cast iron crushed powder having a particle size of not coarser than 200 mesh and containing at least one of 5 to 3% No. 2.11 amount ratio, CI to 6% and Cr2O to 3
Contains 0.5 to 6% of 81 and 0.5 hiss.
Containing at least one type of 5 to 39k OMo,
Plasma spraying 55 to 90% by weight of crushed high chromium cast iron powder with a particle size of 200 mesh and not very coarse, and 10 to 45% by weight of a self-fluxing alloy consisting of atomized powder with a particle size of 250 mesh and not very coarse. A sliding member with a heat-resistant and wear-resistant layer formed on the sliding surface. 3. CI to 6 whispers and Cr2O to 35 in weight ratio
% and further contains 0.5 to 6 mo of 81 and 0.5
High chromium cast iron crushed powder 7 containing at least one type of Mo of 3 to 3 and having a particle size of 200 mm and not coarse grains
A sliding member in which a heat-resistant and wear-resistant layer is formed on a sliding surface by plasma spraying Mo5 to 30% by weight of granulated powder having a grain size not coarser than 350 mesh. 4. Particle size 200 containing C1 to 6 moss and Cr2'0 to 35 moss in weight ratio, and further containing at least one of 0.5 to 6 moss of 81 and 0.5 to 3 moss of Mo. Mo5 to 15% by weight consisting of 70 to 85% by weight of ground high chromium cast iron powder with a grain size of 350m2, Mo5 to 15% by weight of granulated powder with a grain size of 250m2, A sliding member in which a heat-resistant and wear-resistant layer is formed on the sliding surface by plasma spraying a self-fluxing alloy of 10 to 25 weight percent made from atomized powder with less coarse particles. Material.