JPS61157670A - Sliding member - Google Patents

Abstract

PURPOSE:To improve resistances for heat, wear and seisure of sliding member, by mixing high Cr cast iron powder having specified grain sizes and Fe-C-Cr alloy powder so that specified quantities of C and Cr are added to Fe, and plasma spraying the powder mixture to sliding surface. CONSTITUTION:High Cr cast iron powder and Fe-C-Cr alloy powder having <=74mu grain size are mixed to obtain compsn. composed of, by weight 3.0-7.0% C, 25-60% Cr and the balance Fe substantially. The powder mixture is plasma sprayed to sliding surface of sliding member to form the sprayed layer. In case the sliding member is used under more severe condition, Mo-Ni alloy (Mo: about 75%), etc. can be used as rough coat spraying. In this way, wear quantities of sliding member itself and the opposite member are decreased, and sliding member favorable to high performance internal combustion engine is obtd.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a sliding member, and more specifically, it relates to a sliding member that has seizure resistance and wear resistance, such as a piston ring or cylinder liner of an internal combustion engine. This invention relates to a required improvement in the sliding surface of a sliding member.

(Prior Art) In recent years, as internal combustion engines have become smaller and lighter and have higher output, their loads have tended to increase.
More advanced seizure resistance and wear resistance are now required. Normally, in order to satisfy such requirements, a chrome plating layer is applied to the surface of the base material such as piston rings, but in some high-performance internal combustion engines, the heat resistance is insufficient and Burn-in occurs. Therefore, as an alternative to the chrome plating layer, molybdenum spraying is also used in some high-performance
It is used in fA engines, and although it provides excellent seizure resistance, it is slightly inferior to chrome plating in terms of wear resistance, and the raw materials are expensive due to resource constraints, so molybdenum thermal spraying is acceptable. There are limits to the range expansion of internal combustion engines. Furthermore, in order to satisfy the above requirements, we have developed thermal spraying materials with high melting point and high hardness other than molybdenum thermal spraying.
For example, high-grade thermal spray materials mainly made of tungsten carbide have also been proposed in the literature, although they have not been put into practical use. However, although the abrasion resistance of the sliding member itself to which these thermal sprayed materials are applied is extremely high, it has the disadvantage that it increases the abrasion of the mating material such as the cylinder liner, and the overall wear resistance of both members involved in sliding is extremely high. It is insufficient in terms of life (hereinafter referred to as relative life). This drawback can be eliminated to some extent by using special cast iron, for example, cast iron containing alloying elements such as molybdenum, for the cylinder liner as the mating material, but it is possible to eliminate this drawback by using ordinary cast iron material such as FC20 or FC30 for the cylinder block. The linerless type internal combustion engine used significantly increases the wear of the cylinder block. Therefore, it is important to select thermal spraying materials for sliding members of internal combustion engines, taking into account not only their own wear resistance but also the wear of the mating material.

One of the present applicants has disclosed in Japanese Patent Publication No. 57-54547 that the sprayed layer has a weight ratio of 55 to 90% ferrochrome.
and a sliding member characterized by having a composition of 10 to 45% self-fluxing alloy.

(Problems to be Solved by the Invention) The present invention provides a sliding member that has better heat resistance, seizure resistance, and wear resistance than conventional thermal sprayed sliding members, and also reduces wear on mating materials. In particular, it aims to improve the heat resistance and abrasion resistance of conventional sliding members by compositing the chromium-containing iron-based material, which is the main component of the sprayed layer.

(Means and effects for solving the problems) First aspect of the present invention
The feature (hereinafter referred to as the first invention) is that a high chromium cast iron powder whose particle size is not coarser than 74 μm is mixed with Fe-C-Cr alloy powder, and the composition is made by weight ratio of C3.0 to 7.0%, Cr
The sliding member has a thermal sprayed layer formed by plasma spraying a mixed powder containing 25 to 60% Fe and the remainder being substantially Fe.

The second feature of the present invention (hereinafter referred to as the second invention) is to plasma spray a mixture of 65 to 90% by weight of the above mixed powder and further 10 to 35% by weight of Mo powder whose particle size is not coarser than 74 μm. The sliding member has a sprayed layer.

The third feature of the present invention (hereinafter referred to as the third invention) is that high chromium cast iron powder having a grain size not coarser than 74 μm and Fe-C-
By mixing with Cr alloy powder, the composition is C3,0''~ by weight ratio.
Mixed powder containing 7.0%, 25-60% Cr, and the balance being substantially Fe, 65-80% by weight, particle size 74 μm
10-25% by weight of less coarse Mo powder and particle size 7
The sliding member has a sprayed layer formed by plasma spraying a mixed powder mixed with 10 to 25% by weight of a self-fluxing alloy powder having grains not coarser than 4 μm.

(Function) Generally speaking, the porosity of the sprayed layer has an advantageous effect on the seizure resistance of the sliding member from the viewpoint of retention of 7'lI lubricant, but it also has an advantageous effect on the seizure resistance of the sliding member, and the abrasion resistance of the mating material. depends on other properties of the sprayed layer. For example, if the sprayed layer is mainly made of molybdenum, the wear resistance of the sliding member will not be sufficient as described above due to the characteristics of metal molybdenum.On the other hand, even if the sprayed layer is made of a high-hardness metal, the type of sprayed material Depending on the particle size, the bond between the sprayed particles becomes weaker, and the sprayed particles fall off on the surface of the sprayed layer during finishing of the sliding member such as polishing or lapping, resulting in a surface with sharp corners. This phenomenon is particularly noticeable in thermal sprayed materials such as chromium carbide (Cr2C) and tungsten carbide (WC), which have high hardness and excellent wear resistance, but belong to difficult-to-process materials.

In this way, the sliding surface of the piston ring, which has a surface condition with sharp corners, causes excessive wear of the mating cylinder material in the initial wear stage even if the piston ring does not cause sheet metal seizure due to its relationship with the mating cylinder material. Therefore, for sliding members that are required to have heat resistance, abrasion resistance, and an excellent relative lifespan, as seen in internal combustion engines that are the subject of the present invention, and that are finished by polishing, lapping, etc., the sliding surface We found that not only the material but also the microstructure of the sliding surface components is important. The present invention was completed based on this knowledge, and it is found that if the thermal sprayed layer on the surface of the sliding member has high chromium cast iron powder and Fe-C-Cr alloy powder as its basic components, compared to the case where molybdenum is used. It has excellent wear resistance and heat resistance (especially high-temperature oxidation resistance), and on the other hand, compared to chromium carbide and the like, it has a significantly lower tendency to wear out the mating material. Furthermore, the interparticle bonding strength within the sprayed layer is increased, the sprayed particles have less tendency to fall off during processing or sliding of the sliding member, and the seizure resistance, wear resistance and relative lifespan are further improved. There is expected.

It should be noted that high chromium cast iron powder and Fe-C-Cr
When a mixed powder with an alloy powder is plasma sprayed, the high chromium cast iron powder and the Fe-C-Cr alloy powder have mutually complementary effects, which moderately balances the wear of both and improves the scuffing resistance. The aim is to further improve the durability and reliability of internal combustion engines.

High chromium cast iron powder is based on the components shown in Tables 22 and 26 and the explanation below the table on page 865 of "Steel Materials Handbook, Published June 30, 1965", and has a rich Cr content. The property of chromium carbide, which is uniformly dispersed in the cast iron matrix, is utilized as a component of sliding members. In other words, the high chromium cast iron thermal spray layer is finely dispersed in the form of stable carbides, and has excellent heat resistance and wear resistance, as well as corrosion resistance and resistance to complementary acid corrosion. The high chromium cast iron thermal spraying component does not accelerate the wear of the mating material (cylinder) as compared to the case where the Fe-Cr alloy powder is thermally sprayed alone. In addition, high chromium cast iron exhibits a white cast iron structure in the cast state and has excellent crushability, making it easy to produce powder, and it is also available at a lower price than carbide, Fe-C-Cr alloy powders, etc. There are many advantages to plasma spraying as a mixed powder. Further, the high chromium cast iron powder is not limited to a grindable powder, but an atomized powder may also be used. However, in the case of high chromium cast iron, there is a natural limit to the Cr content from the viewpoint of cast iron melting, etc., and single thermal spraying of high chromium cast iron tends to increase wear of piston rings.

Therefore, Fe-C- has a higher Cr content than high chromium cast iron.
By plasma spraying a mixed powder containing Cr alloy powder, a sliding surface that compensates for the drawbacks of each can be obtained.

As Fe-C-Cr alloy powder, Fe-C with medium carbon or higher
r (ferrochrome) alloy powder, especially high carbon Fe-Cr
(ferrochrome) alloy powder is preferable.

Next, the reasons for limiting the composition of the mixed powder of high chromium cast iron powder and Fe--C--Cr alloy powder and Mo powder will be described.

0 is the main component of high chromium cast iron and Fe-C-Cr alloy.
1a and j are elements that have a strong carbide-forming effect, and most of the C contained in each is Cr7C3.

It is fixed as a carbide such as Crλ9C6. These carbides are uniformly and finely dispersed in the base of each cast iron and alloy, and are also included as an intervening phase in the mixed thermally sprayed sliding surface, and have an important function of imparting scuffing resistance. If the Cr content in this mixed powder is less than 25%, the amount of carbide in the sliding surface will be insufficient and the wear resistance and scuffing resistance of the piston ring itself will decrease, and if it exceeds 60%, the wear resistance of the piston ring will decrease. While this improves the performance, it also accelerates the wear of the mating ring. Therefore, the Cr content is 25 to 60% by weight.
The content is more preferably 30 to 55% by weight, and most preferably 30 to 50% by weight.

Most of C should be kept within a range where most of it combines with Cr in the cast iron or alloy to form the chromium carbide, and for this purpose, the C content in the mixed powder should be 3 to 7% by weight.
Preferably it is in the range of 3.5 to 6% by weight. That is, if the C content is less than 3%, the absolute amount of carbides produced will be insufficient, resulting in insufficient wear resistance, and if it exceeds 7%, free carbon ( Since there is a risk that graphite (graphite) may be generated in high Cr cast iron, it is desirable to keep the content to 7% or less. In addition to the above C and Cr, other components of the cast iron material such as Si', Mn, P, S or Co
p V p Ni etc. may be contained in a small amount within a range that does not impair the above characteristics.

Next, the reason why the mixed powder of high chromium cast iron powder and Fe-C-Cr alloy powder is limited to a particle size of 74 μm or less will be described.

Thermal sprayed layers generally have pores, which act as oil pockets and contribute to scuffing resistance. On the other hand, when the pores become coarse, the self-bonding force between the sprayed particles is insufficient and the sprayed particles fall off during sliding. This causes the piston ring and the mating cylinder to wear out. Therefore, from the viewpoint of lubricant retention and wear resistance of both sliding surfaces, the porosity, pore size, and distribution state should be appropriately controlled. Since it is greatly influenced by the particle size of the material, especially the thermal spray powder, the particle size was limited to 74 μm or less in consideration of the above points. Furthermore, the workability of thermal spraying and the properties of the thermal spray layer are also affected by the particle size of the thermal spray powder, and if the powder becomes too fine, the fluidity will decrease and it will be difficult to stably supply the powder to the thermal spray nozzle.
A particle size of 0 μm or more is preferred.

In the second aspect of the present invention, Mo is further mixed and sprayed. Although 6O single thermal spraying has excellent scuffing resistance, it is inferior in abrasive wear resistance and oxidation resistance, so the bonding force between Mo particles in the thermal sprayed layer is weak, and there is often a defect that tends to cause peeling between the eyebrows. .

In the present invention, Mo powder is mixed with high chromium cast iron powder and Fe powder.
Since the Mo particles are sprayed together with the mixed powder of the -C-Cr alloy powder by the plasma spraying method, the sprayed particles coexist in a molten state, and the low oxidation resistance of the Mo particles themselves is alleviated.

The 4O powder may be a single powder, but if a Mo granulated powder in which Mo fine particles are bound with an organic or other binder is used,
A sprayed layer in which Mo particles are finely dispersed is obtained, and it is expected that the bonding strength between the sprayed particles will be improved. Moreover, single powder M
Ultrafine powder, which cannot be used due to its sublimation property, can be used by granulating it to improve uniform distribution. Second
In the invention and the third invention, the particle size of the Mo powder is set to 74 μm or less because if the particle size is coarser than 74 μm, the surface porosity of the sprayed layer will increase, the abrasive wear resistance will deteriorate, and uniform distribution will be impaired. It is from.

The particle size of the Mo powder is preferably 5 μm or more.

Next, regarding the reason for limiting the amount of Mo powder mixed in the second invention, if the amount mixed is less than 10%, M.

Effects such as unique scuffing resistance and resistance to abrasive wear between sliding surfaces due to improved bonding strength between each sprayed particle are not exhibited, and if it exceeds 35%, the oxidation resistance of the sprayed layer deteriorates. This results in a rapid decrease in interparticle bonding force during internal combustion engine operation, promoting abrasive wear.

Therefore, the amount of Mo powder mixed is in the range of 10 to 35% by weight,
Preferably it is in the range of 10 to 30% by weight. On the other hand, the amount of mixed powder of high chromium cast iron powder and Fe-C-Cr alloy powder is limited by the Cr and C content in the above-mentioned mixed powder and also the Cr and C content in the sprayed layer.
o It is 65 to 90% by weight, preferably 70 to 90% by weight, depending on the amount of powder mixed.

The amount of high chromium cast iron powder in the mixed powder is preferably 30 to 55% by weight. The third invention is a mixed powder of high chromium cast iron powder and Fe-C-Cr alloy powder, Mo
It features a combination of powder and self-fluxing alloy powder.

The self-fluxing alloy of the third invention generally has B and/or B as the self-fluxing component.
Or contains Si and has Ni as the main component.

The remainder contains at least one of Co p Fes and Ni-Cr. An example of its composition is shown on page 970 of "Metal Surface Treatment Handbook, Revised New Edition". When a self-fluxing alloy powder containing Ni, Co, Cr, etc., which generally has good heat resistance and oxidation resistance, is mixed and sprayed with the powder, high chromium cast iron powder and Fe-C-Cr alloy are mixed in the sprayed layer. Each mixed particle and MO particle are firmly dispersed and held by the self-fluxing alloy particles, and as a result, the strength of the sprayed layer is also significantly increased. In addition, when a self-fluxing alloy is used, the adhesion strength with the base material is improved, the porosity is controlled to a low level, and when the sliding surface is processed and finished after thermal spraying, an extremely smooth upper surface can be obtained, making it possible to improve the adhesion strength in the initial stage of sliding. Obtain results that are compatible with the mating material.

As mentioned above, self-fluxing alloys have high oxidation resistance and can also improve the strength of the sprayed layer and the adhesion strength to the base material, so they improve the performance of piston rings, etc. under the operating conditions of internal combustion engines with high heat loads and severe oxidation. is improved.

The amount of self-fluxing alloy powder is determined by taking into consideration the relative proportions with other mixed powders in addition to the above-mentioned properties, especially the wear resistance provided by the mixed powder of high chromium cast iron powder and Pe-C-Cr alloy powder. The content should be in the range of 10 to 25% by weight so as not to impede the properties.

If the mixed amount of self-fluxing alloy powder is less than 10%, the above effect will not be sufficient, and if it exceeds 25%, the amount of mixed powder of high chromium cast iron powder and Fe-C-Cr alloy powder, that is, chromium carbide The amount of production and the mixing ratio of powder are relatively reduced. A more preferable range is 10 to 20% by weight. Third
The sliding surface in the invention combines and integrates the characteristics of each mixed powder, and at the same time, mutually complements the defects of the individual powders. The mixing amount of each powder is limited for the same reason as in the first invention, but due to the relationship between the powders, a mixed powder of high chromium cast iron powder and Fe-C-Cr alloy powder of 65 to 80% by weight, Mo powder of 10% ~25% by weight
, 10 to 25% by weight of self-fluxing alloy powder. The more preferable ranges are 65 to 75% by weight and 10 to 20% by weight, respectively.
, 10 to 20% by weight. The particle size of self-fluxing alloy powder is 74
When particles become coarser than μm, particle melting during thermal spraying is insufficient, resulting in increased or coarsened pores, deterioration of interparticle bonding strength, adhesion with the base material, and non-uniform dispersion of each component in the thermal sprayed layer, which are undesirable. bring about results. The preferred particle size is 10 μm or more,
If the particles are finer than this, the self-fluxing alloy will be excessively melted during thermal spraying, and the physical properties of the thermal sprayed layer will deteriorate. Mixing and spraying self-fluxing alloy powder in this way improves heat resistance, oxidation resistance, coating density, interparticle bonding strength,
Adhesion to the base material and workability are improved, and a finished surface with more stable sliding properties can be obtained. When the self-fluxing alloy powder is mixed and thermally sprayed, the porosity is adjusted to 5 to 15%, the pore size is adjusted to 5 μm or less, and the pores are evenly distributed.

The sliding members in the first to third inventions can obtain considerable adhesion strength even when directly sprayed onto cast iron or steel as a base material, but when used under more severe conditions, they can be sprayed as a base material. A Mo-Ni alloy (Mo 75%) or the like may also be used.

Examples of the present invention will be described below, and the effects thereof will be explained in detail. In this example, piston rings according to the present invention and piston rings subjected to various surface treatments for comparison were assembled into an internal combustion engine, and the average wear f in the radial direction of the piston rings was measured.
fi (T dimension) and the maximum wear amount of the cylinder at the top dead center of the piston ring were measured. A prescribed surface treatment was applied to the piston ring (top). The test engine is 77φm
/m (inner diameter) x86 m/m (stroke) x 4 cylinders,
Total displacement = 1770cc, and its cylinder is FC25
It was a considerable amount of material. The test conditions were as follows: The fuel used was leaded gasoline (
Pb 3.2gr/us gal), 5.00Or, p
, mx full load x 200 hours (operating time). The amount of wear on the piston rings was measured after operation for a predetermined period of time, and the amount of wear on the piston rings was converted into a value per 100 hours and shown in the attached drawing.

The surface treatments are shown in the table below.

The composition and particle size of the thermal spray powder used in Examples and Comparative Examples are as follows.

・High chromium cast iron crushed powder 3530% Cr, 5.82% C, balance substantially Fe
and cast iron consisting of impurities with a thickness of 74 μm or less and 20 μm
Grind with a ball mill.

- Fe-C-Cr alloy powder 1) JIS FCrH 374 μm or less (high carbon ferrochrome) 63.5% Cr, 6.52% C.

The remainder is substantially Fe and impurities, 2) JIS FCrM3 74 μm or less (medium carbon ferrochrome) 62.1% Cr, 3.56% C2 The remainder is substantially Fe and impurities/Ni-Cr self-fluxing alloy powder JIS 118303
MSFNi 63μm or less■6.9%Cr, 3.2%B, 3.5%Si,
0.66%C22, 8%Fe, balance NZ.

・Mo powder 99% or more Mo fine powder of 3 to 5 μm is 63 μrr1 or less and 5 μm
Granulated powder granulated with an organic binder to a size of 1 m or more (representative particle size 1
0-44μm, apparent density 2.0-2.5gr/am
) Mo-Ni alloy (Mo: Ni = 7) is used for base thermal spraying.
5:25) was used.

The molybdenum sprayed piston rings as a comparative example were flame sprayed using a wire rod, but in other comparative examples and examples of the present invention, a Meticore MB type plasma spraying device was used to spray each piston ring. The surface was sprayed.

Looking at the results in FIG. 1, the piston rings of the present invention (D,
E and F) significantly reduce the amount of piston ring wear to about 1/6 or less and 1/3 or less, respectively, compared to the hard chrome plating (B) and molybdenum sprayed piston ring (A) of the comparative example, On the other hand, the amount of wear on the cylinder was also reduced to about 50% or less compared to the value for the 0-gate thermally sprayed piston ring. Further, the amount of wear on the piston ring and cylinder is reduced compared to the piston ring (C) sprayed with high chromium cast iron powder, and the effect of improving the amount of wear by the present invention is clear.

In the above example, when the self-fluxing alloy powder was mixed and sprayed (
F) has a better effect than the mixed thermal spraying of Fe-C-Cr alloy powder and high chromium cast iron powder (D), but this is because self-fluxing alloy particles are present in the sprayed layer. The bonding strength between the sprayed particles increases, preventing their peeling, resulting in a smooth and stable processed surface.In addition, self-fluxing alloy particles with excellent oxidation and corrosion resistance are present in the sprayed layer. This is thought to be due to the fact that the thermal sprayed layer as a whole is prevented from deteriorating in high-temperature oxidation and corrosive atmospheres, and these factors combine to cause not only wear of the thermal sprayed layer itself, but also damage to the mating material. In case (E) is added to the wear resistance, the drawback that the metal molybdenum itself has poor wear resistance and oxidation resistance disappears, and on the contrary, the wear resistance of the sliding member (piston ring) is increased, and the wear resistance of the mating material is increased. The effect of lowering is also achieved.

(Effects of the invention) The effects of mixed thermal spraying as described above eliminate the problems that could not be solved with the prior art, and the effect of the present invention of reducing the amount of wear on the sliding member itself and the mating material is the same as in recent years. It is more than compatible with high-performance internal combustion engines.

[Brief explanation of drawings]

FIG. 1 is a graph showing the results of a survey of the wear amount of piston rings and Schilling' when various piston rings are assembled into a gasoline engine (linerless). Cleaning of drawings (R'17 NJ: Change L) Figure 1 procedure correction voluntarily) February 1, 1985

Claims (1)

[Claims] 1. Weight ratio: 3.0 to 7.0% C, 25 to 60% Cr
with a particle size of 74 μm, the remainder consisting essentially of Fe.
A sliding member having a sprayed layer formed by plasma spraying a mixed powder of less coarse-grained high chromium cast iron powder and Fe-C-Cr alloy powder onto the sliding surface. 2. Mo-Ni system, Ni-Al as base spray for thermal spray layer
The sliding member according to claim 1, which is coated with either a base alloy or Mo. 3. Weight ratio: C3.0-7.0%, Cr25-60%
with a particle size of 74 μm, the remainder consisting essentially of Fe.
A mixed powder of 65 to 90% by weight of less coarse-grained high chromium cast iron powder and Fe-C-Cr alloy powder and a particle size of 74μ
A sliding member having a sprayed layer formed by plasma spraying a mixed powder mixed with 10 to 35% by weight of Mo powder whose particles are not coarser than m on a sliding surface. 4. The sliding member according to claim 3, wherein the Mo powder is a granulated powder obtained by granulating Mo fine powder of 10 μm or less with a binder so that the grain size is not coarser than 74 μm. 5. Mo-Ni system, Ni-Al as base spraying for thermal spray layer
A sliding member according to claim 3 or 4, which is coated with either a base alloy or Mo. 6. Weight ratio: C3.0-7.0%, Cr25-60%
with a particle size of 74 μm, the remainder consisting essentially of Fe.
65-80% by weight of a mixed powder of high chromium cast iron powder and Fe-C-Cr alloy powder that is not coarser, 10-25% by weight of Mo powder that is not coarser than 74 μm in particle size, and 74% by weight in Mo powder whose particle size is not coarser than 74 μm.
A sliding member having a sprayed layer formed by plasma spraying a mixed powder containing 10 to 25% by weight of a self-fluxing alloy powder that is not coarser than μm onto a sliding surface. 7. The sliding member according to claim 6, wherein the Mo powder is a granulated powder obtained by granulating Mo fine powder of 10 μm or less with a binder so that the particle size is not coarser than 74 μm. 8. The sliding member according to claim 6 or 7, wherein the self-fluxing alloy powder is a Ni-Cr alloy powder. 9. Mo-Ni system, Ni-Al as base spraying for thermal spray layer
A sliding member according to any one of claims 6 to 8, which is coated with either a base alloy or Mo.