JP3147289B2 - Thermal spray powder, thermal spray sliding surface and method of forming thermal spray sliding surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermal spray powder, a thermal spray sliding surface, and a method of forming a thermal spray sliding surface. The present invention can be applied to a sliding member, for example, a piston ring groove of a piston used in a diesel engine or a gasoline engine, particularly, a top ring groove.

[0002]

2. Description of the Related Art The prior art will be described using a top ring groove of an engine piston as an example. The top ring groove of the engine, especially the piston of the diesel engine, is used under thermally severe conditions. This is because sufficient oil lubrication and cooling cannot be expected in the top ring groove, and the top ring groove is often used without lubrication or near lubrication.

Further, with the recent regulations on exhaust gas purification, oil consumption of diesel engines has been further suppressed, and the combustion temperature of the combustion chamber has been further increased due to the demand for higher engine output. Due to such demands, the conditions for using the top ring groove of the piston become increasingly severe. So in recent years,
Many attempts have been made to form a layer having excellent heat resistance and wear resistance in the top ring groove. Typical examples include a ring-casting technology for wear-resistant rings made of Ni-resist cast iron having a coefficient of thermal expansion close to that of the Al material constituting the piston, and an MMC technology for molding and molding a ceramic compact by high-pressure casting (METAL-MATRI).
X-COMPOSITE), Cu using electron beam
-There is a technique for forming an Al alloy layer. These attempts have been reported in the following references and patent publications. Book “Lubrication of Internal Combustion Engine” (Koshobo) P218 (1987)
JP-A-8-93840, JP-A-1-232152, JP-A-61-41731, JP-A-61-25
2855, JP-A-62-72457 and JP-A-2-78752.

[0004] However, these techniques are not always sufficient and are disadvantageous in responding to intense demands in recent years. Other attempts include thermal spraying. However, a piston ring groove such as a top ring groove is a narrow groove, and it is not easy to laminate a sprayed layer having good wear resistance and adhesion.

[0005] The applicant of the present invention has reported that Japanese Patent Publication No. 3-294.
As disclosed in Japanese Patent No. 3 gazette, thermal spraying has a composition containing 70 to 98% by volume of a Fe-Cr alloy containing a high carbon content and 2 to 30% of an Al-Si alloy powder by volume. A layer is disclosed.

[0006]

However, according to the technique disclosed in this publication, the content of Fe-Cr alloy is 70% by volume.
Most of the thermal sprayed layer is Fe-based in terms of% by weight because it contains about 98%. If the amount of Fe is too large, the cutting property of the sprayed layer is not sufficient, which is disadvantageous for cutting the sprayed layer. Further, during the thermal spraying process, the efficiency of adhesion of the thermal spray powder to the Al-based substrate is not sufficient due to the influence of oxidation combustion of the thermal spray powder. Further, when the base material is an Al-based material, the difference in thermal expansion coefficient between the Fe-based sprayed layer and the Al-based material is large, and there is still room for improvement in the adhesion strength of the sprayed layer.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermal spray coating by adopting a specific thermal spray powder composition in which various powders having a specific composition range are blended. Spray that can form a sprayed layer that has excellent cutting workability, adhesion efficiency of sprayed powder to Al-based substrate, adhesion strength to Al-based substrate, wear resistance and adhesion resistance of sprayed layer It is to provide a powder.

A second object of the present invention is to provide a sprayed sliding surface having excellent wear resistance and adhesion resistance by defining the area ratio. A third object of the present invention is to employ a thermal sprayed powder having the above-described composition, form a concave portion by removing a part of the thermal spray layer in a depth direction, and slide a side surface along the depth direction defining the concave portion. By using the surface, even if the area of the sliding surface is small, the sliding characteristics of the iron-based phase generated by the iron-based powder, the sliding characteristics of the Al alloy generated by the Al alloy powder, This is advantageous for comprehensively exhibiting the sliding characteristics of the hard phase generated by the alloy containing the alloy, and is therefore suitable for obtaining a sliding surface used under severe sliding conditions such as a top ring groove of a piston. An object of the present invention is to provide a method for forming a sprayed sliding surface.

[0009]

According to a first aspect of the present invention, there is provided a thermal spraying powder, wherein a weight percentage of iron-based powder of 0.01 to 1.5% carbon and 0.5% or less of oxygen is 50 to 80% by weight. Al alloy powder of 20% or less of Si is 5 to 20% by weight, Hv 500 to 1
500 carbides or alloys containing carbides in a weight ratio of 5
-40%, is composed of unavoidable impurities.

According to a second aspect of the present invention, the thermal sprayed sliding surface comprises iron-based particles having a carbon content of 0.01 to 1.0% by weight and an area ratio of 40 to 79%.
%, An Al alloy having 11-20% Si by weight is 20-50% in area ratio, and a carbide or alloy containing carbide having Hv 500-1500 is 1-20% in area ratio. It is.

According to a third aspect of the present invention, there is provided a method for forming a sprayed sliding surface.
Iron-based powder containing 0.01 to 1.5% of carbon and 0.5% or less of oxygen by weight is 50 to 80% by weight, and A is 20% or less of Si.
1 alloy powder is 5 to 20% by weight, Hv 500 to 150
0 or a carbide-containing alloy in a weight ratio of 5 to 4
A spraying step of stacking a sprayed layer by spraying the sprayed powder on a surface to be sprayed of an Al-based base material using a sprayed powder composed of unavoidable impurities, and a means for removing a part of the sprayed layer in a depth direction. To form a concave portion, and a removing step in which a side surface along the depth direction defining the concave portion is a thermal spray sliding surface, is sequentially performed.

In this specification,% means% by weight unless otherwise specified. Each of the above-mentioned area ratios means the area ratio of each phase when the thermal spray sliding surface is 100%.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A thermal spray layer constituting a thermal spray sliding surface is:
In general, various properties such as abrasion resistance, adhesion resistance, adhesion to a substrate, and adhesion efficiency of a sprayed powder are required. Further, when grooves or the like are formed in the thermal sprayed layer, it is necessary to have excellent workability. For example, a ring groove such as a top ring groove of a piston provided in a diesel engine will be described as an example.
The adhesion resistance in a high temperature region (for example, a temperature of 200 ° C. or more in consideration of the temperature of the combustion chamber) and the adhesion between the sprayed layer and the Al-based piston are important. When a piston ring groove such as a top ring groove is cut into a sprayed layer, it is necessary to have excellent cutting workability with a cutting tool or the like.

What has been developed to combine these various properties are (A) a sprayed powder, (B) a method for forming a sprayed sliding surface, and (C) a sprayed sliding surface according to the present invention. Below (A)
(B) and (C) are further explained. (A) Thermal Sprayed Powder The role of the powder constituting the thermal sprayed powder and the reasons for limiting the composition will be described.

(Iron-based powder) The iron-based powder generally ensures the strength for maintaining the sprayed layer structure. Further, the iron-based powder plays an excellent role in anti-adhesion to a counterpart material (for example, a piston ring material whose surface layer is nitrided). In consideration of these, the ratio of the iron-based powder was set to 50 to 80% by weight when the whole of the sprayed powder was set to 100%.

As the iron-based powder, powder of carbon steel or powder of alloy steel (alloy element: Ni, Cr) such as stainless steel can be used. The iron-based powder may be an atomized powder having a high solidification rate, a pulverized powder obtained by mechanically pulverizing a coagulated mass, or a powder of another form. In the case of atomized powder, since the solidification rate is high, there are characteristics such as an increase in the amount of solid solution, a finer powder particle structure, and a harder particle. The general particle size of the iron-based powder is not particularly limited, but is, for example, 1 to 75 μm and 5 to 44 μm.
It can be about μm.

The hardness of the iron-based powder is preferably maintained higher than that of niresist cast iron (generally, matrix hardness Hv: 140 to 150). Considering these characteristics, and also considering the case where decarburization occurs during thermal spraying,
At the beginning of development, the lower limit of carbon content was 0.3% and the upper limit was 1.
I knew it was 5%. However, subsequent studies have found that even if the amount of carbon in the iron-based powder of the thermal spray powder is further reduced, the thermal spray layer according to the present invention ensures good wear resistance. Therefore, when the iron-based powder has a carbon steel composition, the lower limit of the amount of carbon can be reduced to about 0.1%. When the iron-based powder has an alloy steel composition such as stainless steel, the lower limit of the carbon amount can be reduced. It was found that the temperature can be further reduced to about 0.01% (see FIG. 4B).

However, depending on the above-mentioned characteristics or the degree of demand for further characteristics, the upper limit of the amount of carbon in the iron-based powder is 1.3% to 1.4%, 1.0% to 1.2%, and 0%. 0.6% ~
0.8%, with a lower limit of 0.03%, 0.4% to 0.1%.
5%, 0.6% to 0.7%, 0.8% to 0.9%. Further, in order to maintain the adhesion efficiency of the thermal spray powder to the base material during the thermal spraying process, the oxygen content in the iron-based powder was set to 0.5% or less when the entire iron-based powder was 100%. This is because if the oxygen content is large, the iron-based powder tends to burn and become an oxide at the time of thermal spraying, which may deteriorate the adhesion efficiency of the thermal spray powder. This tendency is particularly large when thermal spraying is performed in the atmosphere. Considering these, the upper limit of the oxygen content in the iron-based powder is 0.4%, 0.3%, 0.2%,
%. In order to reduce the amount of oxygen, a powder subjected to a reduction treatment may be used.

(Al alloy powder) In addition to the machinability in the sprayed layer, the Al alloy powder has an A.sub.
It is a material that reduces the difference in thermal expansion with the l-based substrate, improves the adhesion strength to the Al-based substrate, and improves the adhesion efficiency of the thermal spray powder, but tends to reduce the anti-adhesion property at high temperatures. Taking these into consideration, when the total amount of the thermal spray powder is 100%, the ratio of the Al alloy powder is 5 to 20% by weight. The Al alloy powder is preferably an atomized powder. Al
The general particle size of the alloy powder is not particularly limited.
It can be about 100 μm and about 10 to 75 μm.

In consideration of the above, as an Al alloy powder,
S is easy to obtain eutectic structure with Al alloy, not pure Al powder
An Al-Si alloy having an i content of 20% or less was employed.
Si content is 100% of the whole Al alloy powder,
For example, it can be 5 to 20%. In such a Si content range, generation of coarse primary crystal Si is not substantially recognized even after thermal spraying, and adhesion to an Al-based substrate is secured.

(Carbide or Alloy Containing Carbide) This alloy is a material that forms a hard phase in the sprayed layer and improves the wear resistance and adhesion resistance of the sprayed layer. There is a tendency for the adhesion to the substrate to deteriorate. This alloy can be blended with the thermal spray powder in powder form,
Depending on the case, it may be contained inside the iron-based powder or inside the Al alloy powder. In the case of a powder form, a form in which the whole powder particles are formed of carbide, or a form in which carbide is dispersed in a base material of the powder particles may be used. The carbide may be a single carbide or a composite carbide.

Examples of the carbide or alloy containing carbide include FeCr alloy containing carbon (for example, Fe-60% Cr-8% C as a typical composition), Fe ₃ C (chill crystal), and chromium carbide (Cr ₃ C ₂ ). Etc. can be adopted. The hardness of this alloy is Hv500-1500. The hardness in this range is such that if it is less than Hv500, it cannot be expected to play a role as a hard phase for obtaining abrasion resistance.
If v1500 is exceeded, the target material is attacked and the target material is excessively worn. However, depending on the requirements of the sliding characteristics, cutting workability, adhesion to the base material, or the like, or according to the type of the mating material, the hardness has an upper limit of 1100 in Hv,
1000, 900, and the lower limit is 650, 700, 7
Can be 50.

In consideration of the above, the amount of carbide or alloy containing carbide is set to 100% of the entire sprayed powder.
, The weight ratio was 5 to 40%. In this range, good sliding characteristics and workability can be obtained. For example, even when applied to the top ring groove of the piston, good sliding characteristics and workability of the sprayed layer can be obtained by adding 5 to 40%. When the alloy is in the form of a powder, the particle size is not particularly limited, but may be, for example, about 1 to 75 μm or about 5 to 44 μm.

(Blending ratio of thermal spraying powder) The blending ratio of the thermal spraying powder is, assuming that the entire thermal spraying powder is 100%, 50 to 80% of iron-based powder and 5 to 20% of Al alloy powder in weight ratio as described above. %, Carbide or alloy containing carbide
~ 40%. However, the upper limit value and the lower limit value of the compounding ratio can be appropriately changed within the above range according to the degree of demand for sliding characteristics and the like. Therefore, iron-based powder has an upper limit of 75
%, 70%, and 65%, and the lower limit is 55%, 57%, and 6%.
0%. Al alloy powder has an upper limit of 18%, 16%
% And 14%, and the lower limit can be 7%, 9% and 11%. For carbides or alloys containing carbides, the upper limit is 33
%, 28%, 23% and the lower limit is 7%, 9%, 11%
Can be.

(Other Powders) According to the thermal spray powder according to the present invention, a soft alloy powder such as a Cu-Al alloy or a Ni alloy can be included depending on the type and application of the thermal spray layer. A soft alloy is effective in improving the toughness of the sprayed layer according to the present invention, is hardly oxidized, and is relatively soft. The basic compounding range of the soft alloy can be 5 to 30% when the entire thermal spray powder is 100%. Note that the upper limit of the soft alloy is 20%, 15%, 10%
% And the lower limit can be 6% or 8%.

These can be added in powder form. These powders may be atomized powders having a high solidification rate, powders obtained by pulverizing coagulated lumps, or powders of other forms. The general particle size of the powder is not particularly limited.
m, especially 10 to 44 μm. The above-mentioned Cu-Al alloy is a Cu-Al alloy in the α region (the entire alloy is
%, Al content is 1 to 10%, especially 8 to 10%)
Can be adopted. The above-mentioned Ni-based alloy is a Ni-Cr-based alloy (containing 5 to 20%, particularly 5 to 10% of Cr when this alloy is 100%), and a Ni-Cr-based alloy further containing at least one of Si and B. (Cr: 5-20% content)
Can also be used. In this self-fluxing alloy, S
At least one of i and B can contain 1 to 8%. (B) Method for Forming Thermal Sprayed Sliding Surface Next, a method according to claim 3 will be described. According to this method, after the thermal spray powder is laminated on the surface to be thermally sprayed of the aluminum-based base material and the thermal spray layer is laminated, a part of the thermal spray layer is removed in the depth direction by the removing means to form a concave portion. The side surface along the depth direction that defines the concave portion is defined as a sliding surface. As the removing means, mechanical means such as cutting and grinding, electric discharge machining means and the like can be employed, but high energy means such as laser irradiation and electron beam irradiation and evaporation processing means may be used. According to the above-described thermal spraying process, the powder particles of the thermal spray powder collide with the surface to be sprayed of the base material at least in a semi-molten state or a molten state, and thus are schematically illustrated in FIG. As shown, the particles of the sprayed thermal spray powder tend to accumulate in a thin shape. If a concave portion is formed in this thermal spray layer and the side surface defining the concave portion is a sliding surface, as shown schematically in FIG. There are many types. Therefore, the sliding characteristics of the specific type of particles in the sprayed powder are less likely to appear, and the overall sliding characteristics of many types of powder particles are easily exhibited. That is, the sliding characteristics by the iron-based phase, the sliding characteristics by the Al alloy phase, and the total sliding characteristics by the carbide or the alloy phase containing the carbide are easily exhibited. The Al-based substrate used in the method of the present invention is S
The i content can be 5% to 40% by weight, especially 20% to 30%. (C) Thermal spray sliding surface According to the thermal spray sliding surface according to the second aspect, the ratio of the iron-based particles is 40 to 79% in area ratio, and generally constitutes a matrix of the thermal spray sliding surface. The reason why the lower limit of the area ratio is set to 40% is to suppress the occurrence of adhesion on the sprayed sliding surface in consideration of the adhesion resistance test result. The reason why the upper limit of the area ratio is set to 79% is that if it exceeds 79%, the iron-based matrix becomes too large, and therefore, the base material to be sprayed is made of Al.
This is because, in the case of a system, the difference in thermal expansion coefficient between the thermal sprayed layer and the Al-based substrate becomes large, and peeling is likely to occur at the interface between the thermal sprayed layer and the substrate. Incidentally, as shown in Table 4, in Comparative Alloy D (the area ratio of the iron-based phase, that is, the iron-based matrix is as large as 85%), the peeling is “present”.

According to the sprayed sliding surface, the proportion of the Al alloy is 20 to 50% in area ratio. The lower limit is set to 20% because if the coefficient of thermal expansion is less than 20%, the difference in thermal expansion between the Al base material and the sprayed layer becomes large, and peeling easily occurs in a thermal shock test. Incidentally, as shown in Table 4, comparative alloy D (Al
In the case where the area ratio of the alloy is as small as 12%), peeling is “present”. The upper limit of the area ratio of the Al alloy is set to 50%,
If it exceeds 50%, adhesion is likely to occur. Incidentally, as shown in Table 4, the area ratio of the comparative alloy E (Al alloy was 60%).
%), Adhesion is "Yes".

According to the above-mentioned thermal spray sliding surface, Hv500
Up to 1500 carbides or alloys containing carbides constitute a hard phase on the sprayed sliding surface and have an area ratio of 1 to 20%. The reason that the lower limit of the area ratio is set to 1% is that L is less than 1%.
This is because the FW wear test is inferior to the target performance. Incidentally, as shown in Table 4, comparative alloy F (the area ratio of the hard phase was 0.5
%), The LFW wear amount is considerably large at 75 μm. The reason why the upper limit of the area ratio of the hard phase is set to 20% is that if it exceeds 20%, the hard phase becomes excessive, and the aggressiveness to the partner piston ring becomes severe in the LFW wear test.
In addition, the wear of the cutting tool during processing increases rapidly.

In the above-mentioned thermal spray sliding surface, the size of the iron-based particles constituting the matrix differs depending on the degree of thermal spraying. However, since the iron-based particles are somewhat flattened by collision with the base material during thermal spraying, Generally, the major axis of the iron-based particles is 5 to 10
0 μm, and the size of the Al alloy is 10 to 200 μm
m, and the size of the carbide or alloy containing the carbide can be 1 to 50 μm.

[0030] The iron-based particles on the sprayed sliding surface according to claim 2 are expressed in terms of% by weight based on 100% of the iron-based particles.
For example, a carbon steel composition or a stainless steel composition (for example, a martensitic composition) can be employed. Generally, the carbon content of the iron-based particles on the thermal spray sliding surface is slightly lower than the carbon content of the iron-based powder in the thermal spray powder constituting the thermal spray sliding surface. This is because the iron-based powder is decarburized by heat generated during thermal spraying. For Al alloy, 1
When it is set to 00%, it has 11 to 20% by weight of Si. The reason why the lower limit of Si% is set to 11% is to suppress the occurrence of Al adhesion at a eutectic composition or higher, and the upper limit of Si is set to 20%. This is because the dropout of metal increases and the workability deteriorates. The composition analysis was based on an electron probe X-ray micro area analyzer (EPMA).

By the way, the component analysis of the sprayed layer coated on the substrate (ICP: Inductively Coupled P
lasma), oxygen was present in the sprayed layer, and as a result of identification by X-ray analysis, it was found that the oxygen component was an oxide of iron (including Cr in the case of stainless steel) and Al. Therefore, the oxygen component in the thermal spray layer mainly exists in the iron-based particles and the Al alloy.

The amount of oxygen in the thermal spray layer is preferably from 0.1 to 2%, when the thermal spray layer coated on the substrate is 100%.
The lower limit of the oxygen content was set to 0.1% because if it was less than this, the frequency of occurrence of adhesion would increase. The upper limit of the oxygen content was set to 2%. This is because peeling easily occurs in the sprayed layer.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. This example is a case where the present invention is applied to a piston used in a diesel engine. Therefore, the piston functions as a base material for the thermal spray layer. The basic composition of this piston is an Al-Si-Mg type (JIS AC8A). According to AC8A, Al is 80 to 86%, and Si is 10 to 1%.
3%, and Mg can be 0.7-1.3%.

As can be understood from FIG. 1, the piston 1 before the thermal spraying process has a ring-shaped groove 11 at the upper end. The groove 11 has a trapezoidal cross section, and has a conical surface 11a and a bottom surface 11c whose groove width increases toward the outer periphery. Note that the maximum groove width of the groove 11 can be 5 to 15 mm. The angle θ1 of the conical surface 1a with respect to the direction perpendicular to the axis of the piston 1 can be about 14 to 45 °.

In this embodiment, a sprayed powder mixed with a specific composition is used. Since the thermal spray deposition rate differs depending on the individual composition of the powder, it is necessary to consider the deposition efficiency of each powder when determining the mixing ratio in order to obtain a desired area ratio. Basically, the mixing ratio of the thermal spray powder is 10% for the Al alloy powder and FeCr for the hard phase, when the entire thermal spray powder is 100%.
C powder is 20%, and carbon steel powder (oxygen amount: 2300 ppm), which can be a matrix of the sprayed layer, is substantially the remainder.

The Al alloy powder described above is a powder formed by an atomizing process, and is a powder containing 15% Si when the entire Al alloy powder is 100%. Since the atomized powder has a high solidification rate, the structure is dense and S
Generally, coarse primary crystal Si is not generated even if the i content is large. The above carbon steel powder is a powder formed by an atomizing process, and is a powder containing 1% carbon (Fe-1% C) when the entire carbon steel powder is 100%. Since carbon steel powder is decarburized during thermal spraying, the carbon content of the carbon steel powder is selected in anticipation of decarburization. In consideration of the composition and the solidification rate, the carbon steel powder is generally assumed to have marsansite and austenite. The above-mentioned FeCrC powder has a 60%
It contains Cr and 8% C, and the balance is substantially Fe.

The general particle diameter of the above powder is about 10 to 70 μm for Al alloy powder, about 10 to 55 μm for carbon steel powder, and about 10 to 45 μm for FeCrC powder. Then, using the sprayed powder blended as described above, a spraying process was performed on the groove 11 of the piston 1 by the spraying device 4 as can be understood from FIG. At this time, at least the surface layer of the thermal spray powder is in a semi-molten state or a molten state, and collides with the groove 11 of the piston 1 at a high speed to be deposited. Thus, the sprayed layer 2 was laminated on the groove 11 of the piston 1. Thermal spraying was performed from the direction perpendicular to the axis of the piston 1, that is, the direction of the arrow A1.

Here, in this embodiment, the HVOF spraying process in the atmosphere is employed for the spraying process. The HVOF spraying process is an abbreviation of High Velocity Oxy-Fuel, and is “supersonic gas flame spraying”. HVO
In the F spraying process, the combustion gas velocity is several times higher than that of a normal plasma spraying process, the spray particle speed is also high (for example, about 600 m / sec), and the sprayed layer 2 has a low porosity (for example, 1 ~ 5 vol%) It is dense and has high adhesion.

In this embodiment, the basic conditions for thermal spraying were as follows. That is, fuel gas (propylene): 42 l / min, oxygen gas: 40 l / min, air: 5
0 liter / min, sprayed powder supply amount = 90 g / min
And Next, as a cutting step, the sprayed layer 2 is cut and cut in the depth direction of the sprayed layer 2 using a cutting tool (removing means) having a cemented carbide tip as a cutting blade, thereby forming a concave portion. A ring groove 3 was formed. This ring groove 3 serves as a top ring groove in the piston 1. The groove width of the ring groove 3 can be set to about 1.5 to 3 mm at the outer peripheral portion.

As shown in FIG. 2, the ring groove 3 has a rectangular cross section, extends in a ring shape, and opposing surfaces 31, 32 facing each other.
And a bottom surface 33 extending in a ring shape. This opposing surface 3
Reference numerals 1 and 32 substantially extend in a direction perpendicular to the axis of the piston 1. FIG. 3A schematically shows a conceptual diagram of the internal structure of the sprayed layer before cutting. At least the surface layer of the sprayed powder is in a semi-molten state or a molten state, and collides with the piston 1 which is the surface to be sprayed at a high speed. Therefore, as shown schematically in FIG. The particles are flattened and crushed. That is, the powder particles of the thermal spray powder in the laminating direction of the thermal spray layer have a thin shape and tend to be deposited.

A ring groove 3 is formed in the thermal sprayed layer 2 and, as schematically shown in FIG. 3B, if the side surfaces 31 and 32 defining the ring groove 3 are sliding surfaces, the sliding groove is formed. The types of particles expressed per unit area of the moving surface increase. This is because the particles are flat and thin. Therefore, the sliding characteristics due to the specific type of particles in the thermal spray powder are less likely to appear on the sliding surface, which is advantageous for expressing the overall sliding characteristics due to many types of powder particles.

When the piston 1 is used, a top ring (material: nitriding of 17% Cr stainless steel) is fitted in the ring groove 3. As the piston 1 reciprocates in the combustion chamber of the engine, the side surfaces 31, 32 of the ring groove 3 slide with the top ring. When sliding in this manner, as shown in FIG. 3B, since there are many types of particles exposed on the side surfaces 31 and 32 of the ring groove 3 according to the present embodiment, as described above, This is advantageous for exhibiting comprehensive sliding characteristics by many types of powder particles. That is, it is easy to expect an overall effect of the sliding characteristics of the carbon steel phase, the sliding characteristics of the Al alloy phase, and the sliding characteristics of the hard phase.

Thus, in the ring groove 3 according to the present embodiment, it is easy to obtain a stable and good sliding characteristic for a long time. Further, as can be understood from FIG. 3B, the particles are oriented in a direction substantially perpendicular to the side surfaces 31 and 33 constituting the sliding surface. Therefore, it is advantageous for avoiding the particles constituting the thermal spray layer from falling off, and in this sense, it is also advantageous for securing the sliding characteristics.

(Test Example) In order to confirm the effect of the present invention, the following test was conducted. Thermal spraying conditions in the test basically followed the above-described example. ○ The carbon steel powder used in the above-described examples was adopted as the iron-based powder, and the relationship between the carbon content in the carbon steel powder and the hardness of the sprayed layer was tested. In this test, the compounding ratio of the thermal spray powder was 10% for the Al alloy powder, 20% for the FeCrC powder, and substantially the carbon steel powder for the remainder when the entire thermal spray powder was 100%. Using the sprayed powder thus mixed, the sprayed layer was laminated on the actual groove of the piston.

FIG. 4A shows the test results. FIG. 4 (A)
As can be understood from the characteristic line, when the carbon content in the carbon steel powder increases, the hardness of the sprayed layer increases. From the region where the amount of carbon exceeds 1.5%, the degree of increase in hardness increases. Here, the hardness of the sprayed layer is preferably equal to or more than the hardness (about Hv150) of the niresist cast iron according to the prior art. The hardness of the sprayed layer is Hv3
If it exceeds 50, it will be difficult to cut the ring groove with a cutting tool in the sprayed layer. Therefore, as can be understood from the characteristic line of FIG. 4A, it is understood that the upper limit of the carbon content in the carbon steel powder is preferably 1.5% in consideration of the hardness characteristics of the sprayed layer.

Further, when the carbon content (X% C) in the carbon steel powder (Fe-X% C) is changed, the LF
A W abrasion test was performed, and the test result is indicated by a circle in FIG. 4 (B). In this test, when the thermal spray powder was 100%, the Al alloy powder was 10%, and the FeCrC powder was 20%.
%, And iron-based powder (carbon steel powder) was 70%. The conditions of the LFW wear test are basically the same as in the case of FIG.

As can be understood from the circles in FIG. 4 (B), except for the case where the amount of carbon in the carbon steel powder is extremely small, LF
The amount of W wear was small, and was therefore equal to or more than the case of the niresist cast iron indicated by hatching in FIG. 4 (B). In consideration of the test results, the lower limit of the carbon content can be set to 0.1% in the case of carbon steel powder. Similarly, stainless steel (martensitic SUS410, Fe-12.
Even when the carbon content (X% C) in 5% Cr-X% C) was changed, an LFW wear test was performed on the sprayed sliding surface, and the test result is shown by a triangle in FIG. 4B. . FIG.
As can be understood from the symbol (B) in (B), even if the amount of carbon in the stainless steel powder is extremely small, the amount of LFW abrasion is as shown in FIG.
In (B), the value was equal to or higher than the case of the niresist cast iron indicated by hatching. Therefore, in consideration of this test result, the lower limit of the amount of carbon in the case of stainless steel powder may be smaller than that in the case of carbon steel powder,
%.

The relationship between the amount of oxygen in the carbon steel powder and the adhesion efficiency at the time of thermal spraying was tested by using the carbon steel powder used in the above Examples. In this test, only carbon steel powder was sprayed in air without blending Al alloy powder or the like. Assuming that the consumption amount of the sprayed powder during the spraying time (= the amount of powder supplied per unit time (g / min) × spraying time) is W1, and the weight increase of the piston before and after spraying is ΔW, the adhesion efficiency is (ΔW / W1 ) × 100%. The test results are shown in FIG. As can be understood from the characteristic line of FIG. 5, it can be seen that as the amount of oxygen in the carbon steel powder increases, the adhesion efficiency during thermal spraying significantly decreases. Therefore, considering the adhesion efficiency, it is understood that the oxygen content in the carbon steel powder is preferably 0.5% or less, particularly preferably 0.4% or less.

The relationship between the addition ratio of the Al alloy powder in the thermal spray powder and the cutting resistance when forming a ring groove in the piston was tested. In this test, the FeCrC powder, Al alloy powder, carbon steel powder (F
e-1% C). And the whole sprayed powder is 100
%, The amount of the FeCrC powder was 20%, the amount of the Al alloy powder was changed, and the remainder was substantially sprayed powder of carbon steel powder. The cutting force was detected by a stress detecting element provided on the rear side of the cutting tool, and was defined as a vector sum of a main component force and a back component force. The test results are shown in FIG. As can be understood from the characteristic line in FIG. 6, it was confirmed that the cutting resistance sharply decreased when the blending amount of the Al alloy powder was 5% or more. But 2
If it exceeds 0%, the cutting force is less reduced.

Further, the relationship between the addition ratio of the Al alloy powder in the thermal spray powder and the adhesion efficiency of the thermal spray powder was examined. The adhesion efficiency was determined in the same manner as described above. In this test, the same FeCrC powder, carbon steel powder, Al
Alloy powder was used. And 100% of the whole sprayed powder
In this case, the spraying powder was used in which FeCrC was set to 20%, the amount of the Al alloy powder was appropriately changed, and the balance was substantially carbon steel powder. The test results are shown in FIG. As can be understood from the characteristic line of FIG. 7, it can be seen that the attachment efficiency of the thermal spray powder increases as the proportion of the Al alloy powder in the thermal spray powder increases. In consideration of the results of these tests, the addition ratio of the Al alloy powder in the thermal spray powder can be 5 to 20%.

Using a flat Al-based test piece, a sprayed layer is laminated on the flat surface of the test piece by spraying from above, and an LFW abrasion test is performed on the sprayed layer.
The W wear amount was measured. In this test, the same FeCrC powder, carbon steel powder, and Al alloy powder as in the above-described examples were employed. Then, when the entire sprayed powder is 100%, F
The eCrC powder was set to 20%, the amount of the Al alloy powder was appropriately changed, and the remainder was substantially sprayed powder of carbon steel powder.

According to the above LFW wear test, FIG.
As shown in the figure, ring material 20 (stainless steel containing 17% Cr (SUS430)) formed of the same material as the top ring
Test piece 2)
The ring member 20 was rotated while being pressed against the sprayed sliding surface of No. 1 with a predetermined load to wear the sprayed sliding surface. The test conditions were a load of 60 kg, a rotation speed of 160 rpm, and a test time of 60 m.
In, lubrication was performed in an engine oil bath. FIG. 8 shows the test results. As can be understood from the characteristic line in FIG.
It can be seen that as the proportion of the Al alloy powder in the thermal spray powder increases, the amount of LFW wear in the thermal spray layer increases. As can be understood from FIG. 8, when the proportion of the Al alloy powder is set to 20% or less, the wear amount is small.

Further, adhesion resistance at high temperature, which is an important factor as sliding characteristics of the piston ring groove, was also tested. In this test, the same FeCrC powder, carbon steel powder, and Al alloy powder as in the example were employed. When the total amount of the sprayed powder is 100%, the FeCrC powder is 2%.
0%, the amount of the Al alloy powder was changed appropriately, and the remainder was substantially sprayed powder of carbon steel powder.

In this adhesion test, Al in the sprayed powder was
The relationship between the ratio of the alloy powder and the amount of adhesive wear was tested. In this adhesion test, as shown in FIG.
Was sprayed from above onto the exposed surface of No. 1 to form a sprayed layer 31 having a sprayed sliding surface. Then, in a state where the ambient temperature is set to 250 ° C. in consideration of the piston operating temperature, a ring material 33 made of the same material as the top ring is used as a mating material, and the thermal spray layer 31 is repeatedly hit while rotating the ring material 33. went. In this adhesion test, the surface pressure was 10 kg / cm ² ,
The rotation speed was 0.5 mm / sec, the test time was 20 min,
The impact cycle is 150 cycles / min and the temperature is 25
At 0 ° C., the atmosphere was a nitrogen gas stream (lubrication = none) in consideration of the low oxygen atmosphere in the combustion chamber of the engine.

FIG. 9 shows the results of the adhesion test. As can be understood from the characteristic line of FIG. 9, it can be seen that as the proportion of the Al alloy powder in the thermal spray powder increases, the amount of cohesive wear in the thermal spray layer increases. In particular, when it exceeds 20%, it can be seen that the amount of adhesive wear increases greatly. In consideration of the results of the above-described tests, it can be said that the addition ratio of the Al alloy powder is preferably 5 to 20% when the entire thermal spray powder is 100%.

The Al alloy powder used in the above embodiment,
The carbon steel powder and the FeCrC powder used in the examples as particles forming the carbide-based hard phase were employed, and an LFW wear test was performed on the sprayed layer. In this test, when the entire sprayed powder was 100%, the Al alloy powder was 10%,
While changing the amount of FeCrC powder, the remainder was substantially sprayed powder of carbon steel powder. In FIG. 10, the test results of the wear amount of the sprayed layer are shown as ○, and the wear amount of the mating material is shown as △. As can be understood from the circles in FIG. 10, it can be seen that the LFW wear amount of the sprayed layer decreases as the proportion of the FeCrC powder in the sprayed powder increases. Further, as can be understood from the triangles in FIG. 10, when the proportion of the FeCrC powder added to the thermal spray powder increases, the aggressiveness to the ring material, that is, the mating material is greatly increased.

Further, instead of FeCrC powder, chromium carbide (Cr ₂
(C ₃ : particle size of 10 to 44 μm) was employed, and in this case also, the amount of the chromium carbide powder was changed, and the LFW abrasion test was similarly performed on the sprayed layer. In FIG. 10, the test results of the wear amount of the sprayed layer are indicated by ●, and the wear amount of the mating member is indicated by ▲ (black triangle). As can be understood from the black circles in FIG. 10, it can be seen that as the proportion of Cr ₂ C ₃ added to the thermal spray powder increases, the LFW wear of the thermal spray layer decreases. As can be understood from the ▲ mark (black triangle mark) in FIG. 10, it can be seen that as the proportion of Cr ₂ C ₃ added to the thermal spray powder increases, the aggressiveness to the ring material, that is, the mating material increases significantly.

The relationship between the addition ratio of the particles forming the carbide-based hard phase and the cutting resistance when forming a ring groove in the piston was tested. Also in this test, the Al alloy powder and the carbon steel powder used in the above-described examples were used. Further, a high-carbon FeCr alloy (general particle size: 10 to 44 μm) is adopted as particles forming the hard phase, and the entire sprayed powder is made 100%.
In this case, a thermal spray powder was used in which the Al alloy powder was 10%, the amount of particles forming the hard phase was changed appropriately, and the balance was substantially carbon steel powder. The test results are shown in FIG.
As can be understood from the characteristic line in FIG. 11, the cutting resistance is not so large when the blending amount of the particles forming the hard phase is about 20% or 30%, but when it exceeds 40%, the cutting resistance sharply increases. I understand. In FIG. 11, the level at which cutting by the die tool is difficult is a cutting resistance of 300
This is the area beyond N. Considering the results of the above-described tests, it can be said that, when the total amount of the sprayed powder is 100%, the addition ratio of the particles forming the hard phase is preferably 5 to 40%.

Further, Cu-9% Al is used as a soft alloy powder.
Using an (α phase, general particle size of 5 to 60 μm) powder, an impact test was carried out to see the effect of improving the toughness of the sprayed layer by the amount of the powder added. Also in this test, the Al alloy powder and carbon steel powder used in the above-described example were adopted, and when the entire sprayed powder was 100%, the Al alloy powder was 10%, and the FeCrC powder was used as particles for forming a hard phase. 2
0%, a sprayed powder was used in which the soft alloy powder was appropriately changed and the balance was substantially carbon steel powder. This sprayed powder is subjected to a spraying treatment, and a prismatic sprayed test piece (size: 10) composed of a sprayed layer is formed.
mm × 5 mm × 40 mm: no notch), and a Charpy impact test was performed using the sprayed test piece.

As another soft alloy powder, Ni-8%
Using a self-fluxing alloy powder of Cr-1.5% B-3% Si (general particle size: 10 to 45 µm), a thermal sprayed test piece composed of a thermal spray layer was similarly prepared. Also in this case, a Charpy impact test was performed to see the effect of improving the toughness of the sprayed layer by the amount of addition. The test results are shown in FIG. In FIG. 12, ● shows the case where an alloy powder of Ni-8% Cr-1.5% B-3% Si was used, and ○ shows the case where a Cu-9% Al powder was used. By adding 5% of each powder,
The effect of increasing the impact value and improving the toughness of the sprayed layer was observed. On the other hand, if the addition amount exceeds 30%, the wear resistance of the sprayed layer is reduced. Therefore, it is understood that the soft alloy powder is preferably 5 to 30% when the entire sprayed powder is 100%.

更 に Further, using the above-mentioned two kinds of soft alloy powders, the amount of LFW wear according to the amount of addition of these powders was measured.
Also in this test, the Al alloy powder and carbon steel powder used in the above-described example were adopted, and when the entire sprayed powder was 100%, the Al alloy powder was 10%, and the FeCrC powder was used as particles for forming a hard phase. Was changed by 20%, and the soft alloy powder was appropriately changed, and the remainder was substantially sprayed powder of carbon steel powder. The test results are shown in FIG. In FIG. 13, ● shows the case where an alloy powder of Ni-8% Cr-1.5% B-3% Si was used, and ○ shows the case where a Cu-9% Al powder was used. In any case, the increase in the amount of LFW wear is not so noticeable up to 30%, but when it exceeds 30%, the amount of LFW wear increases.

The effect of the difference in the spraying direction on the adhesion resistance of the sprayed layer was examined. The test results are shown in FIG. The column T1 in FIG. 14 shows the case where the mating material (nitrided to SUS430) was slid in the deposition direction of the thermal spray powder, that is, in the direction perpendicular to the thermal spraying direction (K1 direction). The column T2 in FIG. 14 shows a case where a similar partner material is slid in parallel to the deposition direction of the thermal spray powder particles, that is, the thermal spraying direction (K1 direction).

In the material 1 used in this test, when the entire sprayed powder was 100%, the Al alloy powder was 10%,
Thermal spray powder was used in which the content of FeCrC powder was 20% and the balance was substantially carbon steel powder. In the material 2 used in this test, when the entire sprayed powder was 100%, the Al alloy powder was 20%, the FeCrC powder was 20%, and the Cu-9% A was used.
1% powder was used, and the remainder was substantially sprayed powder of carbon steel powder. As can be understood from the test results shown in FIG. 14, the amount of adhesive wear in the column T2 is smaller than the amount of adhesive wear in the column T1. The effect of the spray direction contributes,
This is presumed to be the effect of expressing the total sliding characteristics by many types of powder particles.

(Metal Structure) A typical metal structure of the sprayed layer is obtained by spraying a thermal spray powder containing the same powder as the powder used in the above-described examples, as shown in FIGS. (The suffix 79 of the photograph number). This is an optical micrograph (× 200: no etching). The thermal spray layer according to FIG.
The thermal spraying powder used is such that eCrC powder is 20%, Al alloy powder is 10%, and the balance is substantially blended as carbon steel powder. The thermal spray layer according to FIG.
When it is set to 00%, FeCrC is 20%, Al alloy powder is 10%, soft alloy powder (Cu-9% Al) is 10%,
The remainder substantially uses a sprayed powder blended as a carbon steel powder. That is, the ratio of the carbon steel powder has decreased.
In FIGS. 15 and 16, the upper black region indicates the embedded resin. In FIG. 15, the island-shaped particles are clearer than in FIG. Considering the molten form, the particles in island form are
It is presumed that the carbon steel powder had a relatively high melting point.
The direction of arrow K1 indicates the flight direction of the particles, that is, the spraying direction.
This photograph also shows that the particles constituting the thermal spray layer are flattened.

(Abrasion Resistance Test) Further, test pieces (NO. 1 to NO. 20) according to the present invention having the sprayed layer constitution shown in Table 1 were prepared. As can be understood from Table 1, the matrix formed of the iron-based particles shows the test piece No. 1 to NO. No. 15 is a carbon steel composition, and the test piece NO. 16 to NO. In 20,
Stainless steel composition (SUS).

The composition of the matrix and its area ratio, the hard phase and its area ratio, and the Al alloy and its area ratio for each test piece according to the present invention are shown in Table 1, respectively. Generally, Fe constituting the hard phase employed in the above test piece is
-60% Cr-8% C has a hardness of about Hv900 to 1400, and Cr2C3 has a hardness of Hv1200 to 1500.
And the hardness of Fe3C is Hv1000-1200.
SKH54 has a hardness of about Hv 500 to 700.

The column indicated in the purpose column of Table 1 means a test for changing the amount of carbon in the matrix and examining the influence of the amount of carbon. Table 1 shows the test for changing the area ratio of the matrix, the area ratio of the hard phase, and the area ratio of the Al alloy, and examining the influence of the area ratio. The column shown in the purpose column of Table 1 means a test for changing the material of the hard phase and the area ratio thereof to find out the influence thereof. Table 1 shows the purpose column of the Al alloy.
It means a test to change the amount and to see its effect.

As a wear evaluation method, a ring-on-plate type LFW wear test method was used as shown in FIG.
The test conditions were a load of 60 kg, a test time of 60 minutes, and a ring rotation speed of 160 rpm. The wear evaluation was performed in the spray deposition direction (= the flight direction of the sprayed powder particles, arrow K1 in FIG. 17).
The ring material 20, which is a mating material, was obtained by subjecting 17Cr stainless steel to nitriding treatment. Engine oil was used for lubrication.

In the column of LFW wear in Table 2, the test results of the test pieces (NO. 1 to NO. 20) according to the present invention are shown. Table 2
Also indicates the coefficient of thermal expansion and the coefficient of thermal conductivity. FIG. 17 shows the LFW
The results of the abrasion test are shown in a graph. Further, in this test, comparative alloys A to G were employed. As can be seen from Table 3, as a comparative alloy A, a niresist cast iron according to the prior art was employed. Table 3 shows the matrix and its area ratio, the hard phase and its area ratio, the Al alloy and its area ratio, and the like in Comparative Alloys BG. These comparative alloys A to G were similarly tested, and the test results are shown in the LFW wear column of Table 4 and in FIG.

In FIG. 17, the test results of the niresist cast iron are indicated by hatching. As can be understood from FIG. 17, the test pieces (NO. 1 to NO.
0) shows that the wear depth of the sprayed layer is small in all cases, and therefore, it has wear resistance equal to or higher than that of the niresist cast iron indicated by the hatched area. Moreover, according to the test pieces (NO. 1 to NO. 20) according to the present invention, the thermal conductivity is 33.2 to 62.3 W / mk as can be understood from the thermal conductivity column shown in Table 2. Since the thermal conductivity of Niresist cast iron is higher than that of Niresist cast iron (Table 4: 18.8 W / mk), the thermal conductivity of the thermal sprayed layer is good, and the thermal shock is reduced.
It is expected that the wear resistance at high temperatures will be better.

(Adhesion Resistance Test) As shown in FIG. 18, the adhesion resistance was measured by a thrust test method of repeatedly pressing the shaft end face of the ring material 33 against the sprayed sliding surface of the sprayed layer 31 laminated on the test piece. It was evaluated by a dry type abrasion test. Since the occurrence of adhesion on the sprayed sliding surface induces the sticking of the piston ring, etc., the aim is to prevent the occurrence of adhesion. The test conditions were as follows: surface pressure = 10 kg / cm ² , ring rotation: 0.5 m
m / sec, atmosphere: N ₂ , test temperature = 250 ° C. These test conditions assume actual piston operating conditions.

In the adhesion test, the presence or absence of adhesion was evaluated visually and by the presence or absence of plastic flow in the cross section. The test results of the test pieces (NO.1 to NO.20) according to the present invention are as follows:
The results are shown in the column of adhesion test in the wear evaluation in Table 2. As can be understood from the column of the adhesion test in Table 2, according to the test pieces (NO. 1 to NO. 20) of the present invention, the adhesion was "none" and the adhesion was excellent. I understand. Further, the test results of Comparative Alloys A to G are shown in the column of adhesion test in Table 4. As shown in Table 4, according to Comparative Alloy E (the area ratio of the iron-based matrix was as small as 32%), the adhesion was “present”.

(Thermal Shock Resistance Test) Niresist cast iron which has been conventionally employed is designed so that its coefficient of thermal expansion is close to that of the Al alloy as the base material in order to secure the thermal shock resistance. However, in actuality, not only the coefficient of thermal expansion but also the thermal conductivity contributes to the thermal shock resistance against thermal shock. If the thermal conductivity between the base material (Al) and the sprayed layer is not brought close,
It is found that the temperature difference between the two increases during cooling, and tensile stress is generated at the interface between the base material and the sprayed layer. In the thermal shock resistance test, as shown in FIG. 19, a piston 63 having a sprayed sliding surface formed in a ring groove is attached to a rotating disk 61 rotated by a motor 60, and the actual operating temperature of the piston is taken into consideration. The piston 63 is heated by the combustion flame of the gas burner 65 until the rotation of the turntable 61.
The piston 63 was immersed in water at 5 ° C. and evaluated by the number of tests until crack generation. The presence or absence of cracks was confirmed by a color check. The same test was conducted for Comparative Alloy A in which Niresist cast iron was cast.

FIG. 20 shows the test results. As shown in FIG. 20, according to the test pieces (NO. 6 and NO. 7) according to the present invention, the number of tests up to the occurrence of cracks is 70 or more, and the test according to the present invention is more aluminum alloy. Pieces (NO. 8, NO.
According to 9), no crack was generated at the interface between the thermal sprayed layer and the base material even after 100 or more tests. However, as shown in FIG. 20, in the case of the comparative alloy A, cracks occurred in the sprayed layer after 1 to 5 tests. This is because even if the thermal expansion coefficient of the thermal spray layer approaches the thermal expansion coefficient of the base material as described above, when quenching, the thermal conductivity of the thermal spray layer is low, so that the Ni-resist cast iron and the base material (aluminum alloy) It is presumed that the temperature difference between the two became large, and as a result, cracks occurred at the interface between the two.

[0075]

[Table 1]

[0076]

[Table 2]

[0077]

[Table 3]

[0078]

[Table 4] (Other Examples) In the above-described embodiment, the present invention is applied to the top ring groove of the piston of the diesel engine. However, the present invention is not limited to this, and a piston ring groove other than the top ring groove may be used. Further, the present invention can be applied to a ring groove of a piston of a gasoline engine. Further, it can be expected to be applied to other kinds of sliding members having a sliding surface such as gears. The thermal spraying process is not limited to HVOF thermal spraying, but may be atmospheric plasma thermal spraying, reduced pressure plasma thermal spraying, powder type flame thermal spraying, etc. A protective atmosphere, a vacuum state, and the like can be appropriately selected.

[0079]

According to the first aspect of the present invention, since the sprayed powder in which various powders having a specific composition range are blended is employed, the cutting workability of the sprayed layer and the efficiency of adhesion of the sprayed powder to the base material. This is advantageous for forming a thermal sprayed layer having excellent adhesion strength to a substrate, abrasion resistance, adhesion resistance and the like. Particularly, it is advantageous for forming a sprayed layer having excellent wear resistance and adhesion resistance in a high temperature region such as a piston operating temperature.

According to the second aspect, since the area ratio is specified, it is advantageous to form a sprayed sliding surface excellent in abrasion resistance, adhesion resistance and the like. In particular, it is advantageous for forming a sprayed layer having excellent wear resistance and adhesion resistance in a high temperature region such as a piston operating temperature. According to the third aspect, the concave portion is formed in the thermal sprayed layer, and the side surface that defines the concave portion is used as a sliding surface, so that the types of particles expressed per unit area of the sliding surface increase. Therefore, the sliding characteristics due to the specific type of particles in the thermal spray powder are less likely to appear, which is advantageous in exhibiting the overall sliding characteristics due to many types of powder particles. That is, even if the sliding surface has a small area, it is easy to expect the overall effect of the sliding characteristics of the iron phase, the sliding characteristics of the Al alloy phase, and the sliding characteristics of the carbide or the hard phase containing the carbide. As a result, the sliding surface can obtain good sliding characteristics that are stable over a long period of time.

Further, since the particles tend to be oriented in a direction substantially perpendicular to or close to the sliding surface, even when the sliding conditions are severe, it is difficult to form a powder such as an iron-based powder or an Al alloy powder deposited by thermal spraying. This is advantageous for avoiding particles falling off. Also in this sense, it is easy to expect the overall effect of the sliding properties of the iron-based phase, the sliding properties of the Al alloy phase, and the sliding properties of the carbide or alloy phase containing carbide, which is advantageous for securing wear resistance. .

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a configuration diagram showing a configuration in the vicinity of a piston groove before thermal spraying, a configuration in which thermal spraying is performed by a thermal spraying device, and a configuration in the vicinity of a top ring groove after cutting.

FIG. 2 is a cross-sectional view of the vicinity of a top ring groove after cutting.

3A is a cross-sectional view schematically illustrating the concept of a thermal spray layer, and FIG. 3B is a cross-sectional view schematically illustrating the concept of forming a groove in the thermal spray layer.

FIG. 4 (A) is a graph showing the relationship between the carbon content in carbon steel powder and the hardness of the sprayed layer, and FIG. 4 (B) is a graph showing the carbon content of carbon steel powder and the carbon content in stainless steel powder. It is a graph which shows the relationship between the amount and the amount of LFW wear of a sprayed layer.

FIG. 5 is a graph showing the relationship between the amount of oxygen in carbon steel and the adhesion efficiency of thermal spray powder.

FIG. 6 is a graph showing the relationship between the ratio of the Al alloy powder in the thermal spray powder and the cutting resistance of the thermal spray layer.

FIG. 7 is a graph showing the relationship between the ratio of the Al alloy powder in the thermal spray powder and the adhesion efficiency of the thermal spray powder.

FIG. 8 is a graph showing the relationship between the proportion of Al alloy powder in the thermal spray powder and the amount of LFW wear.

FIG. 9 is a graph showing the relationship between the ratio of the Al alloy powder in the thermal spray powder and the amount of adhesive wear.

FIG. 10 shows the ratio of carbide-based hard phase in thermal spray powder and LFW.
It is a graph which shows the relationship with a wear amount.

FIG. 11 is a graph showing the relationship between the ratio of the carbide-based hard phase in the thermal spray powder and the cutting resistance.

FIG. 12 is a graph showing the relationship between the ratio of the soft alloy powder in the thermal spray powder and the impact value.

FIG. 13 is a graph showing the relationship between the addition ratio of a soft alloy powder and the amount of LFW wear.

FIG. 14 is a graph showing the relationship between the deposition direction and the amount of adhesive wear during thermal spraying.

FIG. 15 is a photograph showing a metal structure of a thermal sprayed layer.

FIG. 16 is a photograph showing a metal structure of a sprayed layer according to another example.

FIG. 17 is a graph showing test results indicating the wear depth of the sprayed layer.

FIG. 18 is a configuration diagram of an adhesion test.

FIG. 19 is a configuration diagram of a thermal shock test.

FIG. 20 is a graph showing test results of a thermal shock test.

[Explanation of symbols]

In the figure, 1 is a piston, 11 is a groove, 2 is a sprayed layer, 3 is a ring groove (recess), 31 and 32 are opposing surfaces, and 33 is a bottom surface.

Continuation of front page (72) Inventor Koji Saito 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (58) Field surveyed (Int.Cl. ⁷ , DB name) C23C 4/10 B22F 1/00 C22C 32/00 C22C 38/00

Claims (3)

(57) [Claims] An iron-based powder containing 0.01 to 1.5% of carbon and 0.5% or less of oxygen by weight is 50 to 80% by weight, and an Al alloy powder of 20% or less of Si is 5 to 5% by weight. A sprayed powder characterized in that a carbide or an alloy containing a carbide having an Hv of 500 to 1500 and an alloy containing carbide has an inevitable impurity of 5 to 40% by weight. 2. An aluminum alloy having an area ratio of 40 to 79% by weight of iron-based particles having a carbon content of 0.01 to 1.0% by weight and an aluminum alloy having an area ratio of 20 to 50 by weight of an aluminum alloy having 11 to 20% of Si. %, Wherein the area ratio of carbide or an alloy containing carbide having an Hv of 500 to 1500 is 1 to 20%. 3. An iron-based powder containing 0.01 to 1.5% of carbon and 0.5% or less of oxygen in a weight ratio of 50 to 80% by weight, and an Al alloy powder of 20% or less of Si in a weight ratio of 5 to 5%. 20%, Hv 500-1500 carbide or alloy containing carbide, 5-40% in weight ratio, using thermal spray powder consisting of unavoidable impurities, and spraying the thermal spray powder by stacking it on the surface to be sprayed of the Al base material. A thermal spraying step of stacking layers, and a removing step in which a part of the thermal sprayed layer is removed by a removing means in a depth direction to form a concave portion, and a side surface along the depth direction defining the concave portion is a thermal spray sliding surface. And a method of forming a sprayed sliding surface.