JP2020111788A - Combination structure of valve seat and engine valve - Google Patents

Abstract

To provide a combination structure of a valve seat and an engine valve, capable of suppressing an abrasion by a contact of the valve seat and the engine valve.SOLUTION: In a combination structure of a valve seat and an engine valve having contact with the valve seat, a contact part of the valve seat having contact with the engine valve is composed of a copper base alloy containing a prescribed element, an overlay metal part of the valve seat having contact with the engine valve is composed of a cobalt-chromium-molybdenum base alloy containing a prescribed element, and an average particle diameter of hard particles contained in the copper base alloy is larger than a soft matrix interval (DAS value) of the cobalt-chromium-molybdenum base alloy.SELECTED DRAWING: Figure 4

Description

The present invention relates to a combined structure of a valve seat and an engine valve, specifically, a combination of a valve seat formed or built up with a copper-based alloy and an engine valve built up with a cobalt-chromium-molybdenum-based alloy. Regarding the structure.

Conventional copper-based alloys have been subjected to some surface treatment such as forming an oxide film on the metal surface in order to avoid the problem of adhesion. For example, under frictional wear conditions of high temperature exceeding 200° C., particularly in a material having a low melting point, cohesive wear occurs with a high probability due to contact between metals. However, the surface treatment is generally performed by a heat treatment process, and there is a problem that it takes time and manufacturing cost.

In particular, when a copper-based alloy is used as a build-up material for an exhaust valve seat of an ethanol-containing fuel such as gasoline, it is placed in a reducing atmosphere in which hydrogen has a strong reducing action, and therefore molybdenum, tungsten and Formation of an oxide film on hard particles formed of any one of vanadium and niobium carbide is not promoted, and cohesive wear due to metal contact is likely to occur. If the wear resistance is reduced in this way, wear may occur that exceeds the limit at which the valve seat functions.

Further, when chromium is added for the purpose of improving the corrosion resistance, although the corrosion resistance is improved by forming a chromium passivation oxide film on the material surface of the copper-based alloy, an oxide film of hard particles is formed as described above. There is a problem that it becomes difficult and wear resistance is reduced.

Therefore, for example, in Patent Document 1, at least one selected from the group consisting of molybdenum, tungsten, and vanadium and niobium carbide are contained, and the content of chromium is less than 1.0% by mass. And hard particles dispersed therein, wherein the hard particles are niobium carbide and at least one selected from the group consisting of Nb-C-Mo, Nb-C-W, and Nb-C-V. Abrasion resistant copper-based alloys are described, including.

JP, 2017-36470, A

On the other hand, in the contact between the valve seat and the engine valve, hard particles contained in the copper-based alloy in the contact portion of the valve seat may wear the oxide film on the sliding surface of the engine valve, which also causes deterioration of wear resistance. It was a factor.

Therefore, it is an object of the present invention to provide a combined structure of a valve seat and an engine valve in which wear due to contact between the valve seat and the engine valve is suppressed.

The wear of the oxide film on the sliding surface of the engine valve due to the hard particles contained in the copper-based alloy in the contact portion of the valve seat is affected by the combination of the structure of the valve seat and the engine valve. When the hardfacing alloy of the engine valve includes two phases, a hard phase and a soft phase, if the particle size of the hard particles contained in the copper-based alloy in the contact portion of the valve seat is large, the hard particles of the valve seat are The hard particles contained in the copper-based alloy in the contact portion of the valve seat have a small particle size, whereas the hard particles of the valve seat are only the soft phase of the engine valve. And the oxide film formed in the soft phase is abraded, resulting in metal-to-metal contact and cohesive wear.

As a result of various studies on means for solving the above-mentioned problems, the present inventors have found that a valve seat formed or built up from a copper-based alloy composed of a specific element and a valve seat that is in contact with the valve seat are specified. In a combined structure of an engine valve built up with a cobalt-chromium-molybdenum-based alloy composed of the elements described above, the average particle diameter of the hard particles contained in the copper-based alloy is set to the softness of the cobalt-chromium-molybdenum-based alloy. The inventors have found that the wear amount of the combined structure can be reduced by making it larger than the matrix interval (DAS value), and completed the present invention.

That is, the gist of the present invention is as follows.
(1) A combined structure of a valve seat and an engine valve in contact with the valve seat,
The contact portion of the valve seat that is in contact with the engine valve has Ni: 5% by mass to 18% by mass, Si: 0.5% by mass to 3% by mass, Fe: 3% by mass to 10% by mass, Mo: 6% by mass. % To 20 mass %, Nb: 0.2 mass% or less, and the balance: Cu and a copper-based alloy containing inevitable impurities,
The metal deposit of the engine valve in contact with the valve seat has Cr: 22% by mass to 27% by mass, Mo: 11% by mass to 30% by mass, W: 2.0% by mass to 6.0% by mass, C : 0.40% by mass to 1.3% by mass, Si: 3.0% by mass or less, Ni: 15% by mass or less, Fe: 30% by mass or less, Mn: 1.0% by mass or less, and the balance: Co and A cobalt-chromium-molybdenum-based alloy containing inevitable impurities,
A combined structure in which the average particle size of the hard particles contained in the copper-based alloy is larger than the soft matrix spacing (DAS value) of the cobalt-chromium-molybdenum-based alloy.

According to the present invention, there is provided a combined structure of a valve seat and an engine valve, in which wear due to contact between the valve seat and the engine valve is reduced.

It is a scanning micrograph which shows the structure of a valve seat. 5 is a graph showing the relationship between the average particle diameter of hard particles contained in the copper-based alloy of the valve seat and the maximum diameter of √ hard particles. It is a typical conceptual diagram of a single-body abrasion tester. 3 is a graph showing the relationship between the maximum diameter of √ hard particles of hard particles contained in the copper-based alloy of the valve seat and the wear amount. It is a scanning micrograph which shows the structure of the heap part of an engine valve.

Hereinafter, preferred embodiments of the present invention will be described in detail.
In the present specification, features of the present invention will be described with reference to the drawings as appropriate. In the drawings, the dimensions and shapes of the respective parts are exaggerated for clarity, and the actual dimensions and shapes are not accurately depicted. Therefore, the technical scope of the present invention is not limited to the size and shape of each part shown in these drawings. The combination structure of the valve seat and the engine valve of the present invention is not limited to the following embodiments, and various modifications and improvements can be made by those skilled in the art without departing from the scope of the present invention. Can be carried out.

The present invention provides a combined structure of a valve seat and an engine valve in contact with the valve seat, wherein a contact portion of the valve seat in contact with the engine valve is a copper-based alloy containing a specific element. The engine metal part of the engine valve that is in contact with is a cobalt-chromium-molybdenum-based alloy containing a specific element, and the average particle diameter of the hard particles contained in the copper-based alloy is the cobalt-chromium-molybdenum-based alloy. It relates to a combined structure that is larger than the soft matrix spacing (DAS value).

(Valve seat)
The contact portion of the valve seat in contact with the engine valve in the present invention is made of a copper-based alloy, and in the copper-based alloy, Ni is 5% by mass to 18% by mass, preferably 5% by mass to 16% by mass. Yes, Si is 0.5% by mass to 3% by mass, preferably 0.5% by mass to 2.2% by mass, and Fe is 3% by mass to 10% by mass, preferably 4% by mass to 8% by mass. %, Mo is 6% by mass to 20% by mass, preferably 9% by mass to 15% by mass, and Nb is 0.2% by mass or less, preferably 0.1% by mass or less. The balance of the copper-based alloy contains Cu and inevitable impurities.

Further, in the copper-based alloy, C is usually 0.05 mass% or less, preferably 0.02 mass% or less.

By adjusting the amount of each component of the copper-based alloy (also simply referred to as “copper-based alloy”) in the contact portion of the valve seat that is in contact with the engine valve in the present invention, the hard particles contained in the copper-based alloy √ It becomes possible to control the maximum diameter of hard particles within a certain range.

This is based on the fact that the maximum hard particle diameter of the hard particles contained in the copper-based alloy can be estimated by the following formula from the amount of each component of the copper-based alloy.

√ Hard particle maximum diameter estimated value (√μm) = 12.044 + 0.953 x Mo amount (mass %)-6.475 x Nb amount (mass %) + 1.458 x C amount (mass %) -0.117 x Ni content (mass %)-0.882 x Si content (mass %)-0.084 x Fe content (mass %)

As a reason that the hard particle maximum diameter of the hard particles can be estimated by the amount of components of the copper-based alloy, in addition to the experimental results of the examples described below, the following theory is considered, but the scope of the present invention is the following theory. Not be bound by.

The copper-based alloy has a structure in which hard particles of the main component FeMoSi are dispersed in a Cu-based matrix by a two-liquid separation reaction.

The copper-based alloy has an alloy liquid phase containing Cu (also referred to as “Cu-based alloy liquid phase”) and one or more elements of Mo, W and Nb (also simply referred to as “second element”) at a predetermined temperature. The alloy liquid phase (also referred to as “second liquid phase”) containing is separated (referred to as “two liquid phase separated state”). When the two liquid-phase separated states are vigorously stirred and rapidly solidified, the hard particles in which the second liquid phase is solidified are substantially uniform in the matrix in which the Cu-based alloy liquid phase is solidified (referred to as “Cu-based matrix”). A composite structure dispersed in is obtained. Therefore, the hard particles are mainly composed of an alloy (compound) of the second element, and the hard phase is considered to be a Laves phase containing a large amount of Ni, Si and Fe, a μ phase, or the like.

Multivariate analysis of the relationship between the amount of each component of the copper-based alloy formed in this manner and the maximum diameter of the hard particles contained in the copper-based alloy can be obtained by the multivariate analysis.

The maximum diameter of the hard particles of the hard particles contained in the copper-based alloy can be measured as follows.

(1) The valve seat is embedded in resin and polished.
(2) For the sample polished in (1), a backscattered electron image (magnification: 200) of a scanning microscope is photographed, and the photographed image is binarized by using analysis software, for example, WinROOF, and is mainly used. Hard particles consisting of Fe, Mo and Si are selected.
(3) For each hard particle selected in (2), the equivalent circle diameter is calculated.
(4) The maximum value is obtained from the equivalent circle diameters of the hard particles obtained in (3).
(5) Steps (1) to (4) are repeated 2 to 4 times.
(6) The maximum values of the equivalent circle diameters of the hard particles in the respective images obtained in (5) are averaged to obtain the hard particle maximum diameter.
(7) By calculating the square root of the hard particle maximum diameter obtained in (6), the √ hard particle maximum diameter is obtained.

The √ hard particle maximum diameter measured value of the hard particles contained in the copper-based alloy is approximately the same as the √ hard particle maximum diameter estimated value estimated by the above formula.

Therefore, again, by setting the amount of each component of the copper-based alloy in the present invention within the above range, it is possible to control the √ hard particle maximum diameter of the hard particles contained in the copper-based alloy within a certain range. ..

In other words, the amount of each component of the copper-based alloy in the present invention is such that the √ hard particle maximum diameter estimated value of the hard particles contained in the copper-based alloy is usually 6√μm or more, for example, 10√μm to 20√μm, preferably It can also be determined so as to be 15 √μm to 20 √μm.

Further, the maximum hard particle diameter of the hard particles contained in the copper-based alloy is proportional to the average particle diameter of the hard particles.

The average particle diameter of the hard particles contained in the copper-based alloy is usually 8 μm or more, for example 8 μm to 16 μm, preferably 12 μm to 16 μm.

The average particle size of the hard particles contained in the copper-based alloy can be measured as follows.

(1) The valve seat is embedded in resin and polished.
(2) For the sample polished in (1), a backscattered electron image (magnification: 200) of a scanning microscope is photographed, and the photographed image is binarized by using analysis software, for example, WinROOF, and is mainly used. Hard particles consisting of Fe, Mo and Si are selected.
(3) For each hard particle selected in (2), the equivalent circle diameter is calculated.
(4) The average value of the equivalent circle diameters of the hard particles obtained in (3) is calculated.
(5) Steps (1) to (4) are repeated 2 to 4 times.
(6) The average value of the equivalent circle diameters of the hard particles in each image obtained in (5) is averaged to obtain the average particle diameter of the hard particles.

Therefore, by setting the amount of each component of the copper-based alloy in the present invention in the above range, the average particle size of the hard particles contained in the copper-based alloy can be controlled within a certain range, and as a result, the average particle size of the hard particles. The diameter can be made larger than the soft matrix spacing (DAS value) of the cobalt-chromium-molybdenum-based alloy described below.

The copper-based alloy in the contact portion of the valve seat which is in contact with the engine valve in the present invention can be used as a build-up alloy to be built up on an object. Examples of the surfacing method include a method of surfacing by welding using a high-density energy heat source such as a laser beam, an electron beam, or an arc. In the case of build-up, the copper-based alloy of the present invention is powdered into a material for build-up, and the powder is collected in the build-up portion, and the high density of the laser beam, electron beam, arc, etc. described above. It can be welded and built up using an energy heat source. Further, the above-mentioned copper-based alloy is not limited to powder, and may be a wire-forming or rod-shaped material for build-up. As the laser beam, a laser beam having a high energy density such as a carbon dioxide laser beam or a YAG laser beam is exemplified. Examples of the material of the object to be overlaid include aluminum, aluminum-based alloys, iron or iron-based alloys, copper or copper-based alloys, and the like. As the basic composition of the aluminum alloy constituting the object, an aluminum alloy for casting, for example, any of Al-Si system, Al-Cu system, Al-Mg system, Al-Zn system, etc. can be exemplified. Examples of the object include an engine such as an internal combustion engine. In the case of an internal combustion engine, valve train materials are exemplified. In this case, it may be applied to the valve seat that constitutes the exhaust port, or may be applied to the valve seat that constitutes the intake port. In this case, the valve seat itself may be made of the copper-based alloy of the present invention, or the copper-based alloy of the present invention may be built up on the valve seat. Since the copper-based alloy in the present invention does not contain zinc or tin as a positive element, it is possible to suppress generation of fumes and the like even in the case of overlaying. Since the copper-based alloy in the present invention does not contain aluminum as a positive element, it is possible to suppress the formation of a compound between Cu and Al, thereby maintaining ductility.

(Engine valve)
In the engine valve according to the present invention, the valve body is formed with the metal deposit, and the surface of the metal deposit is the valve face that contacts the valve seat. The deposit portion is a portion in which an alloy powder for overlay deposition containing a specific composition described in detail below is melted by a plasma overlay method or the like, and the melted alloy powder for overlay deposition (overlay metal material) is overlayed.

In the present invention, the valve body of the engine valve may include cast iron or steel material as the metal material, and preferably austenitic heat resistant steel (JIS standard: SUH35, SUH36, SUH660, NCF750, NCF751, NCF800), martensite. Examples include heat-resistant steels (JIS standards: SUH1, SUH4, SUH11) and the like.

When the entire valve body is 100% by mass, the Cr content in the valve body is preferably 16% by mass or more, and more preferably 18% by mass or more. Here, if the content of Cr is less than 16% by mass, Cr of the deposit portion is solid-dissolved and diffused in the valve body during the molding of the deposit portion, and the content of Cr in the deposit portion decreases. As a result, the amount of Cr that forms a solid solution in the Co-based matrix of the heap metal portion decreases, so that it may not be possible to ensure the stable formation of the Cr oxide film on the surface of the metal heap portion.

The metal deposit of the engine valve in contact with the valve seat in the present invention is made of a cobalt-chromium-molybdenum-based alloy, and in the cobalt-chromium-molybdenum-based alloy, Cr is 22% by mass to 27% by mass. , Mo is 11% by mass to 30% by mass, W is 2.0% by mass to 6.0% by mass, C is 0.40% by mass to 1.3% by mass, and Si is , 3.0 mass% or less, Ni is 15 mass% or less, Fe is 30 mass% or less, and Mn is 1.0 mass% or less. The balance of the cobalt-chromium-molybdenum-based alloy contains Co and unavoidable impurities.

Hereinafter, the basis of each element and the numerical range of the element in the engine valve helix will be described in detail.

・Cr (chrome): 22% by mass to 27% by mass
Cr is an element that exerts the corrosion resistance of the engine valve by forming a Cr oxide film (passive oxide film) on the surface of the Co-based matrix of the metal deposit. Further, this Cr oxide film prevents adhesion between the metal deposit and the valve seat. Here, if Cr is less than 22% by mass, stable formation of a Cr oxide film cannot be ensured on the surface of the Co-based matrix, and corrosion resistance is not exhibited. Therefore, in the present embodiment, the lower limit of Cr is set to 22% by mass. On the other hand, when Cr exceeds 27 mass %, not only the build-up property of the alloy powder for build-up deteriorates, but also the toughness of the build-up part deteriorates. Therefore, in the present embodiment, the upper limit value of Cr is specified to be 27% by mass. In the present invention, "metallurgy" means wettability with respect to the valve body during overlaying, and shape stability of the molten deposit in the molten state. Sometimes it means that the shape of the metal deposit (specifically, the shape of the bead) cannot be maintained in a desired shape.

Mo (molybdenum): 11% by mass to 30% by mass
Mo is an element that promotes the formation of the Cr oxide film by forming a solid solution in the Co-based matrix of the heap metal portion, and promotes the regeneration of the Cr oxide film when the Cr oxide film is destroyed. As a result, the corrosion resistance of the metal deposit can be ensured and the adhesion of the valve seat, which is the mating material, can be suppressed. Here, when Mo is less than 11 mass %, the Cr oxide film cannot be stably formed on the surface of the metal deposit, and as a result, the corrosion resistance of the metal deposit decreases. Therefore, in this embodiment, the lower limit of Mo is specified to be 11 mass %. On the other hand, when Mo exceeds 30% by mass, not only the metal forming property is deteriorated but also the toughness of the metal forming part is deteriorated. Therefore, in the present embodiment, the upper limit of Mo is specified to be 30% by mass. ..

*W (tungsten): 2.0 mass%-6.0 mass%
W is an element that contributes to the improvement of the adhesion resistance of the metal deposit. Here, if W is less than 2.0 mass %, the amount of tungsten carbide present in the metal deposit is not sufficient, and the hardness of the base of the Cr oxide film cannot be sufficiently secured. Therefore, the Cr oxide film is easily broken. As a result, the metal parts of the metal deposit and the valve seat adhere to each other, and their wear is promoted. Therefore, in the present embodiment, the lower limit value of W is set to 2.0% by mass. On the other hand, when W exceeds 6.0 mass %, not only the build-up property of the alloy powder for build-up is deteriorated, but also the toughness of the build-up portion is reduced. Therefore, in this embodiment, the upper limit of W is specified to be 6.0% by mass.

C (carbon): 0.40% by mass to 1.3% by mass
C is an element that forms a carbide in the heap portion and improves the strength and wear resistance of the heap portion. Here, if C is less than 0.40% by mass, a hard carbide phase is not formed in the metal deposit, so that the hardness of the base of the Cr oxide film cannot be sufficiently secured and the metal deposit is Easy to wear. In addition to this, since the hardness of the base cannot be ensured, the Cr oxide film is easily broken when the valve seat and the Cr oxide film come into contact with each other. As a result, the metal portion of the metal deposit and the valve seat adheres to each other, and wear of the valve seat is promoted. Therefore, in the present embodiment, the lower limit value of C is set to 0.40 mass %. On the other hand, when C exceeds 1.3% by mass, the carbide phase is excessively formed, and Cr and Mo dissolved in the Co-based matrix are reduced, so that the Cr oxide film is not sufficiently formed and the metal deposit portion is not formed. Corrosion resistance is reduced. As a result, the surface of the metal deposit becomes rough, and the attacking power against the valve seat increases. Therefore, in the present embodiment, the upper limit value of C is set to 1.3% by mass.

-Si (silicon): 3.0 mass% or less Si is an element that improves the metallurgy. When Si exceeds 3.0 mass %, not only the build-up property of the alloy powder for build-up deteriorates, but also the toughness of the build-up part deteriorates. In addition, the aggressiveness of the valve seat to the valve seat increases. Therefore, in this embodiment, the upper limit of Si is specified to be 3.0% by mass.

-Ni (nickel): 15 mass% or less Ni is an element that contributes to the improvement of the toughness and corrosion resistance of the metal deposit. Here, when Ni exceeds 15 mass %, not only the build-up property of the alloy powder for build-up is deteriorated but also the wear resistance of the build-up part is deteriorated. Therefore, in the present embodiment, the upper limit value of Ni is defined as 15% by mass.

-Fe (iron): 30% by mass or less Fe is an element that contributes to the improvement of the toughness of the metal deposit. Here, if Fe exceeds 30 mass %, the corrosion resistance decreases. Therefore, in this embodiment, the upper limit of Fe is specified to be 30 mass %.

-Mn (manganese): 1.0 mass% or less Mn is an element that contributes to the improvement of the metallurgy and is an element that is added as necessary. If Mn exceeds 1.0% by mass, the wear resistance decreases. Therefore, in this embodiment, the upper limit of Mn is specified to be 1.0% by mass.

-Co (cobalt): balance Co is a matrix of the alloy powder for build-up, and is contained in the alloy powder for build-up as the balance on the assumption that the above composition is included. The balance may contain inevitable impurities.

In the present invention, the soft matrix spacing (DAS value) of the cobalt-chromium-molybdenum-based alloy means the phase composed of the eutectic carbide which is the hard phase of the cobalt-chromium-molybdenum-based alloy and the soft matrix (Co solid solution) which is the soft phase. In a structure (secondary dendrite arm) that alternately includes a phase consisting of (1), it means the shortest distance between the hard phase and the hard phase, that is, the length of the short side of the soft phase.

In the present invention, the DAS value of the cobalt-chromium-molybdenum based alloy is usually 3 μm to 6 μm, preferably 4 μm to 5 μm.

As for the DAS value, about three sets of two or more secondary dendrite arms are randomly selected, the distance between the arms is determined, and the average value is used as the DAS value. When powder is used as the material for overlay, the cooling rate becomes faster and the DAS value becomes smaller than when a rod-shaped material is used.

(Valve seat and engine valve combination structure)
The present invention relates to a combination structure in which the valve seat described above and an engine valve in which a portion in contact with the valve seat (that is, a valve face) is overlaid with an alloy powder for overlay welding are combined.

In the present invention, the average particle size of the hard particles contained in the copper-based alloy in the contact portion of the valve seat that is in contact with the engine valve described above is the cobalt-chromium of the overlay alloy (build-up part) of the engine valve described above. Greater than the soft matrix spacing (DAS value) of the molybdenum-based alloy. For example, the average particle diameter of the hard particles contained in the copper-based alloy is usually 5 μm or more, and preferably 8 μm or more, larger than the DAS value of the cobalt-chromium-molybdenum-based alloy.

The average particle size of the hard particles contained in the copper-based alloy in the contact portion of the valve seat that is in contact with the above-mentioned engine valve is the above-mentioned cobalt-chromium-molybdenum-based alloy of the built-up alloy (held portion) of the engine valve. When it becomes larger than the DAS value, the hard particles of the valve seat come into contact with the eutectic carbide that is the hard phase of the engine valve and the soft matrix that is the soft phase at the same time. The contact with only the soft matrix of is suppressed. Therefore, wear of the oxide film generated in the soft phase of the engine valve due to the hard particles of the valve seat is suppressed, and adhesive wear is suppressed.

In an engine having a combination structure of a valve seat and an engine valve as in the present invention, any one of gasoline, ethanol, ethanol mixed gasoline, CNG (compressed natural gas), or LPG (liquefied petroleum gas) is used as a fuel for the engine. You may apply one kind.

When ethanol or gasoline mixed with ethanol is used, a severer corrosive environment than gasoline, such as reduction of an oxide film on the sliding surface of an engine valve by formic acid produced from ethanol, is generated. If the combined structure of the valves is provided, it is possible to suppress adhesive wear between the valve seat and the engine valve even under such an environment.

Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to those examples.

1. Calculation of the relational expression between the amount of each component of the copper-based alloy of the valve seat and the maximum diameter of √ hard particles of the hard particles contained in the copper-based alloy of the valve seat Laser-plated alloy powder having the composition shown in Tables 1 and 2 For each of the four cross sections at 90 degree intervals in each valve seat prepared by the above, based on the measurement method shown below, from the gold-plated structure of the copper-based alloy, the hard particle maximum of hard particles mainly composed of Fe, Mo and Si was determined. The diameter was investigated. As a typical example, FIG. 1 shows a helix structure of a copper-based alloy of the valve seat of Example 1.

(1) The valve seat was embedded in resin and polished.
(2) A backscattered electron image (magnification: 200 times) of a scanning microscope was photographed on one cross section of the sample polished in (1), and the photographed image was binarized using WinROOF analysis software to Hard particles consisting of Fe, Mo and Si were selected.
(3) The equivalent circle diameter was calculated for each hard particle selected in (2).
(4) The maximum value was obtained from the equivalent circle diameters of the hard particles obtained in (3).
(5) Steps (1) to (4) were repeated for the remaining three sections.
(6) The maximum values of the equivalent circle diameters of the hard particles in the images obtained in (5) were averaged to obtain the hard particle maximum diameter.
(7) The maximum hard particle diameter was calculated by calculating the square root of the maximum hard particle diameter obtained in (6).

A multivariate analysis of the relationship between the amount of each component of the copper-based alloy of each valve seat and the √ hard particle maximum diameter of the hard particles contained in the obtained copper-based alloy of each valve seat was performed, and the relationship of the following formula was obtained.

√ Hard particle maximum diameter (√μm)=12.044+0.953×Mo amount (mass %)-6.475×Nb amount (mass %)+1.458×C amount (mass %)-0.117×Ni amount (Mass %)-0.882 x Si content (mass %)-0.084 x Fe content (mass %)

2. Relationship between the maximum diameter of the hard particles and the average particle diameter of the hard particles contained in the copper-based alloy of the valve seat. 7-No. The average particle diameter of hard particles mainly composed of Fe, Mo, and Si was investigated from the heavier texture of the copper-based alloy for the four cross sections at intervals of 90 degrees in the valve seat No. 23, based on the following measurement method.

(1) The valve seat was embedded in resin and polished.
(2) A backscattered electron image (magnification: 200 times) of a scanning microscope was photographed on one cross section of the sample polished in (1), and the photographed image was binarized using WinROOF analysis software to Hard particles consisting of Fe, Mo and Si were selected.
(3) The equivalent circle diameter was calculated for each hard particle selected in (2).
(4) The average value of the equivalent circle diameters of the hard particles obtained in (3) was calculated.
(5) Steps (1) to (4) were repeated for the remaining three sections.
(6) The average value of the equivalent circle diameters of the hard particles in each image obtained in (5) was averaged to obtain the average particle diameter of the hard particles.

FIG. 2 shows the relationship between the average particle diameter of the hard particles contained in the copper-based alloy of the valve seat and the maximum diameter of the hard particles. It can be seen from FIG. 2 that the average particle diameter of the hard particles and the maximum diameter of the hard particles have a proportional relationship.

3. Single Abrasion Test Using a wear tester according to a single abrasion test shown in FIG. 3, the wear amount in a combined structure of a valve seat and an engine valve prepared by laser plating alloy powder having the composition shown in Table 2 was measured. investigated.

In addition, as an engine valve, Co, 22 mass% Cr, 11.9 mass% Mo, 7.3 mass% Ni, 3.6 mass% W, 0.77 mass% C, 0.8 A valve in which an alloy powder of mass% Si and 0.86 mass% Fe was plasma-plated was used.

In the test, a propane gas burner was used as a heating source, and the sliding portion between the metal deposit and the valve seat was set to a propane gas combustion atmosphere. The temperature of the valve seat is controlled to 200° C., a load of 25 kgf is applied by the spring at the time of contact between the deposit and the valve seat, and the deposit and the valve seat are contacted at a rate of 42 times/minute for 2 hours. A wear test was performed. In this abrasion test, the amount of depression of the valve from the reference position was measured. The sunk amount of the valve corresponds to the wear amount (wear depth) of the engine valve and the valve seat, both of which are worn.

The results are shown in Table 2 and FIG. From FIG. 4, the √ hard particle maximum diameter of the hard particles in Examples 1 and 2 is 12 √ μm or more, and the wear amount of Examples 1 and 2 is smaller than the wear amounts of Comparative Examples 1 to 6. I understand.

Further, it can be seen from Table 2 that the average particle diameter of the hard particles in each of Examples 1 and 2 is 14 μm or more, and it can be seen from FIG. 2 showing the relationship between the average particle diameter of the hard particles and the maximum diameter of the hard particles. Also, if the maximum value of √ hard particles of the hard particles is 12 √ μm, it can be estimated that the average particle diameter of the hard particles is at least 6 μm.

On the other hand, the soft matrix spacing (DAS value) of the engine valve can be calculated to be about 4 μm from the micrograph showing the structure of the metal deposit of the engine valve shown in FIG.

From the above results, in Examples 1 and 2, in the combined structure of the valve seat and the engine valve, the average particle diameter of the hard particles contained in the valve seat became larger than the DAS value of the engine valve, and thus the hard particles of the valve seat. Is easily contacted simultaneously with the eutectic carbide which is the hard phase of the engine valve and the soft matrix, whereby the hard particles of the valve seat are prevented from contacting only with the soft matrix of the engine valve, and the valve seat. It is considered that the hard particles of (3) made it difficult for the oxide film of the soft matrix of the engine valve to be scraped off, and the adhesive wear was reduced.

Claims (1)

A combination structure of a valve seat and an engine valve in contact with the valve seat,
The contact portion of the valve seat that is in contact with the engine valve has Ni: 5% by mass to 18% by mass, Si: 0.5% by mass to 3% by mass, Fe: 3% by mass to 10% by mass, Mo: 6% by mass. % To 20 mass %, Nb: 0.2 mass% or less, and the balance: Cu and a copper-based alloy containing inevitable impurities,
The metal deposit of the engine valve in contact with the valve seat has Cr: 22% by mass to 27% by mass, Mo: 11% by mass to 30% by mass, W: 2.0% by mass to 6.0% by mass, C : 0.40% by mass to 1.3% by mass, Si: 3.0% by mass or less, Ni: 15% by mass or less, Fe: 30% by mass or less, Mn: 1.0% by mass or less, and the balance: Co and A cobalt-chromium-molybdenum-based alloy containing inevitable impurities,
A combined structure in which the average particle size of the hard particles contained in the copper-based alloy is larger than the soft matrix spacing (DAS value) of the cobalt-chromium-molybdenum-based alloy.