JP6754671B2 - Overlay alloy and overlay member - Google Patents

Description

The present invention relates to a build-up member provided with a build-up portion and a build-up alloy that can serve as the build-up portion.

Mechanical members have different required mechanical properties depending on the part. For example, a cylinder head or an engine block of an internal combustion engine (referred to as an "engine") is required to have high wear resistance and low friction characteristics in sliding portions. Recent cylinder heads and the like are made of an aluminum alloy (referred to as "Al alloy") that is lightweight and has excellent thermal conductivity and castability, but the Al alloy (casting) itself does not necessarily have sufficient wear resistance and the like. Therefore, the sliding portion (for example, bearing, liner, etc.) is provided with a separate member or is subjected to a modification treatment.

As another example of such a sliding portion, there is a valve seat provided on the peripheral edge of the intake / exhaust port of the cylinder head, which repeatedly contacts the outer peripheral edge of the umbrella portion of the slowly rotating intake / exhaust valve. The intake side valve seat is exposed to air flowing in at high speed and an air-fuel mixture containing various fuel components, and the exhaust side valve seat is exposed to high temperature combustion gas flowing out at high speed. Even in such a harsh environment, the valve seat is required to have high wear resistance (particularly adhesion wear resistance) and lubricity.

Such a valve seat is generally formed by press-fitting (driving) a seat ring made of an iron-based sintered alloy as described in Patent Document 1 into a ring groove formed on the outer peripheral edge of a port of a cylinder head. ing. On the other hand, it has also been proposed to form a valve seat by overlaying using a laser clad method. If the former drive-in type valve seat is changed to the latter built-in type valve seat, not only the intake / exhaust port diameter can be increased, but also the thermal conductivity of the valve seat itself can be improved and the distance from the water jacket on the cylinder head side can be shortened. It is also possible to improve the cooling performance around the valve train.

The built-up valve seat is formed, for example, as follows. First, the copper-based alloy powder (raw material powder) is melted by laser irradiation and then rapidly cooled and solidified. In this way, a built-up portion composed of a rapidly cooled solidified structure in which substantially spherical hard particles are dispersed in the copper base matrix is formed on the peripheral portion of the port. Next, a valve seat having a desired size and surface roughness can be obtained by cutting the built-up portion coaxially with the valve guide.

The following Patent Documents 2 to 7 describe a copper-based alloy suitable for such a built-up portion or a raw material powder thereof. In addition, Patent Document 7 describes a copper-based alloy containing Ag. This copper-based alloy contains Cr as an essential element, which enhances oxidation resistance, and contains at least 1% by weight or more of Cr.

Japanese Unexamined Patent Publication No. 2006-307331 Special Fair 7-17978 Gazette Japanese Patent No. 3305738 Japanese Patent No. 4114922 Japanese Patent No. 4472979 Japanese Patent No. 4603808 Japanese Unexamined Patent Publication No. 2002-194462

The present invention has been made in view of such circumstances, and unlike the conventional overlay alloy, a new overlay alloy capable of achieving both slidability and overlay while suppressing the Cr content is provided. It is an object of the present invention to provide an overlay member having an overlay portion made of the overlay alloy.

As a result of diligent research to solve the above problems, the present inventor has found a new overlay alloy capable of achieving both slidability and overlay by suppressing Cr while containing Ag. By developing this result, the present invention described below has been completed.

《Overlay alloy》
(1) The built-up alloy of the present invention contains a first element group consisting of Cu, Fe, Ni and Si and one or more second elements selected from the second element group consisting of Mo, W and V. , A build-up alloy composed of a copper-based alloy in which the alloy liquid phase containing Cu and the alloy liquid phase containing the second element and Fe can be separated at the time of melting, and the copper-based alloy has a total mass of 100 mass. It is characterized by satisfying the following composition as% (simply referred to as "%").
Cr: Less than 1% One or more third elements selected from the third element group consisting of Ag, Bi, Sn, Zn, In and Pb: 0.1 to 25%

(2) The built-up alloy of the present invention first has an alloy liquid phase containing Cu (also referred to as "Cu-based alloy liquid phase") and an alloy liquid phase containing Fe ("Fe-based alloy") within a predetermined temperature range. It is in a state of being separated from the "liquid phase" (also referred to as "liquid phase") (referred to as "liquid phase separated state"). When rapid solidification is performed as it is, a metal structure in which the liquid phase separated state is frozen can be obtained. In particular, substantially spherical particles (hard particles) in which the Fe-based alloy liquid phase is solidified in a matrix (referred to as "copper-based matrix") in which the Cu-based alloy liquid phase is solidified when the liquid phase is strongly stirred and rapidly cooled and solidified in the liquid phase separated state. ) Is dispersed to obtain a complex structure.

Next, the overlay alloy of the present invention contains a third element such as Ag. The third element is basically a soft metal element, and can form a concentrated portion (phase) in a copper-based matrix (also simply referred to as "matrix") to exhibit a solid lubricating action. As a result, the overlay alloy (overlaid portion) of the present invention has excellent slidability (wear resistance) even in a low oxygen atmosphere in which it is difficult for the second element such as Mo to form an oxide having a high solid lubricity. And low aggression to the other material).

Further, the presence of a soft concentrated portion composed of the third element in the matrix improves the toughness of the matrix, and the overlay alloy of the present invention has excellent overlay properties (reduction of cracks during overlay, quality stability). (Improvement of yield, etc.) can also be demonstrated.

The effect of improving slidability and build-up due to the third element is more likely to occur as the amount of Cr decreases. The reason for this can be inferred as follows. Cr is hardly solid-solved in Cu as the main component of the matrix, precipitated in the matrix as a Ni-Si-Cr compound and _Cr 3 Si. Since these precipitates are hard, they can be mixed with the soft third element concentrated phase during sliding and act as a grinding agent. Therefore, it is considered preferable that the amount of Cr is small.

In addition, the second element can generate an oxide rich in solid lubricity, which can contribute to improving the wear resistance of the overlay alloy and reducing the aggression against the opponent, but forms an oxide more stable than the second element. When the amount of Cr is increased, the oxidation of the second element is hindered and the solid lubricating effect of the oxide of the second element is less likely to be exhibited. This tendency is particularly likely to occur in a low oxygen atmosphere. Therefore, the smaller the amount of Cr, the more preferable. Further, as the amount of Cr decreases, the raw material powder used for overlay is less likely to be oxidized at the time of production or the like, and the manufacturability and yield of the raw material powder can be improved.

<< Overlay member >>
The present invention can be grasped not only as the above-mentioned overlay alloy but also as an overlay member having an overlay portion made of the overlay alloy. That is, the present invention is a build-up member including a base material and a build-up portion formed on the base material, and the build-up member is characterized in that the build-up portion is made of the above-mentioned build-up alloy. Good.

<< Other >>
(1) The "hard" particles according to the present invention mean particles having a hardness larger than that of the copper-based matrix, but may be appropriately paraphrased as dispersed particles, silicide particles, or iron-based particles.

As used herein, "X group ~" is an atomic ratio (atomic%) and means that the X element is contained in a larger amount than any other constituent elements in the overall composition. Specifically, a copper-based alloy means that the entire alloy contains more Cu than other elements. The copper-based matrix also means that the entire matrix contains more Cu than other elements.

Hard particles are intermetallic compound particles of a first element and a second element. However, the hard particles usually contain a large amount of Si. Therefore, the hard particles can also be called silicide particles.

The overlay alloy of the present invention includes both before and after overlay. For example, the overlay alloy may be a raw material powder used for overlay, or may be an overlay portion having a metal structure in which hard particles are dispersed in a copper-based matrix.

The copper-based alloy in the liquid phase separated state is composed of the elements (composition) specified in the present invention, and may be at least in the two liquid phase separated state of the Cu-based alloy liquid phase and the Fe-based alloy liquid phase. Not limited to the orbital alloy, a perite alloy or the like may be used.

The overlay alloy of the present invention contains various modifying elements (for example, 5% or less in total, further 2% or less) and unavoidable impurities that are technically or costly difficult to remove. In addition, "%" regarding a component composition referred to in this specification means "mass%" unless otherwise specified.

(2) In the present specification, the abrasion resistance of the overlay alloy (overlaid portion) and the aggression to the mating material (counterpart aggression) are also simply referred to as "sliding property". Further, the crackability, quality stability, yield, etc. at the time of overlaying the overlay alloy are also simply referred to as "overlayability".

(3) Unless otherwise specified, "x to y" in the present specification includes a lower limit value x and an upper limit value y. A range such as "ab" may be newly established with any numerical value included in the various numerical values or numerical ranges described in the present specification as a new lower limit value or upper limit value.

It is an optical micrograph which shows the metal structure of the overlay part of a sample 3. This is the result of EPMA analysis of the matrix of Sample 3. This is the result of EPMA analysis of the matrix of sample C0. The position where the matrix of sample 3 was quantitatively analyzed by EPMA is shown. The position where the matrix of sample C0 was quantitatively analyzed by EPMA is shown. It is a bar graph which shows the relationship between the oxygen concentration in a wear test and the wear amount of a built-up part. It is a bar graph which shows the relationship between the oxygen concentration in a wear test and the wear amount of a mating material. It is explanatory drawing which showed the state of the build-up by the laser clad method schematically. It is a schematic diagram which shows typically the wear resistance test apparatus.

One or more components arbitrarily selected from the present specification may be added to the components of the present invention described above. The contents described in the present specification may apply not only to the overlay alloy of the present invention but also to the overlay member and its manufacturing method. Also, a methodical component can, in certain cases, be a component of an object. Whether or not which embodiment is the best depends on the target, required performance, and the like.

《Alloy composition》
(1) Third Element Group The copper-based alloy according to the present invention contains one or more third elements selected from the third element group consisting of Ag, Bi, Sn, Zn, In and Pb. The third element may be present in the hard particles, but the overlay alloy of the present invention exhibits excellent slidability or overlayability mainly because it is concentrated and present in the matrix.

The existence form of the third element may be any of solid solution in a matrix, crystallization by itself, crystallization by forming a compound (including an intermetallic compound) with another element, and the like. The existence of Ag ₃ Cu ₂ is known as an Ag _x Cu _y compound, but Cu is a form of a third element that crystallizes in the matrix because it dissolves in Ag, for example, an Ag-Cu solid solution, particularly Ag. -Cu-Ni solid solution is preferable.

The third element is preferably contained in an amount of 0.1 to 25%, 0.5 to 18%, 1 to 13%, and further 3 to 8% with respect to the entire copper-based alloy. If the amount of the third element is too small, its effect is poor, and if it is too large, the matrix itself becomes soft and the wear resistance may rather decrease.

As the third element, Ag, which is easily available and stable, is particularly preferable. Ag is preferably contained in the copper-based alloy in an amount of 1 to 18%, 2 to 14%, and further 4 to 7%.

(2) Group 1 of the first element The overlay alloy of the present invention contains a group of first elements (Cu, Fe, Ni and Si) in addition to the above-mentioned third element. Cu is the main element and constitutes the balance. Ni and Si, together with Cu, are the main elements that make up the copper-based matrix. Fe, together with Cu, is an important element for being in a liquid phase separated state when melted. Fe is an element that constitutes hard particles dispersed in a copper-based matrix together with Si (further Ni) and a second element.

The selection and proportion of each element is adjusted according to the characteristics or structure required for the overlay, but for example, the following composition is preferable. The composition described here is based on 100% by mass of the entire overlay alloy (copper-based alloy).

Fe is preferably contained in an amount of 3 to 20%, 4 to 10%, more preferably 5 to 8%. If Fe is too small, the formation of hard particles is insufficient and the wear resistance may be lowered. When Fe is excessive, the hard particles become coarse and the build-up property and machinability decrease.

Ni is preferably 5 to 30%, 10 to 20%, more preferably 12 to 18%. Ni can be dissolved in a copper-based matrix to increase its strength. In addition, the amount of Ni affects the tendency of two-component phase separation, affects the size of hard particles, and affects the wear resistance of the overlay alloy. If the amount of Ni is too small, the effect of improving the matrix strength is poor, and if the amount of Ni is too large, the tendency of two-component phase separation decreases, and the hard particles become finer, so that the wear resistance decreases.

Si is preferably 0.5 to 5%, 1 to 4%, more preferably 2 to 3%. Si contributes to strengthening the copper-based matrix or improving the build-up. Si also forms a silicide with Fe and the second element, contributing to the formation of hard particles. If the amount of Si is too small, these effects are poor, and if the amount of Si is too large, the toughness of the hard particles decreases, which induces cracking.

(3) Second element group The overlay alloy of the present invention further includes a second element group (one or more of Mo, W and V). They are preferably 3-20%, 5-15% and even 6-10% in total. The second element, together with Fe and Si, facilitates the formation of hard particles. In particular, Mo repels Cu to a higher temperature than Fe, facilitating the formation of a two-component phase separated state, and exhibits self-lubricating property (solid lubricity) to enhance the wear resistance of the built-up portion. If the amount of the second element is too small, their effects are poor, and if the amount of the second element is too large, the hard particles become coarse and the build-up property and machinability deteriorate.

(4) C, Mn, Cr, Co
The copper-based alloy may contain 0.01 to 0.5% of C and further 0.02 to 0.3%. C can contribute to the formation of more stable carbides at high temperatures. C may be present in the copper-based alloy as a carbide of the second element. Such carbides can contribute to the miniaturization of hard particles and the improvement of wear resistance and crack resistance of copper-based alloys.

The copper-based alloy may contain Co. Like Fe, Co is an element that hardly dissolves in Cu and promotes the liquid phase separation state at the time of melting. By containing Co, the toughness of the copper-based alloy can be improved. However, Co is a rare element, expensive, and involves resource risk. Therefore, the copper-based alloy is preferably substantially free of Co (except when it is contained as an impurity), or if it contains Co, it is preferably 0.1 to 2% and further 0.5 to 1.9%. Including these meanings, Co is preferably less than 2%, 1% or less, and even 0.1% or less.

Like Fe and Co, Cr is an element that hardly dissolves in Cu and promotes a liquid phase separation state at the time of melting. However, considering the use in a low oxygen environment, overlayability, yield of raw material powder, environmental load, etc., the overlay alloy of the present invention is one that does not substantially contain Cr except when it is contained as an impurity. Is good. Therefore, Cr is preferably less than 1%, more preferably less than 0.1%.

The overlay alloy (overlaid portion) of the present invention may contain a small amount (for example, 0.01 to 0.1%) of oxygen (O) as an impurity on the surface or inside. O is adsorbed on the surface of the powder particles in the manufacturing process of the raw material powder or the like, or is introduced into the surface or the inside of the overlay portion at the time of overlaying.

《Alloy structure》
(1) The built-up alloy of the present invention can have various metal structures by adjusting the forming process from melting to solidification. From the viewpoint of achieving both wear resistance and overlayability of the overlay portion, the metal structure thereof is a copper-based matrix (Cu-Ni-Si based matrix) and a substantially spherical hard material dispersed in the copper-based matrix. It is preferable that the particles (compound particles such as Fe-Mo-Si) and the concentrated portion (single substance or compound) of the third element mainly dispersed in the copper group matrix are composed.

(2) The average particle size of the hard particles is preferably 10 μm to 10 mm, 50 μm to 5 mm, and more preferably 100 μm to 1 mm. If the hard particles are too small, the abrasion resistance of the copper-based alloy (built-up portion) becomes insufficient, and if the hard particles are excessive, the mating material wears (aggression) increases and the machinability decreases, which is not preferable. The particle size of each hard particle referred to here is the diameter equivalent to the area circle. The area occupied by the concentrated portion of the third element in the matrix is preferably 5 to 30%, more preferably 10 to 20%. Each average value is an arithmetic mean value when observing 17 × 19 microns.

(3) In order to achieve both wear resistance and build-up property, for example, the copper base matrix is 150 to 350 Hv and further 200 to 300 Hv, and the hard particles are 400 to 1500 Hv and further 600 to 1200 Hv, and the third element. The concentrated portion is preferably 50 to 250 Hv, more preferably 100 to 200 Hv.

Each hardness referred to here is the Micro Vickers hardness when the pressing load (test force) of the indenter is measured as 500 gf. The hardness is measured on the outermost surface of the copper-based alloy (overlaid portion), and is the average value of 10 points measured at intervals of about 0.5 mm.

<< Base material / Overlay member >>
The mating material (base material) for overlaying the overlay alloy of the present invention is an iron-based material (including stainless steel) and a non-ferrous material (aluminum-based material, magnesium-based material, titanium-based material, copper-based material, etc.). And so on.

Cu-based overlay alloys do not react excessively with the substrate even when overlayed on a substrate made of pure Al or Al alloy, so for example, from aluminum alloys (casting materials, wrought materials, etc.) It is possible to form a sound build-up portion with few defects (voids, cracks, etc.) on the base material.

For example, it is preferable that the valve seat (overlay portion) formed in the intake port and / or the exhaust port of the cylinder head (casting / base material) for an internal combustion engine made of an aluminum alloy is formed of the overlay alloy of the present invention. The intake side valve seat and the exhaust side valve seat may have different configurations and structures of each overlay portion according to the required characteristics. For example, the wear resistance of the valve seat may be improved by increasing or increasing the number of hard particles as compared with the conventional case. When the overlay alloy of the present invention is used, its abrasion resistance is ensured even in a low oxygen atmosphere.

The overlay member referred to in the present invention is not limited to a cylinder head having a valve seat formed by overlay, and may be overlaid on various members (base materials) made of various materials.

《Laser clad method》
In the present invention, the formation process of the overlay portion is not limited, but for example, the overlay portion having a desired metal structure or characteristics can be formed by a laser clad method.

In the laser clad method, the supplied overlay alloy material (raw material) is melted in a predetermined temperature range using a high-density energy heat source such as a laser beam or an electron beam, and the melt is rapidly cooled and solidified on the surface of the base material. , A method of forming a built-up portion composed of a predetermined metal structure (quenched solidified structure).

Although it is conceivable to use a wire material or a bar material as a raw material, it is preferable to use a powder from the viewpoint of uniformly or stably forming a desired metal structure. Such raw material powders are obtained, for example, by the (gas) atomizing method. The constituent particles of the atomized powder are also a form of the overlay alloy of the present invention. However, at the time of producing the atomized powder, the molten liquid (molten metal before spraying) may be in a one-component phase state.

The raw material powder used in the laser clad method preferably has a particle size of, for example, 32 to 180 μm and further preferably 63 to 106 μm. This particle size is specified by sieving (according to JIS Z 8801). Specifically, the particle size: a to bμm means that the particles do not pass through a sieve with a nominal opening of aμm and are composed of particles having a nominal opening through a sieve of bμm. The raw material powder may be a mixed powder in which a plurality of types of powders having different component compositions are mixed, or a single powder. However, it is easier to form a uniform overlay portion by using a single powder having excellent handleability.

As the laser, a carbon dioxide gas laser, a YAG laser, a semiconductor laser or the like can also be used. In order to obtain a metal structure in which substantially spherical hard particles are uniformly dispersed in the copper-based matrix, it is desirable that the molten pool in the liquid phase separated state is rapidly cooled while being strongly stirred. Such strong stirring can be performed, for example, by periodically intermittently or changing the intensity of a laser that irradiates the raw material powder. Specifically, an oscillator such as that described in Patent Document 4 (Patent No. 4114922) and Patent Document 5 (Patent No. 4472979) described above, such as electronically controlling the output of a semiconductor laser, can be used. Can be done using.

Using raw material powders having different component compositions, overlaying was performed on the substrate by the laser clad method. The structure observed, abrasion resistance, and opponent aggression of the built-up portion thus obtained were evaluated. The present invention will be described in more detail based on these specific examples.

<< Production of sample >>
(1) Base material An aluminum alloy (JIS AC2C) was prepared as a base material for overlaying. The shape of the base material was as follows: tissue observation: plate shape (100 mm × 100 mm × 20 mm), wear test: ring shape (outer diameter φ80 mm × inner diameter φ20 mm × height 50 mm).

(2) Raw Material Powder First, a gas atomized powder having the component composition shown in sample C0 in Table 1 was prepared. This gas atomized powder was produced by spraying a molten alloy prepared at 1800 ° C. in an inert gas atmosphere. The obtained gas atomized powder was classified by sieving. In this way, the particle size was adjusted to 32 to 180 μm. In sample C0, the powder thus obtained (this is referred to as “reference powder”) was used as a raw material powder for overlaying.

Samples 1 to 3 were built up using a mixed powder obtained by mixing Ag powder (particle size: 6 to 13 mm) with the reference powder as a raw material powder. The mixed powder of each sample is obtained by adding Ag powder in the ratio shown in Table 1 to 100 parts by weight of the reference powder. The overall composition of the raw material powder (100% by mass) related to each sample is also shown in Table 1.

(3) Overlay Overlay was performed by a laser clad method using a carbon dioxide laser beam as a heat source, as shown in FIG. Specifically, the laser beam 55 of the carbon dioxide gas laser is irradiated to the powder layer 53 of the raw material powder formed on the overlay portion 51 while moving relative to the base material 50. The overlay is performed while spraying a shield gas (argon gas) from the gas supply pipe 65. The laser beam 55 is irradiated while being swung in the width direction (arrow W direction) of the powder layer 53 by the beam oscillator 57. By this laser irradiation, the powder layer 53 is melted into a two-component phase separated state, and after being strongly stirred, it is rapidly solidified by heat dissipation to the substrate or the like, and the overlay portion 60 (overlay portion 60) is formed on the overlay portion 51. Thickness: about 2 mm, overlay width: about 6 mm) is formed.

The treatment conditions were a laser output: 4.5 kW, a laser spot diameter: 2.0 mm, a relative traveling speed between the laser beam and the base material: 15.0 mm / sec, and a shield gas flow rate: 10 L / min. At the time of overlaying, the description of Patent Document 4 (Patent No. 4114922) and the like was also referred to.

《Observation / Test》
(1) Structure Observation The metallographic structure obtained by observing a 1.4 × 2.4 mm region of the overlay portion of Sample 3 with a scanning electron microscope (SEM) is shown in FIG.

The results of analyzing the matrix regions of Sample 3 and Sample C0 with an electron probe microanalyzer (EPMA) are shown in FIGS. 2A and 2B (both are simply referred to as "FIG. 2"), respectively. Further, Table 2 shows the results of quantitative analysis of the component composition in each matrix structure of Sample 3 and Sample C0 by EPMA. The observation positions of each part that were quantitatively analyzed are shown in FIGS. 3A and 3B (both are simply referred to as "FIG. 3"), respectively.

(2) Wear test The wear test was carried out as follows using a test device as shown in FIG. First, the test piece 100 having the build-up portion 101 is held in the first holder 102. Next, the second holder 108 holds the cylindrical mating material 106 around which the induction coil 104 is wound. A wear test is performed by rotating the end face of the mating material 106, which has been subjected to high-frequency induction heating by the induction coil 104, while pressing it against the built-up portion 101 of the test piece 100.

The test conditions are pressing load: 150 N (surface pressure: 5 MPa), rotation speed: 383 rpm, test time: 30 minutes, mating material temperature: 600 ° C., mating material material: Co-based alloy (stellite equivalent material), atmosphere: It was either 0.5% O + N ₂ , 7.5% O + N ₂ or 21% O + N ₂ (atmosphere).

After the wear test, the amount of wear of the test piece (building part) and the mating material was measured as a weight change (weight loss) before and after the test. The amount of wear obtained for each sample in this manner is shown in FIGS. 4A and 4B (both are simply referred to as "FIG. 4").

<< Evaluation >>
(1) Metal structure As is clear from FIG. 1, the built-up portion of sample 3 was a composite structure in which spherical (hard) particles were dispersed in the matrix. It has been confirmed that the overlay portion of other samples has a similar metal structure. From these, it can be seen that the raw material powder heated by the laser was rapidly cooled and solidified after being melted into a two-component phase separated state.

In each sample, the matrix was a Cu—Ni—Si based alloy and the hard particles were a Fe—Mo—Si based compound (alloy). However, as is clear from FIG. 2, the matrix structures of sample 3 and sample C0 were significantly different. As is clear from FIGS. 3 and 2, the matrix of Sample 3 had a metallic structure in which the concentrated portion (phase) of Ag (third element) was dispersed. It has also been confirmed that Ag is almost absent in the hard particles (100%) (Ag: less than 0.2%).

By the way, the hardness of the hard particles in each sample was 800 to 1200 Hv. The matrix of Samples 1 to 3 had a hardness of 230 to 280 Hv, and the matrix of Sample C0 had a hardness of 200 to 230 Hv.

(2) Abrasion resistance As is clear from FIG. 4A, in an atmosphere where the oxygen concentration is lower than that of the atmosphere, the samples 1 to 3 containing Ag have better abrasion resistance than the sample C0 containing no Ag. I understood it. It was also found that the lower the oxygen concentration in the atmosphere, the better the wear resistance of the sample containing more Ag. However, considering the use in an atmosphere where the oxygen concentration is at the atmospheric level, it can be said that the Ag is preferably 3 to 15% with respect to the entire overlay portion. It can be seen from FIG. 4B that such a tendency is the same with respect to the opponent's aggression.

(3) Overlaying Using the raw material powders of Samples 1 to 3 and Sample C0, an overlay portion to be a valve seat was actually formed at the intake / exhaust port of the cylinder head made of Al alloy. At that time, when the raw material powders of Samples 1 to 3 were used, cracks did not occur during overlaying. On the other hand, when the raw material powder of sample C0 was used, cracks occurred during overlaying. From these results, it was found that Ag not only contributes to high wear resistance and low opponent aggression in a low oxygen environment, but also contributes to improvement of build-up.

Although a mixed powder of Ag powder and a reference powder was used for the production of each of the above-mentioned samples, stable quality and efficiency can be achieved by using a single powder prepared with a desired component composition as a raw material powder. Overlaying is possible. It has also been actually confirmed that such a single powder can be produced by the atomization method.

Claims (9)

Contains Cu, Fe, Ni, Si, Mo and Ag
An overlay alloy made of a copper-based alloy in which the alloy liquid phase containing Cu and the alloy liquid phase containing Mo and Fe can be separated from each other when melted.
The copper-based alloy is a built-up alloy characterized by satisfying the following composition with the whole being 100% by mass (simply referred to as "%").
Fe: 3 to 20%,
Ni: 5 to 30%,
Si: 0.5-5%,
Mo: 3 to 20% ,
Cr: less than 1% ,
Ag: 0.1 to 18% ,
C: 0.01-0.5%,
Remaining: Cu and impurities The overlay alloy according to claim 1, wherein the copper-based alloy further contains less than 2% of Co. The overlay alloy according to claim 1 or 2, wherein the copper-based alloy further contains one or more selected from Bi, Sn, Zn, In and Pb in an amount of 0.1 to 25% in total with Ag. The overlay alloy according to any one of claims 1 to 3, wherein the copper-based alloy contains Ag: 2 to 14%. A copper-based matrix containing Ni and Si,
Approximately spherical hard particles containing Si and Mo and dispersed in the copper group matrix,
The concentrated portion of Ag dispersed in the copper group matrix and
The overlay alloy according to any one of claims 1 to 4 . The overlay alloy according to any one of claims 1 to 5 , which is a raw material powder to be used for overlay. With the base material
The overlay formed on the base material and
It is a build-up member equipped with
The overlay member is a overlay member made of the overlay alloy according to any one of claims 1 to 5 . The overlay member according to claim 7 , wherein the base material is made of an aluminum alloy. The overlay member according to claim 8 , wherein the overlay portion is a valve seat formed in an intake port and / or an exhaust port of a cylinder head for an internal combustion engine.