KR20060109179A - Method of preparing metal matrix composite and coating layer and bulk prepared by using the same - Google Patents

Abstract

A method for preparing a metal matrix composite coating layer or bulk which prevents thermal deformation or thermal shock from causing damage on a matrix and is excellent in wear resistance, and the coating layer and the bulk prepared by using the method are provided. A method for preparing a metal matrix composite comprises the steps of: providing a matrix(S); preparing a mixed powder comprising (i) a first metal powder including particles of metal, alloy or a mixture thereof, (ii) a second metal powder including particles of the metal or an intermetallic compound forming metal for forming intermetallic compounds with alloying elements of the alloy, and (iii) ceramic powder including particles of ceramics or their mixture; injecting the prepared mixed powder into a spray nozzle(140) for coating; coating the mixed powder on the surface of the matrix by accelerating a speed of the mixed powder to a range of 300 to 1,200 m/s in the non-melting state by a flow of a carrier gas flowing through the spray nozzle; and heat-treating a coating layer to form the intermetallic compound.

Description

METHOD OF PREPARING METAL MATRIX COMPOSITE AND COATING LAYER AND BULK PREPARED BY USING THE SAME}

1 is a view schematically showing a cold spray device used to form a metal base composite in the present invention.

2A to 2D are state diagrams illustrating an intermetallic compound that can be formed on an Al base by the metal base composite forming method of the present invention.

3a to 3d are views showing specific embodiments of the nozzles used in the coating layer forming method of the present invention.

Figure 4a is a diagram showing the results of the X-ray diffraction test to confirm the intermetallic compound generation and the degree according to the heat treatment temperature when the ratio of the aluminum powder and nickel powder is 9: 1 ℃.

Figure 4b is a view showing the results of the X-ray diffraction test to determine whether the intermetallic compound is produced according to the heat treatment temperature when the ratio of the aluminum powder and nickel powder 75: 25 and the extent thereof.

FIG. 5 is a diagram showing EDX photographing results of respective portions when the ratio of aluminum powder to nickel powder is 75:25 and the heat treatment temperature is 550 ° C.

FIG. 6 is a diagram showing EDX photographing results of respective portions when the ratio of aluminum powder to nickel powder is 75:25 and the heat treatment temperature is 500 ° C.

FIG. 7A is a diagram illustrating an X-ray diffraction test result confirming whether or not an intermetallic compound is produced according to a heat treatment temperature when the ratio of aluminum powder and titanium powder is 9: 1.

FIG. 7B is a diagram showing the results of X-ray diffraction test to confirm whether and the extent of intermetallic compound formation according to heat treatment temperature when the ratio of aluminum powder and titanium powder is 75:25.

FIG. 8 is a diagram showing EDX photographing results of respective portions when the ratio of aluminum powder to titanium powder is 75:25 and the heat treatment temperature is 630 ° C.

Explanation of symbols on the main parts of the drawings

  2: convergence part 4: throat part

  6: diverging part / straight part 8: exit end

 10: nozzle part 12: injection hole

 20: injection tube 22: starting point

 24: junction 30: buffer chamber

110 gas compressor 120 gas heater

130: powder feeder 140: nozzle

The present invention relates to a metal base composite forming method and to a metal base composite coating layer and a metal base composite bulk prepared by using the same, and more particularly, to a metal base without damaging the base material by the formation process of the coating layer Method for providing a coating layer having a high hardness by dispersion of the liver compound and the ceramic particles and having a good resistance to abrasion resistance and fatigue crack and the bulk produced by separating the coating layer from the base material and the coating layer and the bulk produced thereby will be.

In order to improve the strength, hardness, wear resistance, etc. of an alloy or a metal, dispersion strengthening is mentioned as one of the methods generally used. The dispersion strengthening method has a structure in which an intermetallic compound is dispersed in an alloy or a matrix of a metal, and representative examples thereof are precipitation hardening and dispersion of high hardness particles. In particular, the aluminum alloy is easy to disperse and strengthen the intermetallic compound in the aluminum substrate by precipitation hardening, etc., thereby improving mechanical properties, and in addition to the light weight of aluminum, it is excellent in strength, heat resistance and durability. It is widely used as a material for thermal mechanical parts such as engine parts and aircrafts.

Referring to the aluminum dispersion dispersion method described as follows.

That is, conventionally methods such as casting, powder metallurgy, and thermal spraying are used as a method for producing a dispersion-strengthened aluminum alloy.

The aluminum alloy produced by the casting method exhibits excellent room temperature strength because the precipitated phases in which fine precipitates are precipitated in the aluminum matrix phase are uniformly distributed. However, due to the rapid coarsening of the precipitated phase at high temperature exposure, the strength of the aluminum alloy rapidly decreases. Therefore, dispersion strengthening through precipitation hardening is not suitable for heat-resistant aluminum alloys.

In contrast, powder metallurgy is a method for forming an aluminum alloy by molding and sintering an aluminum and a dispersion (metal powder or ceramic powder) as an additive, in which the finely dispersed phase is uniformly dispersed in the alloy. In addition, in the case of ceramic powder, coarsening of the dispersed phase does not occur at a high temperature, thereby showing excellent high temperature characteristics.

However, in the case of including the metal powder as a dispersion, an additional heat treatment for forming an intermetallic compound is required. On the surface of the aluminum metal powder, a thin aluminum oxide (Al ₂ O ₃ ) film is formed even in the air at room temperature. The film inhibits the reaction of aluminum with other metal elements, preventing the formation of intermetallic compounds. Therefore, in order to generate the intermetallic compound by powder metallurgy, it is essential that the heat treatment be performed at a high temperature higher than the melting point of the alloy, and thus there are problems such as high cost and stability of the equipment due to high temperature formation.

In addition, in order to prevent oxidation of aluminum at a high temperature during the sintering process, there is a complicated problem in the manufacturing process, such as controlling the sintering atmosphere properly, and the powder metallurgy method forms an intermetallic compound with a high melting point transition metal such as Ti or Ni This is known to be extremely difficult. In addition, in the case of powder metallurgy, it is necessary to manufacture a desired shape through a mold, and thus a high cost is used to manufacture a mold, and there are problems such as being restricted in size.

On the other hand, the thermal spraying method is a method of spraying molten metal molten metal and then cooling to produce a dispersion-hardened aluminum alloy. When following this method, the same problem as the casting method occurs. In particular, in the case of an alloy with an aluminum-transition metal produced by a thermal spraying method, a coarse secondary phase is formed in the aluminum matrix phase to exhibit low alloy characteristics.

According to this conventional technique, it is difficult to obtain an aluminum alloy in which a fine intermetallic compound is uniformly dispersed, particularly in the case of an aluminum-transition metal alloy, and only when the intermetallic compound is heat-treated above the melting temperature of the alloy. Has the problem of being formed.

As the example of the aluminum, as for the conventional dispersion strengthening method, all of them require a high temperature process to incur high costs, and there is a difficulty in preventing high reactivity at high temperature during the heat treatment process, and in the case of powder metallurgy Since it is necessary to prepare a mold is limited in size, there is a problem that a high cost occurs.

In addition, in order to prolong the life of mechanical parts used in abrasion environment such as friction, fatigue, erosion or corrosion, methods such as hardening the surface of the part or coating a wear resistant material have been used. high material, that is, the nitride ceramic material is mainly used for carbides, such as Si ₃ N _4, TiN oxide, SiC or TiC, etc., such as alumina.

Specifically, Korean Patent Laid-Open Publication No. 1997-0045010 discloses a method of forming a coating film on the inner wall of a cylinder bore instead of a conventional cast iron liner, which is applied to a thermal spraying method using a plasma or an arc as a heat source. As a result, a coating powder made of a ceramic and a mixture thereof is formed on the inner wall to improve wear resistance.

Korean Patent Laid-Open Publication No. 1998-017171 uses a method of forming a wear resistant coating layer on the bore surface of an aluminum cylinder block by plasma spraying using particles such as silicon carbide.

In addition, Korean Patent Publication No. 2003-0095739 discloses a method of forming a coating by spraying while spraying the spray coating powder composition on the inner surface of the stainless steel cylinder bore with a high temperature heat source, the spray coating powder used at this time The composition is a mixture of alumina and zirconia.

As described above, many attempts have been made to form a wear-resistant coating on a metal base material using a ceramic material having excellent abrasion resistance, but all of these methods are mainly sprayed using plasma or electric arc. This thermal spraying method heats the powder particles to be coated to near or above the melting point to melt at least a portion of the powder particles and provide them to the substrate.

Therefore, the ceramic particles coated on the base material are heated to a high temperature of about 1000 ° C., which is the melting temperature of the general ceramic particles, and are supplied to the base material and are brought into contact with each other. Induces residual stress that occurs in the adhesion strength is reduced and has a problem of shortening the life of the part.

In addition, high-temperature particle spraying increases the risks associated with the operation of the thermal spray equipment and makes it difficult to avoid the disadvantages of complicated operation. In addition, hot molten particles react with impurities on the metal matrix or surface to form new compounds. There is a problem that may adversely affect the properties of the material.

In order to solve the problems of the prior art as described above, the present invention is a method of forming a metal base composite coating layer or bulk having excellent wear resistance and at the same time without causing a risk of thermal deformation or damage to the base material and the coating layer and the bulk The purpose is to provide.

In addition, an object of the present invention is to provide a method for forming a metal-based composite coating layer or a bulk, and a coating layer and the bulk thereof, which can obtain a strengthening dispersion at a relatively low temperature at a low cost.

In addition, the present invention is to prevent the accumulation of heat in the coating layer, and to inhibit the formation of cracks between the base material and the coating layer or in the coating layer to form a metal base composite coating layer or bulk having excellent resistance to cracking caused by fatigue of the coating layer and its It is an object to provide a coating layer and a bulk.

In order to achieve the above object, the present invention

Providing a base material;

Iii) a first metal powder consisting of particles of a metal, an alloy or a mixture thereof, ii) a second metal powder consisting of metal particles for forming an intermetallic compound forming an intermetallic compound with an alloying element of the metal or the alloy, and iii) Preparing a mixed powder comprising a ceramic powder made of ceramic or mixture particles thereof;

Injecting the prepared mixed powder into a spray nozzle for coating;

Coating the mixed powder on the surface of the base material by accelerating the mixed powder at a speed of 300 to 1,200 Pa in a non-melting state by the flow of the carrier gas flowing in the injection nozzle; And

It provides a metal base composite forming method comprising a heat treatment step of forming the intermetallic compound by heat treatment of the coated coating layer.

In addition, the present invention

It provides a metal base composite coating layer characterized in that it is produced by the metal base composite forming method and the metal base composite bulk formed by separating the base material from the base material and the coating layer prepared by the metal base composite forming method. .

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and specific examples.

The present invention relates to a method for forming a metal base composite, comprising the steps of: providing a base material; i) a first metal powder consisting of particles of a metal, an alloy or a mixture thereof, ii) forming an intermetallic compound with an alloy element of the metal or the alloy. Preparing a mixed powder comprising a second metal powder composed of metal particles for forming an intermetallic compound, and iii) a ceramic powder composed of ceramic or a mixture thereof, injecting the prepared mixed powder into a spray nozzle for coating; Coating the mixed powder on the surface of the base material by accelerating the mixed powder at a speed of 300 to 1,200 kPa in a non-melting state by the flow of the carrier gas flowing in the injection nozzle, and heat-treating the coated coating layer to the intermetallic And a heat treatment step to form the compound.

That is, the present invention, in the method of forming a coating layer of the metal base composite on the base material by applying a cold spray (low temperature injection) method, focusing on improving the mechanical properties including the hardness, abrasion resistance, fatigue characteristics, etc. of the coating layer to improve the maximum In addition to mixing the ceramic particles to the metal base, which is a component of the existing metal base composite to further include an intermetallic compound forming metal particles for forming an intermetallic compound and the alloying element of the metal or alloy corresponding to the metal base The present invention relates to a method of forming a metal base composite by spraying and mixing such a mixed powder through a cold spray method at a relatively low temperature compared to a melting method or a sintering temperature.

The cold spray method itself is known in the art and a schematic diagram of the apparatus for such a cold spray is shown in FIG. 1. That is, Figure 1 is a view showing a schematic diagram of a low-temperature spray (cold spray) device 100 for forming a coating layer on the base material (S) in the present invention.

The injection device 100 accelerates the powder to form the coating layer at a subsonic or supersonic speed to provide the base material (S). To this end, the injection device 100 includes a gas compressor 110, a gas heater 120, a powder feeder 130, and a nozzle 140 for injection.

Compressed gas of about 5 to 20 kgf / cm ² provided from the gas compressor 100 is sprayed to the powder provided from the powder feeder 130 at a speed of about 300 ~ 1200 kPa through a spray nozzle 140 for coating. In order to generate the subsonic to supersonic flows as described above, as shown in FIG. 1, the injection nozzle 140 is a convergent-diffusing nozzle (de Laval-Type), and this convergence and divergence process is performed. It can generate supersonic flow through.

The gas heater 120 on the compressed gas supply path in the apparatus 100 is not necessarily required as an additional device for heating the compressed gas in order to increase the kinetic energy of the compressed gas to increase the injection speed in the injection nozzle. In addition, as shown, a portion of the compressed gas of the gas compressor 110 may be supplied to the powder supplier 130 in order to more smoothly supply the powder to the injection nozzle 140.

As the compressed gas in the apparatus, commercial gases such as helium, nitrogen, argon, and air may be used, and the type of gas to be used may be appropriately selected in consideration of the injection speed and economical efficiency of the injection nozzle 140. .

A more detailed description of the operation and structure of the illustrated device is described in detail in U.S. Patent No. 5,305,414 to Anatoly P. Alkimov et al., Which is not described herein.

In cold spray coating using such a device, the first step is to provide the base material. When the base material (S) is aimed at improving wear resistance of parts requiring wear resistance, various known materials serving as the base materials of parts requiring wear resistance may correspond thereto, and may be made of any other material. Specifically, the base material may be aluminum, aluminum alloys, which are widely used as thermal and mechanical members, in particular, Al-Si or Al-Mg-based aluminum alloys, or iron-based alloy materials such as cast iron. It may be a semiconductor material. Preferably, the base material is aluminum or aluminum alloy having a large improvement effect according to the coating layer formation of the present invention is less wear resistance. In addition, in the case of forming a bulk form made of a metal base composite alone, rather than forming a coating layer containing a base material, it is necessary to separate the coating layer from the base material. For this purpose, the base material is a ceramic material having low reactivity with metal powder or a heat treatment step. It is preferable that it is a resin material which can be lost and disappeared from.

In addition, in the present invention, the metal, alloy or mixture particles thereof used in the first metal powder may be a variety of known metals, alloys or mixtures thereof, and preferred examples thereof include iron, nickel, copper, aluminum, molybdenum, It is preferable to use titanium or alloys thereof or mixtures thereof. Specific examples of aluminum and titanium include aluminum, aluminum alloys, mixtures of aluminum and aluminum alloys, mixtures of aluminum and titanium, mixtures of aluminum and titanium alloys, and mixtures of aluminum alloys and titanium alloys. It may be an aluminum alloy or a titanium alloy which is often used as a thermal, mechanical member. More preferably, the metal or alloy may be coated on aluminum or an aluminum alloy base material having a high effect according to the formation of a coating layer of the present invention, which is abrasion resistance, and therefore, may be aluminum or aluminum alloy having high homogeneity.

In addition, the metal particles for the intermetallic compound forming the intermetallic compound with the alloying element of the metal or the alloy used in the second metal powder is determined according to the metal, alloy or mixture particles thereof of the first metal powder.

That is, for example, when the first metal powder is aluminum or an alloy thereof, the second metal powder corresponds to a metal having a higher melting point than aluminum among the transition metals, and specific examples thereof include titanium, nickel, It may be one or more metals selected from the group consisting of chromium and iron. As can be seen through the state diagram of each system shown in FIG. 2, in the case of aluminum, an intermetallic compound may be formed for each of titanium, nickel, chromium, and iron.

Hereinafter, the example between the transition metal element which can form an Al metal and an intermetallic compound is demonstrated based on a state diagram. 2A to 2D are state diagrams for binary aluminum alloys as an example of an aluminum alloy which can be formed by the method of the present invention.

2A is a state diagram of an Al-Ti system. Referring to FIG. 2A, when Ti is added to several tens to several percent by weight, at a temperature of 664 ° C. or lower (937 K), the TiAl ₃ phase, which is an intermetallic compound between Al-Ti and Al-Ti, in which a small amount of Ti is dissolved in the alloy Exists as. In addition, as the Ti content is increased (that is, when 38 wt% or more is added), an Al ₃ Ti phase and an Al ₂ Ti phase exist as a stable phase of the alloy. The relative weight ratio between the Al, Al ₃ Ti and Al ₂ Ti phases present in the alloy depending on the mixed composition of the metal powder is determined by the so-called lever rule, which is widely known to those of ordinary skill in the art. Since it is known, the description is omitted.

2B is a state diagram of an Al-Ni system. Referring to FIG. 2B, it can be seen that intermetallic compounds such as Al ₃ Ni, Al ₃ Ni ₂ , AlNi, and AlNi _{3 form a} stable phase of the alloy at a temperature of 636 ° C. or lower. 2C is a state diagram of an Al-Cr system. Referring to FIG. 2C, it can be seen that the intermetallic compound of CrAl ₇ forms a stable phase with the addition of Cr at a temperature of 663 ° C. (936 K) or lower. On the other hand, Figure 2d is a state diagram of the Al-Fe-based, as shown, even in the case of Al-Fe-based metastable intermetallic compounds such as FeAl ₃ can be formed at a temperature of 654 ℃ (927 K) or less It can be seen.

As described with reference to the above state diagrams, the Al-Ti, Al-Ni, Al-Cr and Al-Fe binary systems have stable intermetallic compounds at a predetermined temperature or less, therefore, Al metal powder, Ti, Ni, It is possible to produce intermetallic compounds in the alloy by mixing Cr or Fe metal powders.

In addition, the second metal component may also include alloying elements capable of obtaining precipitation hardening from the existing Al alloy. That is, as the precipitation hardening aluminum alloy, various alloy systems such as Al-Cu, Al-Li, and Al-Mg are possible. In this case, the alloys precipitate a precipitate corresponding to an intermetallic compound to obtain a dispersion strengthening effect. When the metal base composite coating layer or bulk application field of the present invention is relatively low temperature, the second metal component may include Cu, Li, or Mg.

In addition, in the present invention, the ceramic or the mixture thereof corresponding to the ceramic powder includes various kinds of ceramics and mixtures thereof, which are used in metal-based composites for the improvement of known mechanical properties such as wear resistance, hardness, and fatigue. Oxides, carbides or nitrides. Specifically, the ceramic may be a metal, oxide, metal carbide, metal nitride, etc., more specifically, oxides such as silicon dioxide, zirconia, alumina, nitrides such as TiN, Si ₃ N ₄ , TiC, SiC, etc. Carbide of may be used, and alumina or SiC is preferred for increasing wear resistance.

In addition, the ceramic particles mixed in the mixed powder in the present invention may be provided in the form of agglomerated powder, in this case fine particles in the case of agglomerated powder when the powder particles collide with the substrate in the coating step. Since the furnace is easily pulverized into fine particles, it is advantageous in that fine ceramic particles can be uniformly dispersed in the coating layer.

Particle sizes of the first metal powder, the second metal powder, and the ceramic powder mixed in the mixed powder of such a component may be particles of various sizes used in a known cold spray, and preferably 1 to 100 μm. Having a size is good in terms of dispersion and mixing. More preferably, since the second metal powder is a particle to be changed into an intermetallic compound by a later heat treatment step, the finer particles are better for obtaining even and strong dispersion strengthening effect, and have a smaller particle size than the first metal powder. It is preferable. As a specific example of this, when the aluminum powder and the Ni powder are mixed, the aluminum powder is 50 to 100 μm, and the nickel powder is preferably 1 to 100 μm, preferably 1 to 50 μm, and the aluminum powder and the Ti powder are mixed. In this case, the aluminum powder is 50 to 100 µm, and the Ti powder is 1 to 100 µm, preferably 1 to 50 µm. In addition, the ceramic powder mixed with it may be used a powder of various sizes used in the production of a known metal base composite, preferably having a size of 1 to 100 ㎛ in terms of dispersion and mixing, In the case of using the metal powder, the ceramic powder is preferably SiC or alumina in terms of reactivity and dispersion effect, and the size of the ceramic powder is 1 to 50 µm when the aluminum powder is 50 to 100 µm. It is good to mix the ceramic powder. That is, in the case of the first metal powder and the ceramic powder, when the particle size is too small, the particle weight is small, and despite the high speed, the impact amount is too small when impacting the coating layer, so that work hardening such as shot peening When the particle size is too large, the impact amount is large, but the number of impacts and the area is small, so that the work hardening is small. In the case of the second metal powder and the ceramic powder, when the particle size is too large, the dispersion strengthening effect is reduced. As described above, there is an optimum medium size range that maximizes work hardening and dispersion hardening.

In addition, the mixing ratio of the first metal powder, the second metal powder and the ceramic powder can be used by selecting various mixing ratios, and the design of the metal base composite because the second metal powder is almost changed to an intermetallic compound in a subsequent heat treatment step. It is better to mix at a ratio corresponding to the amount of dispersion required in the city, and in the case of ceramic powders, they all function as dispersions without any reaction, so that they correspond to the amount of dispersion required in the design of the metal base composite. It is better to mix in proportions. In particular, in order to maximize the micro-Vickers hardness value, which is a relative indicator of wear resistance, the mixing ratio of the ceramic powder to the first metal powder is preferably in the range of 1: 1 to 3: 1 in volume ratio of metal to ceramic.

The mixed powder of the first metal powder, the second metal powder, and the ceramic powder may be prepared by a conventional method. The simplest method is a method of dry mixing the powders by v-mill. Dry mixed powders can be used in powder feeders as is without further treatment. The mixing ratio of each powder in the mixed powder may be appropriately adjusted according to the use, but in order to optimize the mechanical properties such as wear resistance, the mixing ratio is mixed within an appropriate ratio range according to the design value, and the volume ratio of the ceramic particles is 50%. When exceeding, the coating layer may not increase beyond a certain thickness, so a problem may occur.

Generally, about 5-20 kgf / cm ² of compressed gas is supplied to the mixed powder in the case of using a converging-diffusing nozzle as the nozzle and having a conventional configuration. Helium, nitrogen, argon, air and the like may be used as the compressed gas. The gas is provided compressed to about 5-20 kgf / cm ² with a gas compressor such as a compressor. If necessary, the compressed gas may be provided in a heated state at a temperature of about 200 to 500 ° C. by a heating means such as the gas heater 120 of FIG. 1.

In the cold spray process, as described above, there are many control variables such as the compression pressure for the powder, the flow rate of the carrier gas, and the temperature of the carrier gas, but preferably, all powders sprayed from the nozzle are coated to increase wear resistance. 50% or more of the total powder is separated after it hits the coating surface in order to contribute to work hardening such as shot peening on the coating surface, so that only 50% of the maximum sprayed powder is substantially coated. It is good for improving hardness and abrasion resistance according to curing. More preferably, the coating efficiency is in the range of 10 to 20%, which is good for improving hardness and increasing wear resistance.

Therefore, in the case of maintaining the coating efficiency, it is preferable to keep the velocity at the time of collision of the mixed powder relatively low, and the speed varies in proportion to the square root of the carrier gas temperature. The temperature of the carrier gas supplied to the nozzle may be maintained at a relatively low temperature. In this case, the temperature of the carrier gas is preferably 280 ± 5 ° C. More preferably, the temperature of the carrier gas is good because it shows the appropriate coating efficiency when the aluminum first metal powder is used.

In particular, the metal of the first metal powder is aluminum or an alloy thereof, and the metal particles for forming the intermetallic compound of the second metal powder may be selected from the group consisting of titanium, nickel, chromium and iron. Regardless of the type of ceramic particles, maintaining the speed of the powder coated on the base material at 300 to 500 kPa can obtain the work hardening effect of the coating layer as described above, and thus, it is preferable to maximize the wear resistance.

In addition to the conventional de Laval-Type convergence-diffusing nozzles as described above, the nozzle of the cold spray device is a convergence-diffusing nozzle or converging as shown in FIG. -A straight nozzle is used, and the injection of the mixed powder can be applied in the form of diverging or straight pipe portion of the nozzle through an injection pipe located through the throat. This is because the injection of the mixed powder is made in the divergence or straight pipe portion is made at a relatively low pressure, so that the pressure for the injection of the mixed powder can be kept low so that the cold spray device can be configured at a low cost, powder in the divergence or straight pipe section Since this is injected, it is preferable to prevent the powder from being coated on the inside of the nozzle, in particular, the throat so that the process can be performed for a long time.

Therefore, in the case of using the nozzle and the injection tube as described above, it is preferable to use a relatively low pressure of 90 to 120 psi which is very low than the normal pressure when the mixed powder is injected into the nozzle.

More preferably, in the case of using the nozzle and the injection tube of the above-mentioned type, the pressure at the time of injection of the mixed powder into the nozzle is 90 to 120 psi, and the temperature of the carrier gas is 280 ± 5 ° C. to form a coating layer having excellent wear resistance. It is particularly good when the first metal powder is aluminum and the ceramic is SiC.

In addition, the mixing ratio of the second metal powder or the ceramic powder to the first metal powder in the coating step may be coated to have a concentration gradient from the surface of the base material to the outer surface, the particle size of the ceramic powder or The particle size of the second metal powder may be coated to have a constant gradient in particle size from the base material surface to the outer surface.

That is, the mixing ratio of the second metal powder to the first metal powder is iii) higher from the base material surface to the outside, or ii) coated lower from the base material surface to the outside, or iii) the middle portion is the highest. The base material surface and the outermost part can be configured to have a low mixing ratio concentration gradient, such as low or the middle part is the lowest, and the base material surface and the outermost part are high, which is equally applicable to ceramic powder. It is possible to control the concentration of the ceramic powder and the second metal powder together, and the concentration gradient direction of the ceramic powder and the second metal powder may be configured differently or vice versa.

In addition, it may be configured to have a gradient even in the case of particle size together with or separately from such a concentration gradient, which in the case of ceramic powder increases the size of the powder particles ⅰ) from the base material surface to the outside, or ii) the base material surface. The smaller the coating from the outside to the outside, or (i) the larger the middle part, the smaller the substrate surface and the outermost part, or iii) the smaller the middle part, and the larger the substrate surface and the outermost part. It can be configured to have a size gradient, it can be applied to the second metal powder in the same way, and to adjust the size of the ceramic powder and the second metal powder together, the particle size of the ceramic powder and the second metal powder The draft direction may be configured differently or vice versa.

Through this, it is possible to minimize the generation of thermal stress due to the difference in thermal expansion coefficient between the base material and the coating layer, and to minimize the peeling and residual stress of the coating layer that may occur due to thermal cycling by activating heat transfer.

Formation of such an additional intermediate layer is also preferably applied when the first metal powder is aluminum and the ceramic is SiC.

As described above, the mixed powder injected at high speed collides with the base material to form a high density coating layer. After the coating step is carried out until a coating layer having a desired thickness is obtained, a heat treatment step of forming the intended intermetallic compound in the step of preparing the mixed powder by heat-treating the coated coating layer is performed. In the present invention, the heat treatment step is characterized in that it is carried out at a low temperature. In the above-described conventional casting and thermal spraying methods, the metal mixed powders are all heat treated at a high temperature of about 900 to 1200 ° C., but the heat treatment step is performed at a temperature of 900 ° C. or less. More specifically, the heat treatment step in the present invention is preferably carried out below the lowest liquidus formation temperature, that is, eutectic temperature that can be achieved by the mixed composition of the different first metal powder and the second metal powder. In the present invention, the term eutectic temperature is used to include peritectic temperature. For example, in the case of a mixed powder in which the first metal powder is Al and the second metal powder is Ti, as shown in FIG. 2A, the heat treatment step of the present invention is preferably performed at a temperature of 664 ° C. or lower. In addition, when the mixed powder of the first metal powder and the second metal powder is Al-Ni, Al-Cr or Al-Fe, the heat treatment step is a temperature of 636 ℃ or less, 663 ℃ or less or 654 ℃ (927 K) or less Preference is given to performing at. More preferably, the heat treatment step may be performed at about 500 ° C. or higher, so that the ease of heat treatment and the formation time of the intermetallic compound are properly maintained.

As such, the coating layer formed on the base material by the heat treatment step forms an Al matrix composite having intermetallic compound and ceramic powder dispersed therein. As in the present invention, when the heat treatment step is performed below the eutectic temperature, the intermetallic compound is formed by solid phase diffusion into a solid phase reaction. Therefore, since the liquid phase does not intervene in the formation of the intermetallic compound as in the casting method or the fusion method, an Al base composite having fine intermetallic compounds dispersed in an Al matrix phase can be obtained.

On the other hand, in the conventional powder metallurgy, it is known that formation of an intermetallic compound between aluminum and another metal is extremely difficult at a low temperature of 900 ° C. or lower, particularly below the eutectic temperature. This seems to be because the oxide formed on the surface of the aluminum powder interferes with the reaction of aluminum with other metals. Therefore, in the conventional powder metallurgy, formation of an intermetallic compound is hardly achieved by the reaction between Al and another metal unless a sufficient amount of liquid phase is formed to destroy the surface coating.

However, according to the present invention, the reaction between Al and other metal powder can be made at a lower temperature. It is believed that this is due to the fact that when the aluminum powder injected in the present invention collides with the surface of the base material, the surface coating is broken by the collision energy, and thus the actual contact between the Al powder and the other metal powder is made.

In addition, the coating layer formed by the method of the present invention has a very high density. Therefore, even if exposed to oxygen contained in the atmosphere or atmosphere gas during the heat treatment process, the possibility of forming an oxide film on the surface of the individual Al powder particles is reduced. For this reason, the heat treatment step of the present invention may be performed in air as well as in an inert gas atmosphere such as nitrogen and argon.

As described above, in the present invention, it is preferable that the heat treatment step is performed at the eutectic temperature (including the cladding temperature), because in the thermodynamic equilibrium state below this temperature, the liquid phase is not interposed in principle, so that the finely dispersed intermetallic compound is used. It is suitable for obtaining. In practical systems, however, the liquid phase is negligible even at a range of temperatures above the eutectic temperature, and the role of the liquid phase in the formation of the actual intermetallic compound is negligible. Therefore, the meaning of the term 'below eutectic temperature' described in the claims of the present specification should not be interpreted strictly as excluding such a range of temperatures.

The heat treatment step may have a heat treatment effect for the formation of the intermetallic compound as well as for improving the adhesion of the machining or coating layer for controlling the surface roughness.

In addition, the metal base composite forming method of the present invention may further comprise the step of separating the coating layer which is a part formed in the coating step in the metal base composite coating layer formed by the metal base composite forming method described above from the base material and This can provide a metal base composite bulk consisting of only the metal base composite.

In another aspect, the present invention provides a metal base composite coating layer, characterized in that formed by the above-described metal base composite forming method. The thickness of the coating layer is preferably 10 ㎛ to 1 mm is too thin to prevent the problem of abrasion resistance, if thick, may occur due to the production cost of the coating layer formation and peeling due to thermal expansion, generation of thermal stress, etc. It is good that it is the said range.

In addition, the present invention is characterized in that the metal base composite bulk formed by the above-described metal base composite coating method further comprises the step of separating the coating layer, which is a part formed in the coating step from the base material metal bulk composite complex To provide.

The wear resistant metal base composite coating layer or bulk obtained by the method of the present invention improves the mechanical properties of the base material, coating or bulk.

First, the wear resistance of the member can be improved by including the high hardness intermetallic compound and the ceramic particles in the coating layer or the bulk.

Secondly, the coating layer or bulk produced by the present invention improves the fatigue properties of the coated part. In other words, due to the high bonding strength between the coating layer and the base material, it suppresses the occurrence of cracks between the base material and the coating layer, and since the coating layer has the characteristics of the metal base composite, the microstructure has the effect of lowering the crack generation and propagation speed inside the coating layer. Improve properties It also makes these parts highly resistant to thermal fatigue failure. Thermal stress due to local temperature difference is a major cause of crack generation and propagation in parts used in heat-resistant engines such as gas turbines. In addition, combustion of the engine in the engine block results in a high temperature on the near side to the cylinder and a low temperature on the far side from the cylinder. This temperature difference generates thermal stresses that cause crack formation on the engine block surface. In particular, it is very important to control thermal fatigue failure characteristics due to periodic thermal stress when periodic combustion and cooling are accompanied, such as an engine. In the present invention, the thermal conductivity of the member can be improved by forming a coating layer using particles having high thermal conductivity such as aluminum, aluminum alloy, or ceramic as SiC. Improving the thermal conductivity characteristics reduces local temperature differences occurring in the component, which in turn improves the thermal fatigue failure characteristics of the component. In addition, since the difference in thermal expansion coefficient with the base material can be reduced according to the formation of the composite, there is an advantage in that the peeling or cracking of the coating layer can be minimized since the thermal stress generated during heating can be reduced.

Hereinafter, the present invention will be described in detail by explaining preferred embodiments of the present invention.

<Example 1>

An Al powder with an average particle size of 77 μm and a Ni powder with an average particle size of 3 μm were used for the metal mixed powder having an Al: Ni weight ratio of 90:10 (Al-10% Ni) and 75:25 (Al-25% Ni), respectively. 5 parts by weight of a SiC powder having an average particle size of 35 µm was mixed with 100 parts by weight of the metal mixed powder to prepare a final mixed powder. The aperture was 4 ㅧ as a standard laval type nozzle. The coating layer was formed by injecting the mixed powder into a carrier gas flow of 7 atm and at 330 ° C. using air as a compressed gas using a nozzle having a thickness of 6 mm and a throat gap of 1 mm. The formed coating was heat treated at about 450 ° C., 500 ° C., 550 ° C. for 4 hours. Heat treatment was carried out in a nitrogen atmosphere. X-ray diffraction patterns of the heat-treated substrate surface were measured, and the results are shown in FIGS. 4A (Al-10% Ni) and 4B (Al-25% Ni). According to the X-ray diffraction results, the higher the content of Ni and the higher the heat treatment temperature, more Al ₃ Ni intermetallic compounds and Al ₃ Ni ₂ intermetallic compounds are formed. It can be seen that generated.

In addition, EDX imaging results for the formation of the intermetallic compound between the Ni powder and the Al base adjacent thereto are shown in FIG. 5. In other words, it was observed that Al ₃ Ni intermetallic compounds were formed at low Al concentrations near the Al base, and Al ₃ Ni ₂ intermetallic compounds were formed at high Ni concentrations toward the inside of the Ni powder particles.

When this reaction did not occur completely, it was observed through FIG. 6 that residual Ni was present inside the Ni powder.

<Example 2>

An Al powder with an average particle size of 77 μm and a Ti powder with an average particle size of 43 μm were prepared using a metal mixed powder having an Al: Ti weight ratio of 90:10 (Al-10% Ti) and 75:25 (Al-25% Ti), respectively. 5 parts by weight of a SiC powder having an average particle size of 35 µm was mixed with 100 parts by weight of the metal mixed powder, to prepare a final mixed powder. The aperture was 4 ㅧ as a standard laval type nozzle. The coating layer was formed by injecting the mixed powder into a carrier gas flow of 7 atm and at 330 ° C. using air as a compressed gas using a nozzle having a thickness of 6 mm and a throat gap of 1 mm. The formed coating was heat treated at about 450 ° C., 500 ° C., 550 ° C., and 630 ° C. for 4 hours. Heat treatment was carried out in a nitrogen atmosphere. X-ray diffraction patterns of the heat-treated substrate surface were measured, and the results are shown in FIGS. 7A (Al-10% Ti) and 7B (Al-25% Ti). According to the X-ray diffraction results, the higher the content of Ti and the higher the heat treatment temperature, the more Al ₃ Ti intermetallic compounds were formed, but the intermetallic compound was surely produced even when the heat treatment temperature was low.

In addition, when the heat treatment temperature is 630 ℃ EDX photographing results for the formation of the intermetallic compound between the Ti powder and the Al base adjacent thereto are as shown in FIG. That is, it was observed that Al ₃ Ti intermetallic compounds were formed at the boundary region of the powder through Al diffusion of Ti atoms. In addition, in the case of Ti, it was observed that intermetallic compounds were formed at the interface due to a relatively low diffusion degree, and that residual Ti, which was not completely reacted, existed inside the Ti powder.

According to the metal base composite forming method of the present invention as described above and the metal base composite coating layer and the bulk formed using the same, the metal base composite in which the intermetallic compound and the ceramic powder are dispersed at a low temperature than in the prior art can be produced in the base material There is no risk of causing damage due to thermal deformation or thermal shock, and the growth of intermetallic compounds is suppressed, so there is an advantage of improving mechanical properties such as high temperature strength, preventing heat from accumulating in the coating layer, and between the base material and the coating layer. Alternatively, the crack formation in the coating layer may be suppressed to improve resistance to crack generation due to fatigue of the coating layer.

In addition, the present invention can be used not only for the production of a member having excellent mechanical strength, but also for dispersion strengthening of the surface of an existing member. In particular, since it is performed at a low heat treatment temperature, it is unlikely to adversely affect the physical properties of the member when the surface is strengthened.

In addition, the present invention has the advantage that the process is possible because the process is possible to maintain a relatively low heat treatment temperature and mixed powder injection pressure and low carrier gas temperature is low manufacturing cost, easy to enlarge.

The present invention described above is not limited to the detailed description, examples, and drawings of the above-described invention, and various one of ordinary skill in the art without departing from the spirit and scope of the present invention described in the claims below. Of course, modifications and variations are also included within the scope of the present invention.

Claims (19)

Providing a base material; Iii) a first metal powder consisting of particles of a metal, an alloy or a mixture thereof, ii) a second metal powder consisting of metal particles for forming an intermetallic compound forming an intermetallic compound with an alloying element of the metal or the alloy, and iii) Preparing a mixed powder comprising a ceramic powder made of ceramic or mixture particles thereof; Injecting the prepared mixed powder into a spray nozzle for coating; Coating the mixed powder on the surface of the base material by accelerating the mixed powder at a speed of 300 to 1,200 Pa in a non-melting state by the flow of the carrier gas flowing in the injection nozzle; And And heat treating the coated coating layer to form the intermetallic compound. The method of claim 1, The metal of the first metal powder is aluminum or an alloy thereof, and the metal particles for forming the intermetallic compound of the second metal powder are metal selected from the group consisting of titanium, nickel, chromium and iron. Complex formation method. The method of claim 1, The ceramic of the ceramic powder is an oxide, carbide, nitride or a mixture thereof. The method of claim 3, The ceramic is a metal-based composite forming method characterized in that the alumina or SiC. The method of claim 3, The ceramic particles are mixed with the mixed powder is a metal-base composite forming method characterized in that provided as a coagulated powder. The method of claim 1, The base material is aluminum, aluminum alloy, cast iron, ceramic or resin, characterized in that the metal-base composite forming method. The method of claim 1, Method of forming a metal base composite, characterized in that to maintain the coating efficiency up to 50% in the coating step. The method of claim 1, The metal of the first metal powder is aluminum or an alloy thereof, and the metal particles for forming the intermetallic compound of the second metal powder are one or more metals selected from the group consisting of titanium, nickel, chromium and iron, and are coated on the base material. Method of forming a metal base composite, characterized in that the speed of the powder is 300 to 500 kPa. The method of claim 1, The nozzle is a convergence-diffusing nozzle having a throat, or a convergent-pipe nozzle, and the injection of the mixed powder is made at the diverging or straight portion of the nozzle through an injection tube positioned through the throat. Metal base complex formation method. The method of claim 9, The injection pressure of the mixed powder into the nozzle, the injection pressure is characterized in that 90 to 120 psi. The method of claim 1, When the coating through the nozzle of the mixed powder, the temperature of the carrier gas supplied to the nozzle is characterized in that the metal-base composite is characterized in that 280 ± 5 ℃. The method of claim 1, The mixing ratio of the second metal powder to the first metal powder or the mixing ratio of the ceramic powder has a concentration gradient toward the outer surface from the base material surface. The method of claim 1, The particle size of the second metal powder or the particle size of the ceramic powder has a predetermined gradient in the particle size toward the outer surface from the base material surface. The method of claim 1, The heat treatment step is a metal-base composite forming method, characterized in that carried out below the eutectic temperature of the first metal powder and the second metal powder. The method of claim 14, The metal of the first metal powder is aluminum or an alloy thereof, and the metal particles for forming the intermetallic compound of the second metal powder are at least one metal selected from the group consisting of titanium, nickel, chromium and iron, and the heat treatment step is at least Metal base composite forming method, characterized in that carried out at 500 ℃. The method according to any one of claims 1 to 15, And after the heat treatment step, separating the portion formed in the coating step from the base material. Metal base composite coating layer, characterized in that formed by the metal base composite forming method of any one of claims 1 to 15. The method of claim 17 The thickness of the coating layer is a metal-based composite coating layer, characterized in that 10 ㎛ to 1 mm. The bulk of the metal base composite, characterized in that formed by the metal base composite forming method of claim 16.

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