KR20050081252A - Porous metal coated member and manufacturing method thereof using cold spray - Google Patents

Abstract

The present invention relates to a coating member having a porous metal coating layer and a method of manufacturing the same. The present invention provides a method for forming a porous coating layer on a base material, the step of providing a base material, each selected from the group consisting of Al, Mg, Zn and Sn on the base material, xA- (1-x) B (0 < x <1, x is a weight ratio of A and B) supplying a powder of a metal composition containing at least two different metals different from each other, providing a high pressure gas to the powder, by the high pressure gas Spraying a metal powder with a supersonic nozzle to coat the base material and heat-treating the coated base material to provide a porous coating layer forming method comprising the step of forming a porous coating layer. According to the present invention, it is possible to freely adjust the pore size and porosity inside the coating member. Thus, it can be applied to various thermal mechanical members.

Description

POROUS METAL COATED MEMBER AND MANUFACTURING METHOD THEREOF USING COLD SPRAY}

The present invention relates to a coating member having a porous metal coating layer and a method of manufacturing the same, and more particularly, to a metal coating member having a controlled pore distribution and size of a coating layer on a surface of a base material and a method of manufacturing the same by applying a low temperature spray method. will be.

The porous coating layer formed on the surface of the member can bring about an improvement in the thermal mechanical properties of the member.

For example, when a porous coating layer consisting of interconnected open pores is formed on the surface of the heat exchanger, the heat exchanger may have a wider contact area with the surrounding air to achieve more efficient heat exchange performance. On the other hand, in the case of the friction member, the member may be required to have a low strength and hardness depending on the relationship with the peripheral components, and the porous coating layer may satisfy this requirement. In addition, in the bonding of the base material and the dissimilar material, stress due to lattice mismatching may occur at the bonding interface, and the porous coating layer may also act as a buffer layer to solve such bonding stress.

Conventionally, various coating methods have been used as a method of forming the metal coating layer on the surface of the thermal mechanical member. For example, electroplating, hot dip plating, or thermal spraying is an example. However, these methods are subject to application field constraints or may cause thermal shock or thermal deformation of the base material. In addition, it is practically difficult to artificially adjust the porosity or control the pore distribution in the coating layer by these methods.

An object of the present invention is to provide a thermal mechanical application member that can be used in a wide range of fields and a method of forming a porous coating layer used therein, without fear of causing thermal deformation or damage to the base material.

In addition, an object of the present invention is to provide a thermal mechanical member capable of controlling the pore distribution, including the porosity and pore size inside the surface coating layer and a method for forming a porous coating layer used therein.

In order to achieve the above technical problem, the present invention is a method of forming a porous coating layer on a base material, providing a base material, each selected from the group consisting of Al, Mg, Zn and Sn on the base material, xA- (1 supplying a powder of a metal composition comprising at least two different metals represented by B (0 <x <1, where x is a weight ratio of A and B), and providing a high pressure gas to the powder. And coating the base metal by spraying the metal powder with the supersonic nozzle by the high pressure gas, and forming the porous coating layer by heat-treating the coated base material.

According to an embodiment of the present invention, in the method, A is Al, and B may be one metal element selected from the group consisting of Mg, Zn, and Sn. In addition, the heat treatment step is preferably carried out at the eutectic temperature of the A and B and below the melting point of the metal having a high melting point of the A and B, specifically, in the temperature range of about 200 ~ 650 ℃. .

In addition, the powder providing step in the method may further comprise the step of changing the powder composition by changing the x.

In order to achieve the above technical problem, the present invention provides a coating layer comprising at least two metal elements represented by xA- (1-x) B (where x is a weight ratio of A and B) on the metal base material and the metal base material. Wherein A and B are each one different metal selected from the group consisting of Al, Mg, Zn and Sn, wherein x is changed in the thickness direction of the coating layer within the range of 0 <x <1 It provides a metal coating member, characterized in that the porosity in the coating layer is changed in accordance with the change of x.

According to an embodiment of the present invention, x in the member increases or decreases in the thickness direction of the coating layer, and the porosity in the coating layer may increase or decrease as the x increases or decreases. In addition, when A is Al and B is one metal selected from the group consisting of Mg, Zn and Sn, x decreases as the metal base and the coating layer move toward the surface of the coating layer. And the porosity of the coating layer increases.

In addition, the present invention is provided with a coating layer comprising a metal base material and at least two or more metal elements represented by AB on the metal base material, wherein A and B are each selected from the group consisting of Al, Mg, Zn and Sn, respectively. Another metal, A or B selected in the group is changed according to the thickness direction of the coating layer, the porosity in the coating layer is changed according to the change of the A or B to provide.

In the present invention, the coating layer may include open pores interconnected to at least a portion of the inside of the coating layer, and in certain applications, the open pores are preferably present on top of the coating layer.

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

1 is a schematic view of a low temperature spraying apparatus 100 for accelerating powder to form a coating layer on a substrate S in the present invention.

The spraying device 100 accelerates the powder to form the coating layer at a subsonic or supersonic speed and provides it to the substrate S. To this end, the injection device 100 includes a gas compressor 110, a gas heater 120, a powder feeder 130, and an injection nozzle 140.

Compressed gas of about 5 to 20 atmospheres of compressed gas provided from the gas compressor 100 delivers about 1 to 50 μm of powder provided from the powder feeder 130 at a speed of about 300 to 1200 mm / s through the injection nozzle 140. Squirt. The powder ejected with the gas impinges on the substrate S, at which time the kinetic energy of the powder plastically deforms the powder upon impact on the substrate S and provides a bonding force to the substrate, resulting in a very high density. To form a coating layer.

The gas heater 120 on the compressed gas supply path in the device 100 is an additional device for heating the compressed gas to increase the kinetic energy of the compressed gas to increase the injection speed of the injection nozzle. In addition, as illustrated, 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 100, 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. Can be.

A more detailed description of the operation and structure of the illustrated device is described in detail in US Pat. No. 5,305,414 to Anatoly P. Alkimov et al., Which is omitted herein.

FIG. 2A is a procedure illustrating each step of forming a coating layer on a base material or a substrate using the spraying apparatus described with reference to FIG. 1.

Referring to Figure 2a, the method of the present invention first supplying a metal powder having a composition of two or more metals in the powder feeder 130 of the injection device 100 (S210) and the high pressure in the gas compressor 110 Providing the compressed gas of (S220) begins.

The powder having a composition of two or more metals in the powder supply step S210 may be a mixture or solid solution of at least two metals selected from the group consisting of Al, Mg, Zn and Sn, or a mixture of both. In addition, each metal selected in the present invention is a different species from each other. For example, when the one metal selected from the group includes Al, the composition of the metal powder is binary system such as Al-Mg, Al-Zn, Al-Sn or ternary system such as Al-Mg-Zn or It may be abnormal. In addition, in addition to the metal groups listed, Ti, Si, Mn, Cr, Fe, Co, Ni, Cu, and the like may be further used as long as it does not contradict the technical idea of the present invention.

In the present invention, the powder of the metal composition may be provided in the form of a solid solution. For example, the metal powder of the Al-Mg composition may be provided in the form of AlMg solid solution called Magal. In addition, the powder of the metal composition may also be provided as a mixture of the solid solution powder and monolithic powder, for example, the metal powder may be a mixture of Al powder and AlMg powder. Metal powders such as Mg have the advantage of being easy to handle by providing in the form of such a solid solution because of the risk of handling such as explosion.

When the coating layer of the present invention is used for a thermal mechanical member, the metal powder preferably includes Al or Al alloy which is widely used as a mechanical member due to relatively excellent thermal mechanical properties such as thermal conductivity and strength with respect to specific gravity.

As the gas provided in the compressed gas providing step S220 of the present invention, helium, nitrogen, argon, air, and the like as described above may be used. The gas is provided compressed to about 5-20 atmospheres 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 ° C. to 500 ° C. by a heating means such as the gas heater 120 of FIG. 1. However, considering the fact that the specific heat of the gas is very small even when the compressed gas is provided in a heated state according to this embodiment, the temperature change of the metal powder is not very large. Therefore, the spraying step of the present invention is different from the thermal spraying method in which the powder is heated and coated near the melting point or above the melting point in terms of low temperature spraying.

On the other hand, a portion of the compressed gas supplied in the compressed gas providing step (S220) can be used as a carrier gas for the continuous and stable supply of the metal powder.

Subsequently, a mixture of the compressed gas and the metal powder is injected into the supersonic injection nozzle (S230). The velocity of the gas-powder mixture injected through the nozzle is determined by the temperature, pressure and particle size and specific gravity of the incoming gas. The gas-powder mixture at the aforementioned inlet gas pressure, temperature conditions and about 1-50 μm particle size exhibits an injection rate of about 300-1200 m / s.

The metal powder injected at high speed collides with the base metal to form a high density coating layer. After performing the spraying step (S230) until a coating layer of a desired thickness is obtained, the formed coating layer is heat treated (S240). In the present invention, the heat treatment temperature is preferably about 200 ~ 650 ℃. A heat treatment temperature of 650 ° C. or higher results in complete melting of the coated metal, and a temperature of 200 ° C. or lower hardly causes a melting of the coated composition, so that a heat treatment effect hardly occurs.

The high density coating layer formed on the base material has a porosity by going through the heat treatment step (S240). In addition, as can be seen in the embodiment of the present invention to be described later, the porosity and pore size of the formed porous coating layer is changed according to the change in the composition of the coated metal powder. The change in composition is used here to mean not only the change in the metal component used but also the change in content.

FIG. 2B illustrates each step of the method of forming a porous coating layer including the step (S250) of changing the composition of the metal powder supplied to control pore distribution in the coating layer in the coating method of the present invention described with reference to FIG. 2A.

According to this method, the composition of the powder supplied during the formation of the coating layer by the nozzle spraying step S240 is changed. For example, a 0.5 Al-0.5Mg composition powder having a weight ratio of Al: Mg of 1: 1 is supplied and then controlled at a ratio of 1: 2 or an Al-Zn composition powder having Al: Zn of 1: 1 instead of Al-Mg is used. It is possible to form a coating layer having a composition gradient in the coating layer thickness direction formed by feeding or the like, or containing different components in the coating layer.

As a specific method of changing the composition of the powder, conventional methods that can be designed by those skilled in the art may be used. For example, a method of sequentially feeding powders of different compositions into one powder feeder or arranging a plurality of powder feeders storing different composition powders and selecting a powder feeder of the composition to be supplied by the valve may be used. will be.

3 is a cross-sectional view conceptually illustrating an example of a coating member 200 comprising a coating layer formed in this manner.

Referring to FIG. 3, an Al—Zn layer 210 having a weight ratio of 2: 1, an Al—Zn layer 220 having a weight ratio of 1: 1, and Al having a weight ratio of 1: 2 on a base material S such as Al Zn layer 230 is formed. According to an embodiment of the present invention to be described later, when the heat-treated coating layer thus laminated, as the Zn content increases, the pore size and porosity therein increases. Accordingly, when the member coated with the composition as shown in FIG. 3 is heat-treated, the coating member having a porosity and / or a pore content increases as it moves away from the base material. Such pore distribution is preferable in terms of ensuring stable coating adhesion at the interface with the base material. In addition, as the porosity and pore content increase in such a structure, pores formed near the surface of the coating layer may be interconnected open pores. These open pores play a particularly important role in improving the heat exchange characteristics of the base metal.

The change in pore distribution in the coating layer described with reference to FIG. 3 can be obtained by changing the components themselves in addition to the method of changing the content of each component as described above. That is, by sequentially laminating an Al-Mg layer / Al-Zn layer / Al-Sn layer on the base material, a coating member having an increased porosity and / or pore size can be obtained from the interface.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

General physical properties of the metal used in each of the examples below are shown in Table 1.

metal Melting Point (℃) Density (g / cm ² ) Al 660.2 2.699 Mg 650 1.74 Zn 419.46 7.133 Sn 231.9 7.298

The injection conditions of each of the following examples are as follows.

Nozzle: standard laval type

Aperture: 4 × 6 mm

Throat gap: 1 mm

Compressed gas: Type: air

Pressure: 7 atmospheres

Temperature: 330 ℃

Feed powder size: <44 μm (325 mesh)

Example 1

A mixed powder of Al powder having a weight ratio of 50:50 and AlMg (eutectic temperature of about 400 ° C.) powder (ie, 0.5 Al-0.5 AlMg) and 7 atmospheres of air were supplied to the spray nozzle and coated on the aluminum substrate.

The formed coating was heat treated at about 620 ° C. for 1 hour. Heat treatment was performed while flowing nitrogen gas in a tubular pipe to prevent oxidation of the metal. After the heat-treated substrate was cut and polished, the cut surface was observed with an optical microscope. Figure 4 shows a photograph of the cut surface of the substrate thus produced.

It can be seen from FIG. 4 that the coating layer is well adhered to the Al substrate, and the interface between the Al substrate and the coating layer is clearly distinguished by pores (black portions) trapped inside the coating layer. These pores were not observed in the coating and were produced after the heat treatment.

Example 2

The coating layer was prepared under the same conditions as in Example 1 except that the weight of AlMg was increased to the mixed powder to make the composition of 0.3Al-0.7AlMg as the metal powder. The coating layer prepared in the same manner as in Example 1 was heat-treated, and its cross section was observed with an optical microscope, which is shown in FIG. 5.

Compared with FIG. 4, it can be seen that the pore size is increased in FIG. 5 and the porosity is increased even with the naked eye.

Example 3

The coating layer was formed while changing the powder composition in the order of Al powder / AlMg powder / Al powder / AlMg powder / Al powder. The remaining coating conditions were the same as in Example 1. Subsequently, the formed coating layer was heat-treated at 620 ° C. for 1 hour.

6 is an optical micrograph showing a cross section of a heat treated substrate. As shown, the pores were not observed well in the pure Al layer, it can be seen that the pores are observed in the AlMg layer.

Example 4

The Al substrate was coated with a mixed powder of 0.667 Al-0.333 Mg, followed by a mixed powder of 0.5 Al-0.5 Mg. The remaining coating conditions were the same as in Example 1. Subsequently, the formed coating layer was heat-treated at a temperature of about 620 ° C. for 1 hour, and its cross section was observed with an optical microscope.

7 is an optical micrograph of the cross section observed. As can be seen in FIG. 7, it can be seen that the porosity of the coating region (surface vicinity) having a composition of 0.5Al-0.5Mg increases compared to the coating region (surface vicinity) having a composition of 0.667Al-0.333Mg. Therefore, it can be seen that an increase in the Mg content results in an increase in porosity in the coating layer. In addition, considering the pore shape and porosity, it can be estimated that the pores near the surface are interconnected open pores. As such, the pores interconnected from the surface of the coating layer to the interior provide a large contact area with the ambient air, and therefore will be particularly suitable for applications requiring good heat exchange or thermal radiation properties.

Example 5

A mixed powder of Al and Sn having a composition of 0.5Al-0.5Sn was coated on an Al substrate. The remaining coating conditions were the same as in Example 1.

The formed coating layer was heat treated at a temperature of about 650 ° C. for 1 hour, and then the cross section was polished and observed under an optical microscope. 8 is a cross-sectional optical micrograph. As can be seen from FIG. 7, a myriad of pores can be found in the coating layer, and these pores are considered to be interconnected in terms of shape and porosity.

Example 6

It was coated in the same manner as in Example 1 with a mixed powder having a composition of 0.667 Al-0.333 Sn, and then further coated with a mixed powder having a composition of 0.5 Al-0.5 Sn. The formed coating layer was heat-treated at 620 ° C. for 1 hour, and the polished cross section was observed under an optical microscope.

FIG. 9 is a cross-sectional photograph showing that when the vicinity of the interface coated with 0.667Al-0.333Sn and the vicinity of the surface coated with 0.5Al-0.5Sn were observed, the size of the pores significantly increased and the porosity also increased near the surface. have. Therefore, it can be seen that increasing the content of Sn promotes pore formation.

Example 7

The Al substrate was coated with a mixed powder having a composition of 0.667Al-0.333Zn and then coated with a mixed powder having a composition of 0.5Al-0.5Zn. Coating conditions were the same as in Example 1. Subsequently, the formed coating layer was heat-treated at a temperature of about 620 ° C. for 1 hour, and the cross section thereof was photographed with an optical microscope and shown in FIG. 10.

It can be seen from FIG. 10 that many pores are formed in the coating layer by the addition of Zn. In addition, in the vicinity of the surface of the high Zn content, very large pores exist and the porosity increases compared to the interface near the relatively low Zn content. Therefore, it can be seen that an increase in the Zn content leads to an increase in pore size and porosity.

From Examples 1 to 7 described above, it can be seen that Mg, Zn, and Sn added together with Al to the coating layer are involved in the formation of pores in the coating layer after the heat treatment. In addition, it can be seen that as the addition amount increases, the pore size and porosity also increase. The resulting pores were interconnected and open-pore with increasing contents of Mg, Zn and Sn.

The present inventors speculate on the cause of such a phenomenon as follows. However, the following description is for the purpose of understanding the present invention and is not presented as a basis for interpretation of the technical scope of the present invention.

Mg, Zn, Sn added with Al forms a eutectic liquid phase with Al at the heat treatment temperature, and Al will partially melt. As such, when the liquid phase is present, the pore coalescence becomes relatively easy, which may result in an increase in the pores observed with the naked eye.

On the other hand, by-product gas such as hydrogen generated as the molten Al reacts with moisture in the air may be cited as a cause of pore formation. It is presumed that not only Al but also Mg, Sn and Zn having a lower melting point than Al cause such a reaction at the heat treatment temperature.

For another reason, it can be assumed that the pores were generated by the density change when each metal powder was alloyed by partial melting.

This conjecture also corresponds to the formation of relatively many pores when Zn or Sn is added as compared to the addition of Mg as in the above-described embodiments. This is because the melting temperature of Zn (419.46 ° C) or the melting temperature of Sn (231.9 ° C) is lower than that of Mg (650 ° C).

In view of the above, the heat treatment temperature in the present invention should be above the eutectic temperature of at least two metals to be mixed. The eutectic temperature is used herein to include the peritectic temperature. However, since each metal powder may contain a small amount of impurities, partial melting may occur even at a eutectic temperature or lower. In the present invention, the heat treatment temperature should not exceed the melting point of the pure Al having the highest melting point. This is because the coating itself cannot have structural stability.

The method of the present invention retains many of the advantages of the low temperature spraying method. That is, since the high temperature treatment is not performed, oxidation of the base material or coating layer is suppressed to the maximum and there is no fear of damaging the base material by thermal shock. In addition, very high coating deposition rates can be achieved, and the thickness control of the deposited layer is very easy.

In particular, Mg, Sn, Zn and the like used together with Al in the coating method of the present invention has a lower melting point than Al. Therefore, it can be applied to most of the thermal mechanical members using Al or Al alloy as the base material by heat treatment below the melting point of Al without damaging the base material.

In addition, the coating method of the present invention changes the porosity formed in the coating layer by changing the coating composition. This method makes it possible to provide a porous coating layer required in each industry in a very easy way.

In addition, the coating member produced by the method of the present invention can freely adjust the pore size and porosity therein. Therefore, it can be used as various thermal mechanical members.

1 is a view schematically showing a low temperature spraying apparatus 100 used to form a coating layer in the present invention.

2A and 2B are procedural diagrams illustrating each step of the porous coating layer forming method according to the embodiment of the present invention, respectively.

3 is a cross-sectional view showing an example of a coating member 200 having a coating layer whose internal composition is changed according to an embodiment of the present invention.

Figure 4 is an optical micrograph taken a cross-section after the heat treatment of the coating layer of 0.5Al-0.5AlMg composition according to an embodiment of the present invention.

FIG. 5 is an optical microscope photograph of a cross section of the coating layer having a composition of 0.3Al-0.7AlMg according to an embodiment of the present invention.

FIG. 6 is an optical microscope photograph of a cross section of a coating layer in which Al / AlMg / Al / AlMg / Al compositions are sequentially stacked according to an embodiment of the present invention.

FIG. 7 is an optical microscope photograph of a cross section of a coating layer in which 0.667Al-0.333Mg / 0.5Al-0.5Mg composition is sequentially laminated according to an embodiment of the present invention.

8 is an optical microscope photograph of a cross section of the coating layer of 0.5Al-0.5Sn composition after heat treatment according to an embodiment of the present invention.

FIG. 9 is an optical microscope photograph of a cross section of a coating layer in which a composition of 0.667Al-0.333Sn / 0.5Al-0.5Sn is sequentially laminated according to an embodiment of the present invention.

10 is an optical microscope photograph of a cross section of a coating layer in which 0.667Al-0.333Zn / 0.5Al-0.5Zn composition is sequentially laminated according to an embodiment of the present invention.

Claims (14)

In the method of forming a porous coating layer on the base material, Providing a base material; Two or more different types selected from the group consisting of Al, Mg, Zn, and Sn on the base material, and represented by xA- (1-x) B (0 <x <1, where x is a weight ratio of A and B); Supplying a powder of a metal composition comprising at least metal; Providing a high pressure gas to the powder; Spraying the metal powder into the supersonic nozzle by the high pressure gas to coat the base material; And Method of forming a porous coating layer comprising the step of heat-treating the coated base material to form a porous coating layer. The method of claim 1, Wherein the powder of the metal composition comprises an alloy powder alloyed with at least two metals selected from the group. The method of claim 1, Wherein A is Al, B is a method of forming a porous coating layer, characterized in that it comprises one metal element selected from the group consisting of Mg, Zn and Sn. The method of claim 1, The gas providing step Compressing the gas; And preheating the compressed gas. The method of claim 1, The heat treatment step is a porous coating layer forming method, characterized in that carried out above the eutectic temperature of the A and B and below the melting point of the metal having a high melting point of the A and B. The method of claim 1, The heat treatment step is a method of forming a porous coating layer, characterized in that carried out at a temperature range of about 200 ~ 650 ℃. The method of claim 1, The powder providing step And changing the powder composition by changing the x. The method of claim 1, The gas is a porous coating layer forming method characterized in that it comprises one selected from the group consisting of helium, nitrogen, argon and air. Metal base material; And A coating layer including at least two metal elements represented by xA- (1-x) B (where x is a weight ratio of A and B) on the metal base material, A and B are each one different metal selected from the group consisting of Al, Mg, Zn, and Sn, and x is changed in the thickness direction of the coating layer within a range of 0 <x <1, and x of Metal coating member, characterized in that the porosity in the coating layer changes in accordance with the change. The method of claim 9, Wherein x is increased or decreased in the thickness direction of the coating layer, the metal coating member, characterized in that the porosity in the coating layer increases or decreases as the increase or decrease of x. The method of claim 10, A is Al, and B is one metal selected from the group consisting of Mg, Zn, and Sn, and x decreases as the metal base and the coating layer advance toward the surface of the coating layer. The porosity of the metal coating member, characterized in that to increase. Metal base material; And It is provided with a coating layer containing at least two or more metal elements represented by A-B on the metal base material, A and B are each one different metal selected from the group consisting of Al, Mg, Zn, and Sn, and A or B selected in the group changes depending on the thickness direction of the coating layer, and A or B Metal coating member, characterized in that the porosity in the coating layer changes in accordance with the change. The method of claim 9 or 12, The coating layer is a metal coating member, characterized in that it comprises openings interconnected to at least a portion of the inside of the coating layer. The method of claim 13, The opening is a metal coating member, characterized in that present on top of the coating layer.