WO2005085490A1

WO2005085490A1 - Method for forming wear-resistant coating comprising metal-ceramic composite

Info

Publication number: WO2005085490A1
Application number: PCT/KR2005/000583
Authority: WO
Inventors: Kyung Hyun Ko
Original assignee: Kyung Hyun Ko
Priority date: 2004-03-04
Filing date: 2005-03-03
Publication date: 2005-09-15
Also published as: KR100794294B1; KR20060114365A

Abstract

Disclosed is a method of forming a wear-resistant coated member. In detail, the present invention relates to a method of providing a coating film which does not cause damage to mother material due to thermal deformation and has excellent resistance to wear and thermal fatigue fracture at a surface thereof. The method comprises providing mother material, feeding mixture powder which includes metal particles and ceramic particles, supplying high pressure gas to the mixture powder, and coating the mother material with a metal-ceramic composite by spraying a gas-powder mixture through an supersonic nozzle. In the present invention, it is possible to form a coating having excellent resistance to wear and thermal fatigue fracture.

Description

[DESCRIPTION]

[invention Title] METHOD FOR FORMING WEAR-RESISTANT COATING COMPRISING METAL-CERAMIC COMPOSITE [Technical Field] The present invention relates, in general, to a method of forming a wear-resistant coated member and, more particularly, to a method of providing a coating film which does not cause damage to mother material due to thermal deformation and has excellent resistance to wear and thermal fatigue fracture at a surface thereof.

[Background Art] To lengthen the lives of machine parts used in an abrasive environment in which friction, corrosion, or erosion occurs, methods of hardening surfaces of the parts or of coating the surfaces with wear-resistant material have been employed. Ceramic material having high hardness, which is exemplified by, oxides, such as alumina, carbides, such as SiC or TiC, nitrides, such as Si₃N₄ or TiN, or the like, is preferred as material for coating. Representative machine parts having a wear-resistant coating structure may be exemplified by engine blocks for automobiles and the related components, and, particularly, many technologies have been developed to suppress abrasion of an internal wall of a cylinder bore. Examples of this are Korean Patent Laid-Open Publication Nos. 1997-0045010, 1998-017171, and 2003-0095739. In detail, Korean Patent Laid-Open Publication No.

1997-0045010 suggests a method of forming a coating film on an internal wall of a cylinder bore instead of forming a conventional liner made of a cast-iron material, in which coating powder including metal, ceramic, or a mixture thereof is applied on the internal wall of the bore through a spraying process employing a plasma or an arc as a heat source, thereby improving wear resistance. Korean Patent Laid-Open Publication No. 1998-017171 discloses a method of forming a wear-resistant coating layer on a bore surface of an aluminum cylinder block through spraying of particles, such as silicon carbide, using a plasma. Furthermore, Korean Patent Laid-Open Publication No. 2003-0095739 discloses a method of forming a film, in which a powder alloy composition for spray coating is melted using a high temperature heat source and sprayed on a bore surface of a cylinder made of stainless steel. The powder alloy composition for spray coating is a mixture of alumina and zirconia. As described above, much effort has been made to form a wear-resistant coating on metal mother material using ceramic having excellent wear resistance. However, these methods mostly adopt a spraying process using a plasma or an electric arc. In the spraying process, powder particles to be applied are heated to a melting point or higher so that the powder particles are, at least partially, melted, and then applied on the mother material. Typically, high temperatures of a few thousand degrees Celsius are required to melt the ceramic particles, but particles melted at high temperatures have a high probability of causing damage to the surface of mother material due to thermal impact or remaining heat stress during a coating process, thereby shortening the lives of the parts. Additionally, a risk increases during operation of a spraying device and operation is complicated because of the spout of high temperature particles. As well, high temperature fused particles may react with metal matrixes or impurities to form novel compounds, thereby negatively affecting the physical properties of the material. Meanwhile, the parts of a heat engine that generates energy by periodically combusting fuels are continuously subjected to heating and cooling processes during the operation of the engine. Heat stress which is locally formed on the parts due to the periodic heating and cooling causes thermal fatigue fracture on parts of the heat engine, resulting in shortened lives of the parts. For example, in a diesel engine block, an insert groove for receiving a glow plug is formed around a cylinder groove, and the portion between the insert groove and the cylinder groove has a high possibility being destroyed by thermal fatigue fracture because of the small interval between two grooves . As described above, it is frequently expected for parts for thermal and mechanical applications to have excellent wear resistance and excellent resistance to thermal fatigue fracture. However, in the conventional coating technology described above, the improvement of wear resistance is watched, but there is no consideration to fatigue fracture.

[Detailed description of Invention] An object of the present invention is to provide a method of forming a wear-resistant coating layer of good quality at a low temperature so that thermal deformation of mother material or damage to the mother material due to thermal impact does not occur. Another object of the present invention is to provide a method of forming a coating layer which has high resistance to thermal fatigue fracture using a composite coating of metal having high thermal conductivity and ceramic . In order to accomplish the above objects, the present invention provides a method of forming a wear-resistant coating layer. The method comprises providing mother material, feeding mixture powder which includes metal particles and ceramic particles, supplying high pressure gas to the mixture powder, and coating the mother material with a metal-ceramic composite by spraying the mixture powder of non-fused state using the high pressure gas through an supersonic nozzle. In the present invention, the metal may include any one metal selected from the group consisting of iron, nickel, copper, aluminum, molybdenum, and titanium. Furthermore, the metal may be a mixture or an alloy of two or more metals selected from the group consisting of iron, nickel, copper, aluminum, molybdenum, and titanium. Alternatively, the metal may be an aluminum alloy or a titanium alloy frequently used as a typical member for thermal and mechanical applications . In the present invention, the ceramic includes metal oxides, metal carbides, or metal nitrides. In detail, it is preferable that the ceramic be alumina or SiC. As well, in the present invention, the metal may be fed in the form of agglomerated powder. In this case, the powder particles collide with the substrate in the coating of the mother material, and are thus pulverized into fine particles. Accordingly, it is possible to form a coating layer in which the fine ceramic particles are uniformly dispersed. According to the present invention, ceramic powder particles having a size of about 1 - 200 μm can be used. A weight ratio of metal and ceramic of the mixture powder available to the present invention is in a very wide range, and it is preferable that the range be 10:1 - 1:1 in the present invention. In the present invention, the coating step is characterized in that the ceramic particles collide with the substrate or the metal particles which are already applied thereon to totally or partially encroach on the substrate or the metal particles.

[Brief Description of Drawings] FIG. 1 schematically illustrates a low temperature spraying device used to form a metal-ceramic composite coating layer in the present invention; FIG. 2 is a flow chart showing the formation of the ceramic-metal composite coating according to a method of the present invention; FIGS. 3a to 3c illustrate a mechanism of formation of the metal-ceramic composite coating layer using the spraying device of FIG. 2, according to the present invention; FIGS. 4a and 4b illustrate coating powders which each include aluminum powder and agglomerated alumina powder according to the present invention, in which FIG. 4a illustrates scanning electron microscope pictures of sections of coating samples formed depending on a weight ratio of alumina on a silicon substrate, and FIG. 4b is an expanded scanning electron microscope picture of a section of a portion of the samples; FIG. 5 illustrates optical microscope pictures of sections of coating samples formed depending on the weight ratio of alumina on an aluminum substrate when aluminum powder and agglomerated alumina powder are used as coating powder, according to the present invention; FIG. 6 illustrates optical microscope pictures of sections of coating samples formed depending on the weight ratio of alumina on an aluminum substrate when aluminum powder and fused alumina powder are used as coating powder, according to the present invention; FIG. 7 illustrates optical microscope pictures of sections of coating samples formed depending on the weight ratio of SiC having a particle size of about 10 - 15 βin on an aluminum substrate when aluminum powder and SiC powder are used as coating powder, according to the present invention; FIG. 8 illustrates optical microscope pictures of sections of coating samples formed depending on the particle size of SiC powder on an aluminum substrate when aluminum powder and SiC powder are used as coating powder in a weight ratio of 10 : 1, according to the present invention; and FIG. 9a is a histogram showing frictional coefficients of composite coating layers produced in such a way that sizes of SiC particles are changed with respect to Al particles of 325 mesh, and FIG. 9b is a histogram showing frictional coefficients of composite coating layers produced in such a way that sizes of SiC particles are changed with respect to Al particles of 200 mesh.

[Best Mode] Hereinafter, a detailed description will be given of preferred examples of the present invention, referring to the drawings . FIG. 1 schematically illustrates a low temperature spraying device 100 for forming a coating layer on a substrate (S) in the present invention. The spraying device 100 accelerates the powder for forming the coating layer at subsonic or supersonic speed to apply it to the substrate (S) . With respect to this, the spraying device 100 comprises a gas compressor 110, a gas heater 120, a powder feeder 130, and a spraying nozzle 140. The powder of about 1 - 200 μsn fed from the powder feeder 130 is sprayed using compressed gas of about 5 - 20 kgf/cm² supplied from the gas compressor 110 through the spraying nozzle 140 at a rate of about 300 - 1200 m/s. An supersonic convergent-divergent nozzle is used as the spraying nozzle of the present invention. In the device 100, the gas heater 120 which is positioned in a path for feeding the compressed gas is a supplementary unit for heating the compressed gas to increase the kinetic energy of the compressed gas so as to increase the spraying speed of the spraying nozzle. Furthermore, as shown in the drawing, a portion of the compressed gas may be fed from the gas compressor 110 into the powder feeder 130 so as to nicely feed the powder into the spraying nozzle 140. The compressed gas for the device may be exemplified by some commercial gases, such as helium, nitrogen, argon, or air, and the kind of gas used may be appropriately selected in consideration of the spraying speed of the spraying nozzle 140 and economic efficiency. The operation and structure of the device are disclosed in detail in US. Pat. No. 5,305,414 by Anatoly P. Alkimov et al . , and a description of them is omitted herein. FIG. 2 is a flow chart showing the modification of a surface of a metal mother material, according to the present invention. With reference to FIG. 2, the mother material on which a coating layer is to be formed is prepared (S210) .

The mother material may be made of predetermined material . For example, the mother material may be made of metal material, such as aluminum, an Al-Si- or Al-Mg-based aluminum alloy, or cast iron, which is extensively used as a member for thermal and mechanical applications, or semiconductor material, such as silicon. Subsequently, a mixture including ceramic powder and metal powder, which is to be applied on the mother material, is prepared (S220) . The ceramic powder may be exemplified by oxides, such as silicon dioxide, zirconia, or alumina, nitrides, such as TiN or Si₃N₄, or carbides, such as TiC or SiC. Through the spirit of the present invention to be described later, it will be apparent to those skilled in the art that various other oxide, carbide, or nitride ceramic particles which are known in the art can be used even though they are not enumerated. The metal powder may be any metal selected from the group consisting of iron, nickel, copper, aluminum, molybdenum, and titanium, a mixture thereof, or an alloy thereof. Furthermore, the metal powder may be aluminum alloy-based powder, such as Al-Si or Al-Mg. A mixture of the ceramic powder and the metal powder may be produced through a typical process. A process of dry-mixing the ceramic powder and the metal powder using a v-mill may be given as an example of the simplest process . The dry-mixed powder can be used in the powder feeder without additional treatment. A mixing ratio of the ceramic powder and the metal powder in the mixture depends on the application. As apparent from the examples of the present invention described later, a process range is very wide with respect to the mixing ratio in the present invention. For example, even if the weight ratio of ceramic particles in the mixture is about 50 %, which depends somewhat on the specific gravity of the metal and ceramic, it is possible to form a coating layer of good quality. However, if the weight ratio of the ceramic particles is more than 50 %, undesirably, the thickness of the coating layer cannot be increased so as to be over a predetermined level. Referring to FIG. 2, compressed gas at about 5 - 20 kgf/cm² is supplied to the mixture powder (S230) . Helium, nitrogen, argon, air or the like may be used as the compressed gas. The compressed gas is supplied while being compressed at about 5 - 20 kgf/cm² using the gas compressor. If necessary, the compressed gas may be supplied while being heated at about 200 - 500^°C using a heating unit, such as the gas heater 120 shown in FIG. 1. However, even though the compressed gas is supplied while being heated according to the present invention, since the specific heat of the gas is very small, the temperature change of the metal- ceramic mixture powder is insignificant, thus the powder is not melted at all . Since the spraying step of the present invention is conducted at low temperature, it is different from a spraying process in which powder is heated to a melting point or higher, melted, and applied. Meanwhile, as described above, a portion of the compressed gas used in the step (S230) of supplying the compressed gas may be used as carrier gas for continuously and stably supplying the metal powder. Subsequently, the above gas and the mixture powder of non-fused state are sprayed using an supersonic spraying nozzle (S240) . The flow rate of the gas-powder mixture sprayed through the nozzle depends on the temperature and pressure of the gas and the particle size and specific gravity of the powder. The gas-powder mixture having the particle size of about 1 - 50 /tin is sprayed at the rate of about 300 - 1200 m/s under the pressure and temperature conditions of the supplied gas . The mixture powder which is sprayed at the high rate collides with the mother material to be applied thereon (S250) . FIGS. 3a to 3c illustrate a mechanism of formation of a coating layer which includes the metal-ceramic composite according to the present invention using the spraying device 100. First, FIG. 3a illustrates the mechanism of application of metal particles . Kinetic energy of metal powder (M) which is sprayed through the spraying nozzle 140 at the high rate plastically deforms the powder when the powder collides with a substrate (S) , and provides bonding strength to the substrate. The plastic deformation of the powder improves the packing of the powder on the surface of the substrate, thereby forming a coating layer having a very high density. FIG. 3b illustrates a mechanism of application of ceramic particles on the substrate . The ceramic particles (C) sprayed at the high rate through the spraying nozzle 140 totally or partially encroach on the surface of the substrate (S) due to their kinetic energy, and are then bonded to the substrate. At this time, the ceramic particles may break due to impact, thus forming fine powder. This especially occurs when using the agglomerated ceramic powder. Accordingly, it is possible to form the composite coating having a fine structure, in which fine powder is uniformly dispersed in the coating, based on the mechanism. FIG. 3c illustrates a mechanism in which the mixture of the metal powder and the ceramic powder is sprayed through the spraying nozzle to form the coating layer. The coating of the mixture is conducted based on a combination of the mechanisms of FIG. 2a and FIG. 2b. In other words, the ceramic particles of the mixture particles encroach on the substrate or metal particles applied on the substrate, and then bond strongly thereto. The metal particles are bonded to the substrate, or to the ceramic particles and/or the metal particles which are already bonded thereto. The applied metal particles provide a novel bonding region to the ceramic particles, and it is possible to form a very thick coating layer using the above mechanism. As well, the entire coating layer has a very dense and fine structure due to plastic deformation of the metal particles. The ceramic-metal composite coating produced according to the present invention improves the physical properties of the mother material, or it has improved physical properties . With respect to this, firstly, the coating includes ceramic particles having high hardness, thus the wear- resistance of a member is improved. Secondly, the coating layer produced according to the present invention enables the member to have high resistance to thermal fatigue fracture. As an example of the principal reason for occurrence of crack and total destruction of a member used in a heat engine, heat stress caused by a local temperature gradient may be given. For instance, the portion of an engine block that is closer to a cylinder is at a high temperature because of the combustion of the engine, and another portion of the engine block, which is far from the cylinder, is at a low temperature. The temperature gradient causes heat stress which causes a crack on a surface of the engine block. Particularly, in the case that combustion and cooling are periodically conducted, as in an engine, it is very important to control a thermal fatigue fracture property caused by periodic heat stress . In the present invention, the coating layer is formed using particles having high thermal conductivity, such as aluminum or an aluminum alloy as metal and SiC as ceramic, thereby increasing a thermal conductive property of the member. The increase in thermal conductive property reduces the local temperature gradient of the member, resulting in an improved thermal fatigue fracture property of the member. In addition, the metal- ceramic coating according to the present invention is expected to improve resistance to thermal fatigue fracture because of the uniqueness of a fine structure of a typical metal-ceramic composite. Turning to FIG. 2, the resultant coating layer may be subjected to an appropriate post-treatment step (S260) , if necessary. For example, the post-treatment step may comprise a mechanical process for controlling the intensity of surface illumination or heat treatment for improving adhesion strength of the coating layer. A better understanding of the present invention may be obtained through the following preferred examples. Spraying conditions of examples are as follows . - Nozzle : standard laval type aperture : 4 X 6 mm throat gap : 1 mm - Compressed gas : type : air pressure : 7 kgf/cm² temperature : 330^°C - Size of metal powder: < 44 μm (325 mesh) (examples 1 4 )

EXAMPLE 1 Al and A1₂0₃ were dry mixed to produce mixture powder, and the powder was sprayed through a nozzle to produce an AI-AI₂O₃ composite coating on a silicon substrate. A1₂0₃ was agglomerated powder having a particle size of 77 m or less, and coating samples were produced so that the weight ratio of Al and A1₂0₃ in each mixture powder was 10:1, 4:1, 2:1, and 1:1. Surfaces of the coating samples thus produced were subjected to X-ray diffraction analysis, and their sections were observed using a scanning electron microscope. Through X-ray diffraction patterns, Al(lll) and Al(200) peaks, and Al₂O₃(104) and Al₂0₃(113) peaks were observed in the coating samples . FIG. 4a illustrates scanning electron microscope pictures of sections of the coating samples . In all of the samples, it was possible to produce coating layers having good adhesion strength to the Si substrate. This means that it is possible to apply the method of the present invention to brittle material, such as the Si substrate. FIG. 4b is an expanded picture of a section of the sample in which the ratio of A1:A1₂0 is 1:1. As indicated by the arrow in the expanded picture, it can be seen that a plurality of fine A1₂0₃ powders is dispersed around coarse Al particles. This is believed to be caused by the pulverization of agglomerated A1₂0₃ particles, colliding with the substrate, into fine particles . EXAMPLE 2

A coating layer was produced under the same powder composition and experiment conditions as example 1 except that an Al substrate was used instead of an Si substrate. FIG. 5 illustrates optical microscope pictures of sections of coating samples formed depending on weight ratios of Al and A1₂0₃. In the pictures, a dark region denotes an A1₂0₃ portion and a bright region denotes an Al portion. It can be seen that the A1₂0₃ content of the coating layer increases as the Al₂0₃ content of the mixture powder increases. Furthermore, even though Al₂0₃ and Al were added in the weight ratio of 1:1, it was possible to produce a dense coating layer having excellent adhesion strength to the substrate. Meanwhile, it was observed that the applied Al₂0₃ particles became very small in comparison with the original size of the powder, which was caused by the pulverization of the agglomerated powder into a plurality of fine particles during the collision.

EXAMPLE 3 An A1-A1₂0₃ coating layer was formed on an Al substrate using Al powder and fused alumina (A1₂0₃) powder.

A1₂0₃ powder having a particle size of about 200 μm or less was used. The content of A1₂0₃ and experimental conditions were the same as the foregoing examples. FIG. 6 illustrates optical microscope pictures of sections of coating samples formed depending on the content of A1₂0₃. From FIG. 6, it can be seen that it is possible to form a coating layer having high density and good adhesion strength between the substrate and the coating layer even though the content of A1₂0₃ is increased so that the weight ratio of aluminum and alumina is 1:1. From comparison with example 2, it can be seen that there are very large Al₂0₃ particles having a particle size of 100 μm or more in the coating layer. This shows that it is possible to use the method of the present invention to apply the coarse ceramic particles having a particle size of 100 μm or more. Additionally, it can be seen that the extent of pulverization of the fused alumina into fine particles is lower in comparison with the agglomerated alumina particles . Meanwhile, from FIG. 6, it can be confirmed that there are particles (see dotted circles) which encroach on the coating layer at the interface between the Al substrate and the coating layer. This shows that the formation of the coating layer is based on the application mechanism as described above. EXAMPLE 4

Al and SiC were dry mixed to produce mixture powder, and the powder was sprayed through a nozzle to produce an Al-SiC composite coating on an aluminum substrate. Coating samples were produced so that the weight ratio of Al and SiC of each mixture powder was 10:1, 4:1, 2:1, and 1:1, and the particle size of SiC was about 20 - 25 μ (800#) , about 10 - 15 μm (2000#), about 3 - 5 μm (6000#), and about 1 - 2 μ (8000#) . The remaining application conditions were the same as the foregoing examples . From observing sections of the resultant coating samples, it can be confirmed that a very dense coating layer having good adhesion strength to the Al substrate is formed. For example, FIG. 7 illustrates optical microscope pictures of sections of the coating samples in which the weight ratio of Al : SiC is 10:1, 4:1, 2:1, and 1:1 when using SiC powder having a particle size of about 10 - 15 μm, and FIG. 8 illustrates optical microscope pictures of sections of the coating samples depending on the particle size of the SiC powder when the weight ratio of Al:SiC is 10:1. From the pictures, it can be seen that, when using the SiC powder, a coating having good adhesion strength and a dense and fine structure is formed regardless of the weight ratio and the particle size, as in the alumina powder.

EXAMPLE 5

As in example 4, Al and SiC were dry mixed to produce a mixture powder, the powder was sprayed through a nozzle to produce an Al-SiC composite coating on an aluminum substrate, and a frictional property of the coating thus produced was observed. To evaluate the effect of particle sizes of Al and SiC on the frictional property, the coatings were formed using the Al particles of 325 mesh (<44 μm) and 200 mesh (<77 μm) , and using SiC particles of 150 mesh (<104 μm) , 400 mesh (<35 μm) , 1000 mesh (<13 μm) , and 2000 mesh (<6.5 μm) . With respect to this, the weight ratio of Al and SiC was set to 1:1. Frictional coefficients of the resultant coating layers were evaluated using Plint TE 97 through a pin on disk method. With respect to this, an alumina pin was used as objective material. FIG. 9a is a histogram showing the frictional coefficients of the composite coating layers produced using the Al particles of 325 mesh and the SiC particles of 150 mesh (150S50%), 400 mesh (400S50%) , 1000 mesh (1000S50%) , and 2000 mesh (2000S50%) , and FIG. 9b is a histogram showing the frictional coefficients of the composite coating layers produced using the Al particles of 200 mesh and the SiC particles of 150 mesh (150S50%) , 400 mesh (400S50%), and 1000 mesh (1000S50%) . From the histograms of FIGS. 9a and 9b, it can be seen that a change of the frictional coefficient according to a change of the particle size of SiC is larger when using the small Al particles (i.e. 325 mesh) than when using the large Al particles (i.e. 200 mesh) . Furthermore, it can be seen that the frictional coefficient increases as the particle size of the Al particle is reduced at the size (for example, 400S50% and 1000S50%) of the predetermined SiC particle. As described above, it is possible to variously change the frictional coefficient of the Al-SiC coating of the present invention by controlling the particle sizes of Al and SiC, thus a member for mechanical applications, which has appropriate frictional coefficient, can be provided depending on mechanical properties, such as hardness, of objective material if it is used as a frictional member. For example, as is apparent from FIG. 9a, when the maximum particle size of Al is 325 mesh or more and the maximum particle size of SiC is 400 - 1000 mesh, the coated member having a high frictional coefficient can be provided. When the maximum particle size of Al is 325 mesh or more and the maximum particle size of SiC is 150 mesh or less or 1000 mesh or more, the coated member having a low frictional coefficient can be provided. [industrial Applicability] According to the present invention, it is possible to produce a coating having excellent wear resistance and excellent resistance to thermal fatigue fracture. The coating layer is used to coat surfaces of machine parts employed in a frictional environment, or improves thermal conductive properties of engine parts operating in a periodic heat stress environment, thereby improving a thermal fatigue fracture property. Furthermore, it is possible to continuously provide bonding sites of applied metal to ceramic particles based on an application mechanism of the present invention, thus forming a thick coating layer. According to a method of the present invention, since it is possible to freely control a weight ratio of metal and ceramic contained in the coating layer, a coating layer which is suitable for the hardness condition of a member can be provided. Particularly, since it is possible to control the frictional coefficient by adjusting the sizes of metal and ceramic particles, it can be used in a member for a mechanical application, which has a frictional property suitable to the mechanical properties of objective material . Additionally, in the method of the present invention, the coating layer is formed using the kinetic energy of the coating particles instead of heat energy. Therefore, the mother material is not exposed to thermal impact, and is not thermally deformed. A novel phase that negatively affects properties of the mother material due to reaction with the mother material is not formed. As well, as described in examples, since it is possible to apply coarse ceramic particles having sizes of 100 μm or more in the method of the present invention and since the ceramic particles are not melted using a plasma or a laser beam, the type of available particles is not limited. Hence, it is possible to provide a metal-ceramic coating which includes various types and sizes of ceramic particles on a surface of the mother material, and the scope of applicability is very wide.

Claims

[CLAIMS] [Claim 1] A method of forming a wear-resistant coating layer, comprising: providing mother material; feeding mixture powder which includes metal particles and ceramic particles; supplying high pressure gas to the mixture powder; and coating the mother material with a metal-ceramic composite by spraying the mixture powder of non-fused state using the high pressure gas through an supersonic nozzle.

[Claim 2] The method as set forth in claim 1, wherein the metal includes any one metal selected from the group consisting of iron, nickel, copper, aluminum, molybdenum, and titanium.

[Claim 3] The method as set forth in claim 1, wherein the metal is a mixture or an alloy of two or more metals selected from the group consisting of iron, nickel, copper, aluminum, molybdenum, and titanium.

[Claim 4] The method as set forth in claim 1, wherein the metal is aluminum or an aluminum alloy.

[Claim 5] The method as set forth in claim 1, wherein the ceramic includes metal oxides, metal carbides, or metal nitrides .

[Claim 6] The method as set forth in claim 5, wherein the ceramic is alumina or SiC .

[Claim 7] The method as set forth in claim 5 or 6, wherein the ceramic is fed in a form of agglomerated powder in the feeding of the mixture powder, and powder particles collide with a substrate and are thus pulverized, thereby forming a coating layer including fine particles in the coating of the mother material.

[Claim 8] The method as set forth in any one of claims 5 to 7, wherein the ceramic consists of the powder particles having a size of about 1 - 200 μm.

[Claim 9] The method as set forth in claim 1 , wherein a weight ratio of metal and ceramic is 10 : 1 - 1 : 1.

[Claim 10] The method as set forth in claim 1, wherein the mother material is aluminum or an aluminum alloy.

[Claim ll] The method as set forth in claim 1, wherein the ceramic particles collide with the mother material or the metal particles which are already applied thereon to totally or partially encroach on the mother material or the metal particles in the coating of the mother material .

[Claim 12] The method as set forth in claim 1, wherein the metal is Al or an Al alloy, the ceramic is SiC, Al or the Al alloy has a maximum particle size of 325 mesh or more, and SiC has a maximum particle size of 400 - 1000 mesh.

[Claim 13] The method as set forth in claim 1, wherein the metal is Al or an Al alloy, the ceramic is SiC, Al or the Al alloy has a maximum particle size of 325 mesh or more, and SiC has a maximum particle size of 150 mesh or less. [Claim 14] The method as set forth in claim 1, wherein the metal is Al or an Al alloy, the ceramic is SiC, Al or the Al alloy has a particle size of 325 mesh or more, and SiC has a maximum particle size of 1000 mesh or more.