Composite material, and method for manufacturing a composite material

Abstract

To improve the productivity of Cr2AlC layers. [Solution] The method for manufacturing the composite material comprises a first coating step of forming a Cr7C3 layer on a substrate and a second coating step of forming a Cr2AlC layer on the Cr7C3 layer. The second coating step is a step of performing a diffusion and penetration treatment of aluminum elements on the Cr7C3 layer.

Description

Technical Field

[0001] The present invention relates to a composite material and a method for manufacturing the composite material.

Background Art

[0002] Patent Document 1 describes a ceramic matrix composite material containing silicon carbide and a MAX phase compound having a chemical composition M AX n As the MAX phase compound, Cr2AlC is exemplified. A ceramic matrix composite material is produced by impregnating a porous fiber preform with a slurry containing silicon carbide particles and a solid particulate material containing a MAX phase precursor. It describes using the produced ceramic matrix composite material as a turbine engine member.

[0003] Patent Document 2 describes a method for manufacturing a spherical graphite cast iron product. It describes performing, in this order, a step of ferriteizing the base metal structure, a first infiltration treatment step of diffusing and infiltrating chromium on the surface of the base, and a second infiltration treatment step of diffusing and infiltrating aluminum on the surface of the base. By performing these steps, an alloy layer containing aluminum is formed on the surface of the base of the spherical graphite cast iron.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in the method of forming a Cr2AlC layer by slurry impregnation described in Patent Document 1, it was sometimes difficult to form the Cr2AlC layer on the uneven surface or the inner surface of a cylindrical body if the substrate had irregularities or was cylindrical. Furthermore, Patent Document 2 does not specify the type of aluminum alloy layer to be formed on the surface of the substrate, and does not disclose the formation of a Cr2AlC layer. There was a need to make it easier to form a Cr2AlC layer on the surface of the substrate, in other words, to improve the productivity of forming Cr2AlC layers. [Means for solving the problem]

[0006] The method for manufacturing a composite material according to Embodiment 1 comprises a first coating step of forming a Cr7C3 layer on a substrate and a second coating step of forming a Cr2AlC layer on the Cr7C3 layer, wherein the second coating step is a step of performing a diffusion and penetration treatment of aluminum elements on the Cr7C3 layer.

[0007] Embodiment 2 is a method for manufacturing a composite material according to Embodiment 1, wherein the first coating step is a step of performing a diffusion and penetration treatment of chromium element on the substrate. Embodiment 3 is a method for manufacturing a composite material according to Embodiment 1 or Embodiment 2, comprising the step of forming a metal carbide layer on the substrate before the first coating step.

[0008] Embodiment 4 is a method for manufacturing a composite material according to any one embodiment of Embodiments 1 to 3, wherein the substrate contains 0.02% by mass or more of carbon. The composite material of embodiment 5 is a composite material having a substrate and a coating layer covering the substrate, wherein the coating layer has a Cr7C3 layer and a Cr2AlC layer in order from the substrate.

[0009] Embodiment 6 is a composite material according to Embodiment 5, wherein a metal carbide layer is provided between the substrate and the Cr7C3 layer. Embodiment 7 is a composite material according to Embodiment 5 or Embodiment 6, wherein the substrate contains 0.02% by mass or more of carbon. [Effects of the Invention]

[0010] According to the present invention, the productivity of Cr2AlC layers can be improved. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional SEM image of the composite material of Example 1. [Figure 2] This is a cross-sectional SEM image of the composite material of Comparative Example 1. [Figure 3] This shows the crystal structure analysis results for the surface of the composite material in Example 1. [Figure 4] This is the calculation result of the three-dimensional phase diagram of iron, chromium, and carbon at 700°C. [Figure 5] This is the calculation result of the three-dimensional phase diagram of iron, chromium, and carbon at 1000°C. [Figure 6] This is the calculation result of the three-dimensional phase diagram of iron, chromium, and carbon at 1200°C. [Modes for carrying out the invention]

[0012] Embodiments of the composite material of the present invention will be described. The composite material of this embodiment comprises a substrate and a coating layer that covers the substrate. The coating layer has a Cr7C3 layer and a Cr2AlC layer in order from the substrate.

[0013] The following provides details about the composite materials. <Base material> The type of the base material is not particularly limited. The base material is preferably a material capable of forming a Cr7C3 layer or a metal carbide layer described later on its surface. The base material preferably contains iron. The base material preferably contains 50% by mass or more of iron as the main component. In addition, the base material preferably contains a carbon element in addition to iron. By containing the carbon element, a Cr2AlC layer can be formed using the carbon element in the base material. Specific examples of the base material containing a carbon element include, for example, steel materials such as steel, cast iron, and stainless steel. Specific examples of other base materials include, for example, aluminum oxide.

[0014] The content of the carbon element in the base material is not particularly limited, but is preferably 0.02% by mass or more, and more preferably 0.3% by mass or more. When the content of the carbon element is 0.02% by mass or more, it becomes easier to form a Cr2AlC layer using the carbon element in the base material. The content of the carbon element is preferably 2.14% by mass or less, and more preferably 1.2% by mass or less. When the content of the carbon element is 2.14% by mass or less, the toughness of the base material is likely to be improved, so that the composite material can be used for applications that require higher toughness. Generally, since steel has a carbon content of about 0.02% by mass or more and 2.14% by mass or less, the above base material is preferably steel.

[0015] The method for measuring the content of the carbon element in the base material is not particularly limited, and a known measurement method can be adopted. For example, it can be measured by the combustion - carbon dioxide gravimetric method, combustion - gas volumetric method, combustion - infrared absorption method, etc. defined in JIS G 1211.

[0016] The shape of the base material is not particularly limited, and a shape suitable for the use of the composite material can be adopted. As described later, for example, when the composite material is used as a component constituting a chain, the shape of each component can be adopted.

[0017] <Coating layer> The coating layer has a Cr7C3 layer and a Cr2AlC layer in order from the closest to the base material. The Cr7C3 layer means a chromium carbide layer having a composition of seven chromium atoms for three carbon atoms. The Cr7C3 layer is preferably formed directly on the surface of the substrate. That is, it is preferable that no other layer exists between the surface of the substrate and the Cr7C3 layer.

[0018] The Cr7C3 layer may have (Cr,Fe)7C3. That is, the Cr7C3 layer may have an alloy phase in which iron element diffuses inside and contains iron element in Cr7C3. However, even if it has (Cr,Fe)7C3, the Cr content in (Cr,Fe)7C3 is preferably 30 at% or more, and the Fe content is preferably 40 at% or less.

[0019] The Cr2AlC layer means a chromium aluminum carbide layer also called chromium aluminum carbide. Cr2AlC is a compound containing Al in transition metal carbides and is generally called a MAX compound. MAX compounds are known to be excellent in wear resistance and corrosion resistance.

[0020] The Cr7C3 layer and the Cr2AlC layer are formed continuously without another layer intervening therebetween. The thickness of each layer constituting the coating layer is not particularly limited. The thickness of the Cr7C3 layer is preferably 1 μm or more, more preferably 3 μm or more, further preferably 5 μm or more, and even more preferably 10 μm or more. Also, it is preferably 50 μm or less, and more preferably 30 μm or less.

[0021] The thickness of the Cr2AlC layer is preferably 1 μm or more, more preferably 2 μm or more, further preferably 3 μm or more. Also, it is preferably 30 μm or less, more preferably 20 μm or less, and further preferably 10 μm or less.

[0022] When the thickness of the Cr7C3 layer is 1 μm or more, as described later, it becomes easier to increase the thickness of the Cr2AlC layer when the Cr2AlC layer is formed by diffusion and penetration treatment of aluminum elements into the Cr7C3 layer. In addition, it becomes easier to suppress the formation of an aluminum-iron alloy phase by the reaction between the aluminum elements and the iron elements of the substrate.

[0023] When the thickness of the Cr2AlC layer is 1 μm or more, the wear resistance and corrosion resistance of the Cr2AlC layer can be suitably exhibited. Furthermore, when the thickness of the Cr2AlC layer is 30 μm or less, the Cr2AlC layer becomes less prone to cracking. In addition, the time required to form the Cr2AlC layer can be shortened, thus reducing manufacturing costs.

[0024] The method for measuring the thickness of the coating layer is not particularly limited, but for example, it can be measured by observing the cross-section or fracture surface of the composite material under a microscope. There may be other coating layers between the substrate and the Cr7C3 layer. The other coating layer is not particularly limited, but examples include a metal carbide layer. Specific examples of the metal carbide layer include vanadium carbide and titanium carbide. The metal carbide layer preferably contains carbon. By containing carbon, the Cr2AlC layer can be formed using carbon. The carbon contained in the metal carbide layer is preferably derived from free carbon.

[0025] <Method for manufacturing composite materials> The composite material can be manufactured by the following manufacturing method. The manufacturing method for the composite material comprises a first coating step of forming a Cr7C3 layer on a substrate and a second coating step of forming a Cr2AlC layer on the Cr7C3 layer.

[0026] (First coating process) The first coating step is preferably a step of performing a diffusion and penetration treatment of chromium element onto the substrate. The diffusion and penetration treatment of chromium element can be carried out by filling a container with chromium powder and the substrate, and then heating it in an inert atmosphere. Specifically, the chromium powder and the substrate are filled into a crucible serving as a container, and then a lid is attached to the crucible to seal the inside. This crucible is then heated in a heat treatment furnace in an inert atmosphere.

[0027] The chromium powder may be metallic chromium powder or chromium alloy powder. An example of chromium alloy powder is iron-chromium alloy powder. For example, iron-chromium alloy powder with a chromium content of 50% by mass or more can be used.

[0028] Chromium powder may be mixed with other powders. That is, chromium powder may be a mixed powder with other powders. Other powders include, for example, antisintering agents and reaction accelerators. An example of an antisintering agent is aluminum oxide. An example of a reaction accelerator is ammonium chloride (NH4Cl). Iron powder may also be mixed in as another powder.

[0029] The proportion of each powder in the mixed powder is not particularly limited. The proportion of chromium powder in the mixed powder is preferably 10% by mass or more, more preferably 50% by mass or more. It is also preferably 95% by mass or less, and more preferably 90% by mass or less. By having a chromium powder content of 95% by mass or less in the mixed powder, the sintering of chromium powder to the inner wall of the heat treatment furnace can be effectively suppressed. Furthermore, by having a chromium powder content of 90% by mass or less, the sintering of chromium powder particles to each other can be effectively suppressed.

[0030] The content of the anti-sintering agent in the mixed powder is preferably 30% by mass or more, more preferably 40% by mass or more. Furthermore, it is preferably 70% by mass or less, and more preferably 60% by mass or less.

[0031] The content of the reaction accelerator in the mixed powder is preferably 0.1% by mass or more, more preferably 0.5% by mass or more. Furthermore, it is preferably 10% by mass or less, and more preferably 5% by mass or less.

[0032] The iron powder content in the mixed powder is preferably approximately the same as the chromium powder content. "Approximately the same content" means that the difference in the content of the two is 10% by mass or less. Preferably, the difference in the content of the two is 5% by mass or less.

[0033] The inert atmosphere used in the diffusion and permeation treatment is not particularly limited, but for example, an argon atmosphere or a nitrogen atmosphere can be used. The heating temperature in the diffusion penetration treatment is not particularly limited, and any temperature that allows chromium to diffuse into the substrate can be used as appropriate. The heating temperature is preferably 700°C or higher, more preferably 900°C or higher, and even more preferably 1000°C or higher. Furthermore, it is preferably 1600°C or lower, more preferably 1400°C or lower, and even more preferably 1200°C or lower.

[0034] The heating time in the diffusion and penetration treatment is not particularly limited, but it can be carried out by holding the temperature at the above-mentioned heating temperature for 5 hours or more and 25 hours or less. In the diffusion and penetration treatment, by employing the above heating temperature and heating time, chromium and ammonium chloride can be reacted to produce chromium chloride gas. If the substrate contains iron, this chloride gas diffuses and reacts with the iron on the substrate surface to release chromium, which then penetrates into the substrate, reacting with the carbon contained in the substrate to form a Cr7C3 layer on the substrate surface.

[0035] As described above, the first coating step facilitates the formation of a Cr7C3 layer on the substrate surface, even if the substrate has a complex shape, by performing a diffusion and penetration treatment of chromium element. For example, even if the substrate has irregularities or is cylindrical, the chloride gas can sufficiently reach the substrate surface, making it easier to form a Cr7C3 layer on the irregular surface or the inner surface of the cylindrical body. Furthermore, it becomes easier to make the thickness of the Cr7C3 layer more uniform. The diffusion and penetration treatment in the first coating step is also called the powder pack method.

[0036] The first coating step is not limited to the diffusion and penetration treatment of chromium element into the substrate. For example, a Cr7C3 layer may be formed on the substrate by physical vapor deposition (also known as PVD) or chemical vapor deposition (also known as CVD). For example, if the substrate is aluminum oxide, a Cr7C3 layer may be formed on the aluminum oxide by PVD or CVD.

[0037] Furthermore, the process may include a step of forming the above-described metal carbide layer on the substrate before the first coating step. The method for forming the metal carbide layer is not particularly limited and may be formed by the powder packing method described above, or by PVD or CVD. If the process includes a step of forming the above-described metal carbide layer on the substrate before the first coating step, a Cr7C3 layer can be formed on the metal carbide layer by the powder packing method.

[0038] (Second coating process) The second coating step is a process of performing a diffusion and penetration treatment of aluminum elements on the Cr7C3 layer formed in the first coating step. The diffusion and penetration treatment of aluminum elements can be carried out by filling a container with aluminum powder and the substrate that has undergone the first coating step, and then heating it in an inert atmosphere. Specifically, the aluminum powder and substrate are filled into a crucible serving as a container, and then a lid is attached to the crucible to seal the inside. This crucible can then be heated in a heat treatment furnace in an inert atmosphere.

[0039] As the aluminum powder, aluminum alloy powder can be used. An example of aluminum alloy powder is iron-aluminum alloy powder. For example, iron-aluminum alloy powder with an aluminum element content of 50% by mass or more can be used.

[0040] The aluminum powder may be a mixed powder with other powders, similar to the first coating step. That is, it may be mixed with powders of sintering inhibitors such as aluminum oxide or reaction accelerators such as ammonium chloride.

[0041] The proportions of each powder in the mixed powder are not particularly limited. It is preferable that the proportion of aluminum powder in the mixed powder be about the same as the proportion of chromium powder in the mixed powder of the first coating step. Furthermore, it is preferable that the proportions of the sintering inhibitor and reaction accelerator in the mixed powder be about the same as those in the mixed powder of the first coating step.

[0042] The inert atmosphere used in the diffusion and permeation treatment is not particularly limited, but for example, an argon atmosphere or a nitrogen atmosphere can be used. The heating temperature in the diffusion penetration treatment is not particularly limited, and any temperature that allows aluminum elements to diffuse into the Cr7C3 layer can be used as appropriate. The heating temperature is preferably 800°C or higher, more preferably 880°C or higher, and even more preferably 900°C or higher. Furthermore, it is preferably 1200°C or lower, more preferably 1100°C or lower, and even more preferably 1000°C or lower.

[0043] The heating time in the diffusion penetration treatment is not particularly limited, but can be carried out by holding the product at the above heating temperature for at least 1 hour and no more than 5 hours. The holding time is preferably 4 hours or less, and more preferably 3 hours or less. If the holding time is 4 hours or less, the diffusion of aluminum elements will not easily reach the substrate. Therefore, in a substrate containing iron, it will be difficult for an alloy phase of aluminum and iron to form.

[0044] In the diffusion penetration treatment, by employing the above heating temperature and heating time, aluminum and ammonium chloride can be reacted to produce aluminum chloride gas. This chloride gas diffuses and reacts with Cr7C3 on the substrate surface to release aluminum, and this aluminum penetrates into the Cr7C3 layer, reacting with Cr7C3 to form a Cr2AlC layer on top of the Cr7C3 layer.

[0045] Furthermore, the inclusion of iron elements derived from iron-aluminum alloy powder in the mixed powder slows down the penetration of chloride gas into the Cr7C3 layer. This makes it easier to form a Cr2AlC layer on top of the Cr7C3 layer while maintaining the state in which the Cr7C3 layer is formed on the surface of the substrate.

[0046] Furthermore, if the process includes a step of forming the aforementioned metal carbide layer on the substrate before the first coating step, then a Cr7C3 layer and a Cr2AlC layer can be formed in this order on the metal carbide layer formed on the surface of the substrate.

[0047] As described above, the second coating step facilitates the formation of a Cr2AlC layer on the substrate surface, even if the substrate has a complex shape, by performing a diffusion and penetration treatment of aluminum elements. For example, even if the substrate has an uneven surface or is cylindrical, the chloride gas can sufficiently reach the substrate surface, making it easier to form a Cr2AlC layer on the uneven surface or the inner surface of the cylindrical body. It also makes it easier to make the thickness of the Cr2AlC layer more uniform. The diffusion and penetration treatment in the second coating step is also called the powder pack method.

[0048] Furthermore, the manufacturing method for the composite material has two coating steps, a first coating step and a second coating step, which allows for more reliable formation of the Cr2AlC layer. In addition, since the Cr2AlC layer can be formed in the second coating step while the thickness of the Cr7C3 layer is increased in the first coating step, it becomes easier to increase the thickness of the Cr2AlC layer.

[0049] Furthermore, when forming a Cr7C3 layer and a Cr2AlC layer in this order on an iron-containing substrate, if the penetration of aluminum into the Cr7C3 layer proceeds excessively, the diffusion of the aluminum element reaches the substrate, forming an aluminum-iron alloy phase. Consequently, it becomes difficult for the Cr2AlC to form in a layered manner. Moreover, the substrate surface becomes a mixture of the Cr7C3 phase, the Cr2AlC phase, and the aluminum-iron alloy phase. In this state, the wear resistance and corrosion resistance tend to decrease compared to an embodiment where the coating layer has a Cr7C3 layer and a Cr2AlC layer in that order, closer to the substrate.

[0050] <Applications of composite materials> The applications of the composite material are not particularly limited. Cr2AlC is a material with excellent wear resistance and corrosion resistance, and can therefore be used in applications where wear resistance and corrosion resistance are required. Examples of applications requiring wear resistance and corrosion resistance include chains, pistons and cylinders used in internal combustion engines and electric motors, screws used in injection molding machines, extrusion molding machines, and kneaders. It can also be used in separators for solid-state batteries. Specific examples of chains include power transmission chains used in engines, transport chains used in logistics and transportation, and cable guide chains that protect and guide cables. Furthermore, the composite material can also be used in sprockets, which are components of chains.

[0051] <Mechanism and Effects> The operation and effects of this embodiment will now be described. (1) The manufacturing method of the composite material of this embodiment comprises a first coating step of forming a Cr7C3 layer on a substrate and a second coating step of forming a Cr2AlC layer on the Cr7C3 layer. The first coating step is a step of performing a diffusion penetration treatment of chromium element on the substrate. The second coating step is a step of performing a diffusion penetration treatment of aluminum element on the Cr7C3 layer.

[0052] In the manufacturing method of this embodiment, by performing a diffusion and penetration treatment with chromium, it becomes easier to form a Cr7C3 layer regardless of the shape of the substrate. Furthermore, by performing a diffusion and penetration treatment with aluminum on the Cr7C3 layer, it becomes easier to form a Cr2AlC layer on the Cr7C3 layer regardless of the shape of the substrate. Therefore, the productivity of the Cr2AlC layer can be improved. In addition, the thickness of the Cr2AlC layer can be made more uniform, and a continuous Cr2AlC layer can be formed. Furthermore, it becomes easier to increase the thickness of the Cr2AlC layer.

[0053] (2) The substrate contains 0.02% by mass or more of carbon. The carbon elements contained in the substrate facilitate the formation of a Cr7C3 layer on the substrate surface. Furthermore, it facilitates the formation of a Cr2AlC layer.

[0054] (3) The composite material of this embodiment comprises a base material and a coating layer that covers the base material. The coating layer has a Cr7C3 layer and a Cr2AlC layer in order from the base material. The presence of the Cr2AlC layer makes it suitable for use in applications where abrasion resistance and corrosion resistance are required.

[0055] <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0056] In this embodiment, the mixed powder used for the diffusion and penetration treatment of chromium element contained, among other powders, a sintering inhibitor, a reaction accelerator, and iron powder, but is not limited to this embodiment. At least one of these powders may be omitted.

[0057] In this embodiment, the first coating step and the second coating step were performed by the powder pack method, but the embodiment is not limited to this. At least one of the first coating step and the second coating step may be performed by a method other than the powder pack method. Examples of methods other than the powder pack method include the paste method, the plating heating method, the fluidized bed furnace method, the molten salt method, and so on.

[0058] The mixed powder used in the diffusion and penetration treatment of chromium element may contain powders other than those specified in this embodiment. Examples of powders other than those specified in this embodiment include carbon powder. Carbon powder can be used to form a Cr7C3 layer on the substrate surface by reacting it with chromium powder. For example, if the substrate containing iron does not contain carbon, or has a carbon content of less than 0.02% by mass, a Cr7C3 layer can be formed on the substrate surface by reacting chromium powder and carbon powder. In other words, the first coating step of this embodiment is not limited to a method of performing a diffusion and penetration treatment of chromium element on an iron-containing substrate. Instead of a method of performing a diffusion and penetration treatment of chromium element on an iron-containing substrate, a method of forming a Cr7C3 layer on the substrate by reacting chromium powder and carbon powder may be adopted. [Examples]

[0059] The following are examples to illustrate the structure and effects of the present invention in more detail, but the present invention is not limited to these examples. (Example 1) As a base material containing iron, a pin made of iron with a diameter of approximately 3 mm and a length of approximately 10 mm was prepared, with a chemical composition of carbon: 0.59-0.66 mass%, silicon: 0.15-0.35 mass%, manganese: 0.60-0.90 mass%, phosphorus: 0.030 mass% or less, sulfur: 0.030 mass% or less, and the remainder being iron and unavoidable impurities. This pin was placed in a bottomed cylindrical porous crucible, and a mixed powder containing chromium powder was filled in so that the pin was embedded. The mixed powder used was a mixture of commercially available iron-chromium alloy powder with a chromium element content of 50 mass% or more, commercially available aluminum oxide powder, and commercially available ammonium chloride powder.

[0060] The mass ratio of iron-chromium alloy powder, aluminum oxide powder, and ammonium chloride powder in the mixed powder was 5:1:1. Next, a lid was attached to the open end of the porous crucible using alumina cement to seal it. After the alumina cement hardened, the porous crucible was placed in a known heat treatment furnace and held at 1000°C for 5 hours under an argon atmosphere to perform the first coating process.

[0061] After cooling, the substrate was removed from the porous crucible. This substrate was placed in a bottomed cylindrical porous crucible, and a mixed powder containing aluminum powder was filled in so that the pins were embedded. The mixed powder consisted of 18.5 g of commercially available iron-aluminum alloy powder with an aluminum element content of 50% by mass or more, 27.8 g of commercially available aluminum oxide powder, and 1.7 g of commercially available ammonium chloride powder.

[0062] The iron-aluminum alloy powder content in the mixed powder was approximately 38% by mass, the aluminum oxide powder content was approximately 58% by mass, and the ammonium chloride powder content was approximately 4% by mass.

[0063] A lid was attached to the open end of the porous crucible using alumina cement to seal it. After the alumina cement hardened, the porous crucible was placed in a known heat treatment furnace and held at 900°C for 3 hours under an argon atmosphere to perform the second coating process. After cooling, the substrate was removed from the porous crucible to obtain a composite material.

[0064] (Comparative Example 1) The composite material was prepared in the same manner as in Example 1, except that the holding time in the second coating step was changed to 10 hours.

[0065] (Evaluation test) The composite materials of Example 1 and Comparative Example 1 were observed in cross-section after the first and second coating processes using a known scanning electron microscope (SEM). The results are shown in Figures 1 and 2.

[0066] Furthermore, the crystal structure of the composite material of Example 1 was analyzed on the surface using a known X-ray diffraction apparatus (also known as an XRD apparatus). For comparison, the X-ray diffraction lines of Cr2AlC are also shown. The results are shown in Figure 3.

[0067] Furthermore, the calculation results of the three-dimensional phase diagrams of iron, chromium, and carbon at 700°C, 1000°C, and 1200°C are shown in Figures 4 to 6, respectively. The three-dimensional phase diagrams were calculated using "Thermo-Calc," a well-known thermodynamic calculation software.

[0068] Figure 1 shows a cross-sectional photograph of the composite material of Example 1 after the second coating process. A first layer with a thickness of approximately 15 μm was observed on the substrate. Furthermore, a second layer with a thickness of approximately 2.5 μm to 5 μm was observed on top of the first layer. The boundary between the first and second layers was clearly defined, and it was confirmed that each layer was composed of a uniform composition in appearance.

[0069] In Figure 3, the locations indicated by multiple arrows are the peak positions of the X-ray diffraction lines of Cr2AlC used for comparison. As shown in Figure 3, it was confirmed that a Cr2AlC layer exists on the outermost surface of the composite material in Example 1.

[0070] As shown in Figures 4-6, it was found that Cr7C3 exists in a stable state in the three-dimensional system of iron, chromium, and carbon at 700°C, 1000°C, and 1200°C. Therefore, it was suggested that in both Example 1 and Comparative Example 1, a Cr7C3 layer is formed on the surface of the substrate after the first coating step. Furthermore, in Example 1, it was suggested that a Cr2AlC layer is formed on top of the Cr7C3 layer.

[0071] Furthermore, as shown in Figures 4-6, even if the Cr7C3 layer in Example 1 contained (Cr,Fe)7C3, the Cr7C3 layer was maintained even after the second coating process. Therefore, it was suggested that the Cr content in (Cr,Fe)7C3 was 30 at% or more, and the Fe content was 40 at% or less.

[0072] Figure 2 shows a cross-sectional photograph of the composite material of Comparative Example 1 after the second coating process. As shown in Figure 2, a layer presumed to be Cr7C3 was observed on the substrate. Furthermore, a phase presumed to be FeAl was observed mixed within the Cr7C3 layer. In addition, a phase presumed to be a mixture of Cr2AlC and FeAl was observed on top of the Cr7C3 layer. The phase containing the mixture of Cr2AlC and FeAl had uneven thickness and discontinuous areas. Therefore, it was confirmed that Cr2AlC did not form a layer.

Claims

1. With respect to the substrate, Cr ７ C ３ A first coating step to form a layer, The aforementioned Cr ７ C ３ Cr on the layer ２ The process includes a second coating step of forming an AlC layer, The second coating step is the Cr ７ C ３ A method for manufacturing a composite material, characterized by a step of performing a diffusion and permeation treatment of aluminum elements on the layers.

2. The method for producing a composite material according to claim 1, wherein the first coating step is a step of performing a diffusion and penetration treatment of chromium element on the substrate.

3. A method for producing a composite material according to claim 1, further comprising the step of forming a metal carbide layer on the substrate before the first coating step.

4. The method for producing a composite material according to claim 1, wherein the substrate contains 0.02% by mass or more of carbon.

5. A composite material having a base material and a coating layer covering the base material, The coating layer has, in order from closest to the base material, a Cr ７ C ３ layer and a Cr ２ AlC layer, and is a composite material characterized thereby.

6. The substrate and the Cr ７ C ３ The composite material according to claim 5, having a metal carbide layer between the layers.

7. The composite material according to claim 5, wherein the base material contains 0.02% by mass or more of carbon.

Images