Aluminum-containing metal powder for plasma spraying

Abstract

Embodiments of the present invention disclose an aluminum-containing metal powder for plasma spraying, relating to the field of high-temperature plasma application technology. The metal powder comprises an aluminum-containing base alloy and a carbon source present in the aluminum-containing base alloy in various forms. When the metal powder is heated to ≤2000°C by a high-temperature plasma jet in an atmospheric atmosphere, the aluminum in the aluminum-containing base alloy is preferentially oxidized to form aluminum oxide. When the metal powder is heated to >2000°C by a high-temperature plasma jet in an atmospheric atmosphere, a portion of the carbon source is preferentially oxidized to form carbon oxides that volatilize, while another portion of the carbon source reduces the aluminum oxide to elemental aluminum. After the metal powder is heated to molten particles exceeding 2000°C by a high-temperature plasma jet in an atmospheric atmosphere, it can be sprayed onto the surface of a substrate to be protected to form a uniform and consistent aluminum-containing coating.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature plasma application and the field of metal material manufacturing, and in particular to aluminum-containing metal powder used for plasma spraying. Background Art

[0002] Plasma spraying is a method that uses a high-speed, high-temperature plasma jet with a temperature of approximately 3000°C to 10,000°C to heat the powder particles fed into it to a completely melted or semi-melted state, accelerate the formation of a high-speed molten droplet flow, and spray the high-speed molten droplet flow onto the surface of the substrate, so that the high-speed molten droplet flow is deposited on the surface of the substrate to form a coating.

[0003] When plasma spraying is carried out in a large atmosphere, when a high-temperature plasma jet is ejected from the spray gun at high speed and flies in the atmosphere, it naturally draws in atmospheric components. As the distance between the jet and the spray gun increases, the content of atmospheric components gradually increases. When the distance increases to more than 50 mm, the proportion of atmospheric components in the high-temperature plasma jet will exceed 50%, making the high-temperature plasma flame oxidizing, and the oxidizing property increases with the increase of distance. Therefore, when plasma spraying metal alloy powder to prepare a metal alloy coating, oxidation will occur, so that the coating contains metal oxide components, resulting in poor quality of the coating and difficulty in ensuring consistency. Analyzing the reasons, first of all, the wettability of metal oxides and molten metal alloys is generally poor. The inclusion of oxides in the coating will cause the interlayer bonding of the deposited particles to deteriorate, which not only increases the porosity of the coating and causes the coating to lose its corrosion protection to the substrate, but also reduces the mechanical properties and wear resistance of the coating. This is because, when the oxidized spray particles are in flight, due to the high melting point and high viscosity of the oxides, they will accumulate in lumps on the particle surface during the deposition process, hindering the spreading of the molten particles along the substrate surface, causing interference and changing the spreading direction, thereby inducing a shielding effect and producing pore inclusions. Secondly, the presence of oxides hinders the direct contact between the spreading metal and the previously deposited and cooled and solidified metal, preventing the formation of metal bonds between the particles. Because the molten metal and the oxides have poor wettability, it is difficult for the molten metal to form a strong chemical bond with the oxides during rapid spreading and cooling. The interface that exists with weak bonding will undergo interface separation during subsequent cooling to form an unbonded interface. The presence of oxides not only causes the composition and structure of the coating to deviate from the expected design composition and structure, but also due to the complexity of the influence of many process factors during the spraying process, the oxide content and distribution in the coating are difficult to control, making it difficult to ensure the consistency of the coating's structure and performance.

[0004] To enhance interparticle bonding within the coating, improve coating performance, improve coating quality consistency by modifying coating composition, and reduce oxidation in plasma-sprayed alloys, one method employed is to spray in an inert gas-protected chamber, i.e., vacuum plasma spraying, also known as low-pressure plasma spraying, to prevent oxidation during spraying. However, due to the limitations of the protected chamber, this method significantly increases equipment investment and operating costs, making it suitable only for spraying certain structural parts where cost is not a concern. Even so, the limited chamber size limits not only spraying flexibility but also the size of the structural workpiece that can be sprayed. Another method is to use a gas shield to protect the plasma. An air- or water-cooled shield is attached to the plasma spray gun to isolate the high-temperature plasma jet from contact and air entrapment. However, gas shield protection also requires the addition of a protective cooling gas, which increases costs and is only suitable for spraying relatively regular structural parts, such as those with nearly flat substrate surfaces. Therefore, how to solve the oxidation of molten metal alloy particles during direct plasma spraying in a large atmosphere is an important problem that researchers and technicians in this field have not yet solved.

[0005] Especially for metal alloys containing aluminum (Al), since Al is easily oxidized by oxygen, when the high-temperature molten droplet contains Al element, Al oxidation will occur to form aluminum oxide, and it will be mixed in the coating during the collision and deposition process of the molten particles, causing the aforementioned increase in the porosity of the coating and reducing the bonding between the deposited particles, causing the coating to lose its corrosion protection effect on the base material. Summary of the Invention

[0006] The embodiment of the present invention provides an aluminum-containing metal powder for plasma spraying to solve the problems of poor coating quality caused by oxidation of aluminum-containing molten particles in current plasma spraying and difficulty in ensuring coating quality consistency and uniformity.

[0007] In order to solve the above problems, an embodiment of the present invention discloses an aluminum-containing metal powder for plasma spraying, comprising:

[0008] A base alloy containing aluminum, and a carbon source present in the base alloy containing aluminum in various forms, wherein:

[0009] When the metal powder is heated to ≤2000° C. by a high-temperature plasma jet in an atmospheric atmosphere, the aluminum element in the aluminum-containing basic alloy is preferentially oxidized to form aluminum oxide;

[0010] When the metal powder is heated to >2000° C. by a high-temperature plasma jet in an atmospheric atmosphere, a portion of the carbon source is preferentially oxidized to form carbon oxides that volatilize, while another portion of the carbon source reduces the aluminum oxide to aluminum element.

[0011] In an embodiment of the present invention, the basic alloy containing aluminum elements includes at least one of an aluminum-based alloy, a metal alloy containing aluminum alloy elements, an alloy of aluminum and other metals forming an intermetallic compound, and an alloy containing an aluminide intermetallic compound.

[0012] In an embodiment of the present invention, the aluminum-based alloy includes pure aluminum and aluminum alloy.

[0013] In an embodiment of the present invention, the metal alloy containing aluminum alloy elements includes an aluminum-containing copper alloy, an aluminum-containing iron-based alloy, an aluminum-containing nickel-based alloy, an aluminum-containing cobalt-based alloy, or an aluminum-containing titanium alloy.

[0014] In an embodiment of the present invention, the alloy of aluminum and other metals forming an intermetallic compound includes:

[0015] Intermetallic compounds of aluminum and other metals, or

[0016] A metal alloy containing intermetallic compounds of aluminum and other metals.

[0017] In an embodiment of the present invention, the carbon source present in the aluminum-containing basic alloy in different forms includes:

[0018] Carbon dissolved in the aluminum-containing base alloy in the form of solid solution, or

[0019] A graphite or diamond phase in the form of carbon allotropes compounded in the base alloy containing the aluminum element, or

[0020] The carbides are compounded in the base alloy containing aluminum in the form of particles.

[0021] In the embodiment of the present invention, the particle size of the metal powder is any value between 10 and 100 μm.

[0022] In an embodiment of the present invention, the content of the carbon source in the metal powder is any value between 1 wt % and 10 wt %.

[0023] The embodiments of the present invention include the following advantages:

[0024] An embodiment of the present invention provides an aluminum-containing metal powder suitable for plasma spraying. The metal powder comprises an aluminum-containing base alloy and a carbon source present in various forms within the aluminum-containing base alloy. During plasma spraying in an atmospheric atmosphere, the metal powder can be heated by a high-temperature plasma jet until it melts, forming oxide-free, high-temperature molten particles. The specific principle is that when the metal powder is heated by the high-temperature plasma jet to ≤2000°C in an atmospheric atmosphere, the aluminum in the aluminum-containing base alloy is preferentially oxidized to form aluminum oxide. When the metal powder is heated by the high-temperature plasma jet to >2000°C in an atmospheric atmosphere, a portion of the carbon source is preferentially oxidized, forming carbon oxides that volatilize, while another portion of the carbon source reduces the aluminum oxide to elemental aluminum. Spraying the oxide-free, high-temperature molten particles onto the surface of a substrate of the corresponding material can form a uniform and consistent aluminum-containing coating, effectively addressing the current problem of poor coating quality caused by oxidation of aluminum-containing molten particles in plasma spraying. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 The cross-sectional structure of the Ni-Al based coating prepared by the metal powder of the embodiment of the present invention is Figure 1 ;

[0027] Figure 2 The cross-sectional structure of the Ni-Al based coating prepared by the metal powder of the embodiment of the present invention is Figure 2 . DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] In response to the technical problems of the present invention, an embodiment of the present invention provides an aluminum-containing metal powder for use in plasma spraying. During plasma spraying in an atmospheric atmosphere, the metal powder can be heated by a high-temperature plasma jet to melt to form molten particles, and then sprayed onto the surface of a substrate of a corresponding material to form an aluminum-containing coating with consistent and uniform coating quality. This can effectively solve the problem of poor coating quality caused by oxidation of aluminum-containing molten particles in the current plasma spraying.

[0030] Specifically, the metal powder includes: a basic alloy containing aluminum elements, and a carbon source present in the basic alloy containing aluminum elements in different forms, wherein: when the metal powder is heated to ≤2000°C by a high-temperature plasma jet in an atmospheric atmosphere, the aluminum element in the basic alloy containing aluminum elements is preferentially oxidized to form aluminum oxide; when the metal powder is heated to >2000°C by a high-temperature plasma jet in an atmospheric atmosphere, a portion of the carbon source is preferentially oxidized to form carbon oxides that volatilize, and another portion of the carbon source reduces the aluminum oxide to elemental aluminum.

[0031] In the concept of the embodiment of the present invention, when the metal powder is heated to a temperature below 2000°C, the aluminum element in the aluminum-containing base alloy is preferentially oxidized to form aluminum oxide, utilizing the characteristics of aluminum's active chemical properties and easy oxygen affinity, while carbon will not be oxidized at this temperature. This protects other alloying elements in the metal powder from oxidation below 2000°C. When the metal powder is heated to a molten state above 2000°C by a high-temperature plasma jet in an atmospheric atmosphere, the carbon source in the metal powder will preferentially react with oxygen adsorbed on the surface of the molten particles to form carbon oxides that volatilize, thereby protecting other alloying elements in the metal powder from oxidation above 2000°C. At the same time, at this temperature, the carbon source also reduces the aluminum oxide formed in the early stage to aluminum element and carbon oxides. The carbon oxides volatilize, thereby removing oxygen from the aluminum oxide, achieving further deoxidation of the molten particles before reaching the substrate surface, thereby effectively improving the quality of the aluminum-containing coating finally formed.

[0032] The basic alloy containing aluminum includes alloy matrix phase elements, elemental metal elements, and auxiliary components. Specifically, the basic alloy containing aluminum includes at least one of an aluminum-based alloy, a metal alloy containing aluminum alloying elements, an alloy in which aluminum forms an intermetallic compound with other metals, and an alloy containing an aluminumide intermetallic compound. The aluminum-based alloy includes pure aluminum or an aluminum alloy with aluminum as the main component; the metal alloy containing aluminum alloying elements is a metal alloy with other metal elements as the matrix and aluminum as the alloying element, such as an aluminum-containing copper alloy, an aluminum-containing iron-based alloy, an aluminum-containing nickel-based alloy, an aluminum-containing cobalt-based alloy, or an aluminum-containing titanium alloy; the alloy in which aluminum forms an intermetallic compound with other metals includes an intermetallic compound formed by aluminum and other metals, such as NiAl or Ni3Al, or a metal alloy containing an intermetallic compound formed by aluminum and other metals, such as a nickel-based high-temperature alloy.

[0033] The carbon source exists in the aluminum-containing base alloy in different forms, including carbon dissolved in the aluminum-containing base alloy in the form of solid solution, or graphite or diamond phase compounded in the aluminum-containing base alloy in the form of carbon allotropes, or carbide compounded in the aluminum-containing base alloy in the form of particles.

[0034] In an embodiment of the present invention, the particle size of the metal powder is any value between 10 and 100 μm, so as to effectively heat the metal powder to above 2000° C.

[0035] In the metal powder, the content of the carbon source is any value between 1wt% and 10wt%, which not only ensures the carbon content in the metal powder for anti-oxidation, but also retains more carbon for alloys containing carbide-forming elements, forming carbides with a strengthening effect; or retains some carbon in the form of graphite, which can achieve lubrication and friction reduction.

[0036] To illustrate the effects of the metal powder of the embodiments of the present invention, some specific examples are used below for illustration:

[0037] Example 1

[0038] Pure aluminum (Al) powder and micron-sized tungsten carbide (WC) particles were used as the carbon source to prepare Al-WC metal powder containing 15wt% WC through mechanical alloying. The powder particle size was 30-60μm. Al-WC metal powder was sprayed by atmospheric plasma at an arc power of 30kW to prepare an aluminum-based coating. Observation of the aluminum-based coating revealed that the cross-section of the coating was dense and no oxides were observed in the structure. It should be noted that the 15wt% content refers to the tungsten carbide content, while the carbon content at this time is still between 1wt% and 10wt%.

[0039] Example 2

[0040] The metal powder of the embodiment of the present invention is a Ni-Al composite powder with a size of 15 to 37 μm and containing 2 wt% micron-sized diamond. The Ni-Al composite powder is sprayed by atmospheric plasma and a Ni-Al-based coating is prepared under the condition of an arc power of 36 kW. The cross-sectional structure of the coating is as follows: Figure 1 and Figure 2 As shown, the coating was found to be dense without obvious oxide inclusions.

[0041] Example 3

[0042] The metal powder in this embodiment of the present invention is a nickel-chromium-aluminum-yttrium (NiCrAlY) superalloy powder with a particle size of 20 to 70 μm and containing 3 wt% micron-sized diamond. A Ni-Al-based superalloy coating was produced by atmospheric plasma spraying of this NiCrAlY superalloy powder at a spraying distance of 120 mm and an arc power of 38 kW. Observation of the Ni-Al-based superalloy coating revealed a dense coating with no apparent oxide inclusions.

[0043] Example 4

[0044] The metal powder of the present invention is an iron-chromium-aluminum (FeCrAl) high-temperature alloy powder with a size of 37 to 70 μm and containing 20 wt% of micron-sized chromium carbide (Cr3C2) as a carbon source. The FeCrAl alloy coating was produced by atmospheric plasma spraying at a spray distance of 100 mm and an arc power of 42 kW. Observation of the FeCrAl alloy coating revealed a dense coating with no apparent oxide inclusions in the cross-section. It should be noted that the 20 wt% content refers to the chromium carbide content, while the carbon content at this point is still between 1 wt% and 10 wt%.

[0045] In summary, the four embodiments provided by the present invention include Al, NiAl (intermetallic compound), nickel-based alloy, iron-based alloy and two different forms of carbon sources. The above embodiments fully illustrate that the embodiments of the present invention provide an aluminum-containing metal powder for plasma spraying, which can be heated to melt by a high-temperature plasma jet to form molten particles during plasma spraying under an atmospheric atmosphere, and can form a uniform aluminum alloy coating with consistent coating quality on the surface of a substrate of the corresponding material, which can effectively solve the problem of poor coating quality caused by oxidation of aluminum-containing molten particles in the current plasma spraying.

[0046] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referenced to each other.

[0047] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0048] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or terminal device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or terminal device that includes the element.

[0049] The technical solution provided by the present invention is introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of the present invention, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An application of aluminum-containing metal powder in plasma spraying under atmospheric atmosphere, characterized in that: Aluminum-containing metal powders include: A base alloy containing aluminum, wherein a diamond phase in the base alloy containing aluminum is compounded in the form of carbon allotropes as a carbon source, wherein during plasma spraying in an atmospheric atmosphere, the metal powder is heated by a high-temperature plasma jet until it melts to form high-temperature molten particles free of oxides, wherein: When the metal powder is heated to ≤2000° C. by a high-temperature plasma jet in an atmospheric atmosphere, the aluminum element in the aluminum-containing basic alloy is preferentially oxidized to form aluminum oxide; When the metal powder is heated to a molten state of more than 2000°C by a high-temperature plasma jet in an atmospheric atmosphere, a portion of the carbon source in the molten particles is preferentially oxidized to form carbon oxides that volatilize, while another portion of the carbon source reduces the aluminum oxide to aluminum element. The aluminum-containing basic alloy is compounded in the aluminum-containing basic alloy in the form of a carbon allotrope, and is a Ni-Al composite powder containing 2wt% micron-sized diamonds and having a size of 15 to 37μm, or a nickel-chromium-aluminum-yttrium high-temperature alloy powder containing 3wt% micron-sized diamonds and having a size of 20 to 70μm.

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