Preparation method of nickel-aluminum coating

Abstract

The invention discloses a method for preparing a nickel-aluminum coating. First, a nickel-aluminum core wire material is obtained, and an anti-wire-jamming treatment is performed on the nickel-aluminum core wire material; then a workpiece to be sprayed is obtained, and a surface treatment is performed on the workpiece to be sprayed; an oxygen-acetylene flame spraying process is adopted to spray the workpiece surface to obtain the nickel-aluminum coating, and the wire feeding rate is 800-1100 mm / min, and the oxygen flow rate: the acetylene flow rate is 1.06-1.09; finally, the nickel-aluminum coating on the surface of the sprayed workpiece is verified; in this scheme, the nickel-aluminum coating is prepared by adopting the nickel-aluminum core wire material, and specific process parameters are selected to realize the spraying processing of the nickel-aluminum core wire material. Compared with the prior art, the coating prepared by the nickel-aluminum core wire material has fewer unmelted particles, smaller unmelted particles, lower interface pollution and higher microhardness, can significantly improve the coating quality, meet the process requirements, and is suitable for the preparation of the nickel-aluminum coating of components such as an axial flow casing, an impeller cover, and a labyrinth sealing sleeve of an aero-engine.

Description

Technical Field

[0001] The invention relates to the technical field of aviation engine metal coatings, and in particular to a method for preparing a nickel-aluminum coating. Background Art

[0002] In the context of pursuing long life and high performance of aircraft engine manufacturing, improving the quality of aircraft engine coating is one of the important ways. Nickel-aluminum coating is a commonly used coating on aircraft engines. It can be used as a bonding layer on the surface of compressor components. Its quality affects the life and performance of aircraft engines.

[0003] However, the coating prepared by traditional nickel-aluminum 20% powder core wire has problems such as too many unmelted particles (7-9%), large maximum unmelted particle size (40μm), high interface contamination (13-15%), and low hardness (HV0.3232), which seriously affect the life and performance of aircraft engines.

[0004] Nowadays, a nickel-aluminum core wire has been developed that has advantages over nickel-aluminum powder core wire in terms of manufacturing process, composition control and storage. However, due to the inconsistency between the wire diameter, structure and organization of the new nickel-aluminum core wire and the traditional nickel-aluminum 20% powder core wire, the existing wire spraying method cannot achieve the spraying of the new nickel-aluminum core wire. Summary of the invention

[0005] The invention provides a method for preparing a nickel-aluminum coating, so as to solve the technical problems that the existing nickel-aluminum coating prepared by using nickel-aluminum powder core wire has too many unmelted particles, too large maximum unmelted particle size, high interface contamination and low hardness.

[0006] According to one aspect of the present invention, a method for preparing a nickel-aluminum coating is provided, which specifically comprises the following steps: S1, obtaining a nickel-aluminum core wire material, and performing an anti-wire-jamming treatment on the nickel-aluminum core wire material; S2, obtaining a workpiece to be sprayed, and performing a surface treatment on the workpiece to be sprayed; S3, spraying the workpiece surface with an oxygen-acetylene flame spraying process to obtain a nickel-aluminum coating, comprising the following spraying process parameters: a wire feeding rate of 800-1100 mm / min, an oxygen flow rate: an acetylene flow rate of 1.06-1.09; S4, verifying the nickel-aluminum coating on the surface of the sprayed workpiece.

[0007] As a further improvement of the above technical solution:

[0008] Furthermore, in step S3, the following spraying process parameters are also included: oxygen pressure is 2.38-2.45 bar, oxygen flow rate is 40-40.5 L / min, acetylene pressure is 1-1.05 bar, and acetylene flow rate is 37-37.5 L / min.

[0009] Furthermore, in step S3, the following spraying process parameters are also included: air pressure is 4.8-4.85 bar, and air flow rate is 727-735 L / min.

[0010] Furthermore, in step S3, the following spraying process parameters are also included: the spraying distance is 150 mm.

[0011] Furthermore, in step S1, a nickel-aluminum core wire material having an aluminum content of 18.7% and a nickel content of 79.8%-81.3% is obtained.

[0012] Furthermore, in step S1, a nickel-aluminum core wire with a wire diameter of 3.01-3.04 mm and a roundness of 0.02 is obtained.

[0013] Furthermore, in step S1, the wire-jamming prevention process specifically includes the following steps: placing the nickel-aluminum core wire in a wire feeding device, and using a hanging device to pull the nickel-aluminum core wire so that the nickel-aluminum core wire and the wire feeding device are on the same horizontal plane.

[0014] Further, step S2 specifically includes the following steps: S201, cleaning the workpiece to be sprayed; S202, performing sandblasting protection on the non-sandblasting area of ​​the surface of the workpiece to be sprayed; S203, roughening the sandblasting area of ​​the surface of the workpiece to be sprayed; S204, performing spraying protection on the non-spraying area of ​​the workpiece to be sprayed.

[0015] Furthermore, step S4 specifically includes the following steps: S401, preparing a metallographic sample; S402, observing the coating structure; S403, measuring the microhardness of the coating.

[0016] Further, in step S4, the thickness of the nickel-aluminum coating is 150-250 μm.

[0017] The present invention has the following beneficial effects:

[0018] The preparation method of the nickel-aluminum coating of the present invention comprises the following steps: firstly obtaining a nickel-aluminum core wire material, and performing an anti-wire-stuck treatment on the nickel-aluminum core wire material to prevent the nickel-aluminum core wire material from getting stuck at the spray gun nozzle during the subsequent spraying treatment. The nickel-aluminum core wire material has advantages over the existing nickel-aluminum powder core wire material in manufacturing process, component control and storage, and is convenient for preparing the coating and ensuring the coating quality; then obtaining a workpiece to be sprayed, and performing a surface treatment on the workpiece to be sprayed, so that the surface quality of the workpiece to be sprayed meets the spraying process requirements, thereby indirectly improving the coating quality; and then adopting an oxygen-acetylene flame spraying process to spray the workpiece surface to obtain the nickel-aluminum coating, wherein the wire feeding rate determines the time for the wire material to contact oxygen and acetylene. When the wire feeding rate is 800-1100 mm / min, the aluminum skin is not easy to oxidize, and the coating quality is high; when the wire feeding rate is greater than 1100 mm / min, the wire material contacts oxygen and acetylene for too long, and the aluminum skin is prone to generate oxygen, thereby hindering the reaction of nickel and aluminum; when the wire feeding rate is less than 800 mm / min, the nickel The aluminum coating formation process is not connected, the nickel-aluminum coating is easy to oxidize, and the coating quality is low; when the oxygen flow rate: acetylene flow rate is between 1.06-1.09, the wire burns fully, nickel and aluminum can complete the exothermic reaction to effectively form nickel-aluminum intermetallic compounds to ensure the coating quality; when the oxygen flow rate: acetylene flow rate is greater than 10.9 or less than 1.06, the wire burns incompletely, nickel and aluminum cannot complete the exothermic reaction, and nickel-aluminum intermetallic compounds cannot be effectively formed, and the coating quality is low; finally, the nickel-aluminum coating on the surface of the sprayed workpiece is checked to ensure the quality of the nickel-aluminum coating; this scheme prepares the nickel-aluminum coating by using nickel-aluminum core wire material, and selects specific process parameters to realize the spraying processing of the nickel-aluminum core wire material. Compared with the prior art, the coating prepared by the nickel-aluminum core wire material has fewer unmelted particles, smaller unmelted particles, lower interface contamination and higher microhardness, which can significantly improve the coating quality and meet the process requirements. It is suitable for the preparation of nickel-aluminum coatings for aircraft engine axial flow casings, impeller covers, labyrinth sealing sleeves and other components.

[0019] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0021] Figure 1 It is a flowchart of the steps of the method for preparing the nickel-aluminum coating according to the preferred embodiment of the present invention; DETAILED DESCRIPTION

[0022] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0023] Figure 1 It is a flowchart of the steps of the method for preparing the nickel-aluminum coating according to the preferred embodiment of the present invention;

[0024] like Figure 1As shown, the preparation method of the nickel-aluminum coating of the present embodiment specifically includes the following steps: S1, obtaining a nickel-aluminum core wire material, and performing an anti-wire-stuck treatment on the nickel-aluminum core wire material; S2, obtaining a workpiece to be sprayed, and performing a surface treatment on the workpiece to be sprayed; S3, spraying the workpiece surface with an oxygen-acetylene flame spraying process to obtain a nickel-aluminum coating, including the following spraying process parameters: a wire feeding rate of 800-1100 mm / min, an oxygen flow rate: an acetylene flow rate of 1.06-1.09; S4, verifying the nickel-aluminum coating on the surface of the sprayed workpiece. Specifically, the preparation method of the nickel-aluminum coating of the present invention first obtains a nickel-aluminum core wire material, and performs an anti-wire-stuck treatment on the nickel-aluminum core wire material to prevent the nickel-aluminum core wire material from getting stuck at the spray gun nozzle during the subsequent spraying treatment. The nickel-aluminum core wire material has advantages over the existing nickel-aluminum powder core wire material in manufacturing process, component control and storage, which is convenient for preparing the coating and ensuring the coating quality; then a workpiece to be sprayed is obtained, and a surface treatment is performed on the workpiece to be sprayed so that the surface quality of the workpiece to be sprayed meets the requirements of the spraying process, thereby indirectly improving the coating quality; and then an oxygen-acetylene flame spraying process is used to spray the workpiece surface to obtain the nickel-aluminum coating, wherein the wire feeding rate determines the time for the wire to contact oxygen and acetylene. When the wire feeding rate is 800-1100mm / min, the aluminum skin is not easily oxidized and the coating quality is high; when the wire feeding rate is greater than 1100mm / min, the wire contacts oxygen and acetylene for too long, and the aluminum skin is prone to produce oxygen, which hinders the reaction of nickel and aluminum; when the wire feeding rate is less than 800mm / min , the nickel-aluminum coating formation process is not connected, the nickel-aluminum coating is easy to oxidize, and the coating quality is low; when the oxygen flow rate: acetylene flow rate is between 1.06-1.09, the wire burns fully, nickel and aluminum can complete the exothermic reaction to effectively form nickel-aluminum intermetallic compounds to ensure the coating quality; when the oxygen flow rate: acetylene flow rate is greater than 1.09 or less than 1.06, the wire burns incompletely, nickel and aluminum cannot complete the exothermic reaction, and nickel-aluminum intermetallic compounds cannot be effectively formed, and the coating quality is low; finally, the nickel-aluminum coating on the surface of the sprayed workpiece is checked to ensure the quality of the nickel-aluminum coating; this scheme prepares the nickel-aluminum coating by using nickel-aluminum wire core wire, and selects specific process parameters to realize the spraying processing of the nickel-aluminum wire core wire. Compared with the prior art, the coating prepared by the nickel-aluminum wire core wire has fewer unmelted particles, smaller unmelted particles, lower interface contamination and higher microhardness, which can significantly improve the coating quality and meet the process requirements. It is suitable for the preparation of nickel-aluminum coatings for components such as aircraft engine axial flow casings, impeller covers, and labyrinth sealing sleeves. It should be understood that since the nickel-aluminum wire core wire material is an aluminum-clad nickel core structure, the preparation process is two steps of drawing and rolling, while the nickel-aluminum powder core wire material is an aluminum-clad nickel-aluminum powder structure, the preparation process is three steps of mixed powder bonding, drawing and rolling, among which the powder drawing process is difficult and has a low yield rate. Therefore, in terms of manufacturing process, nickel-aluminum wire core wire material has more advantages.It should be understood that the nickel-aluminum wire core wire is composed of aluminum skin and nickel core, and the material composition and uniformity are easy to control. The nickel-aluminum powder core wire is composed of aluminum skin and nickel-aluminum powder. The composition uniformity is affected by the drawing process and it is difficult to achieve uniform distribution. Therefore, in terms of composition control, the nickel-aluminum wire core wire has more advantages. It should be understood that the nickel-aluminum wire core wire is an aluminum skin-wrapped nickel wire, and the nickel-aluminum powder core wire is an aluminum skin-wrapped nickel-aluminum powder. When the wire is bent, the nickel-aluminum wire core wire will not fall off, and the powder core of the nickel-aluminum powder core wire will fall off, causing the wire composition to change. Therefore, in terms of storage, the nickel-aluminum wire core wire has more advantages. It should be understood that the oxygen-acetylene spraying process is a typical thermal spraying technology, with simple equipment, easy operation, low cost, and good quality of the obtained coating. It should be understood that by adopting the spraying method of this scheme to spray the nickel-aluminum wire core wire to obtain the nickel-aluminum coating, the flame flow is stable during the spraying process, and the process stability is high. Preferably, the oxygen flow rate: acetylene flow rate is 1.08.

[0025] In this embodiment, in step S3, the following spraying process parameters are also included: oxygen pressure is 2.38-2.45 bar, oxygen flow rate is 40-40.5 L / min, acetylene pressure is 1-1.05 bar, and acetylene flow rate is 37-37.5 L / min. Specifically, when the oxygen content is too large relative to acetylene, aluminum will be severely oxidized, affecting the reaction of aluminum and nickel; when the oxygen content is too small relative to acetylene, acetylene will not burn fully, and the combustion temperature cannot reach the melting point of nickel 1453°C in time, thereby preventing the reaction of aluminum and nickel; therefore, by selecting oxygen pressure of 2.38-2.45 bar, oxygen flow rate of 40-40.5 L / min, acetylene pressure of 1-1.05 bar, and acetylene flow rate of 37-37.5 L / min, the oxygen content is appropriate relative to acetylene to avoid severe oxidation of aluminum and affect the reaction of aluminum and nickel, while making acetylene burn fully, ensuring the combustion temperature, and realizing the reaction of aluminum and nickel. It should be understood that the oxygen pressure controls the oxygen flow rate, and then controls the oxygen flow rate. It should be understood that the acetylene pressure controls the acetylene flow rate, and thus controls the acetylene flow rate. It should be understood that the oxy-acetylene flame spraying of nickel-aluminum wire is a spraying process that uses the reaction of oxygen and acetylene. During the spraying process of nickel-aluminum wire, the heat generated by oxygen and acetylene will be used to melt aluminum and nickel. When the molten aluminum and nickel come into contact, a violent nickel-aluminum chemical reaction will occur, generating a large amount of thermal power and forming a nickel-aluminum intermetallic compound, which will impact the substrate under the huge thermal power.

[0026] In this embodiment, in step S3, the following spraying process parameters are also included: the air pressure is 4.8-4.85 bar, and the air flow rate is 727-735 L / min. Specifically, when the air flow rate is 727-735 L / min, the nozzle and the pipeline can be maintained at a lower temperature to prevent the heat generated by nickel and aluminum from damaging the equipment; when the air flow rate is less than 727 L / min, the direction of the impact of the intermetallic compound cannot be effectively guided, and the coating will be discontinuous and inefficient when formed. At the same time, the equipment will overheat, affecting the stability of the equipment; when the air flow rate is greater than 727 L / min, the heat loss rate is fast, and the temperature of the nozzle and the pipeline is relatively low, which affects the burning speed of the wire, thereby reducing the spraying rate and thus reducing the spraying quality. It should be understood that the air pressure controls the air flow rate, and then controls the air flow rate. It should be understood that in order to control the direction of the impact of the nickel-aluminum intermetallic compound and the cooling equipment, a certain amount of air is needed to control the impact direction of the nickel-aluminum intermetallic compound and reduce the overheating of the equipment.

[0027] In this embodiment, in step S3, the following spraying process parameters are also included: the spraying distance is 150mm. Specifically, the spraying distance directly affects the quality of coating formation. The nickel-aluminum intermetallic compound hits the substrate in a molten state under the action of thermal power. When the spraying distance is 150mm, the spraying equipment is safe and the spraying quality is good; when the spraying distance is greater than 150mm, the longer the cooling time of the nickel-aluminum intermetallic compound, the lower the thermal deformation caused by the impact, the flattening of the coating is reduced, and the porosity is increased; when the spraying distance is less than 150mm, the molten nickel-aluminum intermetallic compound will generate reverse power when hitting the substrate to return to the spray gun, causing damage to the spray gun and deterioration of the coating quality.

[0028] In this embodiment, in step S1, a nickel-aluminum wire core wire material with an aluminum content of 18.7% and a nickel content of 79.8%-81.3% is obtained. Specifically, when the aluminum content is 18.7%, the aluminum content is appropriate, the contact time with oxygen is appropriate, aluminum and nickel can react, and can form a nickel-aluminum intermetallic compound with high bonding strength; when the aluminum content is greater than 18.7%, the aluminum content is too high, the thickness of the aluminum skin will increase, so that the contact time of aluminum with oxygen increases, promotes the formation of aluminum oxide, and thus inhibits the reaction of aluminum and nickel; when the aluminum content is less than 18.7%, the aluminum content is too low, and aluminum and nickel cannot form a nickel-aluminum intermetallic compound with high bonding strength.

[0029] In this embodiment, in step S1, a nickel-aluminum wire core wire with a wire diameter of 3.01-3.04 mm and a roundness of 0.02 is obtained. It should be understood that the wire diameter determines the distance between aluminum and nickel. During the spraying process, the greater the distance between aluminum and nickel, the longer the aluminum is in contact with oxygen, the more serious the aluminum oxidation, and the reaction between aluminum and nickel. The existing process determines that nickel and aluminum cannot achieve seamless contact. According to the aluminum and nickel contents of 18.7% and 79.8% respectively, the optimal wire diameter under the existing preparation process is 3.01-3.04 mm, and the fluctuation is the process error; roundness is an important indicator to measure whether the wire is uniform. When the roundness is 0, the wire cross section is circular. The larger the roundness, the elliptical cross section of the wire and the greater the deformation, therefore, the lower the roundness, the better. Under the existing process, the roundness of nickel-aluminum 20% wire can only be 0.02.

[0030] In this embodiment, in step S1, the anti-wire jamming treatment specifically includes the following steps: arranging the nickel-aluminum core wire in the wire feeding device, and using a hanging device to pull the nickel-aluminum core wire so that the nickel-aluminum core wire and the wire feeding device are at the same horizontal plane. Specifically, the hanging device is a hanging rope or a hook to hook the nickel-aluminum core wire so that the nickel-aluminum core wire and the wire feeding device are at the same horizontal plane to prevent the aluminum skin in the nickel-aluminum core wire from dissolving and blocking the spray gun port.

[0031] In this embodiment, step S2 specifically includes the following steps: S201, cleaning the workpiece to be sprayed; S202, performing sand blasting protection on the non-sand blasting area of ​​the surface of the workpiece to be sprayed; S203, roughening the sand blasting area on the surface of the workpiece to be sprayed; S204, spraying protection on the non-spraying area of ​​the workpiece to be sprayed. Specifically, first use clean water to clean the surface of the workpiece to be sprayed to make the surface of the workpiece to be sprayed clean; then use high-temperature resistant tape to protect the non-sand blasting area of ​​the workpiece to be sprayed; then perform roughening treatment on the sand blasting area on the surface of the workpiece to be sprayed; finally, use high-temperature resistant tape to protect the non-spraying area of ​​the workpiece to be sprayed. Optionally, S203 specifically includes the following steps: select 46# white corundum, the nozzle diameter is Φ7.5~8.5, the sand blasting angle is 60°±15°, the workpiece surface is sand blasted and roughened at a pressure of 0.3MPa-0.5MPa, and then remove the sand blasting protection tape, and use compressed air or acetone to remove the residual sand particles on the workpiece surface.

[0032] In this embodiment, step S4 specifically includes the following steps: S401, prepare metallographic sample; S402, observe coating structure; S403, measure coating microhardness. Specifically, firstly, use wire cutting machine to cut sample and make metallographic sample; then observe coating cross-sectional morphology, porosity, interface contamination, unmelted particle ratio, maximum unmelted particle size, interface contamination under 200 times metallographic microscope; finally, use microhardness tester to measure coating microhardness; to obtain nickel-aluminum coating with dense coating structure, low porosity, few unmelted particles, small maximum unmelted particle size, good interface bonding, low interface contamination, high microhardness, which is better than existing coating quality and significantly improves coating quality.

[0033] In this embodiment, in step S4, the thickness of the nickel-aluminum coating is 150-250 μm. Specifically, when the thickness of the nickel-aluminum coating is 150-250 μm, the coated parts in the engine are not easy to collide with other parts and wear, and the sealing performance of the parts is good; when the thickness of the nickel-aluminum coating is less than 150 μm, the sealing performance of the coated parts is poor; when the thickness of the nickel-aluminum coating is greater than 250 μm, the coated parts in the engine are easy to collide with other parts and wear.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a nickel-aluminum coating, characterized in that: The specific steps include: S1, obtaining a nickel-aluminum core wire material, and performing an anti-wire-stuck treatment on the nickel-aluminum core wire material; S2, obtaining a workpiece to be sprayed, and performing surface treatment on the workpiece to be sprayed; S3, spraying the workpiece surface with an oxygen-acetylene flame spraying process to obtain a nickel-aluminum coating, including the following spraying process parameters: wire feed rate of 800-1100 mm / min, oxygen flow rate: acetylene flow rate of 1.06-1.09; S4, checking the nickel-aluminum coating on the surface of the sprayed workpiece; The nickel-aluminum core wire material is an aluminum-clad nickel wire. In step S1, a nickel-aluminum core wire material with an aluminum content of 18.7% and a nickel content of 79.8%-81.3% is obtained; In step S3, the following spraying process parameters are also included: oxygen pressure is 2.38-2.45 bar, oxygen flow rate is 40-40.5 L / min, acetylene pressure is 1-1.05 bar, acetylene flow rate is 37-37.5 L / min; In step S3, the following spraying process parameters are also included: air pressure is 4.8-4.85 bar, air flow rate is 727-735 L / min; In step S3, the following spraying process parameters are also included: the spraying distance is 150 mm; In step S4, the thickness of the nickel-aluminum coating is 150-250 μm.

2. The method for preparing the nickel-aluminum coating according to claim 1, characterized in that: In step S1, a nickel-aluminum core wire with a wire diameter of 3.01-3.04 mm and a roundness of 0.02 is obtained.

3. The method for preparing the nickel-aluminum coating according to any one of claims 1 to 2, characterized in that: In step S1, the anti-wire jamming process specifically includes the following steps: placing the nickel-aluminum core wire in a wire feeding device, and using a hanging device to pull the nickel-aluminum core wire so that the nickel-aluminum core wire and the wire feeding device are in the same horizontal plane.

4. The method for preparing the nickel-aluminum coating according to any one of claims 1 to 2, characterized in that: Step S2 specifically includes the following steps: S201, cleaning the workpiece to be sprayed; S202, performing sand blowing protection on the non-sand blowing area on the surface of the workpiece to be sprayed; S203, roughening the sandblasting area on the surface of the workpiece to be sprayed; S204, spraying protection is performed on the non-spraying area of ​​the workpiece to be sprayed.

5. The method for preparing the nickel-aluminum coating according to any one of claims 1 to 2, characterized in that: Step S4 specifically includes the following steps: S401, preparing metallographic samples; S402, observe the coating structure; S403, measure the microhardness of the coating.

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