A wear-resistant and high-temperature resistant composite coating for copper alloy surface and its preparation method

Abstract

This invention discloses a wear-resistant and high-temperature-resistant composite coating for copper alloy surfaces and its preparation method. The coating comprises a dilution layer, a bonding layer, an intermediate layer, and a surface layer sequentially clad onto the copper alloy surface. Each layer is metallurgically bonded. The cladding material of the dilution layer is NiCoCrAlY alloy powder, which, by mass fraction, comprises 21.0~25.0% Co, 16.0~18.0% Cr, 10.0~12.0% Al, 0.5~1.0% Y, and the balance being Ni. The cladding material of the bonding layer is NiCrAlY alloy powder, which, by mass fraction, comprises 22.0~31.0% Cr, 6.0~11.0% Al, 0.4~1.0% Y, and the balance being Ni. This achieves a gradient transition in hardness and ductility between the substrate and the coating, and between the coating layers.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and more specifically, to a wear-resistant and high-temperature resistant composite coating for copper alloy surfaces and its preparation method. Background Technology

[0002] Copper possesses high electrical and thermal conductivity, excellent ductility, and corrosion resistance, making it widely used in machinery manufacturing, electrical and electronic industries, aerospace, marine industry, automotive industry, energy, and defense, serving as a crucial foundational material for national economic and technological development. However, copper's low hardness, poor wear resistance, low softening temperature, and lack of resistance to ablation are significant drawbacks, limiting its development in fields such as aerospace and military applications that demand high-temperature operation, wear resistance, and corrosion resistance.

[0003] Due to the high thermal conductivity of copper, it is difficult to form an effective molten pool on the copper surface by laser cladding. Therefore, the preparation of laser cladding coatings on the copper surface is relatively difficult. At the same time, the preparation of coatings by laser cladding has the defect of large dilution rate. The content of the matrix material in the diluted layer can be as high as 80% or more, and the coating effect is significantly different from the performance that the coating should have. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a wear-resistant and high-temperature resistant composite coating for copper alloy surfaces and its preparation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention discloses a wear-resistant and high-temperature resistant composite coating for copper alloy surfaces, comprising a dilution layer, an adhesive layer, an intermediate layer, and a surface layer sequentially fused onto the copper alloy surface, each layer being a fully metallurgically bonded layer;

[0007] The cladding material for the dilution layer is NiCoCrAlY alloy powder, which, by mass fraction, comprises 21.0~25.0% Co, 16.0~18.0% Cr, 10.0~12.0% Al, 0.5~1.0% Y, with the balance being Ni.

[0008] The cladding material of the adhesive layer is NiCrAlY alloy powder, which, by mass fraction, comprises 22.0~31.0% Cr, 6.0~11.0% Al, 0.4~1.0% Y, and the balance is Ni;

[0009] The cladding material of the intermediate layer is a MgO-ZrO2-Ni7Cr2Al mixed powder, which, by mass fraction, is composed of 34.0~36.0% Ni7Cr2Al alloy powder and 64.0~66.0% MgO-ZrO2 composite powder mechanically mixed together.

[0010] The cladding material for the surface layer is a ZrO2-TiO2-Y2O3 composite powder, which, by mass fraction, includes 16.0~20.0% TiO2, 8.0~12.0% Y2O3, and the balance is ZrO2.

[0011] Furthermore, the Ni7Cr2Al alloy powder, by mass fraction, includes 75.0~85.0% Ni, 13.0~25.0% Cr, 1.0~2.0% Al, and the content of other elements is ≤10.0%.

[0012] Furthermore, the MgO-ZrO2 composite powder, by mass fraction, includes 15.0~30.0% MgO, with the balance being ZrO2.

[0013] Furthermore, the raw material powders for the dilution layer, adhesive layer, intermediate layer, and surface layer are all spherical powders with a particle size of 45~80μm.

[0014] A method for preparing a wear-resistant and high-temperature-resistant composite coating on a copper alloy surface, characterized by comprising the following steps:

[0015] S1. Powder preparation and surface pretreatment: Prepare powders for the dilution layer, bonding layer, intermediate layer and surface layer; clean, dry and roughen the surface of the copper alloy substrate by sandblasting;

[0016] S2. Composite coating preparation: Using a high-speed laser cladding equipment, under a protective atmosphere, a dilution layer, an adhesive layer, an intermediate layer, and a surface layer are sequentially clad onto the pretreated substrate surface; before cladding each layer, the surface of the formed coating needs to be cleaned.

[0017] S3. Stress-relief tempering: After step S2 is completed, the workpiece with the composite coating is subjected to vacuum stress-relief tempering treatment.

[0018] Further, in step S2, before cladding the dilution layer, the substrate is preheated to 200~250°C; before cladding the adhesive layer, the workpiece with the dilution layer is preheated to 200~250°C; before cladding the intermediate layer, the workpiece with the dilution layer and adhesive layer is preheated to 250~300°C; before cladding the surface layer, the workpiece with the dilution layer, adhesive layer and intermediate layer is preheated to 280~300°C.

[0019] Furthermore, in step S2, the process parameters for the high-speed laser cladding are: laser power 2300~2800W, spot diameter 2.0~3.0mm, scanning rate 100~120mm / s, powder feeding rate 2.0~3.0g / min, and overlap rate 50~80%.

[0020] Furthermore, in step S2, a coaxial center powder feeding method is adopted, and both the protective gas and the powder feeding gas are argon. The flow rate of the protective gas is 8.0~10.0L / min, and the flow rate of the powder feeding gas is 0.8~2.0L / min.

[0021] Further, in step S3, the conditions for vacuum stress-relief tempering are: vacuum degree ≤ 5 Pa, tempering temperature 340~360℃, holding time 1~2 h, followed by gas cooling, the selected cooling medium is argon gas with a purity ≥ 99.9% and an argon gas pressure of 1~2 bar.

[0022] Furthermore, in step S1, the sandblasting roughening treatment uses quartz sand or corundum with a particle size of 0.1~1.0mm, and the surface cleanliness of the substrate after sandblasting reaches Sa2.5 level, and the roughness Ra is 5~10μm.

[0023] The beneficial effects of this invention are: through the four-layer composite structure of dilution layer, adhesive layer, intermediate layer and surface layer, a gradient transition of hardness and ductility between the substrate and coating, and between each coating, is achieved, effectively avoiding the problem of coating cracking and peeling caused by excessive performance differences. At the same time, the heat insulation design and heat stress distribution design of the intermediate layer significantly improve the service stability of the composite coating in high temperature environment. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the composite coating structure;

[0025] Figure 2 This is a flowchart of a composite coating preparation method.

[0026] Reference numerals: 1. Copper substrate; 2. Diluent layer; 3. Adhesive layer; 4. Intermediate layer; 5. Surface layer. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] like Figure 1 As shown, a wear-resistant and high-temperature resistant composite coating for copper alloy surfaces includes a copper material substrate 1 and a dilution layer 2, an adhesive layer 3, an intermediate layer 4, and a surface layer 5 sequentially fused onto the surface of the substrate, with each layer being a fully metallurgically bonded layer.

[0029] The dilution layer 2 is directly connected to the copper substrate 1, and its main function is to provide a cladding base for the adhesive layer. After NiCoCrAlY is clad onto the substrate 1, it will be diluted by the substrate, forming a Cu-NiCoCrAlY alloy layer (dilution layer 2) with a high copper content (about 40-80%) on the surface of the original substrate 1. This dilution layer can act as a transition in hardness and composition between the substrate 1 and the adhesive layer 3. Cr and Al in the dilution layer continuously replenish and form oxides to protect the substrate 1. The addition of Y can improve the adhesion of these oxides. The resulting dense oxide coating with high adhesion can protect the substrate and improve the bonding environment for subsequent coatings. The presence of Co can improve the ductility and heat corrosion resistance of the coating. While protecting the substrate 1, it avoids the formation of coating cracks, resulting in a good transition in ductility and hardness between the adhesive layer 3 and the substrate 1. The dilution layer 2 itself has an operating temperature ≥1100℃. The dilution layer 2 forms a full metallurgical bond with the substrate 1, with a bond strength ≥420MPa (this limit is the limit of the measured tensile strength of the copper substrate; at 420MPa, the copper substrate fractures, while the bond between the dilution layer 2 and the substrate 1 remains intact).

[0030] The adhesive layer 3 further provides a transition in ductility and hardness between the substrate 1, the dilution layer 2, and the intermediate layer 4 based on the dilution layer 2, preventing cracks from forming in the coating due to excessively large spans in hardness and ductility. Under the action of the dilution layer 2, the adhesive layer 3 is only affected by a small amount of copper in the substrate 1. Most of the diluent in the adhesive layer 3 comes from the surface of the dilution layer 2. The thermal conductivity of the dilution layer 2 is much lower than that of the substrate 1, making it easier for the dilution layer 2 to form a stable molten pool in the shallow surface. The dilution rate of the adhesive layer 3 is much lower, and the copper content in the adhesive layer 3 will not exceed 5%. Under the process of this invention, the surface hardness of the adhesive layer 3 can reach above 500 HV, which is sufficient to provide a sufficient hardness transition for the intermediate layer 4 and support for the coating structure. The service temperature of the coating itself is ≥1100℃. The adhesive layer 3 and the dilution layer 2 are fully metallurgically bonded, and the interfacial bonding strength is ≥420MPa (this limit is the limit of the measured tensile strength of the copper substrate; at 420MPa, the copper substrate fractures, but the bonding position between the adhesive layer 3 and the dilution layer 2 remains intact).

[0031] The intermediate layer 4 can further provide a transition in ductility and hardness between the substrate 1, the dilution layer 2, the adhesive layer 3 and the surface layer 5 on the basis of the dilution layer 2 and the adhesive layer 3. The intermediate layer 4, which is prepared by MgO-ZrO2-Ni7Cr2Al mixed powder, has a thermal expansion coefficient between that of metal and oxide ceramic. It can distribute the thermal stress evenly between the coatings when subjected to high temperature thermal shock, and avoid cracking, peeling and other failures of the intermediate layer 4 and the surface layer 5 under high temperature thermal stress. The intermediate layer 4 has excellent heat insulation effect, which can effectively improve the service performance of the composite coating in high temperature environment and reduce the influence of the low softening temperature of the substrate 1 on the composite coating at high temperature. The surface hardness of the intermediate layer 4 can reach more than 1000 HV and the service temperature is ≥1050℃.

[0032] Surface layer 5 exhibits excellent abrasion resistance, high-temperature corrosion resistance, high-temperature hardness, thermal shock resistance, resistance to sulfidation, chlorination, and sodium hot corrosion, as well as high-temperature oxidation resistance and acid and alkali corrosion resistance. Surface layer 5 also possesses extremely high resistance to high-temperature wear and thermal shock. The surface hardness of surface layer 5 can reach over 2000 HV, and the operating temperature is ≥1100℃. Surface layer 5 and intermediate layer 4 are fully metallurgically bonded.

[0033] Example 1

[0034] A method for preparing a wear-resistant and high-temperature-resistant composite coating on a copper alloy surface, comprising the following specific steps:

[0035] Step 1: Prepare the powder

[0036] Weigh out an appropriate amount of powder according to the cladding area, as follows:

[0037] Diluting layer 2 uses NiCoCrAlY alloy powder: by mass fraction, Co 21.0%, Cr 16.0%, Al 10.0%, Y 0.5%, with the balance being Ni;

[0038] The bonding layer 3 uses NiCrAlY alloy powder: by mass fraction, Cr 22.0%, Al 6.0%, Y 0.4%, with the balance being Ni;

[0039] The intermediate layer 4 uses a MgO-ZrO2-Ni7Cr2Al mixed powder: by mass fraction, it consists of 34.0% Ni7Cr2Al alloy powder and 66.0% MgO-ZrO2 composite powder; wherein the Ni7Cr2Al alloy powder, by mass fraction, contains 75.0% Ni, 13.0% Cr, 2.0% Al, and 10.0% of the remaining elements; the MgO-ZrO2 composite powder, by mass fraction, contains 15.0% MgO, with the balance being ZrO2;

[0040] Surface layer 5 uses ZrO2-TiO2-Y2O3 composite powder: by mass fraction, TiO2 16.0%, Y2O3 8.0%, and the balance is ZrO2.

[0041] All four powders are spherical powders with a particle size of 45~80μm. Each powder is spread evenly in a dry, clean container to a depth not exceeding 10mm, and then placed in a vacuum oven to dry. The pressure inside the vacuum oven is below 5Pa, the drying temperature is 80℃, and the drying time is 60min.

[0042] Step 2: Surface Pretreatment of the Substrate

[0043] Chromium-zirconium copper was selected as substrate 1. It was ultrasonically cleaned to remove surface impurities. After cleaning, it was placed in an oven and dried at 80℃ for 60 minutes. Subsequently, it was sandblasted. The sandblasting particles were 0.1mm diamond abrasive, the working pressure was 0.5MPa, the distance between the nozzle and the substrate surface was 100mm, and the sandblasting angle was 30°. After treatment, the surface cleanliness of substrate 1 reached Sa2.5 level, and the surface roughness was Ra5μm. It was then ready for use.

[0044] Step 3: Preparation of Composite Coating

[0045] Using a high-speed fiber laser and coaxial center-feeding powder, with both the protective gas and the powder feeding gas being Ar, each coating was prepared sequentially:

[0046] Preparation of dilution layer 2: After fixing the substrate 1, preheat it to 200℃ using a hot air gun, and then load it with NiCoCrAlY alloy powder for cladding. Cladding parameters: laser power 2500W, spot size 2.0mm, powder feed rate 2.0g / min, protective gas flow rate 8.0L / min, powder feed gas flow rate 0.8L / min, laser scanning speed 100mm / s, overlap rate 50%. After cladding, the surface of dilution layer 2 is polished with a steel wool pad to remove impurities and dust, and then cleaned with a hair dryer.

[0047] Preparation of Adhesive Layer 3: Remove the remaining NiCoCrAlY alloy powder from the powder feeding cylinder, clean the powder feeder to ensure no residue, and load in NiCrAlY alloy powder. Preheat the substrate with dilution layer 2 to 200℃ and perform cladding. Cladding parameters: laser power 2300W, spot size 2.0mm, powder feeding rate 2.0g / min, protective gas flow rate 8.0L / min, powder feeding gas flow rate 0.8L / min, laser scanning rate 100mm / s, overlap rate 50%. After cladding, polish and clean as described above.

[0048] Preparation of intermediate layer 4: Remove the remaining NiCrAlY alloy powder from the powder feeding cylinder, clean the powder feeder to ensure no residue, and load in MgO-ZrO2-Ni7Cr2Al mixed powder. Preheat the substrate with dilution layer 2 and bonding layer 3 to 250℃ for cladding. Cladding parameters: laser power 2600W, spot size 2.0mm, powder feeding rate 2.0g / min, protective gas flow rate 8.0L / min, powder feeding gas flow rate 0.8L / min, laser scanning rate 100mm / s, overlap rate 50%. After cladding, grind and clean as described above.

[0049] Surface layer 5 preparation: Remove the remaining MgO-ZrO2-Ni7Cr2Al mixed powder from the powder feeding cylinder, clean the powder feeder to ensure no residue, and load in ZrO2-TiO2-Y2O3 composite powder. Preheat the substrate with dilution layer 2, adhesive layer 3, and intermediate layer 4 to 280℃ for cladding. Cladding parameters: laser power 2600W, spot size 2.0mm, powder feeding rate 2.0g / min, protective gas flow rate 8.0L / min, powder feeding gas flow rate 0.8L / min, laser scanning rate 100mm / s, overlap rate 50%. After cladding, polish and clean as described above.

[0050] Step 4: Stress-relieving tempering

[0051] Vacuum tempering was performed with a vacuum degree ≤5Pa, tempering temperature 340℃, and holding time 1h. Subsequently, a 2bar gas was used to simulate an air cooling environment.

[0052] Step 5: Cool and remove from the oven

[0053] After tempering, the workpiece is cooled to below 80°C and then removed from the furnace to obtain the finished product.

[0054] The performance of the composite coating prepared in this embodiment was tested, and the results are as follows:

[0055] Surface hardness: 2000 HV; Long-term service temperature of coating: 1100℃; Long-term service temperature of the entire workpiece: 1050℃; Bond strength between coating and substrate: 420 MPa, which is the limit of the tensile strength of the copper substrate. The copper substrate fractures at 420 MPa, while the bonding surface remains intact; Coating resistance to acid and alkali corrosion: No obvious corrosion is observed after immersion in 5% H2SO4 solution and 5% NaOH solution for 72 hours; High-temperature wear resistance: At 1000℃, the coefficient of friction is ≤0.35, and the wear amount is ≤0.07 mm³.

[0056] Example 2

[0057] A method for preparing a wear-resistant and high-temperature-resistant composite coating on a copper alloy surface, comprising the following specific steps:

[0058] Step 1: Prepare the powder

[0059] Weigh out an appropriate amount of powder according to the cladding area, as follows:

[0060] The dilution layer uses NiCoCrAlY alloy powder: by mass fraction, Co 23.0%, Cr 17.0%, Al 11.0%, Y 0.75%, with the balance being Ni;

[0061] The bonding layer uses NiCrAlY alloy powder: by mass fraction, Cr 26.5%, Al 8.5%, Y 0.7%, with the balance being Ni;

[0062] The intermediate layer uses a MgO-ZrO2-Ni7Cr2Al mixed powder: by mass fraction, it consists of 35.0% Ni7Cr2Al alloy powder and 65.0% MgO-ZrO2 composite powder; wherein the Ni7Cr2Al alloy powder, by mass fraction, contains 80.0% Ni, 18.0% Cr, 1.5% Al, and 0.5% of other elements; the MgO-ZrO2 composite powder, by mass fraction, contains 2.5% MgO2, with the balance being ZrO2;

[0063] The surface layer uses ZrO2-TiO2-Y2O3 composite powder: by mass fraction, TiO2 18.0%, Y2O3 10.0%, and the balance is ZrO2.

[0064] All four powders are spherical powders with a particle size of 45~80μm. Each powder is spread evenly in a dry, clean container to a depth not exceeding 10mm, and then placed in a vacuum oven to dry. The pressure inside the vacuum oven is below 5Pa, the drying temperature is 90℃, and the drying time is 75min.

[0065] Step 2: Surface Pretreatment of the Substrate

[0066] Brass was selected as the substrate 1. It was ultrasonically cleaned to remove surface impurities. After cleaning, it was placed in an oven and dried at 90℃ for 75 minutes. Then, it was sandblasted. The sandblasting particles were 0.55mm quartz sand, the working pressure was 0.55MPa, the distance between the nozzle and the substrate surface was 150mm, and the sandblasting angle was 45°. After treatment, the surface cleanliness of substrate 1 reached Sa2.5 level, and the surface roughness was Ra7.5μm. It was then ready for use.

[0067] Step 3: Preparation of Composite Coating

[0068] Using a high-speed fiber laser and coaxial center-feeding powder, with both the protective gas and the powder feeding gas being Ar, each coating was prepared sequentially:

[0069] Preparation of dilution layer 2: After fixing the substrate 1, preheat it to 225℃ using a hot air gun, and then load NiCoCrAlY alloy powder for cladding. Cladding parameters: laser power 2650W, spot size 2.4mm, powder feed rate 2.5g / min, protective gas flow rate 9.0L / min, powder feed gas flow rate 1.4L / min, laser scanning speed 110mm / s, overlap rate 65%. After cladding, the surface of dilution layer 2 is polished with a steel wool pad to remove impurities and dust, and then cleaned with a hair dryer.

[0070] Preparation of Adhesive Layer 3: Remove the remaining NiCoCrAlY alloy powder from the powder feeding cylinder, clean the powder feeder to ensure no residue, and then load in NiCrAlY alloy powder. Preheat the substrate with dilution layer 2 to 225℃ and perform cladding. Cladding parameters: laser power 2500W, spot size 2.5mm, powder feeding rate 2.5g / min, protective gas flow rate 9.0L / min, powder feeding gas flow rate 1.4L / min, laser scanning rate 110mm / s, overlap rate 65%. After cladding, polish and clean as described above.

[0071] Preparation of intermediate layer 4: Remove the remaining NiCrAlY alloy powder from the powder feeding cylinder, clean the powder feeder to ensure no residue, and load in MgO-ZrO2-Ni7Cr2Al mixed powder. Preheat the substrate with dilution layer 2 and bonding layer 3 to 275℃ for cladding. Cladding parameters: laser power 2700W, spot size 2.5mm, powder feeding rate 2.5g / min, protective gas flow rate 9.0L / min, powder feeding gas flow rate 1.4L / min, laser scanning rate 110mm / s, overlap rate 65%. After cladding, grind and clean as described above.

[0072] Surface layer 5 preparation: Remove the remaining MgO-ZrO2-Ni7Cr2Al mixed powder from the powder feeding cylinder, clean the powder feeder to ensure no residue, and load in ZrO2-TiO2-Y2O3 composite powder. Preheat the substrate with dilution layer 2, adhesive layer 3, and intermediate layer 4 to 290℃ for cladding. Cladding parameters: laser power 2700W, spot size 2.5mm, powder feeding rate 2.5g / min, protective gas flow rate 9.0L / min, powder feeding gas flow rate 1.4L / min, laser scanning rate 110mm / s, overlap rate 65%. After cladding, polish and clean as described above.

[0073] Step 4: Stress-relieving tempering

[0074] Vacuum tempering was performed with a vacuum degree ≤ 5 Pa, a tempering temperature of 350 °C, and a holding time of 1.5 h. Subsequently, a 2 bar gas was used to simulate an air cooling environment.

[0075] Step 5: Cool and remove from the oven

[0076] After tempering, the workpiece is cooled to below 80°C and then removed from the furnace to obtain the finished product.

[0077] The performance of the composite coating prepared in this embodiment was tested, and the results are as follows:

[0078] Surface hardness: 2200 HV; Long-term service temperature of coating: 1150℃; Long-term service temperature of the entire workpiece: 1100℃; Bond strength between coating and substrate: 440 MPa, which is the limit of the tensile strength of the copper substrate. The copper substrate fractures at 440 MPa, while the bonding surface remains intact; Coating resistance to acid and alkali corrosion: No obvious corrosion is observed after immersion in 5% H2SO4 solution and 5% NaOH solution for 72 hours; High-temperature wear resistance: At 1000℃, the coefficient of friction is ≤0.28, and the wear amount is ≤0.04 mm³.

[0079] Example 3

[0080] A method for preparing a wear-resistant and high-temperature-resistant composite coating on a copper alloy surface, comprising the following specific steps:

[0081] Step 1: Prepare the powder

[0082] Weigh out an appropriate amount of powder according to the cladding area, as follows:

[0083] The dilution layer uses NiCoCrAlY alloy powder: by mass fraction, Co 25.0%, Cr 18.0%, Al 12.0%, Y 1.0%, with the balance being Ni;

[0084] The bonding layer uses NiCrAlY alloy powder: by mass fraction, Cr 31.0%, Al 11.0%, Y 1.0%, with the balance being Ni;

[0085] The intermediate layer uses a MgO-ZrO2-Ni7Cr2Al mixed powder: by mass fraction, it consists of 36.0% Ni7Cr2Al alloy powder and 64.0% MgO-ZrO2 composite powder; wherein the Ni7Cr2Al alloy powder, by mass fraction, contains 85.0% Ni, 13.0% Cr, 1.0% Al, and 1.0% of other elements; the MgO-ZrO2 composite powder, by mass fraction, contains 30.0% MgO, with the balance being ZrO2;

[0086] The surface layer uses ZrO2-TiO2-Y2O3 composite powder: by mass fraction, TiO2 is 20.0%, Y2O3 is 12.0%, and the balance is ZrO2.

[0087] All four powders are spherical powders with a particle size of 45~80μm. Each powder is spread evenly in a dry, clean container to a depth not exceeding 10mm, and then placed in a vacuum oven to dry. The pressure inside the vacuum oven is below 5Pa, the drying temperature is 100℃, and the drying time is 90min.

[0088] Step 2: Surface Pretreatment of the Substrate

[0089] White copper was selected as substrate 1. It was ultrasonically cleaned to remove surface impurities. After cleaning, it was placed in an oven and dried at 100℃ for 90 minutes. Then, it was sandblasted. The sandblasting particles were 1.0mm diamond abrasive, the working pressure was 0.6MPa, the distance between the nozzle and the substrate surface was 200mm, and the sandblasting angle was 60°. After treatment, the surface cleanliness of substrate 1 reached Sa2.5 level, and the surface roughness was Ra10μm. It was then ready for use.

[0090] Step 3: Preparation of Composite Coating

[0091] Using a high-speed fiber laser and coaxial center-feeding powder, with both the protective gas and the powder feeding gas being Ar, each coating was prepared sequentially:

[0092] Preparation of dilution layer 2: After fixing the substrate 1, preheat it to 250℃ using a hot air gun, and then load NiCoCrAlY alloy powder for cladding. Cladding parameters: laser power 2800W, spot size 2.8mm, powder feed rate 3.0g / min, protective gas flow rate 10.0L / min, powder feed gas flow rate 2.0L / min, laser scanning speed 120mm / s, overlap rate 80%. After cladding, the surface of dilution layer 2 is polished with a steel wool pad to remove impurities and dust, and then cleaned with a hair dryer.

[0093] Preparation of Adhesive Layer 3: Remove the remaining NiCoCrAlY alloy powder from the powder feeding cylinder, clean the powder feeder to ensure no residue, and load in NiCrAlY alloy powder. Preheat the substrate with dilution layer 2 to 250℃ and perform cladding. Cladding parameters: laser power 2700W, spot size 3.0mm, powder feeding rate 3.0g / min, protective gas flow rate 10.0L / min, powder feeding gas flow rate 2.0L / min, laser scanning rate 120mm / s, overlap rate 80%. After cladding, polish and clean as described above.

[0094] Preparation of intermediate layer 4: Remove the remaining NiCrAlY alloy powder from the powder feeding cylinder, clean the powder feeder to ensure no residue, and load in MgO-ZrO2-Ni7Cr2Al mixed powder. Preheat the substrate with dilution layer 2 and bonding layer 3 to 300℃ for cladding. Cladding parameters: laser power 2800W, spot size 3.0mm, powder feeding rate 3.0g / min, protective gas flow rate 10.0L / min, powder feeding gas flow rate 2.0L / min, laser scanning rate 120mm / s, overlap rate 80%. After cladding, polish and clean as described above.

[0095] Surface layer 5 preparation: Remove the remaining MgO-ZrO2-Ni7Cr2Al mixed powder from the powder feeding cylinder, clean the powder feeder to ensure no residue, and load in ZrO2-TiO2-Y2O3 composite powder. Preheat the substrate with dilution layer 2, adhesive layer 3, and intermediate layer 4 to 300℃ for cladding. Cladding parameters: laser power 2800W, spot size 3.0mm, powder feeding rate 3.0g / min, protective gas flow rate 10.0L / min, powder feeding gas flow rate 2.0L / min, laser scanning rate 120mm / s, overlap rate 80%. After cladding, polish and clean as described above.

[0096] Step 4: Stress-relieving tempering

[0097] Vacuum tempering was performed with a vacuum degree ≤ 5 Pa, a tempering temperature of 360 °C, and a holding time of 2 h. Subsequently, a 2 bar gas was used to simulate an air cooling environment.

[0098] Step 5: Cool and remove from the oven

[0099] After tempering, the workpiece is cooled to below 80°C and then removed from the furnace to obtain the finished product.

[0100] The performance of the composite coating prepared in this embodiment was tested, and the results are as follows:

[0101] Surface hardness: 2350 HV; Long-term service temperature of coating: 1200℃; Long-term service temperature of the entire workpiece: 1150℃; Bond strength between coating and substrate: 450 MPa, which is the limit of the tensile strength of the copper substrate. At 450 MPa, the copper substrate fractures while the bonding surface remains intact; Coating resistance to acid and alkali corrosion: No obvious corrosion is observed after immersion in 5% H2SO4 solution and 5% NaOH solution for 72 hours; High-temperature wear resistance: At 1000℃, the coefficient of friction is ≤0.25 and the wear amount is ≤0.03 mm³.

[0102] In another embodiment, the thickness of the dilution layer 2 accounts for one-tenth of the total thickness, the thickness of the adhesive layer 3 accounts for one-quarter of the total thickness, the thickness of the intermediate layer 4 accounts for one-quarter of the total thickness, and the thickness of the surface layer 5 accounts for three-tenths of the total thickness. A transition layer is provided between the adhesive layer 3 and the intermediate layer 4. The transition layer uses NiCoCrAlY alloy powder and MgO-ZrO2-Ni7Cr2Al mixed powder to achieve a continuous and gradual change in composition between the adhesive layer 3 and the intermediate layer 4, eliminate the discrete interface, and enable better bonding.

[0103] The bonding layer is a NiCrAlY single-phase metallic alloy with a coefficient of thermal expansion of approximately 15.0 × 10⁻⁶. -6 / ℃, the middle layer is a MgO-ZrO2-Ni7Cr2Al high ceramic phase content cermet, with a thermal expansion coefficient of approximately 12.0×10. -6 At ℃, the direct bonding of the two results in a significant abrupt change in the coefficient of thermal expansion, which easily leads to concentrated thermal stress at the interface under high-temperature alternating heat loads, causing coating cracking and peeling failure. A linear transition layer is used to achieve a continuous and gradual change in the proportion of the binder metal powder and the intermediate metal-ceramic powder, thus reducing the coating's coefficient of thermal expansion from 15.0 × 10⁻⁶ to a constant value of 15.0 × 10⁻⁶. -6 / ℃ to 12.0×10 -6 The continuous and stable transition at ℃ completely eliminates the performance abrupt changes at discrete interfaces, allowing high-temperature thermal stress to be evenly distributed throughout the entire transition layer range. This avoids the initiation of interface cracks caused by thermal stress concentration, and significantly improves the coating's thermal shock resistance and long-term service stability under high-temperature conditions above 1000℃.

[0104] The dilution layer is made of NiCoCrAlY alloy, and the bonding layer is made of NiCrAlY alloy. Both belong to the Ni-based high-temperature alloy system, with Ni as the core matrix element and Cr, Al, and Y as the main alloying elements. The composition system is highly homogeneous. The core properties such as thermal expansion coefficient, hardness, melting point, and cladding wettability are highly matched. Direct cladding can form a dense and defect-free metallurgical bond without the risk of performance abrupt change or interface stress concentration, and no additional transition layer is required.

[0105] The intermediate layer uses MgO-ZrO2-Ni7Cr2Al metal-ceramic composite powder, with the core ceramic phase being MgO-stabilized ZrO2. The surface layer uses ZrO2-TiO2-Y2O3 composite ceramic powder, with the core matrix phase being ZrO2-based ceramic. The two ceramic phase systems are homologous, possessing excellent chemical compatibility and cladding wettability. At the same time, the intermediate layer itself is a metal-ceramic composite system, having completed the core performance transition from the metal phase to the ceramic phase. It has a high degree of matching with the surface layer in terms of thermal expansion coefficient and hardness, allowing for direct cladding to form a stable all-metallurgical bond without the risk of interface cracking or peeling, eliminating the need for an additional transition layer.

[0106] Let the total thickness of the coating be H, and the thickness range of the transition layer be , where the starting coordinate of the transition layer is , and the ending coordinate of the transition layer is . Define the linear transition coefficient t as the relative progress of the current position within the transition interval, and its calculation formula is:

[0107]

[0108] In the formula, x is the coordinate in the coating thickness direction, . When t = 0, it corresponds to the starting point of the transition layer, the proportion of the bonding layer powder is 100%, and the proportion of the intermediate layer powder is 0; when t = 1, it corresponds to the ending point of the transition layer, the proportion of the bonding layer powder is 0, and the proportion of the intermediate layer powder is 100%; when 0 < t < 1, a linear gradient transition of the two powders is achieved. The continuous calculation formula for the mass proportion of each powder in the transition layer is:

[0109]

[0110] In the formula, is the mass proportion of the NiCrAlY alloy powder; is the mass proportion of the MgO-ZrO2-Ni7Cr2Al mixed powder.

[0111] When coating the transition layer, a dual-channel powder feeder is used. The powder feeding cylinders of the two powder feeders are respectively filled with the NiCrAlY alloy powder and the MgO-ZrO2-Ni7Cr2Al mixed powder, and the above powder mass proportions are converted into the powder feeding rates of the corresponding powder feeders.

[0112] On the premise of not destroying the core functions of the two layers, the linear transition layer realizes a smooth connection from the metal support structure to the ceramic functional structure, not only ensuring the bonding reliability of the bottom layer of the coating, but also not weakening the core properties of high temperature resistance, wear resistance, and heat insulation of the upper layer of the coating, and realizing the coordinated optimization of the overall performance of the coating. At the same time, the linear transition layer realizes a continuous linear increase in the coating hardness from 500HV to 1000HV. While ensuring the overall hardness gradient transition of the coating, it realizes a smooth decrease in toughness, enabling the coating to have both the anti-deformation coordination ability of the bottom layer and the anti-wear and anti-ablation abilities of the upper layer, avoiding crack initiation and expansion caused by sudden changes in hardness transition, and significantly improving the anti-impact performance and service life of the coating.

[0113] The above is only the preferred implementation mode of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A wear-resistant and high-temperature resistant composite coating for copper alloy surfaces, characterized in that, It includes a dilution layer, an adhesive layer, an intermediate layer, and a surface layer that are sequentially fused onto the surface of the copper alloy; The cladding material of the dilution layer is NiCoCrAlY alloy powder, which, by mass fraction, comprises 21.0~25.0% Co, 16.0~18.0% Cr, 10.0~12.0% Al, 0.5~1.0% Y, and the balance is Ni. The cladding material of the adhesive layer is NiCrAlY alloy powder, which, by mass fraction, comprises 22.0~31.0% Cr, 6.0~11.0% Al, 0.4~1.0% Y, and the balance is Ni. The cladding material of the intermediate layer is a MgO-ZrO2-Ni7Cr2Al mixed powder, which, by mass fraction, is composed of 34.0~36.0% Ni7Cr2Al alloy powder and 64.0~66.0% MgO-ZrO2 composite powder. The cladding material of the surface layer is a ZrO2-TiO2-Y2O3 composite powder, which, by mass fraction, includes 16.0~20.0% TiO2, 8.0~12.0% Y2O3, and the balance is ZrO2.

2. The wear-resistant and high-temperature resistant composite coating for copper alloy surfaces according to claim 1, characterized in that, The Ni7Cr2Al alloy powder, by mass fraction, includes 75.0~85.0% Ni, 13.0~25.0% Cr, 1.0~2.0% Al, and the content of other elements is ≤10.0%.

3. The wear-resistant and high-temperature resistant composite coating for copper alloy surfaces according to claim 1, characterized in that, The MgO-ZrO2 composite powder, by mass fraction, includes 15.0~30.0% MgO, with the balance being ZrO2.

4. The wear-resistant and high-temperature resistant composite coating for copper alloy surfaces according to claim 1, characterized in that, The raw material powders for the dilution layer, binder layer, intermediate layer, and surface layer are all spherical powders with a particle size of 45~80μm.

5. A method for preparing a wear-resistant and high-temperature resistant composite coating on a copper alloy surface as described in any one of claims 1-4, characterized in that, Includes the following steps: S1 Powder preparation and surface pretreatment: Prepare the powder for the dilution layer, bonding layer, intermediate layer and surface layer as described in claim 1; clean, dry and roughen the surface of the copper alloy substrate by sandblasting; S2 composite coating preparation: Using a high-speed laser cladding equipment, under a protective atmosphere, a dilution layer, an adhesive layer, an intermediate layer and a surface layer are sequentially clad on the pretreated substrate surface; S3 Stress-Relief Tempering: After step S2 is completed, the workpiece with the composite coating is subjected to vacuum stress-relief tempering treatment.

6. The method for preparing a wear-resistant and high-temperature resistant composite coating on a copper alloy surface according to claim 5, characterized in that, In step S2, before cladding the dilution layer, the substrate is preheated to 200~250°C; before cladding the adhesive layer, the workpiece with the dilution layer is preheated to 200~250°C; before cladding the intermediate layer, the workpiece with the dilution layer and adhesive layer is preheated to 250~300°C; before cladding the surface layer, the workpiece with the dilution layer, adhesive layer and intermediate layer is preheated to 280~300°C.

7. The method for preparing a wear-resistant and high-temperature resistant composite coating on a copper alloy surface according to claim 6, characterized in that, In step S2, the process parameters for high-speed laser cladding are: laser power 2300~2800W, spot diameter 2.0~3.0mm, scanning rate 100~120mm / s, powder feeding rate 2.0~3.0g / min, and overlap rate 50~80%.

8. The method for preparing a wear-resistant and high-temperature resistant composite coating on a copper alloy surface according to claim 5, characterized in that, In step S2, a coaxial center powder feeding method is adopted. Both the protective gas and the powder feeding gas are argon. The flow rate of the protective gas is 8.0~10.0L / min, and the flow rate of the powder feeding gas is 0.8~2.0L / min.

9. The method for preparing a wear-resistant and high-temperature resistant composite coating on a copper alloy surface according to claim 5, characterized in that, In step S3, the conditions for vacuum stress-relief tempering are: vacuum degree ≤ 5 Pa, tempering temperature 340~360℃, holding time 1~2 h, followed by gas cooling. The selected cooling medium is argon with a purity ≥ 99.9% and an argon pressure of 1~2 bar.

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