Preparation method of high velocity oxy-fuel nickel-chromium-chromium carbide coating on surface of gas turbine part

Abstract

The invention discloses a preparation method for spraying a nickel-chromium-chromium carbide coating on the surface of a gas turbine part through high velocity oxy-fuel, and belongs to the technical field of preparation of the nickel-chromium-chromium carbide coating through thermal spraying. The preparation method comprises the following steps that preparation before spraying is conducted, and nickel-chromium-chromium carbide powder for thermal spraying is placed in a drying oven to be dried; cleaning is conducted, specifically, the spraying area and the adjacent area of the part are wiped and cleaned, and impurities such as oil stains are removed; protection before sand blasting is conducted, specifically, the non-sand-blasting surface and a small part of the spraying area of the part are protected through a high-temperature-resistant adhesive tape; a sand blowing machine is provided with a 0-0.6 MPa adjustable air pressure air source and is provided with an oil-water separator; spraying is conducted, specifically, a nickel-chromium-chromium carbide coating is sprayed through hypersonic flame; and cleaning is conducted, specifically, after spraying is completed, the spraying protection clamp and the adhesive tape are removed, and floating ash on the surface of the part is cleaned. The wear-resistant coating is prepared on the surface of the aero-engine and gas turbine part by adopting the process, a nickel-aluminum bottom layer does not need to be sprayed in advance, the quality is stable, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of preparing nickel-chromium-chromium carbide coating by thermal spraying, and particularly relates to a method for preparing nickel-chromium-chromium carbide coating by supersonic flame spraying on the surface of gas turbine parts. Background Art

[0002] Nickel-chromium-chromium carbide coating is a coating that is resistant to abrasive wear, hard surface wear, hot gas corrosion and erosion. It is also a commonly used wear-resistant coating for aircraft engines and gas turbines, and is used under working conditions below 700°C. Nickel-chromium-chromium carbide coating is a metal-carbide composite coating. The coating is hard and brittle, and is easily oxidized during the spraying process, which reduces the bonding strength of the thermal spray coating and makes it prone to cracking or even peeling. Nickel-aluminum coating is usually required as a base layer to improve the bonding strength of the coating, which increases the overall thickness of the coating and is not conducive to the use of certain key parts. Therefore, the process of directly thermally spraying nickel-chromium-chromium carbide coatings with high hardness and high bonding strength has yet to be developed. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention provides a method for preparing a nickel-chromium-chromium carbide coating by supersonic flame spraying. According to the method, there is no need to spray a nickel-aluminum base layer on the parts in advance. The hardness and porosity of the prepared nickel-chromium-chromium carbide coating meet customer requirements, the oxide content is low, and there are no longitudinal cracks and coating peeling.

[0004] The technical solution adopted by the present invention is as follows:

[0005] Preparation before spraying: Before spraying, the nickel-chromium-chromium carbide powder for thermal spraying is placed in an oven at 80°C to 90°C for 1h to 2h for drying; the nickel-chromium-chromium carbide powder composition is: 25%wtNiCr, 75%wtCr3C2, and the powder particle size is: 15μm to 45μm;

[0006] Cleaning: Wipe and clean the spraying area and adjacent areas of the parts to thoroughly remove oil and other debris on the surface of the parts. After degreasing, blow dry with clean compressed air. Acetone is the preferred cleaning agent. Methanol, trichloroethylene, and halides are prohibited for cleaning titanium alloy parts.

[0007] Before sandblasting, use high temperature resistant tape to protect the non-sandblasting surface of the parts and a small part of the spraying area (to facilitate the measurement of the sample and coating thickness), and make sure that the non-sandblasting surface is not damaged. The high temperature resistant tape must not cover the sandblasting surface;

[0008] Sand blowing is done by an automatic sand blowing machine, which has an adjustable air pressure of 0-0.6MPa and is equipped with an oil-water separator. The process parameters are as follows:

[0009]

[0010] Furthermore, the following requirements apply: 1) Use clean compressed air to blow away the dust on the surface of the parts after sandblasting. The surface after sandblasting is not allowed to be touched by bare hands. 2) Visually inspect the parts after sandblasting. The surface coverage is complete, uniform and free of metallic luster. No leakage or over-blowing is allowed. 3) The parts after sandblasting should be kept in a good clean state to avoid contamination of the surface after sandblasting. The parts after sandblasting should be sprayed within 2 hours. If the time is exceeded, the sandblasting must be repeated. The number of re-sandblasting should not exceed 2 times to avoid the embedding of over-blown sand particles in the interface matrix, which will affect the bonding of subsequent coatings.

[0011] Spraying, supersonic flame spraying nickel-chromium-chromium carbide coating in the specified area. 1) Use clean compressed air to remove the dust on the surface of the parts and fix them on a special fixture. 2) Spray the parts according to the following parameters, paying attention to the spraying angle and surface speed. 3) Install a cooling device and use compressed air to cool the parts. 4) During the spraying process, use intermittent and multiple spraying methods, with an interval of 0.5 minutes between each spraying, to keep the temperature of the parts balanced during the spraying process;

[0012]

[0013] After cleaning and spraying, remove the spray protection fixture and tape, clean the dust on the surface of the parts, and mark them.

[0014] Beneficial effects of the present invention:

[0015] (1) The present invention has determined the process of supersonic flame spraying of nickel-chromium-chromium carbide coating through experimental demonstration.

[0016] (2) This process is used to prepare wear-resistant coatings on the surfaces of aircraft engine and gas turbine parts without the need for pre-spraying of a nickel-aluminum base layer. This is not only convenient to operate and has stable quality, but also reduces production costs.

[0017] (3) It has been proven in actual production that the nickel-chromium-chromium carbide coating prepared by this process has performance indicators such as hardness, bonding strength, porosity and oxide content that meet international standards and meet the needs of component use.

[0018] (4) Generally, the surface hardness of the nickel-chromium-chromium carbide coating sprayed by plasma can reach HR15N 75. The coating prepared by the process of the present invention has a thickness of 0.29 mm, a surface hardness of HR15N of more than 90, no cracks in the coating, uniform distribution of pores, and a porosity of 2%. The coating has better wear resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Metallographic structure of the cross section of the test piece supersonic sprayed nickel-chromium-chromium carbide coating;

[0020] Figure 2 Surface condition of supersonic sprayed nickel-chromium-carbide coatings for gas turbine components;

[0021] Figure 3 Schematic diagram of spraying nickel-chromium-chromium carbide coating on the surface of gas turbine transition section parts. DETAILED DESCRIPTION

[0022] The present invention is described in detail below with reference to the accompanying drawings and embodiments:

[0023] Example 1: The nickel-chromium-chromium carbide coating is sprayed on the surface of the test piece by the method of the present invention. The test piece is placed on a special tooling, and to ensure that the spraying process is stable and controllable, the spray gun is placed on the ABB manipulator IRB4600 for programmed spraying. The specific implementation steps are as follows:

[0024] (1) Preparation before spraying: Place nickel-chromium-chromium carbide powder in an oven at 80° C. and dry it for 2 hours. The nickel-chromium-chromium carbide powder composition is: 25%wtNiCr, 75%wtCr3C2, and the powder particle size is: 15μm-45μm.

[0025] (2) Cleaning: Use a brush dipped in acetone to carefully scrub the parts to thoroughly remove oil and other debris on the surface. After degreasing, blow dry with clean compressed air.

[0026] (3) Before sandblasting, use high temperature resistant tape to protect the non-sandblasting surface of the part and a small part of the spraying area (to facilitate the measurement of the sample and coating thickness). Make sure that the non-sandblasting surface is not damaged. The high temperature resistant tape must not cover the sandblasting surface.

[0027] (4) Sand blasting: automatic sand blasting machine is used for sand blasting. The sand blasting machine has an adjustable air pressure of 0-0.6MPa and is equipped with an oil-water separator. The abrasive particle size is 60 mesh, the air pressure is 0.28MPa, the sand blasting distance is 103mm, and the sand blasting angle is 72°. Visual inspection: the surface of the parts after sand blasting is a uniform rough surface without metallic luster, without leakage or over-blowing; the surface of the parts after sand blasting is in a good clean state, and there is no pollution on the sand blasting surface.

[0028] Blow away the dust on the surface of the parts with clean compressed air filtered through an oil-water separator. Spray immediately after sandblasting.

[0029] (5) Spraying: Supersonic spraying of nickel-chromium-chromium carbide coating is performed in the specified area. The dust on the surface of the part is removed with clean compressed air and fixed on a special fixture. The spraying parameters used are as follows: spray gun JP-5000, cooling air pressure 0.30MPa, cooling air duct 300mm away from the part, angle 80°, oxygen pressure 11bar, oxygen flow 882NLPM, kerosene pressure 10bar, kerosene flow 19NLPM, carrier gas type Ar, carrier gas flow 8NLPM, powder feeding rate 61.2g / min, spraying distance 363mm. During the spraying process, an intermittent and multiple spraying method is adopted, with an interval of 0.5min for each spraying, a spraying angle of 90°, a temperature of the test piece controlled between 80-90°C, a coating deposition efficiency of 0.01mm / pass, and a surface speed of 1450mm / s.

[0030] (6) Performance testing: metallographic testing and hardness testing of the coating are performed to comprehensively evaluate the coating. Figure 1 This is the metallographic structure diagram of the cross section of the test piece after spraying. The metallographic test piece specifications are 40×20×2mm, the coating thickness is 0.29mm, the interface contamination rate between the coating and the substrate is 5%, the bonding is good, and there is no stratification. The coating has no cracks, the pores are evenly distributed, and the porosity is 2%. The sample specifications for the hardness test are: 50×30×(5-6)mm, and the bonding strength test piece specifications are: φ25.4×5-6mm. The test results are shown in Table 1 below, and the coating hardness is qualified.

[0031] Table 1

[0032]

[0033] Embodiment 2: As attached Figure 2 As shown, the method of the present invention is used to spray a nickel-chromium-chromium carbide coating on the surface of a transmission shaft part, and the specific spraying area is the EC area in the figure. Due to the complex shape of the workpiece surface, in order to ensure that the spraying process is stable and controllable, the spray gun is placed on the ABB manipulator IRB4600 for programmed spraying. The specific implementation steps are as follows:

[0034] (1) Preparation before spraying: Place nickel-chromium-chromium carbide powder in an oven at 85° C. and dry for 1.5 hours. The nickel-chromium-chromium carbide powder composition is: 25%wtNiCr, 75%wtCr3C2, and the powder particle size is: 15 μm to 45 μm.

[0035] (2) Cleaning: Use a brush dipped in acetone to carefully scrub the parts to thoroughly remove oil and other debris on the surface. After degreasing, blow dry with clean compressed air.

[0036] (3) Before sandblasting, use high temperature resistant tape to protect the non-sandblasting surface of the part and a small part of the spraying area (to facilitate the measurement of the sample and coating thickness). Make sure that the non-sandblasting surface is not damaged. The high temperature resistant tape must not cover the sandblasting surface.

[0037] (4) Sand blasting: automatic sand blasting machine is used for sand blasting. The sand blasting machine has an adjustable air pressure of 0-0.6MPa and is equipped with an oil-water separator. The abrasive particle size is 60 mesh, the air pressure is 0.32MPa, the sand blasting distance is 100mm, and the sand blasting angle is 70°. Visual inspection: the surface of the part after sand blasting is a uniform rough surface without metallic luster, without leakage or over-blowing; the surface of the part after sand blasting is in a good clean state, and the sand blasting surface is not polluted.

[0038] Blow away the dust on the surface of the parts with clean compressed air filtered through an oil-water separator. Spray immediately after sandblasting.

[0039] (5) Spraying: Supersonic spraying of nickel-chromium-chromium carbide coating is performed in the specified area. The dust on the surface of the part is removed with clean compressed air and fixed on a special fixture. The spraying parameters used are as follows: spray gun JP-5000, cooling air pressure 0.20MPa, cooling air duct 300mm away from the part, angle 80°, oxygen pressure 10bar, oxygen flow 878NLPM, kerosene pressure 8bar, kerosene flow 20NLPM, carrier gas type Ar, carrier gas flow 9NLPM, powder feeding rate 63.5g / min, spraying distance 355mm. During the spraying process, an intermittent and multiple spraying method is adopted, and the interval time for each spraying is 0.5min. The temperature of the part is kept below 100℃ during the spraying process, which is conducive to avoiding thermal cracks in the coating. The spraying angle is 90°, the coating deposition efficiency is 0.017mm / pass, and the surface speed is 1370mm / s.

[0040] (6) Cleaning: After spraying, remove the spray protection fixture and tape, clean the dust on the surface of the parts, and mark them.

[0041] (7) Visual inspection: The coating color is uniform, without discoloration due to overburning, the coating is complete, and there are no defects such as cracks, peeling, delamination, and edge warping.

[0042] Embodiment 3: As attached Figure 3 As shown, the method of the present invention is used to spray a nickel-chromium-chromium carbide coating on the surface of a transition section part AB of a gas turbine. To ensure that the spraying process is stable and controllable, the spray gun is placed on the ABB manipulator IRB4600 for programmed spraying. The specific implementation steps are as follows:

[0043] (1) Preparation before spraying: Place nickel-chromium-chromium carbide powder in an oven at 90° C. and dry for 1 hour. The nickel-chromium-chromium carbide powder composition is: 25%wtNiCr, 75%wtCr3C2, and the powder particle size is: 15 μm to 45 μm.

[0044] (2) Cleaning: Use a brush dipped in acetone to carefully scrub the parts to thoroughly remove oil and other debris on the surface. After degreasing, blow dry with clean compressed air.

[0045] (3) Before sandblasting, use high temperature resistant tape to protect the non-sandblasting surface of the part and a small part of the spraying area (to facilitate the measurement of the sample and coating thickness). Make sure that the non-sandblasting surface is not damaged. The high temperature resistant tape must not cover the sandblasting surface.

[0046] (4) Sand blasting: automatic sand blasting machine is used for sand blasting. The sand blasting machine has an adjustable air pressure of 0-0.6MPa and is equipped with an oil-water separator. The abrasive particle size is 60 mesh, the air pressure is 0.35MPa, the sand blasting distance is 110mm, and the sand blasting angle is 70°. Visual inspection: the surface of the part after sand blasting is a uniform rough surface without metallic luster, without leakage or over-blowing; the surface of the part after sand blasting is in a good clean state, and the sand blasting surface is not polluted.

[0047] Blow away the dust on the surface of the parts with clean compressed air filtered through an oil-water separator. Spray immediately after sandblasting.

[0048] (5) Spraying: Supersonic spraying of nickel-chromium-chromium carbide coating is performed in the specified area. The dust on the surface of the part is removed with clean compressed air, and the part is fixed on a special fixture. The spraying parameters used are as follows: spray gun JP-5000, cooling air pressure 0.27MPa, cooling air duct 300mm away from the part, angle 80°, oxygen pressure 12bar, oxygen flow 890NLPM, kerosene pressure 7.5bar, kerosene flow 22NLPM, carrier gas type Ar, carrier gas flow 8NLPM, powder feeding rate 69.5g / min, spraying distance 375mm. During the spraying process, an intermittent and multiple spraying method is adopted, and the interval time for each spraying is 0.5min. The temperature of the part is kept balanced during the spraying process, which is conducive to avoiding cracks in the coating. The spraying angle is 75°, the coating deposition efficiency is 0.009mm / pass, and the surface speed is 1620mm / s.

[0049] (6) Cleaning: After spraying, remove the spray protection fixture and tape, clean the dust on the surface of the parts, and mark them.

[0050] (7) Visual inspection: The coating color is uniform, without discoloration due to overburning, the coating is complete, and there are no defects such as cracks, peeling, delamination, and edge warping.

Claims

1. A method for preparing a nickel-chromium-chromium carbide coating on the surface of a gas turbine part by supersonic flame spraying, characterized in that: The steps include: Preparation before spraying: Before spraying, the nickel-chromium-chromium carbide powder for thermal spraying is placed in an oven for drying; Cleaning: Wipe and clean the spraying area and adjacent areas of the parts to thoroughly remove oil and other debris on the surface of the parts. After degreasing, blow dry with clean compressed air; Protection before sandblasting: Use high temperature resistant tape to protect the non-sandblasting surface and a small part of the spraying area of ​​the parts; Sand blowing: the sand blowing machine has an adjustable air pressure source of 0-0.6MPa and is equipped with an oil-water separator; Spraying: High velocity flame spraying of nickel-chromium-chromium carbide coating in the specified area; After cleaning and spraying, remove the spray protection fixture and tape, clean the dust on the surface of the parts, and mark them.

2. The method for preparing a nickel-chromium-chromium carbide coating by supersonic flame spraying on the surface of a gas turbine part according to claim 1, characterized in that: The nickel-chromium-chromium carbide powder has the following components: 25%wtNiCr, 75%wtCr3C2, and the powder particle size is 15μm-45μm.

3. The method for preparing a nickel-chromium-chromium carbide coating by supersonic flame spraying on the surface of a gas turbine part according to claim 1, characterized in that: The sand blasting process parameters include: abrasive particle size: 30 mesh ~ 80 mesh; wind pressure: 0.2MPa ~ 0.35MPa; sand blasting distance: 80mm ~ 120mm; sand blasting angle 60° ~ 85°.

4. The method for preparing a nickel-chromium-chromium carbide coating by supersonic flame spraying on the surface of a gas turbine part according to claim 1, characterized in that: The parts after sand blasting should be sprayed within 2 hours. If the time is exceeded, sand blasting should be repeated. The number of times of sand blasting shall not exceed 2 times.

5. The method for preparing a nickel-chromium-chromium carbide coating on the surface of a gas turbine part by supersonic flame spraying according to claim 1, characterized in that: During the spraying process, an intermittent and multiple spraying method is adopted, with an interval of 0.5min for each spraying to keep the temperature of the parts balanced during the spraying process; the spraying process parameters include: oxygen pressure: 10±2Bar; oxygen flow: 890±50NLPM; kerosene pressure: 8±2Bar; kerosene flow: 21±3L / h; carrier gas flow: 8.0±2NLPM; powder feeding rate: 68±5g / min; spraying distance: 350±30mm; deposition efficiency: 0.013±0.005mm / pass; spraying angle: 60~90°; surface speed: 1500±200mm / s; part / test piece temperature: <150℃.

6. The method for preparing a nickel-chromium-chromium carbide coating on the surface of a gas turbine part by supersonic flame spraying according to claim 1, characterized in that: The prepared coating has a thickness of 0.29 mm, a surface hardness HR15N of more than 90, no cracks in the coating, uniformly distributed pores, and a porosity of 2%.

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