A method for additive repair of damaged KK3 aluminum bronze aircraft cams

Abstract

This invention relates to the field of additive repair technology, specifically a method for additive repair of damage to a KK3 aluminum bronze aircraft cam. The repair method comprises the following steps: S1, preparing an alloy; S2, determining material-level test items and performance indicators based on the product's stress conditions, and conducting material-level tests; S3, carrying out laser additive repair of the aircraft cam damage. This invention selects GH4169 and KK3 repair powders based on the characteristics of the substrate material, effectively ensuring that the mechanical properties after repair meet usage requirements. It also strictly controls the inter-layer temperature, waiting until the temperature of the previous repair layer drops below 40°C before proceeding with the next laser additive repair layer to avoid deformation due to heat accumulation.

Description

Technical Field

[0001] This invention relates to the field of additive repair technology, specifically a method for additive repair of damage to a KK3 aluminum bronze aircraft cam. Background Technology

[0002] KK3 aluminum bronze, designated QAL10-4-4-1 according to GB / T5231, is a heat-treatable aluminum bronze with aluminum, iron, nickel, and manganese as the main alloying elements. In its final heat-treated state, it has a tensile strength of (900~1010) MPa and a hardness of (250~300) HB. KK3 aluminum bronze is characterized by its low specific gravity, high tensile strength, and wear and corrosion resistance, and is mainly used in landing gear, door components, and drag chute parts for a certain type of aircraft. Currently, aircraft cams made of KK3 aluminum bronze are used in conjunction with 300M steel piston rods. The 300M steel piston rods have a tungsten carbide wear-resistant coating. During aircraft tilting, friction occurs between the KK3 aluminum bronze cam and the tungsten carbide coating on the piston rod. Since the hardness of KK3 aluminum bronze is lower than that of the tungsten carbide coating, aluminum bronze is less wear-resistant, leading to wear on the KK3 aluminum bronze cam during use. This results in dimensional deviations in the cam's inner wall, making it difficult to install seals at this location and reducing overall performance. Currently, damaged aerospace parts are generally repaired using additive manufacturing to restore their function. Laser additive manufacturing is increasingly being used for repairing damaged aerospace components due to its high energy density, low heat input, fast crystallization speed, fine grain size in the repair layer, and good mechanical properties.

[0003] Because the damaged area of ​​the inner wall of an aircraft cam is large and the repair layer is required to have good bonding performance with the substrate, conventional laser additive repair processes are prone to deformation and metallurgical defects. Therefore, this invention provides an additive repair method for damaged aircraft cams made of KK3 aluminum bronze. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes an additive repair method for damaged KK3 aluminum bronze aircraft cams.

[0005] A method for additive repair of damaged KK3 aluminum bronze aircraft cams, the specific steps of which are as follows:

[0006] S1. Alloy Preparation: Based on the chemical composition of the aircraft cam material, heat treatment process, and the stress conditions of the product, the repair powder is determined to be two powders of the same material, GH4169 and KK3, with the specific composition as follows:

[0007] (1) GH4169 alloy powder was prepared by gas atomization or plasma rotating electrode method. The specific chemical composition requirements (Wt.%) are as follows: C: ≤0.08; Cr: 17-21; Ni: 50-55; Mo: 2.8-3.3; Al: 0.2-0.8; Ti: 0.65-1.15; Nb: 4.75-5.5; O: ≤0.02; Fe: Bal;

[0008] (2) The chemical composition requirements for KK3 alloy powder prepared by gas atomization are as follows: Wt.%: Al: 8.5-11; Fe: 3-5; Ni: 3-5; Mn: 0.5-2; O: ≤0.03; Cu: Bal;

[0009] S2. Determine the material-level test items, performance indicators, and conduct material-level tests based on the product's stress conditions:

[0010] (1) The repair powder exhibits frictional wear along the cylinder wall direction;

[0011] (2) According to the product stress requirements, the tensile strength and shear strength of the product shall not be less than 90% of the base material, and the friction coefficient of the repair layer shall be less than 0.28;

[0012] (3) Material-level testing:

[0013] Tensile, shear, and tribological wear samples were prepared using KK3 matrix, KK3 matrix laser additive GH4169 powder, and KK3 matrix laser additive KK3 powder. The performance of the samples was tested. Laser additive repair using GH4169 powder and KK3 powder showed that the tensile strength and shear force were not less than 90% of the matrix material, and the friction coefficient was less than 0.28.

[0014] S3. Conduct laser additive repair of aircraft camshaft damage:

[0015] (1) Structural analysis of the aircraft cam. The aircraft cam needs to be clamped on the positioner to carry out rotary laser additive manufacturing. At the same time, before the repair, the holes on the repair surface need to be sealed with fireproof putty to avoid damage to the round holes during laser additive manufacturing.

[0016] (2) After the aircraft cam is clamped, laser cladding is carried out. Laser additive repair is carried out by rotating the positioner and fixing the laser cladding head. To reduce the generation of defects in the cladding layer, small spot repair is used. The next layer is repaired by laser additive repair after the temperature of the previous repair layer drops below 40℃. The interlayer temperature is monitored by an infrared thermometer.

[0017] (3) After the cam is repaired by laser additive manufacturing, mechanical processing is carried out according to the aircraft cam drawings;

[0018] (4) Once the machined aircraft cams show no cracks after fluorescent flaw detection, they can be put into use.

[0019] The sphericity of the GH4169 alloy powder in step S1 is ≥0.9.

[0020] The GH4169 alloy powder in step S1 has a particle size range of 53μm-150μm, of which <53μm accounts for ≤5% and >150μm accounts for ≤5%.

[0021] The sphericity of the KK3 alloy powder in step S1 is ≥0.9.

[0022] The particle size range of the KK3 alloy powder in step S1 is 53μm-150μm, of which <53μm accounts for ≤5% and >150μm accounts for ≤5%.

[0023] The diameter of the light spot in step S3 is controlled to be 1-1.2 mm.

[0024] The beneficial effects of this invention are: based on the characteristics of the matrix material, GH4169 and KK3 are selected as the two repair powders, which effectively ensures that the mechanical properties after repair meet the requirements of use; the temperature between passes is strictly controlled, and the next laser additive repair is carried out only after the temperature of the previous repair layer drops below 40°C, so as to avoid deformation due to heat accumulation. Attached Figure Description

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] Figure 1 This is a schematic diagram of the workpiece structure of the present invention;

[0027] Figure 2 This is a schematic diagram of the process structure of the present invention. Detailed Implementation

[0028] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below.

[0029] like Figures 1 to 2 As shown, an additive manufacturing method for repairing damage to a KK3 aluminum bronze aircraft cam is described. Figure 1 In the attached diagram, reference numeral a represents three non-repair holes on the annular surface, and reference numeral b represents the worn area on the annular surface to be repaired. The specific steps are as follows:

[0030] S1. Alloy Preparation: Based on the chemical composition of the aircraft cam material, heat treatment process, and stress conditions of the product, the powder composition for laser additive repair was determined. Considering the wear resistance of the repair coating and material matching requirements, two powders of the same material, GH4169 and KK3, were selected for repair. Two repair powders were optimized based on the characteristics of the matrix material, effectively ensuring that the mechanical properties after repair meet the usage requirements. The specific composition is as follows:

[0031] (1) GH4169 alloy powder was prepared by gas atomization or plasma rotating electrode method. The specific chemical composition requirements (Wt.%) are as follows: C: ≤0.08; Cr: 17-21; Ni: 50-55; Mo: 2.8-3.3; Al: 0.2-0.8; Ti: 0.65-1.15; Nb: 4.75-5.5; O: ≤0.02; Fe: Bal;

[0032] (2) The chemical composition requirements for KK3 alloy powder prepared by gas atomization are as follows: Wt.%: Al: 8.5-11; Fe: 3-5; Ni: 3-5; Mn: 0.5-2; O: ≤0.03; Cu: Bal;

[0033] S2. Determine the material-level test items, performance indicators, and conduct material-level tests based on the product's stress conditions:

[0034] (1) The repair powder is subject to friction and wear along the cylinder wall direction. Therefore, the repair layer is subjected to friction, shear force perpendicular to the cylinder wall and bonding force between the repair layer and the substrate. Therefore, material-level tests are conducted to detect room temperature tensile strength, friction and wear and shear force.

[0035] (2) According to the product stress requirements, the tensile strength and shear strength of the product shall not be less than 90% of the base material, and the friction coefficient of the repair layer shall be less than 0.28;

[0036] (3) Material-level testing:

[0037] Tensile, shear, and tribological wear samples were prepared using KK3 matrix, KK3 matrix laser additive GH4169 powder, and KK3 matrix laser additive KK3 powder. The performance of the samples was tested, and the results are shown in the table below. After performance comparison, the tensile strength and shear force of the laser additive repair using GH4169 powder and KK3 powder are not less than 90% of the matrix material, and the friction coefficient is less than 0.28.

[0038]

[0039] S3. Conduct laser additive repair of aircraft camshaft damage:

[0040] (1) Structural analysis of the aircraft cam shows that the aircraft cam needs to be clamped on the positioner to carry out rotary laser additive manufacturing. At the same time, before the repair, the holes on the repair surface need to be sealed with fireproof putty to avoid damage to the round holes during laser additive manufacturing.

[0041] (2) After the aircraft cam is clamped, laser cladding is carried out. Laser additive repair is carried out by rotating the positioner and fixing the laser cladding head. At the same time, small spot repair is used to reduce the generation of defects in the cladding layer. To prevent the cam from deforming due to heat accumulation from continuous laser additive repair, the interlayer temperature is strictly controlled. The next layer is repaired by laser additive repair only after the temperature of the previous repair layer drops below 40°C. The interlayer temperature is monitored by an infrared thermometer.

[0042] The specific process parameters for a single pass are shown in the table below;

[0043]

[0044] (3) After the cam is repaired by laser additive manufacturing, mechanical processing is carried out according to the aircraft cam drawings;

[0045] (4) The machined aircraft cams can be put into use after fluorescent flaw detection and no cracks are found. The product repair cycle is greatly shortened, avoiding the need for replacement and the long procurement cycle of spare parts, which effectively ensures production.

[0046] The sphericity of the GH4169 alloy powder in step S1 is ≥0.9.

[0047] Fireproof putty is used to seal areas that do not require repair, preventing damage to these areas from laser penetration and thus improving repair quality.

[0048] The GH4169 alloy powder in step S1 has a particle size range of 53μm-150μm, of which <53μm accounts for ≤5% and >150μm accounts for ≤5%.

[0049] The sphericity of the KK3 alloy powder in step S1 is ≥0.9.

[0050] The particle size range of KK3 alloy powder in step S1 is 53μm-150μm, of which <53μm accounts for ≤5% and >150μm accounts for ≤5%. Using GH4169 and KK3 powder to repair aircraft cams effectively ensures that the mechanical properties of the aircraft cams after repair meet the usage requirements.

[0051] In step S3, the spot diameter is controlled at 1-1.2 mm. Small-diameter spot repair is used, which results in high laser energy density, small deformation, and improved repair quality. At the same time, the interpass temperature is strictly controlled. The next laser additive repair is carried out only after the temperature of the previous repair layer drops below 40°C to avoid deformation due to heat accumulation.

[0052] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely prisms of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for additive repair of damaged KK3 aluminum bronze aircraft cams, characterized in that: The specific steps are as follows: S1. Alloy Preparation: Based on the chemical composition of the aircraft cam material, the heat treatment process, and the stress conditions of the product, the repair powder was determined to be KK3 homologous powder, with the following specific composition: The chemical composition requirements for KK3 alloy powder prepared by gas atomization are as follows: Wt.%: Al: 8.5-11; Fe: 3-5; Ni: 3-5; Mn: 0.5-2; O: ≤0.03; Cu: Bal; S2. Determine the material-level test items, performance indicators, and conduct material-level tests based on the product's stress conditions: (1) The repair powder is subject to frictional wear along the cylinder wall direction. Therefore, the repair layer is subjected to frictional force, shear force perpendicular to the cylinder wall and bonding force between the repair layer and the substrate. Therefore, material-level tests are conducted to detect room temperature tensile strength, frictional wear and shear force. (2) According to the product stress requirements, the tensile strength and shear strength of the product shall not be less than 90% of the base material, and the friction coefficient of the repair layer shall be less than 0.28; (3) Material-level testing: Tensile, shear, and tribological wear samples were prepared on KK3 matrix and KK3 matrix laser additive KK3 powder. The performance of the samples was tested. Laser additive repair was carried out using KK3 homogeneous powder. The tensile strength and shear force were not less than 90% of the matrix material, and the friction coefficient was less than 0.

28. S3. Conduct laser additive repair of aircraft camshaft damage: (1) Structural analysis of the aircraft cam. The aircraft cam needs to be clamped on the positioner to carry out rotary laser additive manufacturing. At the same time, before the repair, the holes on the repair surface need to be sealed with fireproof putty to avoid damage to the round holes during laser additive manufacturing. (2) After the aircraft cam is clamped, laser cladding is carried out. Laser additive repair is carried out by rotating the positioner and fixing the laser cladding head. To reduce the generation of defects in the cladding layer, small spot repair is used. The next layer of laser additive repair is carried out after the temperature of the previous repair layer drops below 40℃. The interlayer temperature is monitored by an infrared thermometer. The specific process parameters for single-pass laser cladding are: laser power 1200W, cam rotation linear speed 10mm / s, spot diameter 1.1mm, powder feeding rate 0.6r / min, powder feeding gas flow rate 5L / min, protective gas flow rate 20L / min, and overlap rate 50%. (3) After the cam is repaired by laser additive manufacturing, mechanical processing is carried out according to the aircraft cam drawings; (4) Once the machined aircraft cams show no cracks after fluorescent flaw detection, they can be put into use.

2. The additive manufacturing method for repairing damage to a KK3 aluminum bronze aircraft cam according to claim 1, characterized in that: The sphericity of the KK3 alloy powder in step S1 is ≥0.9.

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