Preparation of powder for repairing aircraft worm gear damage and its repair method

Abstract

This invention relates to the field of aircraft worm gear damage repair technology, specifically to a powder preparation method for aircraft worm gear damage repair and its repair method. The preparation method includes: step (I) specifying the technical indicators of the repair powder; step (II) batching; step (III) alloy rod preparation; step (IV) plasma rotating electrode powder preparation; step (V) powder collection and sieving; and step (VI) powder performance testing and evaluation. This invention, by providing a powder preparation method for aircraft worm gear damage repair and its repair method, applies powder design and preparation technology and laser repair processes to the laser additive repair of aircraft worm gears. This solves the problem that conventional powders and conventional processes are insufficient to meet the requirements of aircraft worm gear repair, thus improving the quality of laser additive repair of aircraft worm gears.

Description

Technical Field

[0001] This invention relates to the field of aircraft worm gear damage repair technology, specifically to the preparation of powder for aircraft worm gear damage repair and its repair method. Background Technology

[0002] Traditionally, steel that, after nitriding, not only achieves a nitrided layer with high hardness and fatigue strength, but also possesses sufficient strength and toughness in its core, is called nitrided steel. 30Cr2Ni2WA is an aerospace-grade nitrided steel. Its nitrided layer depth is typically (0.15-0.35) mm, its core hardness is generally HRC (32-37.5), and its nitrided layer hardness HV≥600. This steel exhibits high hardenability, good comprehensive mechanical properties, and wear resistance, and is primarily used in aircraft landing gear parts. Aircraft worm gear parts made of 30Cr2Ni2WA steel are prone to corrosion, abrasion, and cracking under extremely harsh load-environment coupling. They are typically repaired using laser additive manufacturing to restore their function. However, commonly used alloy powders for repair often fail to guarantee that the overall mechanical properties after repair meet usage requirements. Furthermore, in conventional laser additive manufacturing processes, nitrogen in the nitrided steel surface forms nitrogen gas during the initial cladding layer under laser thermal cycling, causing porosity in the cladding layer and compromising repair quality. Therefore, to address the issue of conventional alloy powders and repair processes failing to meet usage requirements for aircraft worm gear damage, a novel alloy powder was designed and prepared, along with a laser repair process, to effectively improve the quality of laser additive manufacturing repair for aircraft worm gears. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a powder preparation method for repairing aircraft worm gear damage and a method for repairing the worm gear.

[0004] The technical problem to be solved by this invention is achieved by the following technical solution:

[0005] A method for preparing powder for repairing damage to aircraft worm gears includes the following steps:

[0006] Step (1) Specify the technical specifications of the repair powder:

[0007] Based on the current alloy powder composition, the optimized design is as follows: The components by mass percentage are: C: 0.27%–0.34%, Mn: 0.3%–0.6%, Si: 0.17%–0.37%, Cr: 1.6%–2.0%, Ni: 1.4%–1.8%, W: 0.8%–1.2%, S: ≤0.015%, P: ≤0.015%, O: ≤0.03%, rare earth elements: 0.005%–0.03%, balance: Fe;

[0008] The final optimized composition of the above components is as follows: C: 0.30%, Mn: 0.4%, Si: 0.2%, Cr: 1.8%, Ni: 1.5%, W: 0.9%, S: ≤0.015%, P: ≤0.015%, O: 0.02%, rare earth: 0.01%, balance: Fe;

[0009] Step (2) Ingredient Preparation:

[0010] Pre-process the precast alloy base material according to the final optimized composition, and then take samples to analyze the chemical composition, gas content and impurity content. If the requirements are met, proceed to step (3). If the requirements are not met, reconfigure until the requirements are met.

[0011] Step (3) Preparation of alloy rods:

[0012] Set the melting power to 40KW~50KW and the melting frequency to 3KHz~4KHz. Melt the base material prepared in step (1) to obtain an alloy solution. Cast the alloy solution into an alloy rod and machine it into a Φ30mm×200mm rod.

[0013] Step (IV) Plasma rotating electrode powder preparation:

[0014] Process parameters are set as follows: electrode rotation speed: 16000 r / min~18000 r / min, current intensity: 900 A~1300 A, feed rate: 0.8 mm / s~1.2 mm / s, inert gas environment;

[0015] Step (5) Collection and sieving:

[0016] The prepared alloy powder was collected in a powder collection tank by a cyclone separator. The powder collection tank was directly transferred to a glove box under a sealed condition and sieved with a 60-mesh standard sieve. The -60-mesh powder was stored in a stainless steel container. The whole process was carried out in an argon-protected environment. Powder with a particle size of 53μm-150μm was obtained by sieving with 270-mesh and 100-mesh sieves.

[0017] Step (VI) Powder Performance Testing and Evaluation:

[0018] Step (61) Grind the area around the part to be repaired on the sample within a 20mm radius to expose the metallic luster, and clean with acetone;

[0019] Step (62) involves laser remelting without powder feeding in all areas to be repaired, so that the nitrogen element in the nitrided layer can be released as nitrogen gas under the action of laser thermal cycling, thus avoiding the formation of pores later.

[0020] Step (63) involves laser powder feeding and cladding with sufficient machining allowance;

[0021] Step (64) Machining and magnetic particle inspection for cracks. If cracks are found, repeat steps (61) to (63).

[0022] Preferably, the rare earth element is at least one of Se, Lu, and Yb.

[0023] Preferably, the rare earth element is Se.

[0024] Preferably, the powder has the following requirements: flowability: ≤20S / 50g, high sphericity: ≥0.99, low oxygen content: ≤0.03%, and coefficient of thermal expansion: 10×10⁻⁶. －6 K －1 ~15×10 －6 K －1 Melting point: 1600℃-1800℃; Wetting angle in molten state: ≤60°; Particle size distribution range: 53um~150um; Mechanical properties: ≥90% of the matrix material.

[0025] A method for repairing damage to an aircraft worm gear, comprising the following steps: using powder prepared by the aforementioned method for preparing powder for repairing damage to an aircraft worm gear, and performing laser cladding repair on the aircraft worm gear.

[0026] Step (1) Use a wire brush or mechanical grinding tool to remove the oxide layer within 20mm around the damaged area to be repaired on the aircraft worm gear, ensuring that the metal luster is exposed, the surface is clean, and then clean with acetone;

[0027] Step (2) uses laser to remelt the area to be repaired without filling powder, so that the nitrogen element in the near-surface nitriding layer of the repair area forms nitrogen gas under laser thermal cycling, thus avoiding the generation of pores during the repair process;

[0028] Step (3) involves repairing the product using laser cladding technology;

[0029] Step (4) Machining is performed on the surface of the aircraft worm gear after laser cladding, including grinding with an electric grinding head or pneumatic grinding, turning and grinding.

[0030] Step (5) Mechanical property verification:

[0031] Tensile test bars were fabricated using the same material as aircraft worm gears. Pre-made grooved notches were machined on the test bars, and the grooved notches were filled using laser cladding. X-ray flaw detection was performed to check for internal defects in the cladding area. Tensile tests were conducted on a WDW-100 testing machine under a maximum load of 100KN and a loading rate of 1mm / S to examine the mechanical properties of the test bars.

[0032] Preferably, the laser remelting process parameters in step (2) are as follows: laser cladding equipment: complete set of laser cladding equipment; carrier gas: 99.999% high-purity argon; laser power: 1200W~1500W; scanning speed: 8mm / s~10mm / s; powder feeder reading: low%; protective gas: 380L / h~400L / h; overlap rate: 40%~50%; spot diameter: 1.5mm~2.5mm.

[0033] Preferably, the laser cladding process parameters in step (3) are as follows: laser cladding equipment: complete set of laser cladding equipment; carrier gas: 99.999% high-purity argon; repair powder: powder prepared by composition optimization design; powder size: 53μm~150μm; laser power: 1200W~1500W; scanning speed: 8mm / s~10mm / s; powder feeder reading: low%; carrier gas: 380L / h~400L / h; overlap rate: 50%~60%; spot diameter: 1.5mm~2.5mm.

[0034] The beneficial effects of this invention are:

[0035] This invention provides a powder preparation method for repairing aircraft worm gear damage and a method thereof. It applies powder design and preparation technology and laser repair process to the laser additive repair of aircraft worm gears, solving the problem that conventional powders and conventional processes are difficult to use to meet the requirements of aircraft worm gears, and improving the quality of laser additive repair of aircraft worm gears. Attached Figure Description

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0037] Figure 1 This is a flowchart of the powder preparation process of the present invention;

[0038] Figure 2 A top view of the additive repair specimen.

[0039] Figure 3 This is a schematic diagram of the main structure of the additive repair specimen. Detailed Implementation

[0040] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0041] like Figure 1 As shown, a method for preparing powder for repairing damage to aircraft worm gears includes the following steps:

[0042] Step (1) Specify the technical specifications of the repair powder:

[0043] The composition of the alloy powder used for laser additive repair of 30Cr2Ni2WA steel by mass percentage is as follows: C: 0.27%–0.34%, Mn: 0.3%–0.6%, Si: 0.17%–0.37%, Cr: 1.6%–2.0%, Ni: 1.4%–1.8%, W: 1.2%–1.8%, S: ≤0.015%, P: ≤0.020%, O: ≤0.04%, balance: Fe.

[0044] To address the influence of various elements on alloy properties, the composition of the current 30Cr2Ni2WA steel alloy powder was optimized as follows:

[0045] The components by mass percentage are as follows: C: 0.27%–0.34%, Mn: 0.3%–0.6%, Si: 0.17%–0.37%, Cr: 1.6%–2.0%, Ni: 1.4%–1.8%, W: 0.8%–1.2%, S: ≤0.015%, P: ≤0.015%, O: ≤0.03%, rare earth elements: 0.005%–0.03%, balance: Fe.

[0046] Further narrowing the range of alloying element content:

[0047] The components by mass percentage are as follows: C: 0.30%–0.34%, Mn: 0.3%–0.6%, Si: 0.17%–0.37%, Cr: 1.6%–2.0%, Ni: 1.4%–1.8%, W: 0.8%–1.2%, S: ≤0.015%, P: ≤0.015%, O: ≤0.03%, rare earth elements: 0.008%–0.012%, balance: Fe.

[0048] Based on the synergistic effect of each element on the alloy properties, the final composition optimization design of the powder is as follows: C: 0.30%, Mn: 0.4%, Si: 0.2%, Cr: 1.8%, Ni: 1.5%, W: 0.9%, S: ≤0.015%, P: ≤0.015%, O: 0.02%, rare earth: 0.01%, balance: Fe.

[0049] Among them, rare earth elements are at least one of Se, Lu, and Yb, with Se being the preferred rare earth element.

[0050] Based on the repair requirements, the prepared repair powder should meet the following requirements:

[0051] Flowability: ≤20S / 50g; High sphericity: ≥0.99; Low oxygen content: ≤0.03%; Coefficient of thermal expansion: 10×10 － 6 K －1 ~15×10 －6 K －1Melting point: 1600℃-1800℃, should be as close as possible to the material of the component being repaired to reduce residual stress in the alloy layer; good wettability, which is related to surface tension. The lower the surface tension, the smaller the wetting angle and the better the liquid flow. Wetting angle in the molten state: ≤60°; Particle size distribution range: 53um~150um; Mechanical properties: ≥90% of the matrix material.

[0052] Step (2) Ingredient Preparation:

[0053] Pre-process the precast alloy base material according to the final optimized composition, and then take samples to analyze the chemical composition, gas content and impurity content. If the requirements are met, proceed to step (3). If the requirements are not met, reconfigure until the requirements are met.

[0054] Step (3) Preparation of alloy rods:

[0055] Set the smelting power to 40KW~50KW and the smelting frequency to 3KHz~4KHz. Smelt the base material prepared in step (I) to obtain an alloy solution. Cast the alloy solution into an alloy rod and machine it into a Φ30mm×200mm rod.

[0056] Step (IV) Plasma rotating electrode powder preparation:

[0057] Process parameters are set as follows: electrode rotation speed: 16000r / min~18000r / min, current intensity: 900A~1300A, feed rate: 0.8mm / S~1.2mm / S, inert gas environment.

[0058] Step (5) Collection and sieving:

[0059] The prepared alloy powder was collected in a powder collection tank by a cyclone separator. The powder collection tank was directly transferred to a glove box under a sealed condition and sieved with a 60-mesh standard sieve. The -60-mesh powder was stored in a stainless steel container. The entire process was carried out in an argon-protected environment. Powder with a particle size of 53μm-150μm was obtained by sieving with 270-mesh and 100-mesh sieves.

[0060] Step (VI) Powder Performance Testing and Evaluation:

[0061] Step (61) Grind the area around the part to be repaired on the sample within a 20mm radius to expose the metallic luster, and then clean it with acetone.

[0062] Step (62) involves laser remelting of all areas to be repaired without powder feeding, so that the nitrogen element in the nitrided layer can be released as nitrogen gas under the action of laser thermal cycling, thus avoiding the formation of pores later.

[0063] Step (63) uses laser powder feeding for cladding and leaves sufficient machining allowance.

[0064] Step (64) Machining and magnetic particle inspection for cracks. If cracks are found, repeat steps (61) to (63).

[0065] A method for repairing damage to an aircraft worm gear, comprising the following steps: using powder prepared by the aforementioned method for preparing powder for repairing damage to an aircraft worm gear, and performing laser cladding repair on the aircraft worm gear.

[0066] Step (1) Use a wire brush or mechanical grinding tool to remove the oxide layer within 20mm around the damaged area to be repaired on the aircraft worm gear, ensuring that the metal luster is exposed, the surface is clean, and then clean with acetone.

[0067] Step (2) involves laser remelting of the area to be repaired without powder filling. This allows nitrogen in the near-surface nitrided layer of the repaired area to escape as nitrogen gas under laser thermal cycling, preventing porosity during the repair process. The laser remelting process parameters are as follows:

[0068] Laser cladding equipment: Complete laser cladding equipment (2KW IPG laser, KUKA robot, etc.); Carrier gas: 99.999% high-purity argon; Laser power: 1200W~1500W; Scanning speed: 8mm / s~10mm / s; Powder feeder reading: low%; Protective gas: 380L / h~400L / h; Overlap rate: 40%~50%; Spot diameter: 1.5mm~2.5mm.

[0069] Step (3) involves repair using laser cladding. The process parameters are as follows:

[0070] Laser cladding equipment: Complete laser cladding equipment (2KW IPG laser, KUKA robot, etc.); Carrier gas: 99.999% high-purity argon; Repair powder: Powder prepared using optimized composition design; Powder size: 53μm~150μm; Laser power: 1200W~1500W; Scanning speed: 8mm / s~10mm / s; Powder feeder reading: low%; Carrier gas: 380L / h~400L / h; Overlap rate: 50%~60%; Spot diameter: 1.5mm~2.5mm.

[0071] Step (4) Machining is performed on the surface of the aircraft worm gear after laser cladding, including grinding with an electric grinding head or pneumatic grinding, turning and grinding.

[0072] Step (5) Mechanical property verification:

[0073] The tensile test bar is manufactured using the same material as the aircraft worm gear, and a pre-fabricated groove notch is machined on the test bar, such as... Figure 2 and Figure 3As shown, the pre-fabricated groove notch is located at the center of the specimen. The groove notch on the specimen is filled by laser cladding, and X-ray flaw detection is performed to check the internal defects of the cladding area. Under the conditions of a maximum load of 100KN and a loading rate of 1mm / S, a tensile test is performed on a WDW-100 testing machine to check the mechanical properties of the specimen.

[0074] To further demonstrate that the alloy powder in this embodiment is the optimally designed, the following six sets of comparative experiments were conducted:

[0075] Option 1: Composition of each ingredient by mass percentage:

[0076] C 0.30%, Mn 0.4%, Si 0.2%, Cr 1.8%, Ni 1.5%, W 0.9%, S ≤ 0.015%, P ≤ 0.015%, O 0.02%, Se 0.01%, balance: Fe.

[0077] Option 2, the components are composed of the following by mass percentage:

[0078] C 0.30%, Mn 0.4%, Si 0.2%, Cr 2.0%, Ni 1.5%, W 0.9%, S ≤ 0.015%, P ≤ 0.015%, O 0.02%, Lu 0.01%, balance: Fe.

[0079] Option 3, Composition of each component by mass percentage:

[0080] C 0.30%, Mn 0.4%, Si 0.2%, Cr 2.0%, Ni 1.5%, W 0.9%, S ≤ 0.015%, P ≤ 0.015%, O 0.02%, Yb 0.01%, balance: Fe.

[0081] Option 4: Composition of each component by mass percentage:

[0082] C 0.30%, Mn 0.4%, Si 0.2%, Cr 2.0%, Ni 1.5%, W 0.9%, S ≤0.015%, P ≤0.015%, O 0.02%, Yb 0.005%, Lu 0.005%; Balance: Fe.

[0083] Option 5: Composition of each component by mass percentage:

[0084] C 0.30%, Mn 0.4%, Si 0.2%, Cr 2.0%, Ni 1.5%, W 1.2%, S ≤0.015%, P ≤0.015%, O 0.02%, Yb 0.002%, Lu 0.008%; Balance: Fe.

[0085] Option 6: Composition of each component by mass percentage:

[0086] C 0.30%, Mn 0.4%, Si 0.2%, Cr 2.0%, Ni 1.8%, W 1.2%, S ≤0.015%, P ≤0.015%, O 0.02%, Yb 0.008%, Lu 0.002%; Balance: Fe.

[0087] For the above six schemes, powder preparation was carried out sequentially according to the powder preparation method described above.

[0088] The performance of the powders prepared by the six schemes after repair was tested, and the test results are shown in the table below.

[0089]

[0090]

[0091] Based on the table above, after comprehensive analysis, Scheme 1 is the optimal powder composition design, which is the optimal powder composition design in this embodiment.

[0092] 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 preparing powder for repairing damage to aircraft worm gears, characterized in that: Includes the following steps: Step (1) Specify the technical specifications of the repair powder: Based on the current alloy powder composition, the optimized design is as follows: The components by mass percentage are: C: 0.27%–0.34%, Mn: 0.3%–0.6%, Si: 0.17%–0.37%, Cr: 1.6%–2.0%, Ni: 1.4%–1.8%, W: 0.8%–1.2%, S: ≤0.015%, P: ≤0.015%, O: ≤0.03%, Rare Earth: 0.005%–0.03%, Balance: Fe; The final optimized composition of the above components is as follows: C: 0.30%, Mn: 0.4%, Si: 0.2%, Cr: 1.8%, Ni: 1.5%, W: 0.9%, S: ≤0.015%, P: ≤0.015%, O: 0.02%, Rare Earth: 0.01%, Balance: Fe; Step (two) Ingredient preparation: Pre-process the precast alloy base material according to the final optimized composition, and then take samples to analyze the chemical composition, gas content and impurity content. If the requirements are met, proceed to step (three); if the requirements are not met, reconfigure until the requirements are met. Step (3) Preparation of alloy rods: Set the smelting power to 40KW~50KW and the smelting frequency to 3KHz~4KHz. Smelt the base material prepared in step (1) to obtain an alloy solution. Cast the alloy solution into an alloy rod and machine it into a Φ30mm×200mm rod. Step (IV) Plasma rotating electrode powder preparation: Process parameters are set as follows: electrode rotation speed: 16000 r / min~18000 r / min, current intensity: 900 A~1300 A, feed rate: 0.8 mm / s~1.2 mm / s, inert gas environment; Step (5) Collection and sieving: The prepared alloy powder was collected in a powder collection tank by a cyclone separator. The powder collection tank was directly transferred to a glove box under a sealed condition and sieved with a 60-mesh standard sieve. The -60-mesh powder was stored in a stainless steel container. The whole process was carried out in an argon-protected environment. Powder with a particle size of 53μm-150μm was obtained by sieving with 270-mesh and 100-mesh sieves. Step (VI) Powder Performance Testing and Evaluation: Step (61) Grind the area around the part to be repaired on the sample within a 20mm radius to expose the metallic luster, and clean with acetone; Step (62) involves laser remelting without powder feeding in all areas to be repaired, so that the nitrogen element in the nitrided layer can be released as nitrogen gas under the action of laser thermal cycling, thus avoiding the formation of pores later. Step (63) involves laser powder feeding and cladding with sufficient machining allowance; Step (64) Machining and magnetic particle inspection for cracks. If cracks are found, repeat steps (61) to (63).

2. The method for preparing powder for repairing damage to aircraft worm gears according to claim 1, characterized in that: Rare earth elements are at least one of Lu and Yb.

3. The method for preparing powder for repairing damage to aircraft worm gears according to claim 1, characterized in that: Powder requirements: Flowability: ≤20S / 50g, High sphericity: ≥0.99, Low oxygen content ≤0.03%, Coefficient of thermal expansion: 10×10 －６ K －1 ~15×10 －６ K －1 Melting point: 1600℃-1800℃, wetting angle in molten state: ≤60°, particle size distribution range: 53um~150um, mechanical properties: ≥90% of the matrix material.

4. A method for repairing damage to an aircraft worm gear, characterized in that: Using the powder prepared by the method for preparing powder for repairing aircraft worm gear damage according to any one of claims 1 to 3, laser cladding repair of aircraft worm gear is performed, comprising the following steps: Step (1) Use a wire brush or mechanical grinding tool to remove the oxide layer within 20mm around the damaged area to be repaired on the aircraft worm gear, ensuring that the metal luster is exposed, the surface is clean, and then clean with acetone; Step (2) Laser is used to remelt the area to be repaired without filling powder, so that the nitrogen element in the near-surface nitriding layer of the repair area forms nitrogen gas under laser thermal cycling, thus avoiding the generation of pores during the repair process; Step (3) involves repairing the product using laser cladding technology; Step (4) Machining is performed on the surface of the aircraft worm gear after laser cladding, including grinding with an electric grinding head or pneumatic grinding, turning and grinding. Step (5) Mechanical property verification: Tensile test bars were fabricated using the same material as aircraft worm gears. Pre-made grooved notches were machined on the test bars, and the grooved notches were filled using laser cladding. X-ray flaw detection was performed to check for internal defects in the cladding area. Tensile tests were conducted on a WDW-100 testing machine under a maximum load of 100KN and a loading rate of 1mm / S to examine the mechanical properties of the test bars.

5. The method for repairing damage to an aircraft worm gear according to claim 4, characterized in that: The laser remelting process parameters in step (2) are as follows: laser cladding equipment: complete set of laser cladding equipment; carrier gas: 99.999% high-purity argon; laser power: 1200W~1500W; scanning speed: 8mm / s~10mm / s; powder feeder reading: low%; protective gas: 380L / h~400L / h; overlap rate: 40%~50%; spot diameter: 1.5mm~2.5mm.

6. The method for repairing damage to an aircraft worm gear according to claim 4, characterized in that: The laser cladding process parameters in step (3) are as follows: Laser cladding equipment: complete set of laser cladding equipment; Carrier gas: 99.999% high-purity argon; Repair powder: powder prepared by composition optimization design; Powder size: 53μm~150μm; Laser power: 1200W~1500W; Scanning speed: 8mm / s~10mm / s; Powder feeder reading: low%; Carrier gas: 380L / h~400L / h; Overlap rate: 50%~60%; Spot diameter: 1.5mm~2.5mm.

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