Method for improving corrosion resistance of aero-engine accessory casing shell

Abstract

The invention relates to a method for improving the corrosion resistance of an accessory case shell of an aero-engine. The problem that an accessory case is poor in corrosion is solved. The method comprises the steps that firstly, surface treatment is conducted on a deposition area, and surface corrosives and impurities are removed; secondly, deposition powder for repairing is AlMgScZrMn superfine powder, the powder particle size ranges from 15 micrometers to 53 micrometers, and the deposition powder comprises, by weight, 3.6 wt%-4.1 wt% of Mg, 0.7 wt%-0.8 wt% of Sc, 0.3 wt%-0.4 wt% of Zr, 0.4 wt%-0.5 wt% of Mn, 0.5 wt%-0.15 wt% of Fe, 0.01 wt%-0.04 wt% of O and the balance Al; and thirdly, an ultrafast solid deposition method is adopted, a high-pressure nozzle is used, the distance between the nozzle and the base body is 20-40 mm, gas is helium, the pressure of the helium is 3-3.5 MPa, the gas preheating temperature is 400-450 DEG C, the powder feeding amount is 8-10 g / min, and the deposition speed is 300-400 mm / s. And fourthly, after deposition is completed, the redundant size of the surface is ground and polished. The method can solve the problem that the surface is loose and porous due to aluminum alloy and magnesium alloy casting; and secondly, the salt corrosion resistance, the high temperature corrosion resistance and the stress corrosion resistance of the surface of the accessory casing shell are obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine manufacturing and maintenance technology, and relates to a method for improving the corrosion resistance of aero-engine accessory casing. Background Technology

[0002] Light metals such as aluminum and magnesium alloys are widely used in the manufacture of aero-engine accessory casings. In complex environments, these alloys are prone to electrochemical and thermal corrosion, leading to structural failure. Currently, to prevent corrosion, aero-engine aluminum and magnesium alloy casings are often anodized during manufacturing, forming an approximately 20μm anodized layer on the surface to prevent substrate corrosion. However, during long-term service, this 20μm anodized layer is prone to failure, leading to accelerated substrate corrosion. During repair, aluminum and magnesium alloy substrates have poor weldability, easily resulting in defects such as cracks and holes. Thermal spraying methods offer poor adhesion, failing to meet the requirements of extreme service environments. With the increasing demands for complex environments and rapid support in the future, there is an urgent need to develop a method to improve the corrosion resistance of the surfaces of various light metal parts made of aluminum and magnesium alloys. Summary of the Invention

[0003] The purpose of this invention is to provide a method for improving the corrosion resistance of aero-engine accessory housing shells, solving the problem of poor corrosion resistance of accessory housing shells. This invention proposes an ultrafast solid-state deposition technology, which firstly solves the problem of surface porosity caused by aluminum alloy and magnesium alloy casting; and secondly, significantly improves the surface resistance to salt corrosion, high-temperature corrosion, and stress corrosion of the accessory housing shell.

[0004] The specific steps are as follows: Step 1: Use manual grinding or mechanical processing to treat the surface of the deposition area to remove surface corrosion and impurities; Step 2: The deposited powder used for remediation is an AlMgScZrMn ultrafine powder with a particle size of 15~53μm. The chemical composition (wt%) of the deposited powder is: Mg 3.6-4.1, Sc 0.7~0.8, Zr 0.3~0.4, Mn 0.4~0.5, Fe 0.5~0.15, O 0.01~0.04, and Al as the remainder. Step 3: Use the ultrafast solid-state deposition method with a high-pressure nozzle. The distance between the nozzle and the substrate is 20-40 mm. The gas is helium with a pressure of 3-3.5 MPa and a preheating temperature of 400-450℃. The powder feed rate is 8-10 g / min and the deposition rate is 300-400 mm / s.

[0005] Step 4: After deposition, use manual grinding or mechanical processing to grind and polish the excess dimensions on the surface.

[0006] Advantages of using this method for repair: (1) Due to the extremely low self-corrosion potential of aluminum and magnesium alloys, potential differences are easily formed. The AlMgScZrMn deposition powder proposed in this method has Sc and Zr added to its composition, which promotes the precipitation of Al3(Sc,Zr) phase and forms nanoscale ultrafine equiaxed crystals, which can significantly reduce grain boundary segregation and corrosion channels. In addition, the potential difference between the Al3(Sc,Zr) precipitated phase and the matrix is ​​extremely small, which will not form local corrosion microcells and avoid galvanic corrosion. The nano-precipitated phase structure can promote the uniform coverage of Al2O3 oxide film, which significantly improves resistivity; (2) This method proposes an ultrafast solid-state deposition method. Compared with traditional welding or thermal spraying methods, there is no loss of powder elements, the powder composition is consistent with the composition after repair, there is no thermal effect during the deposition process, and the deformation of the parts is small. In terms of microstructure, due to the small heat input, the deposition surface retains the nanostructure of the powder, which can ensure excellent corrosion resistance after deposition; (3) The density of the deposition zone reaches more than 99.5%, which can solve the problem of loose and porous surface of the casting and improve the corrosion resistance of the accessory casing. (4) The bonding strength of the deposition interface is >80 MPa, and the tensile strength of the deposition zone is >450 MPa, which is much higher than the deposition strength of traditional aluminum alloys such as AlSi10Mg and 6061. (5) Compared with traditional surface treatment, the ultrafast solid deposition method based on AlMgScZrMn deposition powder proposed in this invention can be applied in marine environment, high temperature corrosion environment and stress corrosion environment, avoiding the surface treatment problems of different aero engines in complex environments, and can be applied in batches in engineering. Attached Figure Description

[0007] Figure 1 It is the metallographic morphology after spraying; Figure 2 It is the surface morphology of the helium-sprayed coating. Detailed Implementation

[0008] Example 1: The accessory housing of a certain type of aero-engine is made of aluminum alloy, and the damage is caused by corrosion. The powder and method of this invention are used for surface deposition. The specific process is as follows: (1) The deposition area is treated by manual grinding to remove surface corrosion and impurities.

[0009] (2) The repair powder is an AlMgScZrMn ultrafine powder with an average particle size of 15~53μm. The chemical composition (wt%) of the repair powder is: Mg 3.6, Sc 0.7, Zr 0.3, Mn 0.4, Fe 0.5, O 0.01, and Al remaining.

[0010] (3) The ultrafast solid deposition method is adopted, a high-pressure nozzle is used, the distance from the nozzle to the substrate is 30 mm, the gas is helium, the helium pressure is 3MPa, the gas preheating temperature is 400℃, the powder feed rate is 8g / min, and the deposition rate is 300mm / s.

[0011] (4) After deposition, use manual grinding to polish the excess size of the surface.

[0012] The metallographic structure after deposition was examined. The metallographic structure of the deposition zone prepared using helium was very dense, with no obvious porosity and a porosity of less than 0.5%. Surface morphology of the deposition zone showed that the powder particles maintained their powder form during deposition, with no particle melting observed. Furthermore, the embedding of powder particles within the deposited particles was clearly visible, accompanied by strong plastic deformation. Performance tests were performed after deposition. The bonding strength at the deposition interface was 115 MPa, the tensile strength of the deposition zone was 456 MPa, and the density was 99.5%. The corrosion current density was tested using an electrochemical corrosion method, and the result was 0.212 μA / cm². 2 .

[0013] Comparative Example 1: The deposition powder used was 6061 aluminum alloy. Ultrafast solid-state deposition was performed under the same matrix and process parameters. Post-deposition performance testing showed an interface bonding strength of 68 MPa, a tensile strength of 289 MPa in the deposition zone, and a density of 99.6%. The corrosion current density was measured using an electrochemical corrosion method, yielding a result of 114 μA / cm². 2 .

[0014] Example 2: The accessory housing of a certain type of aero-engine is made of magnesium alloy, which is prone to electrochemical corrosion on the mounting surface. The powder and method of this invention are used for deposition. The specific process is as follows: (1) The deposition area is surface treated by mechanical processing to remove surface corrosion and impurities.

[0015] (2) The powder in the deposition zone is an AlMgScZrMn ultrafine powder with an average particle size of 15~53μm. The chemical composition (wt%) of the powder is: Mg 4.1, Sc 0.8, Zr 0.4, Mn 0.5, Fe 0.15, O 0.04, and Al remaining.

[0016] (3) The ultrafast solid deposition method is adopted, a high-pressure nozzle is used, the distance from the nozzle to the substrate is 40 mm, the gas is helium, the helium pressure is 3.5 MPa, the gas preheating temperature is 450℃, the powder feed rate is 10 g / min, and the deposition rate is 400 mm / s.

[0017] (4) After the deposition area is completed, the excess dimensions on the surface are polished by mechanical processing.

[0018] Performance testing was conducted on the deposition zone. The bonding strength at the deposition interface was 102 MPa, the tensile strength of the deposition zone was 458 MPa, and the density was 99.5%. The attached accessory casing operated stably on the aero-engine for 500 hours after deposition without secondary corrosion. This indicates that the corrosion resistance of the deposition zone is significantly better than that of the substrate after ultrafast solid-state deposition.

[0019] Example 3: The casing of an accessory housing for a certain type of aero-engine is made of magnesium alloy, which is prone to electrochemical corrosion on the mounting surface. The powder and method of this invention are used for deposition. The specific process is as follows: (1) The deposition area is surface treated by mechanical processing to remove surface corrosion and impurities.

[0020] (2) The powder in the deposition zone is an AlMgScZrMn ultrafine powder with an average particle size of 15~53μm. The chemical composition (wt%) of the powder is: Mg 3.8, Sc 0.75, Zr 0.35, Mn 0.45, Fe 0.35, O 0.02, and Al remaining.

[0021] (3) The ultrafast solid deposition method is adopted, a high-pressure nozzle is used, the distance from the nozzle to the substrate is 30 mm, the gas is helium, the helium pressure is 3.7 MPa, the gas preheating temperature is 425℃, the powder feed rate is 9 g / min, and the deposition rate is 350 mm / s.

[0022] (4) After the deposition area is completed, the excess dimensions on the surface are polished by mechanical processing.

Claims

1. A method for improving the corrosion resistance of an aero-engine accessory housing, characterized in that: Including the following The steps are as follows: Step 1: Perform surface treatment on the deposition area to remove surface corrosion and impurities; Step 2: The deposited powder used for remediation is an AlMgScZrMn ultrafine powder with a particle size of 15~53μm. The chemical composition of the deposited powder by weight percentage is: Mg 3.6-4.1, Sc 0.7~0.8, Zr 0.3~0.4, Mn 0.4~0.5, Fe 0.5~0.15, O 0.01~0.04, and Al as the remainder. Step 3: Use the ultrafast solid-state deposition method with a high-pressure nozzle. The distance between the nozzle and the substrate is 20-40 mm. The gas is helium with a pressure of 3-3.5 MPa and a preheating temperature of 400-450℃. The powder feed rate is 8-10 g / min and the deposition rate is 300-400 mm / s. Step 4: After deposition, grind and polish any excess material on the surface.

2. The method for improving the corrosion resistance of an aero-engine accessory casing according to claim 1, characterized in that: The chemical composition of the deposited powder by weight percentage is: Mg 3.85, Sc 0.75, Zr 0.35, Mn 0.45, Fe 0.35, O 0.03, with Al remaining.

3. The method for improving the corrosion resistance of an aero-engine accessory housing according to claim 1, characterized in that: In step three, the distance from the nozzle to the substrate is 30 mm, the helium pressure is 3.3 MPa, the gas preheating temperature is 425℃, the powder feed rate is 9 g / min, and the deposition rate is 350 mm / s.

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