A process for laser cladding toughening repair of aermet 100 super strength steel aircraft landing gear

Abstract

The application relates to the technical field of ultrasonic impact and laser cladding, in particular to a laser cladding toughening and strengthening repair process for AerMet100 super-strength steel airplane landing gears, and the specific steps are as follows: S1, powder preparation; S2, mixing; S3, pretreatment; S4, making the sample to be cladded in argon protection; S5, polishing; S6, impact treatment; under the same laser cladding repair process, the repaired samples are prepared, ultrasonic impact strengthening treatment and non-ultrasonic impact strengthening treatment are respectively adopted to compare and verify the ultrasonic impact strengthening treatment effect, and experiments prove that the tensile strength of the repaired samples with different repair depths is all higher than 85% of the tensile strength of the base material, and the impact work of the repaired samples with the same repair depth is obviously improved after the ultrasonic impact strengthening treatment.

Description

Technical Field

[0001] This invention relates to the fields of ultrasonic impact and laser cladding technology, specifically a laser cladding strengthening and toughening repair process for AerMet100 ultra-strong steel aircraft landing gear. Background Technology

[0002] AerMet100 is an ultra-high-strength steel with high strength and toughness, widely used in the aerospace field and considered an ideal next-generation material for aircraft landing gear. However, A100 ultra-high-strength steel is highly susceptible to fatigue failure and cracking during frequent takeoffs and landings, posing a safety hazard and necessitating repair. Furthermore, traditional processes cannot effectively repair and strengthen A100 ultra-high-strength steel, presenting certain limitations. With the continuous development of laser cladding repair technology, the rapid melting and solidification process generates significant thermal stress and strain. Combined with the relatively high hardness of AerMet100 ultra-high-strength steel, its resistance to cracking is relatively weak. Improper control during laser cladding can easily lead to microcracks. These microcracks may gradually expand during subsequent use, forming larger crack defects.

[0003] Ultrasonic impact technology can significantly improve the fatigue strength of ultra-high strength steel, reduce stress concentration and warping deformation. At the same time, ultrasonic impact strengthening treatment has a significant effect on reducing porosity defects in welded joints. By implementing ultrasonic vibration on the material surface after welding, strong shock waves are generated on the material surface, thereby generating compressive stress and reducing the generation of porosity. Meanwhile, the tensile strength and impact plasticity of the repaired specimens after ultrasonic impact treatment are improved, especially the impact toughness is significantly improved. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a laser cladding process for strengthening and toughening AerMet100 ultra-strong steel aircraft landing gear.

[0005] A laser cladding process for strengthening and toughening AerMet100 high-strength steel aircraft landing gear, the specific steps of which are as follows:

[0006] S1. Powder preparation: AerMet100 ultra-strong steel powder is obtained by using a plasma rotating electrode powder preparation method.

[0007] S2. Mixing: NiTi and A100 high-strength steel powders are mixed according to a pre-formulated ratio of 5:1 to obtain mixed powder.

[0008] S3. Pretreatment: Polish the substrate surface with a polishing machine or fine sandpaper to remove surface oxides; clean the substrate surface with acetone and alcohol to remove oil, shavings and other impurities.

[0009] S4. Place the sample to be clad in argon protection: Select different laser power and scanning speed according to the different cladding powder systems, and fix the circular spot for laser cladding repair;

[0010] S5. Polishing: Polish the polished repair sample with diamond polishing paste. The polished repair sample is used for microhardness distribution test of the cross section of the cladding sample.

[0011] S6. Impact treatment: After the laser cladding repair is completed, a handheld ultrasonic impact device is used to perform ultrasonic impact treatment on the cladding sample. The impact head moves back and forth along the laser scanning direction, and at the same time, the impact head performs high-frequency impact motion along the normal direction of the arc surface of the cladding sample until the cladding sample is subjected to uniform ultrasonic impact treatment.

[0012] In step S2, the mixture is ball-milled at a speed of 200 r·min⁻¹ under argon protection for 2 hours to obtain a mixed powder.

[0013] The cladding substrate in step S6 is AerMet100 high-strength steel.

[0014] In step S4, before laser cladding repair, the protective argon gas is filled into the chamber at a flow rate of 15 L / min for a duration of 3 min.

[0015] The cladding powder systems in step S4 are AerMet100-NiTi and AerMet100, respectively.

[0016] The grinding and polishing in step S5 involves sequentially using 400#, 600#, 800#, 1000#, 1500# and 2000# metallographic sandpaper, followed by polishing with diamond polishing paste with a particle size of 5μm.

[0017] The hardness distribution test in step S5 is performed using a Vickers hardness tester. The test conditions are: a load of 200g is applied for 10s, the test point spacing is 0.2mm, and the measurement is performed along the direction perpendicular to the fusion line towards the side of the substrate to be repaired.

[0018] In step S6, to reduce substrate deformation caused by localized heat concentration during laser forming, a substrate thickness of not less than 10 mm is recommended when conducting single-pass and single-layer multi-pass additive manufacturing process tests; and a substrate thickness of not less than 18 mm is recommended when conducting cladding repair process tests.

[0019] The laser repair cladding in step S6 has a power of 1600W, a scanning speed of 10mm / s, a spot diameter of 3mm, and a powder feeding rate of 12g / min.

[0020] The ultrasonic impact strengthening test process parameters in step S6 are: frequency 20KHz, amplitude 25μm, and impact needle diameter 5mm.

[0021] The beneficial effects of this invention are as follows: Repair samples were prepared under the same laser cladding repair process, and the effect of ultrasonic impact strengthening treatment was compared and verified by using ultrasonic impact strengthening treatment and not using ultrasonic impact strengthening treatment. The experiment showed that the tensile strength of the repair samples with different repair depths was higher than 85% of the tensile strength of the parent material. After ultrasonic impact strengthening treatment, the impact energy of the repair samples with the same repair depth was significantly improved. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Figure 1 This is a schematic diagram of the cladding repair process for the AerMet100-NiTi composite layer of the present invention;

[0024] Figure 2 This is a schematic diagram of the macroscopic morphology of the untreated and repaired sample of the present invention.

[0025] Figure 3 This is a schematic diagram of the macroscopic morphology of the side surface of the untreated repaired sample of the present invention.

[0026] Figure 4 This is a schematic diagram of the macroscopic morphology of the ultrasonically repaired sample of the present invention.

[0027] Figure 5 This is a schematic diagram of the macroscopic morphology of the side surface of the ultrasonically impacted repair sample according to the present invention.

[0028] Figure 6 This is a schematic diagram of the microstructure of the untreated repair sample of the present invention.

[0029] Figure 7 This is a schematic diagram of the microstructure of the ultrasonically impacted repair sample of the present invention.

[0030] Figure 8 This is a schematic diagram of the microstructure of the untreated repair sample of the present invention.

[0031] Figure 9 This is a schematic diagram of the microstructure of the ultrasonically impacted repair sample of the present invention.

[0032] Figure 10 This is a schematic diagram of the tensile strength of the 5mm AerMet100 ultra-strong steel cladding repair sample and the AerMet100 base material in accordance with the present invention.

[0033] Figure 11This is a schematic diagram of the impact energy of a 5mm AerMet100 ultra-strong steel cladding repair sample for the present invention. Detailed Implementation

[0034] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below.

[0035] like Figures 1 to 11 As shown, a laser cladding strengthening and toughening repair process for AerMet100 ultra-strong steel aircraft landing gear includes the following specific steps:

[0036] S1. Powder preparation: AerMet100 ultra-strong steel powder is obtained by using a plasma rotating electrode powder preparation method.

[0037] S2. Mixing: Mix NiTi and A100 high-strength steel powders according to the pre-made ratio, with a ball-to-material ratio of 5:1, to obtain mixed powder;

[0038] S3. Pretreatment: Polish the substrate surface with a polishing machine or fine sandpaper to remove surface oxides; clean the substrate surface with acetone and alcohol to remove oil, shavings and other impurities.

[0039] S4. Place the sample to be clad in argon protection: Select different laser power and scanning speed according to the different cladding powder systems, and fix the circular spot for laser cladding repair;

[0040] S5. Polishing: Polish the polished repair sample with diamond polishing paste. The polished repair sample is used for microhardness distribution test of the cross section of the cladding sample.

[0041] S6. Impact Treatment: After laser cladding repair is completed, a handheld ultrasonic impact device is used to perform ultrasonic impact treatment on the cladding sample. The impact head moves back and forth along the laser scanning direction, and at the same time, the impact head performs high-frequency impact motion along the normal direction of the arc surface of the cladding sample until the cladding sample is subjected to uniform ultrasonic impact treatment, in order to solve the problem of easy cracking and low toughness in ultra-high strength steel cladding repair.

[0042] Figure 1 In the attached figures, a represents the direction of argon gas introduction, b represents the repair direction, c represents the notch, d represents the laser, e represents the powder, and f represents the repair layer.

[0043] In step S2, the mixture is ball-milled at a speed of 200 r·min⁻¹ under argon protection for 2 hours to obtain a mixed powder.

[0044] The cladding substrate in step S6 is AerMet100 high-strength steel.

[0045] In step S4, before laser cladding repair, the protective argon gas is filled into the chamber at a flow rate of 15 L / min for a duration of 3 min.

[0046] The cladding powder systems in step S4 are AerMet100-NiTi and AerMet100, respectively. The specific process parameters are shown in the table below:

[0047]

[0048] The grinding and polishing in step S5 involves sequentially using 400#, 600#, 800#, 1000#, 1500# and 2000# metallographic sandpaper, followed by polishing with diamond polishing paste with a particle size of 5μm.

[0049] The hardness distribution test in step S5 is performed using a Vickers hardness tester. The test conditions are: a load of 200g is applied for 10s, the test point spacing is 0.2mm, and the measurement is performed along the direction perpendicular to the fusion line towards the side of the substrate to be repaired.

[0050] In step S6, to reduce substrate deformation caused by localized heat concentration during laser forming, a substrate thickness of not less than 10 mm is recommended when conducting single-pass and single-layer multi-pass additive manufacturing process tests; a substrate thickness of not less than 18 mm is recommended when conducting cladding repair process tests. Repair samples are prepared under the same laser cladding repair process, and the effect of ultrasonic shock strengthening treatment is compared and verified by using ultrasonic shock strengthening treatment and not using ultrasonic shock strengthening treatment.

[0051] When the repair depth is 2 mm, the warping deformation of the repaired sample is relatively slight; when the repair depth is 4 mm and 5 mm, the warping deformation of the repaired sample is very obvious. As the repair depth increases, the warping deformation of the repaired sample also increases.

[0052] The laser repair cladding in step S6 has a power of 1600W, a scanning speed of 10mm / s, a spot diameter of 3mm, and a powder feeding rate of 12g / min.

[0053] The ultrasonic impact strengthening test parameters in step S6 are: frequency 20 kHz, amplitude 25 μm, and impact needle diameter 5 mm. With the addition of ultrasonic impact treatment, defects such as porosity and shrinkage cavities inside the repaired specimen are improved or eliminated. For specimens with the same repair depth, after ultrasonic impact treatment, the tensile fracture surface of the repaired specimen shows a dense and relatively deep distribution of dimples; without ultrasonic impact treatment, the tensile fracture surface of the repaired specimen has fewer and shallower dimples, and even localized tearing occurs. However, the plasticity and tensile strength of the repaired specimens after ultrasonic impact treatment are significantly improved. The tensile strength of repaired specimens with different repair depths is higher than 85% of the tensile strength of the parent material.

[0054] The impact energy of the AerMet100 high-strength steel base material is 45 J. The impact energy of the AerMet100 high-strength steel clad-repaired specimens with a repair depth of 2 mm (without ultrasonic impact) is 37.2 J and 39.6 J, respectively. The impact energy of the AerMet100 high-strength steel clad-repaired specimens with a repair depth of 4 mm (without ultrasonic impact) is 15.0 J and 23.0 J, respectively. The impact energy of the AerMet100 high-strength steel clad-repaired specimens with a repair depth of 50% (without ultrasonic impact) is 17.0 J and 26.5 J, respectively. The impact energy of the repaired specimen with a repair depth of 2 mm is higher than 85% of the impact energy of the base material, while the impact energy of the repaired specimens with other repair depths does not reach 85% of the impact energy of the base material. After ultrasonic impact strengthening treatment, the impact energy of the repaired specimens with the same repair depth was significantly improved.

[0055] Example:

[0056] Using AerMet100 high-strength steel as the substrate, the three dimensions are 40mm×20mm×10mm. Before laser cladding repair, the substrate surface is polished with a polishing machine or fine sandpaper, and then cleaned with acetone and alcohol.

[0057] AerMet100 high-strength steel and NiTi powder were selected as laser cladding powders. First, argon gas was introduced into the chamber as a protective gas. The flow rate of argon gas was 15 L / min and the filling time was 3 min, so that the sample to be clad was under argon protection.

[0058] Then, different laser power and scanning speed are selected according to different cladding powder systems. The diameter of the circular spot is fixed at 3mm for laser cladding. After the repair is completed, the top surface is smoothed with metallographic sandpaper. Then, the smoothed surface is polished with diamond polishing paste with a particle size of 5μm.

[0059] The polished cladding sample was cleaned with anhydrous ethanol, dried, and then etched with 4% nitric acid alcohol solution as a metallographic etching agent for 10-15 seconds. The residual stress of the laser cladding repair sample was measured using an ASTER XL640 X-ray residual stress analyzer.

[0060] AerMet100 powder was selected as the cladding material. The laser power was 800-1600W, the scanning speed was 4-10mm / s, the laser beam spot diameter was 3mm, the powder feeding rate was 12g / min, the corresponding powder feeder parameters were 1r / min, and the protective gas delivery volume was 10L / min.

[0061] The Yipu Technology UIT-500 piezoelectric ultrasonic impactor was used with a frequency of 20KHz, an amplitude of 25μm, and an impact needle diameter of 5mm.

[0062] The impact gun reciprocates along the laser scanning direction, while the impact needle performs high-frequency impact motion along the normal direction of the arc surface of the cladding sample until the cladding sample is subjected to uniform ultrasonic impact treatment.

[0063] like Figures 2 to 5 As shown, the impact energy of the AerMet100 high-strength steel base material is 45 J. The impact energy of the AerMet100 high-strength steel cladding repair specimen with a repair depth of 2 mm without ultrasonic impact and after ultrasonic impact is 37.2 J and 39.6 J, respectively. The impact energy of the AerMet100 high-strength steel cladding repair specimen with a repair depth of 4 mm without ultrasonic impact and after ultrasonic impact is 15.0 J and 23.0 J, respectively.

[0064] like Figures 6 to 9 As shown, the impact energy of the A100 high-strength steel cladding repair specimens with a repair depth of 50% without ultrasonic impact and after ultrasonic impact are 17.0J and 26.5J, respectively. The impact energy of the repair specimen with a repair depth of 2mm is higher than 85% of the impact energy of the base material, while the impact energy of the repair specimens with other repair depths does not reach 85% of the impact energy of the base material.

[0065] like Figure 10 and Figure 11 As shown, the impact energy of repaired samples with the same repair depth was significantly improved after ultrasonic impact strengthening treatment.

[0066] 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 laser cladding strengthening and toughening repair process for AerMet100 ultra-strong steel aircraft landing gear, characterized in that: The specific steps are as follows: S1. Powder preparation: AerMet100 ultra-strong steel powder is obtained by using a plasma rotating electrode powder preparation method. S2. Mixing: Mix NiTi and AerMet100 ultra-strong steel powders according to the pre-made ratio, with a ball-to-material ratio of 5:1, to obtain mixed powder; S3. Pretreatment: Polish the substrate surface with a polishing machine or fine sandpaper to remove surface oxides; clean the substrate surface with acetone and alcohol to remove oil, grinding debris and impurities. S4. Place the sample to be clad in argon protection: Select the laser power and scanning speed according to the cladding powder system, and fix the circular spot for laser cladding repair; S5. Polishing: Polish the polished repair sample with diamond polishing paste. The polished repair sample is used for microhardness distribution test of the cross section of the cladding sample. S6. Impact treatment: After the laser cladding repair is completed, a handheld ultrasonic impact device is used to perform ultrasonic impact treatment on the cladding sample. The impact head moves back and forth along the laser scanning direction, and at the same time, the impact head performs high-frequency impact motion along the normal direction of the arc surface of the cladding sample until the cladding sample is subjected to uniform ultrasonic impact treatment. In step S2, the mixture is ball-milled at a speed of 200 r·min⁻¹ under argon protection for 2 hours to obtain a mixed powder. In step S4, before laser cladding repair, the protective argon gas is introduced into the chamber at a flow rate of 15 L / min for a duration of 3 min. The cladding powder system in step S4 is AerMet100-NiTi. In step S5, the polishing is performed by sequentially using 400#, 600#, 800#, 1000#, 1500#, and 2000# metallographic sandpaper, followed by polishing with diamond polishing paste with a particle size of 5 μm. The ultrasonic impact strengthening test process parameters in step S6 are: frequency 20 kHz, amplitude 25 μm, and impact needle diameter 5 mm.

2. The laser cladding strengthening and toughening repair process for AerMet100 ultra-strong steel aircraft landing gear according to claim 1, characterized in that: The hardness distribution test in step S5 is performed using a Vickers hardness tester. The test conditions are: a load of 200g is applied for 10 seconds, the test point spacing is 0.2 mm, and the measurement is performed along the direction perpendicular to the fusion line towards the side of the substrate to be repaired.

3. The laser cladding strengthening and toughening repair process for AerMet100 ultra-strong steel aircraft landing gear according to claim 1, characterized in that: The cladding substrate in step S4 is AerMet100 high-strength steel.

4. The laser cladding strengthening and toughening repair process for AerMet100 ultra-strong steel aircraft landing gear according to claim 1, characterized in that: In step S4, the substrate thickness is not less than 10 mm.

5. The laser cladding strengthening and toughening repair process for AerMet100 ultra-strong steel aircraft landing gear according to claim 1, characterized in that: The laser repair cladding in step S4 has a power of 1600W, a scanning speed of 10mm / s, a spot diameter of 3mm, and a powder feeding rate of 12 g / min.

6. The laser cladding strengthening and toughening repair process for AerMet100 ultra-strong steel aircraft landing gear according to claim 4, characterized in that: When conducting cladding repair process tests, the substrate thickness should not be less than 18mm.

Images