Ultrasonic impact assisted electric spark repair method for casting defects of high-aluminum-titanium high-temperature alloy

Abstract

The invention discloses an ultrasonic impact assisted electric spark repair method for casting defects of a high-aluminum-titanium high-temperature alloy. The ultrasonic impact assisted electric spark repair method comprises the following steps: removing defect parts by adopting a mechanical removal method, and cleaning a machined surface; depositing a repair alloy material at the defect-removed part by using an electric spark deposition technology; the surface of the repairing layer is polished, so that the deposition surface is smooth; performing impact strengthening on the deposition area by using an ultrasonic impact head; continuously carrying out electric spark deposition repair, polishing and flattening and ultrasonic impact treatment for multiple times until the repaired area is filled with metal; and finally, the ultrasonic impact head is used for conducting high-power impact strengthening on the repairing area again, and repairing is completed. The method can be used for high-performance repair of the casting defects of the nickel-based high-temperature alloy with the high aluminum and titanium content, and the defects such as cracks and pores generated during repair of a traditional fusion welding method are avoided.

Description

Technical Field

[0001] The invention relates to the field related to defect repair technology of nickel-based high-temperature alloy castings, and in particular to an ultrasonic impact-assisted electric spark repair method for high-aluminum-titanium high-temperature alloy casting defects. Background Art

[0002] Cast nickel-based high-temperature alloys with high aluminum and titanium content are widely used in the manufacture of key components such as aero-engine working blades, tail nozzle adjustment plates, guide vanes, and casings due to their excellent mechanical properties, good corrosion resistance, and fatigue resistance. Moreover, most of the above-mentioned components serve under extremely harsh conditions such as high temperature, high pressure, and high-speed airflow impact, and the working environment is very harsh. Therefore, in order to improve the performance of the workpiece and extend its service life, various alloy elements such as W, Mo, Mn, Al, and Ti are added to the nickel-based high-temperature alloys. However, during the casting process of the workpiece, due to process or operation problems, defects such as pores, shrinkage cavities, and cracks are inevitably generated. Therefore, it is necessary to seek appropriate methods to repair them, which can reduce losses and improve economic benefits.

[0003] At present, my country has made great progress in conventional repair technology for aviation parts, but there is still a big gap compared with Western developed countries. my country's conventional repair technologies include spray repair technology, fusion welding repair technology, brazing repair technology and laser additive repair technology, etc. These repair technologies have problems such as high energy input and severe deformation of parts after repair. And for thin-walled high-aluminum-titanium-nickel-based high-temperature alloy parts, high energy input will cause problems such as cracking and deformation in the repair area, and ultimately lead to repair failure.

[0004] Electrospark deposition technology is usually used to prepare surface coatings for workpieces. Its principle is to use pulse circuit charging and discharging technology. When the distance between the electrode connected to the positive pole of the power supply and the repair workpiece connected to the negative pole reaches the distance that generates high-frequency pulses, a discharge phenomenon is formed between the electrode and the workpiece. The discharge process lasts for 10 ～6 ~10 ～5 The process is completed within s, and an instantaneous high temperature and high pressure micro-region of 8000-10000℃ is generated at the discharge position. The large energy generated by this process can melt the electrode material and deposit it on the surface of the workpiece material, forming a high-strength metallurgical bond between the two. The electrospark deposition repair process has the characteristics of short discharge time, high energy density, and small thermal impact on the workpiece. It has a high application value for defect repair of nickel-based high-temperature alloys with high aluminum and titanium content.

[0005] However, during the electrospark deposition repair process, the molten electrode material is deposited on the repaired surface of the workpiece in a sputtering state. The deposition process is relatively complex and changeable, resulting in a low density of the deposited layer. The internal defects are mostly pores of about 200 μm and unfused defects, which seriously reduce the mechanical properties of the repaired area.

[0006] At present, there are few studies on the repair of nickel-based high-temperature alloys by electrospark deposition, and there is a lack of effective methods to improve the density of the electrospark deposited layer. Ultrasonic impact, as a typical external auxiliary energy field technology, can effectively improve the density of the repair layer. Its mechanism is to use high-power energy to drive the impact head to impact the metal surface at a frequency of more than tens of thousands times per second, and produce a large compression deformation on the metal surface, improve the density, release the residual tensile stress inside the material, and introduce appropriate compressive stress.

[0007] The present invention aims at the defects such as pores and interlayer unfusion in the process of electrospark deposition repairing high-aluminum-titanium nickel-based high-temperature alloy, and proposes a process method for repairing nickel-based high-temperature alloy, especially high-aluminum-titanium nickel-based high-temperature alloy casting defects by ultrasonic impact assisted electrospark deposition. The equipment required for the repair method is simple to operate and is suitable for different complex environments. At the same time, the nickel-based high-temperature alloy repaired by the method has high density in the repaired area and good interface bonding. Summary of the invention

[0008] The purpose of the present invention is to provide an ultrasonic impact assisted electrospark repair method for high aluminum titanium high temperature alloy casting defects. On the basis of electrospark deposition repair of nickel-based high temperature alloy, ultrasonic impact is applied to the deposited layer to achieve the purpose of densification of the repair area structure.

[0009] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows: an ultrasonic impact assisted electric spark repair method for high aluminum titanium high temperature alloy casting defects, the repair method is as follows:

[0010] Step 1: Processing of defective parts of parts; Processing of metal parts at defective parts to remove original defects and ensure smooth surface of materials after defect removal; Cleaning of the processed parts to be repaired with electrode materials to remove surface oxide film; Processing includes grinding with grinding wheel, angle grinder and mechanical milling;

[0011] Step 2: Prepare repair materials and equipment; put the cleaned parts to be repaired and electrode materials into a vacuum drying box for drying, and set vacuum drying parameters; set protective gas in the vacuum drying box, connect the protective gas to the repair equipment at a certain gas flow rate to ensure that the protective gas can flow evenly from the spark electrode head;

[0012] Step 3: Electrospark deposition repair of parts: Use electrode materials of appropriate size to perform electrospark deposition repair on the repaired parts;

[0013] Step 4: Polishing the repair layer: After repairing one layer, polish the surface of the repair layer to make the deposited surface smooth;

[0014] Step 5: Ultrasonic impact densification treatment of the repair layer: Use ultrasonic impact equipment to perform ultrasonic impact densification treatment on each repair deposition layer;

[0015] Step 6: Repeat steps 3 to 5 until the entire area to be repaired is repaired;

[0016] Step 7: Ultrasonic impact strengthening treatment of the repaired area; after the repaired parts are repaired, the ultrasonic impact equipment is used again to impact strengthen the repaired area;

[0017] Step 8: Surface processing of the repaired area: Process the surface of the repaired area to restore the surface quality of the parts. Use diamond grinding wheel grinding and mechanical milling methods to process the surface of the repaired area.

[0018] Step 9: After the repair is completed, disconnect the protective gas, turn off the power, and take out the repaired parts.

[0019] Furthermore, in the first step, the electrode material prepared for processing the defective part of the part is a metal electrode rod of the same material as the repair material or a metal electrode rod with a composition close to that of the repair material and performance that can meet the use requirements, and the size is selected within the range of 1 to 5 mm.

[0020] Furthermore, in the first step, the cleaning process is specifically as follows: the defective parts and electrode materials are placed in an ultrasonic cleaning machine filled with acetone for cleaning, the defective parts and electrode materials are completely immersed in the liquid, and the cleaning time is not less than 10 minutes to remove possible oil stains on the defective parts and electrode materials.

[0021] Furthermore, in the first step, the shape requirements of the defective parts after processing are as follows: the defective parts after processing are semicircular pits or V-shaped or U-shaped grooves opening upward, the opening angle is greater than 120°, and the bottom arc of the defective parts has a smooth transition.

[0022] Furthermore, in the second step, the drying parameters of the repaired parts and electrode materials are as follows: vacuum drying and processing of the repaired parts and electrode materials is performed in a vacuum drying box, and the vacuum degree of the drying box should be better than 10 ～1 Pa, the drying temperature is 100-150℃, and the drying time is longer than 60min.

[0023] Furthermore, in the second step, the protective gas is specifically: during the electrospark deposition repair process, argon or nitrogen with a purity better than 99.99% is used as the protective gas, and the protective gas flow rate is 10 to 30 L / min.

[0024] Furthermore, in the third step, the electric spark deposition repair of the parts is specifically as follows: start the repair from the bottom middle of the area to be repaired, and complete the repair of the entire repair layer from the inside to the outside point by point and line by line; the thickness of each repair layer is not more than 0.2mm at a time; the repair parameter requirements include: the diameter of the electrode rod is 1~5mm, the electrode speed is 500~1500r / min, the voltage is 30~60V, the capacitance is 100~150μF, and the frequency is 150~250Hz.

[0025] Furthermore, in the fourth step, the surface of the repair layer is polished, specifically: a spherical diamond grinding wheel is used to polish the surface of the repair layer to improve the surface flatness of the repair layer. During polishing, only surface protrusions are removed, and the deposited repair layer is not processed.

[0026] Furthermore, in the fifth step, the repair layer is densified by ultrasonic impact, specifically: the tip of the ultrasonic impact head in the ultrasonic impact equipment is a center plane of a circle with a diameter of 0.2 to 1 mm, the ultrasonic frequency is 20 to 30 kHz, the ultrasonic amplitude output range is 50 to 100 μm, and the impact time is not less than 5 minutes.

[0027] Furthermore, in the seventh step, the repair area is subjected to ultrasonic impact strengthening treatment, specifically: the repair area is subjected to ultrasonic impact strengthening treatment again, the frequency of ultrasonic impact is increased to 30-40kHz, the ultrasonic amplitude output range is 50-100μm, and the impact time is 5-10min.

[0028] Furthermore, in the eighth step, the surface processing process of the repaired area includes: performing surface processing on the repaired area using milling, disc-shaped diamond grinding wheel grinding, etc., and stopping when the repaired area is at the same height as the undamaged area of ​​the part, and the repair process ends.

[0029] Furthermore, the defective part is removed by mechanical removal method and the processed surface is cleaned; the repair alloy material is deposited at the defect removal part by using electric spark deposition technology, and the thickness of each deposition layer is controlled within 0.2mm; the surface of the repair layer is polished to make the surface flat; the repair layer is impact densified for about 5 minutes by using an ultrasonic impact head; the electric spark deposition repair, polishing and ultrasonic impact densification treatment are continued for multiple times until the repair area is filled; finally, the repair area is impact strengthened for 5 to 10 minutes by using an ultrasonic impact head, and the surface of the repair area is polished to complete the repair. This method can be used for high-performance repair of casting defects of nickel-based high-temperature alloys with high aluminum and titanium content, avoiding defects such as cracks and pores during repair by traditional fusion welding methods.

[0030] Furthermore, the present invention has concluded through theoretical research and experimental verification that the defective parts need to be processed before repair, and the area to be repaired must be smooth and flat, which can greatly reduce the low density of the electrospark deposition repair tissue caused by the uneven surface. In addition, by using ultrasonic impact to impact and compact each layer of electrospark deposition repair layer, the defects such as unfused and pores inside the deposition layer can be reduced, and the density of the repair layer can be improved. And grinding the surface of each deposition layer can effectively remove the protrusions on the surface of the deposition layer, facilitating the high-quality deposition of the next layer of electrospark repair.

[0031] The beneficial effect of the present invention is that the method of ultrasonic impact assisted electrospark deposition repair in the present invention can effectively solve the problems of cracking and low density of the repaired area during the repair process of high aluminum-titanium content nickel-based high-temperature alloys, while achieving uniformity and strengthening of the repaired area structure, thereby improving the density and mechanical properties of the repaired area.

[0032] At present, there are few studies on the repair methods of high aluminum titanium nickel-based superalloys. The commonly used repair methods are very likely to cause cracks in the repair area, resulting in repair failure. Taking K424 high aluminum titanium nickel-based superalloy as an example, this alloy contains a large amount of (γ+γ') and carbide eutectic structure. During the laser repair process, it is very easy to cause cracks due to excessive heat input, affecting the repair quality. As a surface treatment technology, electrospark deposition has a high instantaneous temperature, and the energy is mostly applied to the electrode, causing it to melt and deposit on the surface of the substrate. The whole process takes 10 ～6 ~10 ～5 The repair process is completed within s, and the thermal impact on the substrate is minimal, which will not cause the melting of the repaired workpiece material or the formation of cracks. However, the traditional electrospark deposition repair process has the problem of low density of the repaired material. In the electrospark deposition repair process, the thickness of each deposition layer is reduced, and by adding ultrasonic assisted impact, the density of the repair layer can be greatly improved.

[0033] The present invention proposes to use electric spark deposition repair technology to repair nickel-based high-temperature alloy layer by layer, and to perform impact compaction, densification and strengthening treatment on each deposited layer through ultrasonic impact, which can reduce the internal pores of the deposit and improve the density of the repaired area. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described below in conjunction with the accompanying drawings:

[0035] Figure 1 Flow chart of ultrasonic impact assisted electrospark repair method for high aluminum titanium nickel-based high temperature alloy casting defects;

[0036] Figure 2 It is the microstructure characteristics of the repaired area of ​​laser repaired high aluminum titanium nickel-based high temperature alloy;

[0037] Figure 3 It is the microstructure characteristics of the repaired area of ​​high-aluminum-titanium-nickel-based superalloy repaired by electrospark deposition without ultrasonic impact;

[0038] Figure 4 It is the microstructure characteristics of the repaired area of ​​high-aluminum-titanium-nickel-based high-temperature alloy repaired by electrospark deposition under ultrasonic impact. DETAILED DESCRIPTION

[0039] like Figure 1 As shown, the present invention works and is implemented in this way: an ultrasonic impact assisted electric spark repair method for high aluminum titanium high temperature alloy casting defects, the repair method is as follows:

[0040] Step 1: Processing of defective parts of parts. Select K424 alloy parts with casting defects. Use grinding machines, angle grinders, mechanical milling and other processing methods to process the defective parts of the parts to remove the original defects. Ensure that the shape of the defective part of the processed part should be a semicircular pit with an opening facing upward, the opening angle is greater than 120°, the arc at the bottom of the defect has a smooth transition, and the surface of the material is smooth and flat after the defect is removed. Then select a K424 alloy electric rod with the same material as the defective part and a diameter of 2mm. Subsequently, the processed parts to be repaired and the electrode materials for repair are placed in an ultrasonic cleaning machine filled with acetone for cleaning. The parts and electrode materials must be completely immersed in the liquid and ultrasonically cleaned for 15 minutes to remove possible oil stains and other contamination on the parts and electrode materials.

[0041] Step 2: Preparation of repair materials and repair equipment. Place the cleaned parts to be repaired and electrode materials in a vacuum drying box for drying. Vacuum the drying box to ensure that the vacuum degree in the box is better than 10 ～1 Pa. At the same time, the drying temperature is set to 120°C and the drying time is set to 100 min. Connect the high-purity argon gas with a purity of 99.999% to the EDM equipment, set the gas flow rate to 15 L / min, and ensure that the protective gas can flow evenly from the EDM electrode head.

[0042] Step 3: Spark deposition repair of parts. Install the cleaned K424 alloy electrode rod into the spark electrode head, with the electric shock rod extending 15mm from the electrode head. Use a clamp to fix the processed defective parts and connect the spark cathode to it. Open the protective gas valve and the spark equipment power supply, and set the parameters of the spark equipment to an electrode speed of 1000r / min, a voltage of 40V, a capacitance of 120μF, and a frequency of 200Hz. Holding the spark electrode head, contact the high-speed rotating K424 alloy electric shock rod with the bottom middle of the part to be repaired, and start repairing point by point and line by line from the inside to the outside. When the thickness of the deposited layer is approximately 0.1 to 0.2mm, turn off the spark power supply to complete the repair of this layer.

[0043] Step 4: Grinding the repair layer. After repairing one layer, use a spherical diamond grinding wheel to grind the surface of the repair layer to remove the protrusions on the surface of the deposited layer and improve the surface flatness of the repair layer.

[0044] Step 5: Ultrasonic impact densification treatment of the repair layer. Install a circular flat ultrasonic impact head with a diameter of 0.5 mm into the ultrasonic impact equipment, turn on the power of the ultrasonic impact equipment, and set the parameters of the ultrasonic impact equipment to use an ultrasonic frequency of 20 kHz and an ultrasonic amplitude output range of 100 μm. Use the ultrasonic impact equipment to perform ultrasonic impact on the deposited layer for 10 minutes.

[0045] Step 6: Repeat steps 3 to 5 until the entire area to be repaired is repaired.

[0046] Step 7: Ultrasonic impact strengthening treatment of the repaired area. After the defect here is repaired, the parameters of the ultrasonic impact equipment are increased to 40kHz, the ultrasonic amplitude output range is 100μm, and the ultrasonic impact equipment is used again to impact strengthen the repaired area for 10 minutes.

[0047] Step 8: Surface processing of the repaired area. Use diamond grinding wheel grinding, mechanical milling and other methods to process and grind the surface of the repaired area. When the repaired area is smooth, without obvious protrusions, and is at the same height as the undamaged area of ​​the part, stop processing and complete the surface processing of the repaired area.

[0048] Step 9: After the repair is completed, disconnect the protective gas, turn off the power of all equipment, loosen the clamp and take out the repaired parts.

[0049] The cross-sectional microstructure of the alloy structure in the defect repaired area according to the method of the present invention was observed, and the results were as follows: Figure 4 As shown. Figure 4 It can be observed that there is no obvious porosity defect in the repaired area of ​​the high-temperature alloy repaired by ultrasonic impact assisted electrospark deposition, no cracks are generated at the junction of the repaired area and the substrate, the repair layers are tightly bonded to each other, the repair layers have a high density, and the repair quality is good. Figure 2 and Figure 3 This shows that ultrasonic impact-assisted electrospark repair of high-temperature alloys can effectively improve the density of the repair layer and provide an effective means for repairing nickel-based high-temperature alloys with high aluminum and titanium contents.

Claims

1. Ultrasonic impact assisted electric spark repair method for high aluminum titanium high temperature alloy casting defects, characterized by: Here’s how to fix it: Step 1: Processing of defective parts of parts; Processing of metal parts at defective parts to remove original defects and ensure smooth surface of materials after defect removal; Cleaning of the processed parts to be repaired with electrode materials to remove surface oxide film; Processing includes grinding with grinding wheel, angle grinder and mechanical milling; Step 2: Prepare repair materials and equipment; put the cleaned parts to be repaired and electrode materials into a vacuum drying box for drying, and set vacuum drying parameters; set protective gas in the vacuum drying box, connect the protective gas to the repair equipment at a certain gas flow rate to ensure that the protective gas can flow evenly from the spark electrode head; Step 3: Electrospark deposition repair of parts: Use electrode materials of appropriate size to perform electrospark deposition repair on the repaired parts; Step 4: Polishing the repair layer: After repairing one layer, polish the surface of the repair layer to make the deposited surface smooth; Step 5: Ultrasonic impact densification treatment of the repair layer; Use ultrasonic impact equipment to perform ultrasonic impact densification treatment on each repair deposit layer; Step 6: Repeat steps 3 to 5 until the entire area to be repaired is repaired; Step 7: Ultrasonic impact strengthening treatment of the repaired area; after the repaired parts are repaired, the ultrasonic impact equipment is used again to impact strengthen the repaired area; Step 8: Surface processing of the repaired area: Process the surface of the repaired area to restore the surface quality of the parts. Use diamond grinding wheel grinding and mechanical milling methods to process the surface of the repaired area. Step 9: After the repair is completed, disconnect the protective gas, turn off the power, and take out the repaired parts.

2. The ultrasonic impact-assisted electric spark repair method for high-aluminum-titanium high-temperature alloy casting defects according to claim 1 is characterized in that: In the first step, the electrode material prepared for the treatment of the defective part of the part is a metal electrode rod of the same material as the repair material or a metal electrode rod with a composition close to that of the repair material and performance that can meet the use requirements, and the size is selected within the range of 1 to 5 mm.

3. The ultrasonic impact-assisted electric spark repair method for high-aluminum-titanium high-temperature alloy casting defects according to claim 2 is characterized in that: In the first step, cleaning is performed, specifically: the defective parts and electrode materials are placed in an ultrasonic cleaning machine filled with acetone for cleaning, the defective parts and electrode materials are completely immersed in the liquid, and the cleaning time is not less than 10 minutes to remove possible oil stains on the defective parts and electrode materials.

4. The ultrasonic impact-assisted electric spark repair method for high-aluminum-titanium high-temperature alloy casting defects according to claim 3 is characterized in that: In the first step, the shape requirements of the defective parts after processing are as follows: the defective parts after processing are semicircular pits or V-shaped or U-shaped grooves opening upward, the opening angle is greater than 120°, and the bottom arc of the defective parts has a smooth transition.

5. The ultrasonic impact-assisted electric spark repair method for high-aluminum-titanium high-temperature alloy casting defects according to claim 4 is characterized in that: In the second step, the drying parameters of the repaired parts and electrode materials are as follows: use a vacuum drying box to vacuum dry and treat the repaired parts and electrode materials. The vacuum degree of the drying box should be better than 10 ～1 Pa, the drying temperature is 100-150℃, and the drying time is greater than 60min.

6. The ultrasonic impact-assisted electric spark repair method for high-aluminum-titanium high-temperature alloy casting defects according to claim 5 is characterized in that: In the second step, the protective gas is specifically: during the electrospark deposition repair process, argon gas or nitrogen gas with a purity better than 99.99% is used as the protective gas, and the protective gas flow rate is 10 to 30 L / min.

7. The ultrasonic impact-assisted electric spark repair method for high aluminum-titanium high temperature alloy casting defects according to claim 6 is characterized in that: In the third step, the parts are repaired by electrospark deposition, specifically: starting from the bottom middle of the area to be repaired, and completing the repair of the entire repair layer from the inside to the outside point by point and line by line; the thickness of each repair layer shall not exceed 0.2mm at a time; The repair parameter requirements include: the diameter of the electrode rod is 1 to 5 mm, the electrode speed is 500 to 1500 r / min, the voltage is 30 to 60 V, the capacitance is 100 to 150 μF, and the frequency is 150 to 250 Hz.

8. The ultrasonic impact-assisted electric spark repair method for high-aluminum-titanium high-temperature alloy casting defects according to claim 7 is characterized in that: In the fourth step, the surface of the repair layer is polished. Specifically, a spherical diamond grinding wheel is used to polish the surface of the repair layer to improve the surface flatness of the repair layer. During polishing, only surface protrusions are removed, and the deposited repair layer is not processed.

9. The ultrasonic impact-assisted electric spark repair method for high-aluminum-titanium high-temperature alloy casting defects according to claim 8 is characterized in that: In the fifth step, the repair layer is densified by ultrasonic impact, specifically: the tip of the ultrasonic impact head in the ultrasonic impact equipment is a center plane of a circle with a diameter of 0.2 to 1 mm, the ultrasonic frequency is 20 to 30 kHz, the ultrasonic amplitude output range is 50 to 100 μm, and the impact time is not less than 5 minutes.

10. The ultrasonic impact-assisted electric spark repair method for high-aluminum-titanium high-temperature alloy casting defects according to claim 9, characterized in that: In the seventh step, the repair area is subjected to ultrasonic impact strengthening treatment, specifically: the repair area is subjected to ultrasonic impact strengthening treatment again, the frequency of ultrasonic impact is increased to 30-40kHz, the ultrasonic amplitude output range is 50-100μm, and the impact time is 5-10min.

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