Selective laser melting forming repairing method for titanium alloy rocker arm part

Abstract

The invention relates to the field of additive manufacturing, and particularly discloses a titanium alloy rocker arm part selective laser melting forming repair method which comprises the following steps of damaged part pretreatment, repair model data processing, repair powder pretreatment, repair cabin preparation, forming process, stress relief annealing and machining. A selective laser melting forming process is used for repairing the aircraft titanium alloy rocker arm, and finally a repaired part which is free of deformation, the oxygen content rising amount is controlled within 100 ppm, the repairing precision reaches 0.1 mm, the tensile strength reaches 770 MPa, and the elongation is 13% is obtained and recovered to the original part level. The defects of large deformation, high oxygen content and low repairing precision of a conventional repairing means of the aircraft titanium alloy rocker arm are overcome. The repairing method has extremely high economic benefits.

Description

Technical Field

[0001] The invention relates to a repair method, in particular to a repair method for a titanium alloy rocker arm part by selective laser melting forming, and belongs to the field of additive manufacturing. Background Art

[0002] TC2 titanium alloy is widely used in the aviation field due to its excellent mechanical properties. TC2 titanium alloy rocker arms mainly play a transmission role in aircraft. During the service process, the rocker arm key shaft will crack or even break. Repairing the broken parts to restore the external dimensions and mechanical properties of the damaged parts can reduce costs and shorten the maintenance cycle.

[0003] At present, conventional repair methods include argon arc welding, arc surfacing, laser cladding repair, plasma arc welding, etc. Argon arc welding, arc surfacing and plasma arc welding have large heat input, large welding deformation and rough surface. Although laser cladding repair has high laser energy density, small heat input and smooth repair surface, it is difficult to meet the process requirements in terms of forming accuracy and oxygen content control.

[0004] The selective laser melting forming technology is similar to the laser cladding repair principle. It has the advantages of high forming accuracy and good oxygen content control, and is widely used in the manufacturing of high-precision parts. Since the selective laser melting forming technology requires the substrate surface to be flat, its application in the repair field is limited. The fracture surface can be processed using a high-precision grinder or milling machine to meet the flatness requirements.

[0005] The patents related to selective laser melting forming and repair are as follows: The existing patent with patent number 202211176953.4 discloses a fixed leveling device for SLM repair of turbine blades, which can conveniently and quickly realize the clamping and posture adjustment of turbine blades, but the device is large in size, wastes powder, and has limited accuracy. The existing patent with patent number 201410083380.x discloses a selective laser melting deep hole supplementary repair device, which has a customized workbench and is not very versatile and difficult to use in conventional SLM equipment. The existing patent with patent number 202211176953.4 discloses a laser selective melting repair method for special-shaped end caps and a special fixture for end caps. This method designs a special fixture, but it is difficult to accurately position the repair area and control the flatness. Summary of the invention

[0006] In view of the problems in the prior art, the present invention provides a method for selective laser melting forming and repairing a titanium alloy rocker arm part.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A method for repairing a titanium alloy rocker arm part by selective laser melting forming comprises the following steps:

[0009] Step 1: Pre-treatment of the damaged parts: fix the damaged rocker arm parts on the substrate, and trim the fracture surface of the damaged rocker arm parts so that the trimmed fracture surface maintains a preset flatness with the upper end surface of the substrate;

[0010] Step 2: Repair model data processing, import the established 3D model of the rocker arm defective part into the data processing software of the SLM equipment for processing, arrange the 3D model, slice and layer it, and generate the repair scanning path;

[0011] Step 3: Pre-treatment of repair powder: vacuum drying the titanium alloy powder used for repair, and after the titanium alloy powder is cooled, take it out and put it into the powder bin of the SLM equipment for standby use;

[0012] Step 4: Prepare the repair chamber, lower the damaged rocker arm part with the base plate to the preset repair position of the fracture surface, and adjust the repair environment of the repair chamber to the preset state;

[0013] Step 5: During the molding process, the fracture surface of the damaged rocker arm parts is repaired layer by layer according to the preset repair process parameters and repair scanning path;

[0014] Step 6: Stress relief annealing: put the repaired rocker arm parts into a vacuum heat treatment furnace for stress relief annealing;

[0015] Step 7: Machining: Finish the rocker arm parts after stress relief annealing until they meet the preset process requirements.

[0016] Optionally, the substrate is made of stainless steel or titanium alloy, the roughness of the substrate side edge is less than Ra1.6, and the flatness of the substrate side edge is between -50 μm and 50 μm.

[0017] Optionally, a limiting groove adapted to the bottom end of the damaged rocker arm part is opened in the middle of the substrate, and the fracture surface of the damaged rocker arm part after repair maintains a preset flatness of -50μm to 50μm with the upper end surface of the substrate.

[0018] Optionally, after the fracture surface of the damaged rocker arm component is trimmed, the height between the fracture surface and the upper end surface of the substrate and the placement distance of the center of the fracture surface relative to the center of the substrate are measured.

[0019] Optionally, the titanium alloy powder used for the repair is TC4 titanium alloy powder, the particle size of the titanium alloy powder is ≤60μm, the titanium alloy powder is prepared by vacuum induction melting and gas atomization, the drying temperature is 90-120°C, and the drying time is 1-4h.

[0020] Optionally, the three-dimensional model is placed as a three-dimensional model of the twin substrate and the damaged parts of the rocker arm in the data processing software.

[0021] Optionally, the preset repair process parameters are: internal laser power 160W~180W, internal exposure time 50μs~70μs, internal point spacing 60μm~75μm, scanning track spacing 80μm~110μm, contour laser power 170W, contour exposure time 60μs, contour point spacing 75μs, powder layer thickness 30μm and scanning strategy adopts 67° rotation scanning, and the gap between the soft scraper and the fracture surface of the damaged rocker arm part is -100μm~0μm.

[0022] Optionally, the stress relief annealing process is to perform the stress relief annealing at a vacuum degree of 6.67×10 -3 Pa~6.67×10 -2 Pa and keep it at a temperature of 545℃ ~ 585℃ for 2h ~ 4h, and then cool it in air or in the furnace.

[0023] Optionally, the preset state of the repair environment of the repair chamber is to use an inert gas with a purity of 99.999% as the protective gas, preheat the substrate to 80-170° C., and the oxygen content is ≤1000ppm.

[0024] Beneficial effects of the present invention:

[0025] The aircraft titanium alloy rocker arm was repaired by selective laser melting forming process, and finally a repaired part with no deformation, oxygen content increased within 100ppm, repair accuracy of 0.1mm, tensile strength of 770MPa, and elongation of 13% was obtained, which was restored to the original level. The conventional repair methods of aircraft titanium alloy rocker arm have solved the shortcomings of large deformation, high oxygen content and low repair accuracy. This repair method has extremely high economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0027] Figure 1 It is a schematic diagram of the substrate structure of the present invention.

[0028] Figure 2 For the present invention Figure 1 Side view of.

[0029] Figure 3 It is a schematic diagram of the cover plate structure of the present invention.

[0030] Figure 4 It is a schematic diagram of the substrate structure of the present invention.

[0031] In the figure: 2, cover plate; 3, groove; 4, bolt hole; 5, limit groove; 6, base plate. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] See also Figure 1-4 As shown, a method for selective laser melting forming and repairing a titanium alloy rocker arm part comprises the following steps:

[0034] Step 1: pre-treatment of the damaged part, fixing the damaged rocker arm part on the substrate 6, trimming the fracture surface of the damaged rocker arm part, so that the trimmed fracture surface maintains a preset flatness with the upper end surface of the substrate 6;

[0035] Use a milling machine or grinder to level the fracture surface of the damaged TC2 titanium alloy rocker arm parts to make subsequent measurement data more accurate and facilitate subsequent model establishment. In addition, use ethanol or acetone to clean the damaged rocker arm parts to remove surface oil stains.

[0036] Step 2: Repair model data processing, import the established 3D model of the defective part of the rocker arm into the data processing software of the SLM equipment for processing, arrange the 3D model, slice and layer it, and after each slice is limited to the cross-sectional layer of the fracture surface, it is convenient to generate a repair scanning path, so that the fracture surface can be accurately repaired layer by layer; the 3D model of the defective part of the rocker arm is established through the CATIA modeling software based on the digital model of the rocker arm part and according to the actual defect situation.

[0037] Step 3: Pre-treatment of repair powder: vacuum drying the titanium alloy powder used for repair, and after the titanium alloy powder is cooled, take it out and put it into the powder bin of the SLM equipment for standby use;

[0038] Step 4: Prepare the repair chamber, lower the damaged rocker arm part with the base plate 6 to the preset repair position of the fracture surface, and adjust the repair environment of the repair chamber to the preset state;

[0039] Step 5: During the molding process, the SLM equipment is used to perform layer-by-layer additive repair on the fracture surface of the damaged rocker arm parts according to the preset repair process parameters and repair scanning path;

[0040] Step 6: Stress relief annealing: put the repaired rocker arm parts into a vacuum heat treatment furnace for stress relief annealing;

[0041] Step 7: Machining: Finish the rocker arm parts after stress relief annealing until they meet the preset process requirements. Through machining, the size and surface condition of the repaired parts meet the preset process requirements and can be restored to the original level to the greatest extent.

[0042] Specifically, the substrate 6 is one of stainless steel or titanium alloy, the roughness of the side of the substrate 6 is less than Ra1.6, the flatness of the side of the substrate 6 is -50μm to 50μm, and the fracture surface of the damaged rocker arm component after repair and the upper end surface of the substrate 6 maintain a preset flatness of -50μm to 50μm. This makes the flatness error smaller, the subsequent measured data and the established three-dimensional model have higher accuracy, which is conducive to improving the accuracy of the final repair.

[0043] Specifically, the base plate 6 has a limiting groove 5 in the middle thereof, which matches the bottom end of the damaged rocker arm part. The bottom end of the damaged rocker arm part can be placed in the limiting groove 5 on the base plate 6, and a cover plate 2 is installed on the bottom end of the damaged rocker arm part to further limit it. The bottom of the cover plate 2 is also provided with a groove 3 which matches the upper surface of the bottom end of the damaged rocker arm part. The cover plate 2 and the base plate 6 clamp and fix the bottom end of the damaged rocker arm part. The damaged rocker arm part will not shake on the base plate 6, and can be kept in the same position during the repair process and the data measurement process, which improves the positioning accuracy and makes the final repair accuracy higher.

[0044] Bolt holes 4 are provided on both the cover plate 2 and the base plate 6, so that the cover plate 2 can be fixed to the base plate 6 by bolts when limiting the bottom end of the damaged rocker arm part.

[0045] Specifically, after the fracture surface of the damaged rocker arm part is repaired, a three-coordinate measuring machine is used to measure the height between the fracture surface and the upper end surface of the substrate 6 and the placement distance of the center of the fracture surface relative to the center of the substrate 6. The placement distance measurement method is to measure the distance from the center of the rocker arm key shaft to the center of the substrate 6 along the direction perpendicular to the side of the substrate 6. The center of the rocker arm key shaft is Figure 1 The center of the inner end of the groove at the right end of the middle. When the rocker arm parts are damaged and installed with the base plate 6, if Figure 2 Arranged in the state shown.

[0046] Specifically, the three-dimensional model is placed as a three-dimensional model of the twin substrate 6 and the damaged parts of the rocker arm in the data processing software.

[0047] Specifically, the titanium alloy powder used in the repair is TC4 titanium alloy powder, the particle size of the titanium alloy powder is ≤60μm, the preparation method of the titanium alloy powder is vacuum induction melting gas atomization, the drying temperature is 90-120°C, and the drying time is 1-4h. The TC2 titanium alloy rocker arm parts are repaired with the treated TC4 titanium alloy powder, so that the laid titanium alloy powder is more uniform, the interior of the repaired TC2 titanium alloy rocker arm parts is more uniform, the deformation is smaller, and the subsequent repair accuracy is higher.

[0048] Specifically, the preset repair process parameters are: internal laser power 160W~180W, internal exposure time 50μs~70μs, internal point spacing 60μm~75μm, scanning track spacing 80μm~110μm, contour laser power 170W, contour exposure time 60μs, contour point spacing 75μs, powder layer thickness 30μm and scanning strategy adopts 67° rotation scanning, and the gap between the soft scraper and the fracture surface of the damaged part of the rocker arm part is -100μm~0μm.

[0049] Specifically, the stress relief annealing process is to perform the stress relief annealing at a vacuum degree of 6.67×10 -3 Pa~6.67×10 -2 Pa and 545℃~585℃ for 2h~4h, and then air cool or furnace cool. Stress relief annealing can reduce the residual stress of parts and facilitate subsequent machining.

[0050] Specifically, the preset state of the repair environment of the repair chamber is to use an inert gas with a purity of 99.999% as the protective gas, the substrate 6 is preheated to 80-170°C, and the oxygen content is ≤1000ppm. Before the repair molding, the preset state of the repair environment of the repair chamber is adjusted to a preset appropriate state, which can make the subsequent repair process more accurate, and the different layers of the repaired additive material are uniform, so that the final repaired parts have high precision, small deformation, and low oxygen content.

[0051] Comparison Items Traditional laser cladding repair Selective laser melting forming repair Accuracy 1mm 0.1mm Heat affected zone 0.6mm 0.015mm Production cycle (excluding heat treatment) ＜5h ＜3h Oxygen ppm 1500～2000 ＜100

[0052] The above table is a data comparison of the repair of the same part using the traditional laser cladding repair method and the selected area laser melting forming repair method in this article.

[0053] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for repairing titanium alloy rocker arm parts by selective laser melting forming, characterized in that: The following steps are involved: Step 1: Pre-treatment of the damaged parts: fix the damaged rocker arm parts on the substrate, and trim the fracture surface of the damaged rocker arm parts so that the trimmed fracture surface maintains a preset flatness with the upper end surface of the substrate; Step 2: Repair model data processing, import the established 3D model of the rocker arm defective part into the data processing software of the SLM equipment for processing, arrange the 3D model, slice and layer it, and generate the repair scanning path; Step 3: Pre-treatment of repair powder: vacuum drying the titanium alloy powder used for repair, and after the titanium alloy powder is cooled, take it out and put it into the powder bin of the SLM equipment for standby use; Step 4: Prepare the repair chamber, lower the damaged rocker arm part with the base plate to the preset repair position of the fracture surface, and adjust the repair environment of the repair chamber to the preset state; Step 5: During the molding process, the fracture surface of the damaged rocker arm parts is repaired layer by layer according to the preset repair process parameters and repair scanning path; Step 6: Stress relief annealing: put the repaired rocker arm parts into a vacuum heat treatment furnace for stress relief annealing; Step 7: Machining: Finish the rocker arm parts after stress relief annealing until they meet the preset process requirements.

2. The method for selective laser melting forming and repairing a titanium alloy rocker arm part according to claim 1 is characterized in that: The substrate is made of stainless steel or titanium alloy, the roughness of the substrate side edge is less than Ra1.6, and the flatness of the substrate side edge is between -50 μm and 50 μm.

3. The method for selective laser melting forming and repairing a titanium alloy rocker arm part according to claim 2 is characterized in that: A limiting groove matching the bottom end of the damaged rocker arm part is opened in the middle of the base plate, and the fracture surface of the damaged rocker arm part after repair maintains a preset flatness of -50μm to 50μm with the upper end surface of the base plate.

4. The method for selective laser melting forming and repairing a titanium alloy rocker arm part according to claim 1 is characterized in that: After the fracture surface of the damaged rocker arm part is trimmed, the height between the fracture surface and the upper end surface of the substrate and the placement distance of the center of the fracture surface relative to the center of the substrate are measured.

5. The method for selective laser melting forming and repairing a titanium alloy rocker arm part according to claim 1 is characterized in that: The titanium alloy powder used for the repair is TC4 titanium alloy powder, the particle size of the titanium alloy powder is ≤60 μm, the preparation method of the titanium alloy powder is vacuum induction melting gas atomization, the drying temperature is 90-120° C., and the drying time is 1-4 hours.

6. The method for selective laser melting forming and repairing a titanium alloy rocker arm part according to claim 1 is characterized in that: The three-dimensional model is arranged as a three-dimensional model of the twin substrate and the damaged parts of the rocker arm in the data processing software.

7. The method for selective laser melting forming and repairing a titanium alloy rocker arm part according to claim 1 is characterized in that: The preset repair process parameters are: internal laser power 160W~180W, internal exposure time 50μs~70μs, internal point spacing 60μm~75μm, scanning track spacing 80μm~110μm, contour laser power 170W, contour exposure time 60μs, contour point spacing 75μs, powder layer thickness 30μm and scanning strategy adopts 67° rotation scanning, and the gap between the soft scraper and the fracture surface of the damaged rocker arm part is -100μm~0μm.

8. The method for selective laser melting forming and repairing a titanium alloy rocker arm part according to claim 1 is characterized in that: The stress relief annealing process is to heat the product under vacuum at 6.67×10 -3 Pa~6.67×10 -2 Pa and keep it at a temperature of 545℃ ~ 585℃ for 2h ~ 4h, and then cool it in air or in the furnace.

9. The method for repairing a titanium alloy rocker arm part by selective laser melting forming according to claim 1, characterized in that: The preset state of the repair environment of the repair chamber is to use an inert gas with a purity of 99.999% as the protective gas, preheat the substrate to 80-170° C., and the oxygen content is ≤1000ppm.

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