Titanium alloy repairing and remanufacturing method based on selective laser melting

Abstract

The invention belongs to the technical field of titanium alloy repairing and remanufacturing, and particularly relates to a titanium alloy repairing and remanufacturing method based on selective laser melting, which comprises the following steps of: (1) grinding a grafting surface of a titanium alloy part, fixing the titanium alloy part on a positioning clamp of a base plate, and enabling the grafting surface to be parallel to the base plate; (2) loading into selective laser melting equipment, manually adjusting a grafting surface to a focal plane position, and then pre-paving a layer of titanium alloy powder; (3) calibrating a focal plane; (4) the titanium alloy powder is subjected to repair forming according to the to-be-repaired three-dimensional model through a selective laser melting forming method; and (5) the repaired and formed titanium alloy part is detected. According to the method, unqualified titanium alloy parts caused by equipment shutdown can be repaired and remanufactured while the structural strength is guaranteed, and meanwhile the manufacturing efficiency is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of titanium alloy repair and remanufacturing, and particularly relates to a method for titanium alloy repair and remanufacturing based on selective laser melting. Background Art

[0002] The additive manufacturing of titanium alloy products is expensive, and the raw material powder and machine time cost are several times that of subtractive and equal material processing. Moreover, once the equipment stops, internal defects such as faults and cracks will occur in the target parts, resulting in unqualified products, which can only be scrapped, causing great waste.

[0003] Selective laser melting (SLM) belongs to metal additive manufacturing technology, which has the characteristics of strong flexibility, high forming density, and high manufacturing efficiency. The working process is as follows: The printer controls the laser to selectively irradiate the powder laid above, and the metal powder is heated to complete melting and then formed. Then the piston lowers the workbench by one unit height, a new layer of powder is spread on the formed current layer, and the equipment loads the data of the new layer cross-section for laser melting and bonds with the previous layer cross-section. This process is cycled layer by layer until the entire object is formed. Summary of the Invention

[0004] In order to reduce the loss and waste caused by unqualified products due to equipment downtime during the additive manufacturing process, the present invention provides a method for titanium alloy repair and remanufacturing based on selective laser melting, which can effectively repair and remanufacture the target parts while ensuring the structural strength, and has high manufacturing efficiency.

[0005] Specifically, the present invention provides the following technical solutions:

[0006] A method for titanium alloy repair and remanufacturing based on selective laser melting, comprising the following steps:

[0007] (1) Grind the grafting surface of the titanium alloy part, then fix it on the positioning fixture of the substrate, and make the grafting surface parallel to the substrate;

[0008] (2) Install the substrate with the fixed titanium alloy part into the selective laser melting equipment, manually adjust the grafting surface to the focal plane position, and then pre-lay a layer of titanium alloy powder;

[0009] (3) Calibrate the focal plane;

[0010] (4) Use the selective laser melting forming method to repair and form the titanium alloy powder according to the three-dimensional model to be repaired;

[0011] (5) Detect the repaired and formed titanium alloy part.

[0012] In the present invention, the grafting surface refers to the surface of the remaining part to be repaired and remanufactured after identifying the defective part of the non-conforming product and cutting out the defective part using wire cutting.

[0013] In the present invention, according to the contour information of the grafting surface, the initial end face matching it in the three-dimensional model of the titanium alloy part is searched to obtain the three-dimensional model to be repaired.

[0014] Preferably, in step (1), the titanium alloy part is prepared by selective laser melting and the material is TC4 or TA15. The titanium alloy repair and remanufacturing method of the present invention is particularly applicable to titanium alloy parts prepared by selective laser melting using two titanium alloy powder materials of TC4 and TA15.

[0015] Preferably, in step (1), the flatness of the ground grafting surface is not greater than 0.05 mm.

[0016] Preferably, in step (1), the parallelism between the grafting surface and the substrate is not greater than 0.02 mm.

[0017] Preferably, in step (2), the pre-laid titanium alloy powder layer is flush with the grafting surface and it is ensured that there is no titanium alloy powder on the grafting surface. If there is titanium alloy powder on the grafting surface, it will cause the quality of the laser-formed grafting layer to be uneven.

[0018] Preferably, in step (3), the calibration focal plane includes: importing the three-dimensional model to be repaired of the titanium alloy part into the selective laser melting equipment, performing a single sintering, and detecting whether the focal plane is aligned with the grafting surface; if not aligned, measuring the actual error of the focal plane, adjusting the position of the titanium alloy part according to the error value, and then performing a single sintering again until the focal plane is completely calibrated with the grafting surface.

[0019] The scraper moving from the left to the right and then back to the left is one stroke. The single sintering in the present invention means that the scraper completes one stroke and the laser performs a single sintering on the powder-laid surface completed in this stroke.

[0020] Further preferably, the method for detecting whether the focal plane is aligned with the grafting surface is specifically as follows: scanning the inside of the selective laser melting equipment using a 3D laser scanner. If the flatness of the layer formed by single sintering on the grafting surface is not greater than 0.05 mm, then the focal plane is completely calibrated with the grafting surface.

[0021] Preferably, in step (4), the powder layer thickness of the selective laser melting forming method is 40% of the powder layer thickness used when originally preparing the titanium alloy part (for example, when the powder layer thickness used when originally preparing the titanium alloy part is 60 μm, the layer thickness used in the repair and remanufacturing of the present invention is 24 μm);

[0022] The laser power of the selective laser melting forming method is 80% of the laser power used in the original preparation of titanium alloy parts (for example, the laser power used in the original preparation of titanium alloy parts is 300 - 400 W, and the laser power used in the repair and remanufacturing of the present invention is 240 - 320 W).

[0023] By reducing the layer thickness and correspondingly lowering the laser power, the present invention can improve the internal grain density of the initial grafting layer in the repair and remanufacturing, and enhance the performance of the grafting layer.

[0024] Preferably, in steps (2) and (4), the titanium alloy powder used has the same material as the titanium alloy powder used in the preparation of titanium alloy parts, and more preferably, it is the titanium alloy powder raw material purchased in the same batch.

[0025] Preferably, in step (5), the inspection of the repaired and formed titanium alloy parts includes: non-destructive inspection, external dimension inspection, and sample tensile test of the repaired and formed titanium alloy parts;

[0026] The non-destructive inspection includes X-ray radiography inspection and / or industrial CT inspection;

[0027] The external dimension inspection includes coordinate measuring machine inspection and / or three-dimensional scanning inspection.

[0028] The beneficial effects achieved by the present invention:

[0029] (1) A titanium alloy repair and remanufacturing method based on selective laser melting provided by the present invention can repair and remanufacture unqualified titanium alloy parts caused by equipment shutdown, reducing losses and waste.

[0030] (2) A titanium alloy repair and remanufacturing method based on selective laser melting provided by the present invention is particularly suitable for the repair and remanufacturing of titanium alloy parts prepared by selective laser melting using two titanium alloy powder materials, TC4 and TA15.

[0031] (3) A titanium alloy repair and remanufacturing method based on selective laser melting provided by the present invention ensures high structural strength after repair and remanufacturing through a specific method of calibrating the focal plane.

[0032] (4) A titanium alloy repair and remanufacturing method based on selective laser melting provided by the present invention can improve the internal grain density of the initial grafting layer in the repair and remanufacturing and enhance the performance of the grafting layer by reducing the layer thickness and correspondingly lowering the laser power. Description of the Drawings

[0033] Figure 1 It is a schematic structural diagram of the repaired and remanufactured target part in Embodiment 1 of the present invention.

[0034] Figure 2 This is the finished product drawing of the repaired and remanufactured target part in Embodiment 1 of the present invention. Detailed implementation manners

[0035] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention. For those without specific technical or conditions noted in the embodiments, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications.

[0036] In the following embodiments, the scraper used in the selective laser melting equipment is replaced with a carbon fiber brush scraper, with a size of 255 mm, a thickness of 3 mm, ground on both sides, and the edge angle α is 30 degrees.

[0037] Embodiment 1

[0038] Refer to Figure 1 , the target part for repair and remanufacturing in this embodiment is the upper cross arm of metal. Its material is TC4 titanium alloy, and the forming method is selective laser melting. Three pieces are formed on the substrate as a group. The fault position is located at the hole position near the top, which is caused by the non-natural shutdown of the equipment.

[0039] The repair and remanufacturing method for the above-mentioned target part provided in this embodiment is as follows:

[0040] (1) Take out the whole substrate, keep the original positions of the target part and related supports, and use a grinding machine to grind the grafting surface. The flatness of the ground grafting surface is not greater than 0.05 mm, and at the same time, ensure that the parallelism between the grafting surface and the substrate is not greater than 0.02 mm.

[0041] (2) Put the target part back into the forming chamber and fasten the substrate; manually adjust the grafting layer to the focal plane position; manually and evenly add titanium alloy powder into the forming chamber until it reaches the grafting surface, adjust the scraper for powder spreading, and keep the powder flush with the part surface and no powder on the surface to be grafted.

[0042] (3) Import the three-dimensional model to be repaired of the target part into the equipment, perform a single sintering, and detect whether the XY focal plane is aligned with the surface to be grafted of the part; if not aligned, it is necessary to measure the actual error of the XY focal plane, adjust the position of the part according to this value, and then perform a single sintering again until the focal plane is completely calibrated with the grafting surface.

[0043] (4) Use the selective laser melting forming method to repair and form the TC4 titanium alloy powder according to the three-dimensional model to be repaired. The results are shown in Figure 2 , and its manufacturing process parameters are as follows:

[0044] Equipment: BLT-S400, Selective Laser Melting (SLM) additive manufacturing process;

[0045] Material: TC4 powder of the same batch;

[0046] Scanning strategy: Z-shaped checkerboard;

[0047] Scanning angle: 65°;

[0048] Scanning direction: Random scanning;

[0049] Scanning rate: 1200 mm / s;

[0050] Strip width: 0.3 mm;

[0051] Laying thickness: 24 μm, which is 40% of the laying thickness used for the original non-conforming products;

[0052] Laser power: 350 W, which is 80% of the laser power used for the original non-conforming products;

[0053] Laser spot diameter: 0.2 mm.

[0054] (5) After the repair and remanufacturing were completed, two parts of the grafting layer were randomly selected for X-ray inspection to determine the nature of the delamination and crack defects, and the determination result was none.

[0055] Although the present invention has been described in detail above with general descriptions, specific embodiments and experiments, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. A method for repairing and remanufacturing titanium alloy based on selective laser melting, characterized in that, It includes the following steps: (1) Grind the grafting surface of the titanium alloy part, then fix it on the positioning fixture of the substrate, and make the grafting surface parallel to the substrate; (2) Install the substrate with the fixed titanium alloy part into the selective laser melting equipment, manually adjust the grafting surface to the focal plane position, and then pre-lay a layer of titanium alloy powder; (3) Calibrate the focal plane; (4) Repair and form the titanium alloy powder by the selective laser melting forming method according to the three-dimensional model to be repaired; (5) Detect the titanium alloy part after repair and forming.

2. The method for repairing and remanufacturing titanium alloy based on selective laser melting according to claim 1, characterized in that, The titanium alloy part is prepared by selective laser melting, and the material is TC4 or TA15.

3. A method for repairing and remanufacturing titanium alloy based on selective laser melting according to claim 1 or 2, characterized in that, In step (1), the parallelism between the grafting surface and the substrate is not greater than 0.02 mm.

4. A method for repairing and remanufacturing titanium alloy based on selective laser melting according to claim 1 or 2, characterized in that In step (2), the pre-laid titanium alloy powder layer is flush with the grafting surface and ensure that there is no titanium alloy powder on the grafting surface.

5. A method for repairing and remanufacturing titanium alloy based on selective laser melting according to claim 1 or 2, characterized in that, In step (3), the calibration of the focal plane includes: import the three-dimensional model to be repaired of the titanium alloy part into the selective laser melting equipment, perform a single sintering, and detect whether the focal plane is aligned with the grafting surface; if not aligned, measure the actual error of the focal plane, adjust the position of the titanium alloy part according to the error value, and then perform a single sintering again until the focal plane is completely calibrated with the grafting surface.

6. A method for repairing and remanufacturing titanium alloy based on selective laser melting according to claim 5, characterized in that, The method for detecting whether the focal plane is aligned with the grafting surface is specifically: scan the inside of the selective laser melting equipment with a 3D laser scanner. If the flatness of the layer formed by a single sintering on the grafting surface is not greater than 0.05 mm, the focal plane is completely calibrated with the grafting surface.

7. A method for repairing and remanufacturing titanium alloy based on selective laser melting according to claim 1 or 2, characterized in that, In step (4), the powder layer thickness of the selective laser melting forming method is 40% of the powder layer thickness used when the original titanium alloy part was prepared; The laser power of the selective laser melting forming method is 80% of the laser power used when the original titanium alloy part was prepared.

8. A method for repairing and remanufacturing titanium alloy based on selective laser melting according to claim 1 or 2, characterized in that, In step (5), the detection of the titanium alloy part after repair and forming includes: non-destructive testing, external dimension testing and tensile testing of the sample piece for the titanium alloy part after repair and forming; The non-destructive testing includes X-ray testing and / or industrial CT testing; The external dimension testing includes coordinate measuring machine testing and / or three-dimensional scanning testing.

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