CN114434086A - Method for repairing surface cracks of titanium alloy thin-walled workpiece - Google Patents
Method for repairing surface cracks of titanium alloy thin-walled workpiece Download PDFInfo
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- CN114434086A CN114434086A CN202111606339.2A CN202111606339A CN114434086A CN 114434086 A CN114434086 A CN 114434086A CN 202111606339 A CN202111606339 A CN 202111606339A CN 114434086 A CN114434086 A CN 114434086A
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P6/00—Restoring or reconditioning objects
- B23P6/04—Repairing fractures or cracked metal parts or products, e.g. castings
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
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- C23C24/10—Coating starting from inorganic powder by application of heat or pressure and heat with intermediate formation of a liquid phase in the layer
- C23C24/103—Coating with metallic material, i.e. metals or metal alloys, optionally comprising hard particles, e.g. oxides, carbides or nitrides
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Abstract
Aiming at the repair requirement of a titanium alloy thin-wall part with the thickness of 0.5 mm-0.7 mm, the method aims to overcome the defects of poor feasibility, edge burning during arc striking, large thermal stress after fusion welding and complex heat treatment process after welding in the prior art. The invention provides a method for repairing cracks on the surface of a titanium alloy thin-walled part, which considers the laser heat concentration of laser cladding and adopts low power to carry out laser cladding without curling and burning through a titanium alloy skin. However, the titanium alloy powder cannot be fully melted at low power, the laser cladding technology and the direct-current argon arc welding technology are combined, and argon arc welding is performed on the basis that the titanium alloy powder is already fused and coated, so that the titanium alloy powder is further fused and filled, the repair of cracks on the surface of the ventral fin titanium alloy skin is realized, the repair efficiency is improved, the quality of a cladding layer is ensured, the repair cost is reduced, the pneumatic appearance of the ventral fin structure is restored, the peripheral area is not damaged, the structural bearing capacity is ensured, and the bottleneck problem of repair of the cracks on the surface of the ventral fin titanium alloy skin is solved.
Description
Technical Field
The invention relates to a method for repairing surface cracks of a titanium alloy thin-wall part, which combines a laser cladding technology and an argon arc welding technology to repair surface cracks of a titanium alloy skin of an aero-plane ventral fin of the titanium alloy thin-wall part with the thickness of 0.5-0.7 mm.
Background
In the process of overhauling a certain type of airplane, a plurality of cracks are found at the joint of the surface of the ventral fin titanium alloy skin and the internal reinforcing rib, the length of each crack is 17-25 cm, the cracks extend along the joint of the surface titanium alloy skin and the reinforcing rib, the cracks have fault damage deeply and penetrate through the second layer, and the use safety of the airplane is seriously damaged. If the mode of replacing a new product is directly adopted for repair, firstly, the maintenance cost is too high, and the ventral fin is scrapped due to crack failure and is seriously wasted. And secondly, a repair factory does not have a production and manufacturing means, the period of purchasing new products is long, and the repair factory is limited by people and is difficult to ensure the normal delivery cycle of the airplane. Therefore, the development of the ventral fin surface crack repairing technology can effectively avoid resource waste, shorten the repairing period and have great economic benefit.
The ventral fin is of a titanium alloy double-layer thin-wall structure, the material of the ventral fin is TC4 titanium alloy, the ventral fin is manufactured by superplastic forming and diffusion connection, the thickness of the outermost titanium alloy skin is about 0.5-0.7 mm, the thickness of the second titanium alloy skin is not more than 1mm, and glue solution is arranged in the interlayer. The titanium alloy has the characteristics of high melting point, active chemical property, poor heat conductivity, large heat capacity and the like, is easy to oxidize at high temperature to influence the welding quality, and has high repair difficulty. The traditional argon arc welding repair technology has large heat input quantity, the thickness of the surface layer of the titanium alloy skin is 0.5-0.7 mm, the titanium alloy skin is easily curled, even the titanium alloy skin is directly burnt through, and the fault range is enlarged; the titanium alloy interlayer is filled with glue solution, the melting point of the glue solution is much lower than that of the titanium alloy, and the glue solution is easy to enter a molten pool when being melted, so that dense air holes are generated in a titanium alloy welding line; and the gas generated after the glue solution is combusted enables argon arc welding protective gas argon not to directly act above the molten pool, so that titanium alloy is oxidized. The laser cladding technology belongs to precision machining, can control a repair track, can strictly control the thickness of a cladding layer by adjusting laser power and powder feeding amount, has the remarkable advantages of small heat input amount, small influence on the organization and performance of a base material and the like, and can be applied to repair of titanium alloy thin-walled parts.
The invention with the publication number of CN1966201 discloses a laser cladding repair method for a titanium alloy thin-wall shell, which comprises the steps of cleaning a solder electric corrosion layer, removing hydrogen by vacuum annealing of the solder, then carrying out laser cladding under the protection of argon, realizing the metallurgical bonding of a cladding layer and a base body, having small heat affected zone and small deformation amount of the base body, wherein the repair material is BT20, the wall thickness is 2mm, and for a ventral fin thin-wall part with the thickness of 0.5 mm-0.7 mm, the risk of burning through the thin-wall part exists.
The invention with the publication number of CN109207988A discloses cold spraying powder for repairing surface damage of a titanium alloy thin-wall part and a repairing method thereof, wherein He is used as carrier gas, and TC4, Ti and Al are mixed2O3And cold spraying the mixed powder on the damaged surface of the titanium alloy thin-wall plate to reduce the heat input of powder spraying deposition, and carrying out heat treatment on the titanium alloy thin-wall plate after deposition. The method is adopted to repair crack faults, and because the cold spraying bonding strength is low, the powder porosity is high, the structure is not compact, and the risk of falling off exists in the using process of the airplane.
The invention with the publication number of CN110983103A discloses a 3D printing laser repair method for a TB6 titanium alloy, which is used for carrying out laser strengthening processing on the surface of the titanium alloy by adjusting laser process parameters to obtain a laser remanufacturing repair layer without pore defects and with good performance. TB6 is beta type titanium alloy, and TC4 is alpha + beta titanium alloy, and two alloy types are different, and the performance difference is great, and this invention laser instrument power is great (900W ~ 2000W), is not suitable for the restoration of thin wall spare.
The invention with the publication number of CN113088962A discloses a laser cladding multi-azimuth repairing method of a titanium alloy thin-wall blade damage piece, the laser power is 700W-1000W, a plurality of rows are clad on a groove in the direction from left to right by using coaxial powder feeding laser cladding, and the rows are clad in a way of spirally ascending from the groove bottom to the groove opening. The laser power in the invention is as high as 1000W, the heat input is too large, the gas-guiding thin-wall part is easy to deform, and the method is not suitable for repairing the ventral fin thin-wall part.
The invention with the publication number of CN1224494C discloses a local high-efficiency cooling method for thin-wall parts in laser cladding, thermal spraying and welding processing, and the problems of excessive heating, deformation, overburning, burning through and the like of the parts in an unsteady severe heating process can be effectively prevented by placing a lead sheet and a tin sheet below a welding line. Unfortunately, the method still cannot solve the problems of curling, ablation and the like of the arc-starting titanium alloy skin in the repair process.
The technical research institute of Shenyang aircraft technology (group) of Zhonghang industry, published in the journal of test and mechanism analysis in 2012 "research on laser cladding repair of titanium alloy surface defects", comparative tests on results of laser cladding and argon arc welding repair of TA15 titanium alloy samples show that laser cladding can realize effective repair of titanium alloy surface defects, and the performance of each aspect is much higher than that of argon arc welding repair. The test is not comprehensive enough, and aiming at irregular complex defects, the accessibility of a laser region is poor, the operability is poor, and the bonding strength of cladding powder and a matrix needs to be improved.
Disclosure of Invention
Based on the background technology, aiming at the repair requirement of a titanium alloy thin-wall part with the thickness of 0.5 mm-0.7 mm, the defects of poor feasibility, edge burning during arc striking, large thermal stress after fusion welding and complex heat treatment process after welding in the prior art are overcome. The invention provides a method for repairing cracks on the surface of a titanium alloy thin-walled part, which considers the laser heat concentration of laser cladding and adopts low power to carry out laser cladding without curling and burning through a titanium alloy skin. But the titanium alloy powder can not be fully melted with small power, the laser cladding technology and the direct-current argon arc welding technology are combined, the argon arc welding is carried out on the basis that the titanium alloy powder is already fused and coated, the titanium alloy powder is further fused and filled, and the repair of cracks on the surface of the ventral fin titanium alloy skin is realized.
The invention conception of the invention is as follows: firstly, in order to prevent an interlayer glue solution of a titanium alloy sheet from being melted by heat to cause pollution to a surface to be repaired and ensure the bonding strength of a substrate and a cladding layer, the invention is based on laser cladding equipment, adopts TC4 alloy powder which is made of the same material as a ventral fin substrate, has good sphericity and has a particle size of 75-125 mu m (the powder is too fine and has poor solid fluidity, so that the powder is not uniformly fed, and the powder is too coarse to melt and is easy to form defects), uses argon as a protective gas, mainly solves the problems of titanium alloy oxidation and forming in the laser cladding process, selects proper laser cladding process parameters, accurately controls energy input (adopts low-power laser), and prevents secondary damage. And then, performing direct-current argon arc welding fusion on the region where the cladding layer is not flat and is not fused by using argon arc welding equipment and a low-current process, so that the surface is in smooth transition, and the bonding quality of the cladding layer is improved.
The technical scheme of the invention is as follows:
a method for repairing surface cracks of a titanium alloy thin-wall part is characterized by comprising the following steps:
step 1: pretreatment before welding
1.1, polishing the surface of a titanium alloy thin-wall part till the metallic luster is exposed, finding out all cracks on the titanium alloy thin-wall part, polishing the back of the area where the titanium alloy thin-wall part is located till the metallic luster is exposed for the cracks penetrating through the wall thickness of the titanium alloy, forming grooves at the found cracks to facilitate the adhesion cladding of titanium alloy powder, and forming crack-stopping holes at two ends of the cracks penetrating through the wall thickness of the titanium alloy after forming the grooves;
1.2, polishing and flattening the surface to be repaired, and removing stains on the surface of the thin-walled part;
1.3 the area which does not need to be repaired near the crack is protected to prevent laser sputtering damage;
1.4 introducing inert protective gas into a cavity formed by the titanium alloy thin-wall part;
step 2: laser cladding repair
2.1 drying TC4 titanium alloy powder with the particle size of 75-125 μm at the temperature of 130 +/-5 ℃ for at least 4 hours at the vacuum degree of-0.8-1 bar;
2.2 determining repair Path
Determining the number of laser cladding tracks and the number of layers according to the width and the depth of a groove formed by cracks on the surface of the titanium alloy skin, wherein the surface of the cladding layer is higher than the surface of the titanium alloy thin-walled part;
2.3 laser cladding
2.3.1 preheating before repair:
preheating a surface to be repaired by using 200-plus-300W low-power laser, wherein the number of the preheating layers is 1, the flow of lens protective gas is set to be 8-12L/min before preheating, the flow of powder feeding gas is 6-10L/min, the powder feeding speed is 1-1.2r/min, and the scanning speed of a laser cladding head is 400 mm/min;
2.3.2 surface repair welding:
performing surface welding repair by using laser power of 400-500W, wherein during the surface welding repair, the lens protective gas flow, the powder feeding speed and the scanning speed of the laser cladding head are consistent with the preheating parameters before repair in 2.3.1;
and step 3: d.c. argon arc welding
Selecting a TC4 welding wire, and fusing the area with uneven cladding layer and not fused by welding current of 20-30A to enable the welding surface to be in smooth transition;
and 4, step 4: polishing allowance
Polishing allowance to enable the repair surface to be flat and consistent with the surface roughness of the titanium alloy thin-walled workpiece;
and 5: nondestructive flaw detection;
step 6: and (6) metallographic testing.
Further, the groove formed in the step 1.1 is a V-groove.
Further, the step 4 specifically includes:
4.1 the cladding layer higher than the surface of the titanium alloy skin is polished by a grinding wheel, a small amount of grinding is carried out for many times, the processing stress is reduced, and the smoothness of the repair surface is ensured.
4.2, grinding by using fine sand paper to remove burrs, so that the roughness of the repair surface is consistent with that of the titanium alloy skin surface.
Further, the step 5 specifically includes:
and carrying out fluorescent inspection on the laser cladding repair area on the surface of the polished titanium alloy thin-walled workpiece to ensure that a welding seam and a nearby area have no crack or weld penetration defect.
Compared with the prior art, the invention has the following advantages:
1. aiming at repairing cracks on a titanium alloy thin-walled part with the thickness of 0.5-0.7 mm, the method adopts a laser cladding technology, uses inert shielding gas as shielding gas before welding and in the welding process, can effectively prevent the oxidation of the surface and the back of a welding seam, and leads argon gas to protect the back of the welding seam, so as to protect and reduce the oxidation, take away heat, accelerate cooling and prevent the warping and ablation in the repairing process; through a large number of process tests and parameter debugging, the laser cladding pre-welding is adopted for preheating, the preheating power is 200W-300W, the low-power laser preheats the substrate, the temperature difference is reduced, the stress is reduced, and overheating and burnthrough caused by over-large local heating of the substrate can be effectively avoided; under the condition of ensuring the fusion quality, strictly controlling the laser power, wherein the fusion covering power is 400-500W, reducing the heat input quantity, having small deformation quantity, and effectively avoiding the influence of the interlayer glue solution of the titanium alloy sheet on the welding quality caused by the heated melting and gushing; the laser cladding heat affected zone is small, and the influence on the matrix structure and the strength is small; because the low power is adopted during cladding, the heat input is small, and partial powder is not fully melted under the condition of deeper cracks, an argon arc welding process is required to be added on the basis of a laser cladding layer at the later stage, so that the powder is fully melted, smooth transition of local uneven places can be ensured, and stress concentration is reduced.
2. On the basis of a laser cladding layer, the invention adopts a low-current direct-current argon arc welding process, controls the welding current within the range of 20A-30A, leads the welding surface to be in smooth transition and further ensures the quality of a welding seam.
3. The method gives full play to the advantages of the laser cladding technology and the argon arc welding technology, and can be popularized and applied to repair of titanium alloy thin-wall damage parts in the fields of aviation, ships and automobiles.
Drawings
Fig. 1 shows the failure of the ventral fin skin of the titanium alloy thin-wall part in the embodiment 1.
FIG. 2 is the appearance of the titanium alloy thin-walled part ventral fin skin after laser cladding repair in example 1.
FIG. 3 is the morphology of the titanium alloy thin-walled part ventral fin skin after argon arc welding repair in example 1.
FIG. 4 is the appearance of the titanium alloy thin-walled part ventral fin skin after polishing in example 1.
FIG. 5 is a fluorescent coloring display of the repair area of the ventral fin skin of the titanium alloy thin-wall part in example 1.
FIG. 6 is a microstructure and morphology diagram of a bonding surface of a cladding layer and a substrate of a titanium alloy sample piece in example 1.
FIG. 7 is the appearance of the titanium alloy thin-walled part ventral fin skin after laser cladding repair in example 2.
FIG. 8 is the morphology of the titanium alloy thin-walled part ventral fin skin after argon arc welding repair in example 2.
FIG. 9 shows the polished appearance of the ventral fin skin of the titanium alloy thin-walled member in example 2.
FIG. 10 is a fluorescent coloring display of the repair area of the ventral fin skin of the titanium alloy thin-walled member in example 2.
FIG. 11 is a microstructure diagram of a bonding surface of a cladding layer and a substrate of a titanium alloy test piece in example 2.
Detailed Description
The invention is further illustrated by the following figures and examples.
Example 1:
the embodiment is a method for repairing cracks on the surface of a titanium alloy thin-wall part, the failure mode is shown in figure 1, the method adopts a mode of combining laser cladding and direct-current argon arc welding technologies, strictly controls process parameters to ensure the structural integrity and the repair quality stability of a matrix, recovers the flatness and the smoothness of a repair surface by grinding through a grinding wheel, and detects the defects of cracks, unfused fusion and the like by combining a nondestructive inspection means, and comprises the following specific steps:
step 1: pretreatment before welding
1.1, polishing the coating and the oxide layer on the surface of the titanium alloy skin by using a grinding wheel till the metallic luster is exposed, finding out all cracks on the surface of the titanium alloy skin, and polishing the coating and the oxide layer on the back of the titanium alloy thin-wall part area where the cracks are located and nearby till the metallic luster is exposed to prevent the welding seam from being polluted for the cracks penetrating through the wall thickness of the titanium alloy. Forming a V-shaped groove at each found crack to be repaired so as to facilitate the adhesion cladding of titanium alloy powder, and forming crack-stopping holes at two ends of the crack after forming the V-shaped groove for the crack penetrating through the wall thickness of the titanium alloy; in the step, all places where cracks are likely to expand need to be removed when the cracks are found, one crack extends and expands along a crack source, or expands along a plurality of directions, and the expanded cracks need to be removed, because if the crack source is left without being completely removed, the cracks can expand when the cracks are used; whether the cracks are completely removed can be judged through fluorescent inspection;
1.2, polishing the surface to be repaired by using 240-mesh abrasive paper to enable the surface to be smooth without defects of pits, sharp corners, burrs and the like, and cleaning oil stains and sweat stains on the surface of the titanium alloy skin by using alcohol;
1.3, protecting the area which does not need to be repaired near the crack by using a high-temperature adhesive tape to prevent laser sputtering damage;
1.4 introducing argon (or other inert shielding gas) for protection, so that the argon fills the whole inside of the ventral fin, the surface and the back of the welding seam are prevented from being oxidized, and cooling is accelerated.
Step 2: laser cladding repair
2.1 selecting TC4 titanium alloy powder with the particle size of 75-125 μm to carry out drying treatment, wherein the drying temperature is 135 ℃, the drying time is 4 hours, and the vacuum degree is-1 bar.
2.2 determining repair Path
According to the width and the depth of the groove formed by the surface crack of the titanium alloy skin, the number of laser cladding tracks and the number of laser cladding layers are respectively set to 6 and 6 until the groove is completely covered by the cladding layers, and the surface of each cladding layer is higher than that of the titanium alloy skin, so that the heat input is reduced, and meanwhile, the sufficient machining allowance is ensured.
2.3 laser cladding
2.3.1 preheating before repair:
in order to reduce crack initiation and ensure good fusion of a cladding layer and a substrate and the strength of a bonding surface, a to-be-repaired surface is preheated by adopting low-power laser, the power of the preheated laser is 200W, and the number of preheated layers is 1 (not counted into the number of coating layers); considering the problem of forming after the titanium alloy is melted, setting the flow of lens protective gas to be 8L/min and the flow of powder delivery gas to be 6L/min; in order to ensure that the titanium alloy powder is well combined with the surface to be repaired, the powder feeding speed is set to be 1r/min, and the scanning speed of the laser cladding head is set to be 400 mm/min.
2.3.2 surface repair welding:
in order to ensure that TC4 titanium alloy powder is fully melted and improve the fusion quality, the heat input quantity needs to be controlled, so the laser power is 400W when the surface is welded and repaired, and the other parameters are consistent with the preheating parameters before laser cladding and repairing in 2.3.1.
The surface appearance of the titanium alloy skin after laser cladding repair is shown in fig. 2, and it can be seen that the surface of the repaired cladding layer is relatively flat, basically free of oxidation, good in fusion condition and free of damage near the repair area.
And step 3: d.c. argon arc welding
The method selects a TC4 welding wire and welding current 20A, accurately controls the welding current and time of arc striking, welding and arc closing, fuses the areas with uneven cladding layers and not fused, leads the welding surface to be in smooth transition, and ensures the internal quality of the welding seam.
The surface appearance of the titanium alloy skin after argon arc welding repair is shown in fig. 3, the coating powder on the surface of the cladding layer is fully melted, and the fusion quality is improved.
And 4, step 4: polishing allowance
4.1 the cladding layer higher than the surface of the titanium alloy skin is polished by a grinding wheel, a small amount of grinding is carried out for many times, the processing stress is reduced, and the smoothness of the repair surface is ensured.
4.2, using fine sand paper to polish and remove burrs, so that the roughness of the repair surface is consistent with that of the titanium alloy skin.
The surface appearance after polishing is shown in figure 4, the repaired surface is flat and smooth, and the technical requirements are met.
And 5: nondestructive inspection
And performing fluorescent inspection on the laser cladding repair area on the surface of the polished ventral fin to ensure that the weld joint and the adjacent area have no defects such as cracks, welding opacity and the like. The polished surface is subjected to fluorescent coloring as shown in fig. 5, and it can be seen that the laser cladding repair area on the polished surface of the ventral fin has no crack defects and unfused holes.
Step 6: metallographic test
In order to further verify the internal quality of the cladding layer under the condition of the process parameters so as to be combined with the matrix thin-wall part, a sample part with the same process parameters as the repaired titanium alloy thin-wall part is selected for metallographic analysis, and a microstructure photo is shown in fig. 6. The left side of the picture is a cladding layer structure, and the right side of the picture is a heat affected zone structure, so that a typical lath-shaped as-cast structure is presented. The joint surface of the cladding layer and the matrix has no defects of micro-crack, non-fusion, air holes, inclusion and the like, and the heat affected zone of the cladding layer is small.
Example 2:
the embodiment is a method for repairing surface cracks of a titanium alloy thin-wall part, which comprises the following specific steps:
step 1: pretreatment before welding
This step is the same as step 1 in example 1.
Step 2: laser cladding repair
2.1 selecting TC4 titanium alloy powder with the particle size of 75-125 μm to carry out drying treatment, wherein the drying temperature is 135 ℃, the drying time is 4 hours, and the vacuum degree is-1 bar.
2.2 determining repair Path
And respectively setting the number of laser cladding tracks and the number of laser cladding layers to 7 and 8 according to the width and the depth of the groove formed by the crack until the surface of the cladding layer is higher than that of the titanium alloy skin, so that the heat input is reduced and the sufficient machining allowance is ensured.
2.3 laser cladding
2.3.1 preheating before repair:
in order to reduce crack initiation and ensure good fusion of a cladding layer and a substrate and the strength of a bonding surface, a low-power laser is firstly adopted to preheat a surface to be repaired, the power of the preheating laser is 300W, the number of preheating layers is 1, the flow of lens protective gas is 12L/min, the flow of powder feeding gas is 10L/min, the powder feeding speed is 1.2r/min, and the scanning speed of a laser cladding head is 400 mm/min.
2.3.2 surface repair welding:
in order to ensure that TC4 titanium alloy powder is fully melted, improve the fusion quality and control the heat input quantity, the laser power is 500W, and the other parameters are consistent with the laser cladding preheating parameters. The surface appearance of the titanium alloy skin after laser cladding repair is shown in fig. 7, and it can be seen that the surface of the repaired cladding layer is relatively flat, basically free of oxidation, good in fusion condition and free of damage near the repair area.
And step 3: d, direct-current argon arc welding:
selecting a TC4 welding wire and a welding current of 30A, accurately controlling the welding current and time of arc starting, welding and arc closing, fusing the regions with uneven cladding layers and unfused regions, enabling the surfaces to be in smooth transition, ensuring the internal quality of welding seams, and observing that the surface of the cladding layers is fully melted by coating powder and the fusing quality is improved as shown in figure 8 by the surface appearance of the titanium alloy skin after argon arc welding.
And 4, step 4: the polishing allowance is maintained, the surface appearance after polishing is shown in figure 9, and the repaired surface is flat and smooth and meets the technical requirements.
And 5: nondestructive inspection and fluorescent coloring are shown in fig. 10, and it can be seen that the laser cladding repaired area after polishing has no crack defects and unfused holes.
Step 6: metallographic test, microstructure photo is shown in fig. 11, the left side of the picture is cladding layer structure, the right side is heat affected zone structure, and typical lath-shaped as-cast structure is presented. The joint surface of the cladding layer and the matrix has no defects of micro-crack, non-fusion, air holes, inclusion and the like, and the heat affected zone of the cladding layer is small.
Steps 4 to 6 are the same as in example 1.
Claims (4)
1. A method for repairing cracks on the surface of a titanium alloy thin-wall part is characterized by comprising the following steps:
step 1: pretreatment before welding
1.1, polishing the surface of a titanium alloy thin-wall part till the metallic luster is exposed, finding out all cracks on the titanium alloy thin-wall part, polishing the back of the area where the titanium alloy thin-wall part is located till the metallic luster is exposed for the cracks penetrating through the wall thickness of the titanium alloy, forming grooves at the found cracks to facilitate the adhesion cladding of titanium alloy powder, and forming crack-stopping holes at two ends of the cracks penetrating through the wall thickness of the titanium alloy after forming the grooves;
1.2, polishing and flattening the surface to be repaired, and removing stains on the surface of the thin-walled part;
1.3, protecting the area which does not need to be repaired near the crack to prevent laser sputtering damage;
1.4 introducing inert protective gas into a cavity formed by the titanium alloy thin-wall part;
step 2: laser cladding repair
2.1 selecting TC4 titanium alloy powder with the particle size of 75-125 μm to carry out drying treatment on the titanium alloy powder, wherein the drying temperature is 130 +/-5 ℃, the drying time is not less than 4 hours, and the vacuum degree is-0.8-1 bar;
2.2 determining repair Path
Determining the number of laser cladding tracks and the number of layers according to the width and the depth of a groove formed by cracks on the surface of the titanium alloy skin, wherein the surface of the cladding layer is higher than the surface of the titanium alloy thin-walled part;
2.3 laser cladding
2.3.1 preheating before repair:
preheating a surface to be repaired by adopting 200-300W low-power laser, wherein the number of preheating layers is 1, the flow of lens protective gas is set to be 8-12L/min before preheating, the flow of powder feeding gas is 6-10L/min, the powder feeding speed is 1-1.2r/min, and the scanning speed of a laser cladding head is 400 mm/min;
2.3.2 surface repair welding:
performing surface welding repair by using laser power of 400-500W, wherein during the surface welding repair, the lens protective gas flow, the powder feeding speed and the scanning speed of the laser cladding head are consistent with the preheating parameters before repair in 2.3.1;
and step 3: d.c. argon arc welding
Selecting a TC4 welding wire, and fusing the area with uneven cladding layer and unfused area by welding current of 20-30A to enable the welding surface to be in smooth transition;
and 4, step 4: polishing allowance
Polishing allowance to enable the repair surface to be flat and consistent with the surface roughness of the titanium alloy thin-walled workpiece;
and 5: nondestructive flaw detection;
and 6: and (6) metallographic testing.
2. The method for repairing the surface crack of the titanium alloy thin-walled workpiece according to claim 1, wherein:
the groove formed in the step 1.1 is a V-shaped groove.
3. The method for repairing the surface crack of the titanium alloy thin-walled workpiece according to claim 1, wherein:
the step 4 specifically comprises the following steps:
4.1 the cladding layer higher than the surface of the titanium alloy skin is polished by a grinding wheel, a small amount of grinding is carried out for many times, the processing stress is reduced, and the smoothness of the repair surface is ensured.
4.2, using fine sand paper to polish and remove burrs, so that the roughness of the repair surface is consistent with that of the titanium alloy skin.
4. The method for repairing cracks on the surface of a titanium alloy thin-walled workpiece according to claim 1, wherein:
the step 5 specifically comprises the following steps:
and carrying out fluorescent inspection on the laser cladding repair area on the surface of the polished titanium alloy thin-walled workpiece to ensure that a welding seam and a nearby area have no crack or weld penetration defect.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111606339.2A CN114434086B (en) | 2021-12-26 | 2021-12-26 | Surface crack repairing method for titanium alloy thin-wall part |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN114959682A (en) * | 2022-05-13 | 2022-08-30 | 东华大学 | Preparation of Al on surface of aluminum alloy 3 Laser cladding method of Ti coating |
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| CN115386873A (en) * | 2022-09-06 | 2022-11-25 | 北京航星机器制造有限公司 | Defect repairing method for TA15 titanium alloy part formed by selective laser melting |
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| CN115255805A (en) * | 2022-08-04 | 2022-11-01 | 湖北超卓航空科技股份有限公司 | Method for quickly repairing notch fault of aircraft wing fuel tank skin |
| CN115386873A (en) * | 2022-09-06 | 2022-11-25 | 北京航星机器制造有限公司 | Defect repairing method for TA15 titanium alloy part formed by selective laser melting |
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