CN112570729A - Laser additive manufacturing method for reducing cracking sensitivity - Google Patents
Laser additive manufacturing method for reducing cracking sensitivity Download PDFInfo
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- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y10/00—Processes of additive manufacturing
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- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
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- B33Y70/00—Materials specially adapted for additive manufacturing
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- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
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- C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
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- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
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Abstract
A laser additive manufacturing method for reducing cracking sensitivity is characterized in that internal stress and distortion energy are preset and are cooperated with laser synchronous heat treatment to realize control of recrystallization dimension in a continuous deposition forming process, the internal stress is appropriately released on line, a strip-shaped continuous crystal boundary alpha is converted into a broken line shape or an interrupted shape, the stress level and the cracking sensitivity are reduced, meanwhile, the plastic storage of a deposited component is improved by controlling the recrystallization degree, the cracking resistance under high stress is improved, the cracking-free one-time continuous forming of a large titanium alloy additive manufacturing component can be conveniently realized in a short process, the structure performance does not need to be regulated and controlled by subsequent heat treatment, and the method can be directly applied to engineering.
Description
Technical Field
The invention relates to the field of laser processing of metal materials, in particular to a laser additive manufacturing method for reducing cracking sensitivity.
Background
The laser additive manufacturing of the large titanium alloy component has the advantages of large temperature gradient, high cooling rate, long continuous deposition time, serious stress accumulation and mutual coupling of internal mechanical constraint stress, solid phase change stress, solidification shrinkage stress, thermal stress and the like, and is very easy to cause serious buckling deformation and macroscopic cracking in the forming process. On the other hand, the titanium alloy component manufactured by laser additive manufacturing is in a columnar crystal structure, and the columnar crystal grain boundaries are strip-shaped continuous grain boundaries alpha, are easy to crack under the action of long-time stress and belong to positions easy to crack. The macroscopic cracking caused by the two reasons is difficult to control, and becomes a bottleneck problem limiting the application of laser additive manufacturing engineering of large titanium alloy components.
At present, only a few dominant research organizations at home and abroad realize the forming and engineering application of partial larger structural parts, and the basic idea adopts a first scheme, namely the overall stress level is reduced to avoid macroscopic cracking, specifically, the deformation cracking control is realized through the macroscopic structure dispersion, namely, the macroscopic structure is split into a plurality of substructures to be formed and then connected or formed in sections. According to the method, through structure splitting, the stress level in the forming process of each substructure is reduced, and deformation cracking is avoided. The method has a connecting area and a sectional bonding interface, is difficult to control the consistency of the structure performance of other parts, and has the defects of complex and tedious turnover process, long production period and reduction of the manufacturing efficiency of the laser additive manufacturing technology because special tools are matched, and multiple heat treatment, oxide layer removal and other processes are inserted. Therefore, a laser additive manufacturing method and equipment for reducing cracking sensitivity are urgently needed to be provided, which can convert a strip-shaped continuous crystal boundary alpha into a curve shape or an interrupted shape, reduce cracking sensitivity, realize independent control of stress accumulation level, conveniently realize non-cracking one-time continuous forming of a large titanium alloy component in a short flow, further improve the laser additive manufacturing efficiency of the large component, and simultaneously ensure the tissue and performance consistency of each part.
Disclosure of Invention
A laser additive manufacturing method for reducing cracking sensitivity can convert a strip-shaped continuous crystal boundary alpha into a curve shape or an interrupted shape, reduce cracking sensitivity, realize independent controllability of stress accumulation level, conveniently realize non-cracking one-time continuous forming of a large titanium alloy member through a short flow, further improve laser additive manufacturing efficiency of the large member, and simultaneously ensure the consistency of the structure and performance of each part.
In order to overcome the defects of the prior art, the invention provides a laser additive manufacturing method for reducing cracking sensitivity, the equivalent weight of the titanium alloy [ Mo ] is 3.0-9.0, the main idea is to realize the control of recrystallization dimension in the continuous deposition forming process by presetting internal stress and distortion energy and coupling laser synchronous heat treatment, properly release the internal stress on line, convert a strip-shaped continuous crystal boundary alpha into a broken line shape or an interrupted shape, reduce the stress level and the cracking sensitivity, simultaneously promote the plastic reserve of a deposited member by controlling the recrystallization degree, improve the anti-cracking capability under high stress, realize the non-cracking one-time continuous forming of a large titanium alloy additive manufacturing member conveniently in a short process, and can be directly applied in engineering without regulating and controlling the structure performance by subsequent heat treatment.
The invention is realized by the following technical scheme: a laser additive manufacturing method that reduces crack susceptibility, comprising the steps of:
firstly, titanium alloy powder with the granularity specification of 60-150 mu m is filled into a powder feeder, and the oxygen content in the powder is more than 0.08 wt%;
secondly, fixing the substrate on a workbench of an inert argon processing chamber filled with argon with the purity of not less than 99.999 percent;
thirdly, when the water and oxygen content in the processing chamber is less than 50ppm, starting titanium alloy laser additive manufacturing and forming; continuously melting and depositing the synchronously fed titanium alloy powder on a substrate under the action of laser;
fourthly, removing the laser powder feeding head after 3-4 layers of the powder are continuously deposited; performing raster scanning on the deposited layer by using a laser heat source, so that a columnar crystal structure with the volume fraction of 20-30% and the width of 0.15-0.3 mm is obtained while the deposited layer is not melted, a discontinuous crystal boundary alpha and an isometric crystal structure with the volume fraction of 70-80% and the diameter of less than 100 mu m are obtained at the crystal boundary, the crystal boundary is a broken line-shaped or discontinuous crystal boundary alpha, the microstructure is a spheroidized primary alpha phase with the volume fraction of 60-70% and the length-width ratio of less than 2-2.9, and the cracking sensitivity of the large titanium alloy component is reduced;
and fifthly, repeating the third step and the fourth step, and continuously depositing and manufacturing the laser additive manufacturing large-scale titanium alloy member which has no crack and can directly meet the engineering application requirement without subsequent heat treatment.
As a preferable technical scheme, in the third step, in the deposition process, the energy density of the deposition area is controlled to be 41-50J/mm2The width-height ratio of the molten pool is 3-5, the lap joint rate is 40% -50%, and the cooling rate in the solid-liquid conversion of the component is 103～105k/s, preparing columnar crystals with the layer height of 0.7-1.2 mm, the volume fraction of 20-30 percent and the width of 0.15-0.25 mm and isometric crystals with the volume fraction of 60-70 percent and the diameter of 50-100 mu m, wherein the dislocation density is more than 1017m-2The titanium alloy sample provides driving force for subsequent macro-micro recrystallization and reduction of cracking sensitivity.
As a preferred technical solution, in the fourth step, the laser grating type scanning process parameters are as follows: the laser power is 0.6-1 kW, the scanning speed is 50-100 mm/s, the spot diameter is 1-3 mm, and the laser synchronous heat treatment time is 10-15 min; the laser synchronous heat treatment enables the deposited layer to be subjected to controlled recrystallization, most of columnar crystals are converted into isometric crystals, and the crystal boundary of the columnar crystals is a discontinuous broken line-shaped crystal boundary alpha, so that the cracking sensitivity is reduced, the macroscopic cracking of the columnar crystal structure which is easy to occur in a high stress forming state is avoided, meanwhile, the anisotropy of the deposited structure is eliminated by controlling the recrystallization degree, the plasticity is improved, and the obdurability adaptation is realized.
As a preferable technical scheme, the equivalent of [ Mo ] in the titanium alloy is within the range of 3.0-9.0.
The invention has the beneficial effects that: the invention drives the laser additive continuous deposition forming process to generate recrystallization by coupling laser synchronous heat treatment in the laser additive manufacturing process to obtain discontinuous broken line-shaped crystal boundary alpha, appropriately releases internal stress on line and reduces cracking sensitivity, and simultaneously realizes the high-performance one-time continuous forming manufacturing of the crack-free large titanium alloy structural member without subsequent heat treatment by controlling the recrystallization scale.
The invention is not restricted by the product structure, and can realize the low-stress high-plasticity laser additive manufacturing of large titanium alloy structural parts aiming at any structure. Taking the example of manufacturing the TC11 titanium alloy structural member by laser additive manufacturing coupled with laser synchronous heat treatment as an example, the deposited columnar crystal and equiaxed crystal structure can be timely converted into a nearly-holoaxial crystal structure, and the long-strip-shaped continuous grain boundary alpha is converted into a broken-line shape or an intermittent shape, as shown in FIG. 2, the tensile mechanical property at room temperature is obviously higher than the national standard requirement, as shown in Table 1. The invention does not relate to alternate multi-time segmented heat treatment and subsequent heat treatment, does not need special tools and clamping and positioning, and obviously shortens the production and turnover period.
Drawings
FIG. 1 is a macroscopic structure of TC11 titanium alloy obtained by the present invention;
FIG. 2 shows the final TC11 titanium alloy macrostructure obtained by the present invention.
TABLE 1 laser additive manufacturing TC11 titanium alloy tensile properties at room temperature
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
As shown in fig. 1-2, an example of laser additive manufacturing Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy is a laser additive manufacturing method for reducing crack sensitivity, which is characterized by comprising the following steps:
firstly, titanium alloy powder with the granularity specification of 60-150 mu m is filled into a powder feeder, and the oxygen content in the powder is more than 0.08 wt%;
secondly, fixing the substrate on a workbench of an inert processing chamber filled with argon with the purity of 99.999 percent;
thirdly, when the oxygen content of argon in the working chamber is less than 50ppm, starting titanium alloy additive manufacturing and forming; continuously melting and depositing the synchronously fed titanium alloy powder on a substrate under the action of laser;
fourthly, removing the laser powder feeding head after 3-4 layers of the powder are continuously deposited; performing raster scanning on the deposited layer by using a laser heat source, so that the deposited layer is not melted, and simultaneously, columnar crystals with the macroscopic structure of 20-30% of volume fraction and the width of 0.15-0.25 mm are obtained, the crystal boundary is a zigzag or discontinuous crystal boundary alpha, the volume fraction of the equiaxial crystal structure is 70-80%, the diameter of the equiaxial crystal structure is less than 100 mu m, the microstructure is a spheroidized primary alpha phase with the volume fraction of 60-70% and the length-width ratio of less than 2-2.9, and the cracking sensitivity of the large titanium alloy component is further reduced;
and fifthly, repeating the third step and the fourth step, and continuously depositing and manufacturing the laser additive manufacturing large-scale titanium alloy member which has no crack and can directly meet the engineering application requirement without subsequent heat treatment.
The deposited columnar crystal and isometric crystal tissues are converted into isometric crystal tissues through laser synchronous heat treatment by using laser additive manufacturing and laser synchronous heat treatment, as shown in figure 2, the room-temperature mechanical property of the product is obviously higher than the standard requirement, as shown in table 1, the invention does not relate to the insertion of multiple segmented heat treatment and subsequent heat treatment, and the production and turnover period is obviously shortened.
According to the invention, by introducing laser synchronous heat treatment in the laser additive manufacturing process, recrystallization scale control in the continuous deposition forming process is realized to improve the component plasticity, internal stress is properly released on line and cracking sensitivity is reduced, and high-performance integrated manufacturing of a crack-free large titanium alloy structural component without subsequent heat treatment can be realized.
Example 2
As shown in fig. 1-2, for example, a Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy is manufactured by laser additive manufacturing, a method for manufacturing laser additive with reduced crack sensitivity includes the following steps:
firstly, titanium alloy powder with the granularity specification of 60-150 mu m is filled into a powder feeder, and the oxygen content in the powder is more than 0.08 wt%;
secondly, fixing the substrate on a workbench of an inert processing chamber filled with argon with the purity of 99.999 percent;
thirdly, when the oxygen content of argon in the working chamber is less than 50ppm, starting titanium alloy additive manufacturing and forming; continuously melting and depositing the synchronously fed titanium alloy powder on a substrate under the action of laser; in the deposition process, the energy density of a deposition area is controlled to be 41-50J/mm2The width-height ratio of the molten pool is 3-5, the lap joint rate is 40% -50%, and the cooling rate in the solid-liquid conversion of the component is 103～105k/s, preparing columnar crystals with the layer height of 0.7-1.2 mm, the volume fraction of 20-30 percent and the width of 0.15-0.25 mm and isometric crystals with the volume fraction of 60-70 percent and the diameter of 50-100 mu m, wherein the dislocation density is more than 1017m-2The titanium alloy sample reduces the cracking sensitivity of large titanium alloy components;
fourthly, removing the laser powder feeding head after 3-4 layers of the powder are continuously deposited; performing raster scanning on the deposited layer by using a laser heat source, so that the deposited layer is not melted, and simultaneously, columnar crystals with the macroscopic structure of 20-30% of volume fraction and the width of 0.15-0.25 mm are obtained, the crystal boundary is a zigzag or discontinuous crystal boundary alpha, the volume fraction of the equiaxial crystal structure is 70-80%, the diameter of the equiaxial crystal structure is less than 100 mu m, the microstructure is a spheroidized primary alpha phase with the volume fraction of 60-70% and the length-width ratio of less than 2-2.9, and the cracking sensitivity of the large titanium alloy component is further reduced;
and fifthly, repeating the third step and the fourth step, and continuously depositing and manufacturing the laser additive manufacturing large-scale titanium alloy member which has no crack and can directly meet the engineering application requirement without subsequent heat treatment.
The deposited columnar crystal and isometric crystal tissues are converted into isometric crystal tissues through laser synchronous heat treatment by using laser additive manufacturing and laser synchronous heat treatment, as shown in figure 2, the room-temperature mechanical property of the product is obviously higher than the standard requirement, as shown in table 1, the invention does not relate to the insertion of multiple segmented heat treatment and subsequent heat treatment, and the production and turnover period is obviously shortened.
According to the invention, by introducing laser synchronous heat treatment in the laser additive manufacturing process, recrystallization scale control in the continuous deposition forming process is realized to improve the component plasticity, internal stress is properly released on line and cracking sensitivity is reduced, and high-performance integrated manufacturing of a crack-free large titanium alloy structural component without subsequent heat treatment can be realized.
Example 3
As shown in fig. 1-2, an example of laser additive manufacturing Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy is a laser additive manufacturing method for reducing crack sensitivity, which is characterized by comprising the following steps:
firstly, titanium alloy powder with the granularity specification of 60-150 mu m is filled into a powder feeder, and the oxygen content in the powder is more than 0.08 wt%;
secondly, fixing the substrate on a workbench of an inert processing chamber filled with argon with the purity of 99.999 percent;
thirdly, when the oxygen content of argon in the working chamber is less than 50ppm, starting titanium alloy additive manufacturing and forming; continuously melting and depositing the synchronously fed titanium alloy powder on a substrate under the action of laser; in the deposition process, the energy density of a deposition area is controlled to be 41-50J/mm2The width-height ratio of the molten pool is 3-5, the lap joint rate is 40% -50%, and the cooling rate in the solid-liquid conversion of the component is 103～105k/s, preparing columnar crystals with the layer height of 0.7-1.2 mm, the volume fraction of 20-30 percent and the width of 0.15-0.25 mm and isometric crystals with the volume fraction of 60-70 percent and the diameter of 50-100 mu m, wherein the dislocation density is more than 1017m-2The titanium alloy sample reduces the cracking sensitivity of large titanium alloy components;
fourthly, removing the laser powder feeding head after 3-4 layers of the powder are continuously deposited; performing raster scanning on the deposited layer by using a laser heat source, so that the deposited layer is not melted, and simultaneously, columnar crystals with the macroscopic structure of 20-30% of volume fraction and the width of 0.15-0.25 mm are obtained, the crystal boundary is a zigzag or discontinuous crystal boundary alpha, the volume fraction of the equiaxial crystal structure is 70-80%, the diameter of the equiaxial crystal structure is less than 100 mu m, the microstructure is a spheroidized primary alpha phase with the volume fraction of 60-70% and the length-width ratio of less than 2-2.9, and the cracking sensitivity of the large titanium alloy component is further reduced; the laser scanning process parameters are as follows: the laser power is 0.6-1 kW, the scanning speed is 50-100 mm/s, the spot diameter is 1-3 mm, and the laser synchronous heat treatment time is 10-15 min; the laser synchronous heat treatment enables the deposited layer to be subjected to controlled recrystallization, most of columnar crystals are converted into isometric crystals, and the crystal boundary of the columnar crystals is a discontinuous broken line-shaped crystal boundary alpha, so that the cracking sensitivity is reduced, the macroscopic cracking of the columnar crystal structure which is easy to occur in a high stress forming state is avoided, meanwhile, the anisotropy of the deposited structure is eliminated, the plasticity is improved, and the obdurability matching is realized;
and fifthly, repeating the third step and the fourth step, and continuously depositing and manufacturing the laser additive manufacturing large-scale titanium alloy member which has no crack and can directly meet the engineering application requirement without subsequent heat treatment.
The deposited columnar crystal and isometric crystal tissues are converted into isometric crystal tissues through laser synchronous heat treatment by using laser additive manufacturing and laser synchronous heat treatment, as shown in figure 2, the room-temperature mechanical property of the product is obviously higher than the standard requirement, as shown in table 1, the invention does not relate to the insertion of multiple segmented heat treatment and subsequent heat treatment, and the production and turnover period is obviously shortened.
According to the invention, by introducing laser synchronous heat treatment in the laser additive manufacturing process, recrystallization scale control in the continuous deposition forming process is realized to improve the component plasticity, internal stress is properly released on line and cracking sensitivity is reduced, and high-performance integrated manufacturing of a crack-free large titanium alloy structural component without subsequent heat treatment can be realized.
Example 4
As shown in fig. 1-2, a laser additive manufacturing method for reducing crack sensitivity is characterized by comprising the following steps:
firstly, titanium alloy powder with the granularity specification of 60-150 mu m is filled into a powder feeder, and the oxygen content in the powder is more than 0.08 wt%;
secondly, fixing the substrate on a workbench of an inert processing chamber filled with argon with the purity of 99.999 percent;
thirdly, when the oxygen content of argon in the working chamber is less than 50ppm, starting titanium alloy additive manufacturing and forming; continuously melting and depositing the synchronously fed titanium alloy powder on a substrate under the action of laser;
fourthly, removing the laser powder feeding head after 3-4 layers of the powder are continuously deposited; performing raster scanning on the deposited layer by using a laser heat source, so that the deposited layer is not melted, and simultaneously, columnar crystals with the macroscopic structure of 20-30% of volume fraction and the width of 0.15-0.25 mm are obtained, the crystal boundary is a zigzag or discontinuous crystal boundary alpha, the volume fraction of the equiaxial crystal structure is 70-80%, the diameter of the equiaxial crystal structure is less than 100 mu m, the microstructure is a spheroidized primary alpha phase with the volume fraction of 60-70% and the length-width ratio of less than 2-2.9, and the cracking sensitivity of the large titanium alloy component is further reduced;
and fifthly, repeating the third step and the fourth step, and continuously depositing and manufacturing the laser additive manufacturing large-scale titanium alloy member which has no crack and can directly meet the engineering application requirement without subsequent heat treatment.
The deposited columnar crystal and isometric crystal tissues are converted into isometric crystal tissues through laser synchronous heat treatment by using laser additive manufacturing and laser synchronous heat treatment, as shown in figure 2, the room-temperature mechanical property of the product is obviously higher than the standard requirement, as shown in table 1, the invention does not relate to the insertion of multiple segmented heat treatment and subsequent heat treatment, and the production and turnover period is obviously shortened.
According to the invention, by introducing laser synchronous heat treatment in the laser additive manufacturing process, recrystallization scale control in the continuous deposition forming process is realized to improve the component plasticity, internal stress is properly released on line and cracking sensitivity is reduced, and high-performance integrated manufacturing of a crack-free large titanium alloy structural component without subsequent heat treatment can be realized.
Example 5
As shown in fig. 1-2, a laser additive manufacturing method for reducing crack sensitivity is characterized by comprising the following steps:
firstly, titanium alloy powder with the granularity specification of 60-150 mu m is filled into a powder feeder, and the oxygen content in the powder is more than 0.08 wt%;
secondly, fixing the substrate on a workbench of an inert processing chamber filled with argon with the purity of 99.999 percent;
thirdly, when the oxygen content of argon in the working chamber is less than 50ppm, starting titanium alloy additive manufacturing and forming; continuously melting and depositing the synchronously fed titanium alloy powder on a substrate under the action of laser; in the deposition process, the energy density of a deposition area is controlled to be 41-50J/mm2The width-height ratio of the molten pool is 3-5, the lap joint rate is 40% -50%, and the cooling rate in the solid-liquid conversion of the component is 103～105k/s, preparing columnar crystals with the layer height of 0.7-1.2 mm, the volume fraction of 20-30 percent and the width of 0.15-0.25 mm and isometric crystals with the volume fraction of 60-70 percent and the diameter of 50-100 mu m, wherein the dislocation density is more than 1017m-2The titanium alloy sample reduces the cracking sensitivity of large titanium alloy components;
fourthly, removing the laser powder feeding head after 3-4 layers of the powder are continuously deposited; performing raster scanning on the deposited layer by using a laser heat source, so that the deposited layer is not melted, and simultaneously, columnar crystals with the macroscopic structure of 20-30% of volume fraction and the width of 0.15-0.25 mm are obtained, the crystal boundary is a zigzag or discontinuous crystal boundary alpha, the volume fraction of the equiaxial crystal structure is 70-80%, the diameter of the equiaxial crystal structure is less than 100 mu m, the microstructure is a spheroidized primary alpha phase with the volume fraction of 60-70% and the length-width ratio of less than 2-2.9, and the cracking sensitivity of the large titanium alloy component is further reduced;
and fifthly, repeating the third step and the fourth step, and continuously depositing and manufacturing the laser additive manufacturing large-scale titanium alloy member which has no crack and can directly meet the engineering application requirement without subsequent heat treatment.
The deposited columnar crystal and isometric crystal tissues are converted into isometric crystal tissues through laser synchronous heat treatment by using laser additive manufacturing and laser synchronous heat treatment, as shown in figure 2, the room-temperature mechanical property of the product is obviously higher than the standard requirement, as shown in table 1, the invention does not relate to the insertion of multiple segmented heat treatment and subsequent heat treatment, and the production and turnover period is obviously shortened.
According to the invention, by introducing laser synchronous heat treatment in the laser additive manufacturing process, recrystallization scale control in the continuous deposition forming process is realized to improve the component plasticity, internal stress is properly released on line and cracking sensitivity is reduced, and high-performance integrated manufacturing of a crack-free large titanium alloy structural component without subsequent heat treatment can be realized.
Example 6
As shown in fig. 1-2, a laser additive manufacturing method for reducing crack sensitivity is characterized by comprising the following steps:
firstly, titanium alloy powder with the granularity specification of 60-150 mu m is filled into a powder feeder, and the oxygen content in the powder is more than 0.08 wt%;
secondly, fixing the substrate on a workbench of an inert processing chamber filled with argon with the purity of 99.999 percent;
thirdly, when the oxygen content of argon in the working chamber is less than 50ppm, starting titanium alloy additive manufacturing and forming; continuously melting and depositing the synchronously fed titanium alloy powder on a substrate under the action of laser; in the deposition process, the energy density of a deposition area is controlled to be 41-50J/mm2The width-height ratio of the molten pool is 3-5, the lap joint rate is 40% -50%, and the cooling rate in the solid-liquid conversion of the component is 103～105k/s, preparing columnar crystals with the layer height of 0.7-1.2 mm, the volume fraction of 20-30 percent and the width of 0.15-0.25 mm and isometric crystals with the volume fraction of 60-70 percent and the diameter of 50-100 mu m, wherein the dislocation density is more than 1017m-2The titanium alloy sample reduces the cracking sensitivity of large titanium alloy components;
fourthly, removing the laser powder feeding head after 3-4 layers of the powder are continuously deposited; performing raster scanning on the deposited layer by using a laser heat source, so that the deposited layer is not melted, and simultaneously, columnar crystals with the macroscopic structure of 20-30% of volume fraction and the width of 0.15-0.25 mm are obtained, the crystal boundary is a zigzag or discontinuous crystal boundary alpha, the volume fraction of the equiaxial crystal structure is 70-80%, the diameter of the equiaxial crystal structure is less than 100 mu m, the microstructure is a spheroidized primary alpha phase with the volume fraction of 60-70% and the length-width ratio of less than 2-2.9, and the cracking sensitivity of the large titanium alloy component is further reduced; the laser scanning process parameters are as follows: the laser power is 0.6-1 kW, the scanning speed is 50-100 mm/s, the spot diameter is 1-3 mm, and the laser synchronous heat treatment time is 10-15 min; the laser synchronous heat treatment enables the deposited layer to be subjected to controlled recrystallization, most of columnar crystals are converted into isometric crystals, and the crystal boundary of the columnar crystals is a broken line-shaped or discontinuous crystal boundary alpha, so that the cracking sensitivity is reduced, the macroscopic cracking of the columnar crystal structure which is easily caused in a high stress forming state is avoided, meanwhile, the anisotropy of the deposited structure is eliminated, the plasticity is improved, and the obdurability matching is realized;
and fifthly, repeating the third step and the fourth step, and continuously depositing and manufacturing the laser additive manufacturing large-scale titanium alloy member which has no crack and can directly meet the engineering application requirement without subsequent heat treatment.
The deposited columnar crystal and isometric crystal tissues are converted into isometric crystal tissues through laser synchronous heat treatment by using laser additive manufacturing and laser synchronous heat treatment, as shown in figure 2, the room-temperature mechanical property of the product is obviously higher than the standard requirement, as shown in table 1, the invention does not relate to the insertion of multiple segmented heat treatment and subsequent heat treatment, and the production and turnover period is obviously shortened.
According to the invention, by introducing laser synchronous heat treatment in the laser additive manufacturing process, recrystallization scale control in the continuous deposition forming process is realized to improve the component plasticity, internal stress is properly released on line and cracking sensitivity is reduced, and high-performance integrated manufacturing of a crack-free large titanium alloy structural component without subsequent heat treatment can be realized.
Example 7
In any of embodiments 4 to 6, the titanium alloy has an equivalent of [ Mo ] of 3.0 to 9.0.
The deposited columnar crystal and isometric crystal tissues are converted into isometric crystal tissues through laser synchronous heat treatment by using laser additive manufacturing and laser synchronous heat treatment, as shown in figure 2, the room-temperature mechanical property of the product is obviously higher than the standard requirement, as shown in table 1, the invention does not relate to the insertion of multiple segmented heat treatment and subsequent heat treatment, and the production and turnover period is obviously shortened.
According to the invention, by introducing laser synchronous heat treatment in the laser additive manufacturing process, recrystallization scale control in the continuous deposition forming process is realized to improve the component plasticity, internal stress is properly released on line and cracking sensitivity is reduced, and the integral manufacturing of a high-performance laser additive manufacturing large titanium alloy component which has no cracking and can meet the engineering application requirements without subsequent heat treatment can be realized.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (8)
1. A laser additive manufacturing method for reducing cracking sensitivity is characterized by comprising the following steps:
firstly, titanium alloy powder with the granularity specification of 60-150 mu m is filled into a powder feeder, and the oxygen content in the powder is more than 0.08 wt%;
secondly, fixing the substrate on a workbench of an inert argon processing chamber filled with argon with the purity of not less than 99.999 percent;
thirdly, when the water and oxygen content in the processing chamber is less than 50ppm, starting titanium alloy laser additive manufacturing and forming; continuously melting and depositing the synchronously fed titanium alloy powder on a substrate under the action of laser;
fourthly, removing the laser powder feeding head after 3-4 layers of the powder are continuously deposited; performing raster scanning on the deposited layer by using a laser heat source, so that the deposited layer is not melted, and simultaneously, a columnar crystal structure with a macroscopic structure of 20-30% of volume fraction and a width of 0.15-0.25 mm is obtained, a grain boundary is a broken line-shaped or discontinuous grain boundary alpha, an isometric crystal structure with a volume fraction of 70-80% and a diameter of less than 100 mu m is obtained, and a micro-structure is a spheroidized primary alpha phase with a volume fraction of 60-70% and an aspect ratio of less than 2-2.9;
and fifthly, repeating the third step and the fourth step, and continuously depositing and manufacturing the laser additive manufacturing large-scale titanium alloy member which has no crack and can directly meet the engineering application requirement without subsequent heat treatment.
2. The laser additive manufacturing method for reducing crack sensitivity of claim 1, wherein: in the third step, in the deposition process, the energy density of a deposition area is controlled to be 41-50J/mm2The width-height ratio of the molten pool is 3-5, the lap joint rate is 40% -50%, and the cooling rate in the solid-liquid conversion of the component is 103～105k/s。
3. The laser additive manufacturing method for reducing crack sensitivity according to claim 2, wherein: in the fourth step, columnar crystals with the layer height of 0.7-1.2 mm, the volume fraction of 20-30% and the width of 0.15-0.25 mm and isometric crystals with the volume fraction of 70-80% and the diameter of 50-100 mu m are prepared, and the dislocation density is more than 1017m-2The titanium alloy test piece of (1).
4. The laser additive manufacturing method for reducing crack sensitivity of claim 1, wherein: in the fourth step, the laser scanning process parameters are as follows: the laser power is 0.6-1 kW, the scanning speed is 50-100 mm/s, the spot diameter is 1-3 mm, and the laser synchronous heat treatment time is 10-15 min.
5. The laser additive manufacturing method for reducing crack sensitivity of claim 4, wherein the laser additive manufacturing method comprises the following steps: and in the fourth step, controlled recrystallization is carried out on the deposited layer through laser synchronous heat treatment, most of columnar crystals are converted into isometric crystals, and the grain boundary of the columnar crystals is a broken line-shaped or discontinuous grain boundary alpha.
6. The laser additive manufacturing method for reducing crack sensitivity of claim 1, wherein: in the first step, the particle size of the titanium alloy powder is 60-150 mu m.
7. The laser additive manufacturing method for reducing crack sensitivity of claim 1, wherein: the equivalent of [ Mo ] in the titanium alloy is in the range of 3.0 to 9.0.
8. The laser additive manufacturing method for reducing crack sensitivity of claim 1, wherein: a titanium alloy having a composition of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si was produced.
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