阅读说明：本技术 激光增材制造镍基合金过程中抑制Laves相析出的方法 (Method for inhibiting Laves phase precipitation in laser additive manufacturing process of nickel-based alloy ) 是由 姚建华 张群莉 张�杰 陈智君 姚喆赫 于 2021-07-29 设计创作，主要内容包括：本发明公开了激光增材制造镍基合金过程中抑制Laves相析出的方法,具体包括以下步骤：将基材放在具有冷却装置的工作台上,将同步抑制装置安装好,打开半导体激光器和沸腾式送粉器开始进行金属粉末的熔覆,同时同步抑制装置的三根激冷铜管对熔池边缘进行激冷,加工完成后对试样进行扫描观察其横截面组织情况。本发明在镍基高温合金的激光增材制造或再制造过程中,对液态熔池周围增加激冷源,能够实现熔池内部温度场的再分布,增加固液界面前沿温度梯度,加快熔池凝固速度,有效减少了Nb、Al和Ti等偏析元素在枝晶间的集聚,为后续时效处理过程中强化相的析出提供保障。(The invention discloses a method for inhibiting Laves phase precipitation in a process of manufacturing a nickel-based alloy by using a laser additive, which specifically comprises the following steps: the method comprises the steps of placing a base material on a workbench with a cooling device, installing a synchronous suppression device, opening a semiconductor laser and a boiling type powder feeder to begin cladding metal powder, simultaneously chilling the edge of a molten pool by three chilling copper pipes of the synchronous suppression device, and scanning a sample to observe the cross-section structure condition after machining is finished. In the laser additive manufacturing or remanufacturing process of the nickel-based superalloy, the laser source is added around the liquid molten pool, the redistribution of a temperature field in the molten pool can be realized, the temperature gradient at the front edge of a solid-liquid interface is increased, the solidification speed of the molten pool is accelerated, the aggregation of segregation elements such as Nb, Al, Ti and the like among dendrites is effectively reduced, and the precipitation of a strengthening phase in the subsequent aging treatment process is guaranteed.)

1. A method for inhibiting Laves phase precipitation in a process of manufacturing a nickel-based alloy by laser additive manufacturing is characterized in that: the method specifically comprises the following steps:

the method comprises the following steps: placing a base material made of nickel-based high-temperature alloy on a workbench with a cooling device (1) as a sample, opening the cooling device (1), and cooling the lower end of a base body (2) by the cooling device (1) so as to relieve heat accumulation in the initial stage of laser forming manufacturing to the maximum extent;

step two: installing a synchronous suppression device, wherein the synchronous suppression device comprises a gas cylinder group (5), a circulating liquid cooling device (4), a gas cooling valve (6) and a nozzle gas cooling device (7), the gas cylinder group (5) is connected with the circulating liquid cooling device (4) through a pipeline and supplies gas for the circulating liquid cooling device (4), the circulating liquid cooling device (4) is connected with the nozzle gas cooling device (7) through a pipeline, the circulating liquid cooling device (4) provides cooling gas for the nozzle gas cooling device (7), the gas cooling valve (6) is arranged at the outlet of the circulating liquid cooling device (4) and controls the flow of the cooling gas, the nozzle cooling device (1) is a chilling copper pipe which is arranged on the laser processing head (3) and moves along with the laser processing head (3), the number of the chilling copper pipes is three, and the three chilling copper pipes are respectively aligned to the edge position of a molten pool formed by metal powder, a laser beam and the base body (2);

step three: the method comprises the following steps that a semiconductor laser is turned on, laser emitted by the semiconductor laser irradiates a substrate (2), prepared and dried metal powder is sent to the substrate (2) by using a boiling type powder feeder, a laser processing head (3) of the semiconductor laser and a powder feeding head of the boiling type powder feeder are arranged at the movable end of the same moving mechanism, the laser processing head (3) of the semiconductor laser and the powder feeding head of the boiling type powder feeder move synchronously, and the semiconductor laser carries out cladding on the metal powder on the substrate (2); the power of the semiconductor laser is 900-2000W, the diameter of a light spot of an emitted laser beam irradiated on the substrate (2) is 4mm, the scanning speed is 360-420 mm/s, and the powder feeding amount of the boiling type powder feeder is 10-15 g/min;

step four: in the process of cladding metal powder on a substrate (2) by a semiconductor laser, the metal powder, a laser beam and the substrate (2) form a molten pool, after the forming position of the molten pool is determined, the positions of three chilling copper pipes of a synchronous suppression device are adjusted, the three chilling copper pipes are enabled to face the left, the right and the back in the scanning direction, the heights of the three chilling copper pipes are 5-10 mm higher than the thickness of a single layer of a formed cladding layer, an air cooling valve (6) of the synchronous suppression device is opened, and the flow of cold air is adjusted to be 3-20L/min until the material increasing process of a sample is completed;

step five: after the material increase process is finished, closing a laser processing head (3) of the semiconductor laser and a powder feeding head of the boiling type powder feeder, moving to an initial position, and taking down a sample after material increase;

step six: and (3) cutting, inlaying, roughly grinding, finely polishing and corroding the sample, and observing the condition of the cross-section structure by using a scanning electron microscope.

2. The method for inhibiting Laves phase precipitation in the process of laser additive manufacturing of the nickel-based alloy according to claim 1, wherein the method comprises the following steps: the cooling device (1) used in the first step is uniformly paved below the whole matrix (2), and the cooling medium used by the cooling device (1) is ice water or liquid nitrogen.

3. The method for inhibiting Laves phase precipitation in the process of laser additive manufacturing of the nickel-based alloy according to claim 1, wherein the method comprises the following steps: the metal powder enters the molten pool in a coaxial powder feeding mode or a lateral powder feeding mode.

4. The method for inhibiting Laves phase precipitation in the process of laser additive manufacturing of the nickel-based alloy according to claim 1, wherein the method comprises the following steps: in the fourth step, the scanning direction of the semiconductor laser is taken as the front, a molten pool formed by laser beams emitted by the semiconductor laser on the metal powder and the substrate (2) is circular, the three chilled copper pipes face to the right left, right and back of the scanning direction, and the three chilled copper pipes all aim at the edge of the molten pool to blow out cold air, so that a chilled environment is formed at the edge of the molten pool.

5. The method for inhibiting Laves phase precipitation in the process of laser additive manufacturing of the nickel-based alloy according to claim 1, wherein the method comprises the following steps: the gas provided by the gas bottle group (5) is inert gas, and the chilling copper pipe is used for cooling and dehumidifying the inert gas.

6. The method of claim 5, wherein the method for inhibiting Laves phase precipitation during the laser additive manufacturing of the nickel-based alloy comprises the following steps: the inert gas comprises argon, nitrogen, helium and a combination of two or more of the three gases.

7. The method for inhibiting Laves phase precipitation in the process of laser additive manufacturing of the nickel-based alloy according to claim 1, wherein the method comprises the following steps: the three chilling copper pipes of the synchronous suppression device are made of copper with good heat conduction performance.

Technical Field

The invention relates to the field of laser additive manufacturing, in particular to a method for inhibiting Laves phase precipitation in a laser additive manufacturing nickel-based alloy process.

Background

The laser additive manufacturing technology has the characteristics of rapid cooling and rapid solidification, but serious segregation of elements such as Nb and the like is easy to occur at a solid-liquid interface, and a long-chain Laves phase is further formed. In addition, in the laser additive manufacturing process, precipitation of reinforcing phases such as gamma' - (Ni3Nb) and gamma "-Ni 3(Al, Ti) is often inhibited, and the mechanical properties of the reinforcing phases are further influenced. Generally, in order to eliminate the Laves phase and to improve the structure and mechanical properties of the as-deposited nickel-base superalloy to the maximum extent, homogenization or solution treatment is generally required. However, in the case of a remanufactured product, if the homogenization and solution treatment are performed at a high temperature as a whole, the growth of the structure of the base material and the coarsening of the reinforcing phase are inevitably caused. However, if the aging treatment is directly carried out without the solution treatment, the mechanical properties of the additive manufactured part or the remanufactured part are influenced to a certain extent because the Laves phase cannot be effectively eliminated.

At present, in most researches, elimination of the Laves phase in the laser deposition state is still achieved through solid solution or homogenization treatment. Document 1(Rare Metal Materials and Engineering,2010,39(9), 1519-. Document 2 (surface technology, 2019,48 (2), 47-53) finds that when the solid solution temperature is low, a significant δ phase exists around the undissolved Laves phase, the Laves phase changes from a long chain to a granular state with the increase of the solid solution temperature, and the dissolution rate of the Laves phase is faster with the higher solid solution temperature. Control of the Laves phase was achieved by most researchers only by technological means before heat treatment. Document 3 (transformation of non-ferrous metals Society of China,2016,26,431-436) studies the structure change under the same linear energy condition, and finds that the cooling speed of the molten pool is increased along with the reduction of the laser power and the scanning speed, thereby being beneficial to the inhibition of Nb element segregation. Document 4 (doctor thesis of schnam university, showa, 2017) studies the influence of solidification rate on the segregation behavior of the Nb element in the Inconel718 alloy by changing basic parameters such as laser power, scanning speed and the like, and the result shows that the higher the cooling rate is, the more favorable the Nb element inhibition and the formation of Laves phase are. Document 5 (liu hong steel, shanghai university of traffic master paper, 2012) compares the precipitation of Laves phase under the conditions of laser power of 5kW and 1.5kW, and shows that reducing the laser power can improve the cooling speed of the molten pool and reduce the precipitation of Laves phase. Document 6 (yaowang, doctor thesis of shanghai university of transportation, 2013) discloses a method for effectively increasing the cooling rate while reducing the formation of Laves phases by using a high cladding rate and a fast laser remelting method. In addition, besides reducing energy input, the cooling speed can be effectively increased by increasing heat dissipation, and document 7 discloses (Surface Engineering,2013,29(6),414-418) a method of increasing the cooling speed by using a substrate liquid nitrogen cooling method, so as to inhibit the precipitation of Laves phase, but as the material adding process proceeds, the bottom cooling method has no obvious influence on the part far away from the substrate due to heat accumulation. The influence of different carrier gas types on the structure and the performance is researched in the document 8 (surface technology, 2018,47(7), 185-190), and the result shows that the helium is used as the carrier gas to effectively increase the cooling speed of the molten pool and inhibit the precipitation of the Laves phase. Document 9 (rare metal materials and engineering, 2019,48(11), 3393-3599) discloses a method for realizing effective control of Laves phase by using an electromagnetic field. Document 10(Materials Letters,2017,188,260-262) realizes control of Laves phase by changing laser light source mode through a laser modulation technique.

According to the above reports, the solidification behavior of the molten pool can be adjusted to some extent by increasing the cooling rate of the molten pool in the interdendritic Laves phase. The traditional laser cladding adopts a laser to clad, a powder feeder feeds special powder onto a base body along a processing path, laser emitted by the laser melts the special powder onto the base body, and a laser processing head of the laser and a powder feeding head of the powder feeder synchronously move along the processing path, so that continuous laser cladding is realized; generally, the situation of inhibiting the Laves phase is very limited only by changing the laser power and the scanning speed, and some of the currently mentioned additional regulating and controlling devices are complex, cumbersome for field repair, high in maintenance cost and low in cost performance.

Disclosure of Invention

The invention aims to solve the problems that the situation of Laves phase inhibition is very limited only by adjusting the laser power and the scanning speed, an additional regulating and controlling device is complex, the field repair is complicated, the maintenance cost is high, and the cost performance is not high, and provides a method for inhibiting the Laves phase precipitation in the process of manufacturing a nickel-based alloy by using a laser additive.

The invention realizes the purpose through the following technical scheme: a method for inhibiting Laves phase precipitation in a process of manufacturing a nickel-based alloy through laser additive manufacturing specifically comprises the following steps:

the method comprises the following steps: placing a base material made of nickel-based high-temperature alloy on a workbench with a cooling device as a sample, opening the cooling device, and cooling the lower end of the base body by the cooling device, so that the heat accumulation in the initial stage of laser forming manufacturing is relieved to the greatest extent;

step two: the method comprises the steps that a synchronous suppression device is installed well, the synchronous suppression device comprises a gas cylinder group, a circulating liquid cooling device, a gas cooling valve and a nozzle gas cooling device, the gas cylinder group is connected with the circulating liquid cooling device through a pipeline and does not supply gas to the circulating liquid cooling device, the circulating liquid cooling device is connected with the nozzle gas cooling device through a pipeline, the circulating liquid cooling device provides cooling gas for the nozzle gas cooling device, the gas cooling valve is arranged at the outlet of the circulating liquid cooling device and controls the flow of the cooling gas, the nozzle cooling device is a chilling copper pipe which is installed on a laser processing head and moves along with the laser processing head, the number of the chilling copper pipes is three, and the three chilling copper pipes are respectively aligned to the edge position of a molten pool formed by metal powder, a laser beam and a base body;

step three: opening a semiconductor laser, irradiating laser emitted by the semiconductor laser on a substrate, simultaneously sending prepared and dried metal powder to the substrate by using a boiling type powder feeder, arranging a laser processing head of the semiconductor laser and a powder feeding head of the boiling type powder feeder at the movable end of the same moving mechanism, synchronously moving the laser processing head of the semiconductor laser and the powder feeding head of the boiling type powder feeder, and cladding the metal powder on the substrate by the semiconductor laser; the power of the semiconductor laser is 900-2000W, the diameter of a light spot of an emitted laser beam irradiated on the substrate is 4mm, the scanning speed is 360-420 mm/s, the powder feeding amount of the boiling type powder feeder is 10-15g/min, and the flow rate of protective gas and carrier gas is 10-20L/min;

step four: in the process of cladding metal powder on a substrate by a semiconductor laser, the metal powder, a laser beam and the substrate form a molten pool, after the forming position of the molten pool is determined, the positions of three chilled copper pipes of a synchronous suppression device are adjusted, the three chilled copper pipes face to the left, the right and the back of the scanning direction, the heights of the three chilled copper pipes are 5-10 mm higher than the single-layer thickness of the formed cladding layer, an air cooling valve of the synchronous suppression device is opened, and the flow of cold air is adjusted to be 3-20L/min until the material increasing process of a sample is completed;

step five: after the material increase process is finished, closing a laser processing head of the semiconductor laser and a powder feeding head of the boiling type powder feeder, moving to an initial position, and taking down a sample after material increase;

step six: and (3) cutting, inlaying, roughly grinding, finely polishing and corroding the sample, and observing the tissue condition of the cross section by using a scanning electron microscope.

Further, the cooling device used in the first step is uniformly paved below the whole matrix, and the cooling medium used by the cooling device is ice water or liquid nitrogen.

Further, the metal powder enters the molten pool by means of coaxial powder feeding or lateral powder feeding. The laser processing head of the semiconductor laser and the powder feeding head of the boiling type powder feeder are arranged at the movable end of the same moving mechanism, the powder feeding head is arranged adjacent to the laser processing head or the powder feeding head is arranged on the side surface of a molten pool on the substrate, and the powder feeding head sends metal powder to the substrate along the scanning path of the laser processing head sent by the laser processing head.

Furthermore, in the fourth step, the scanning direction of the semiconductor laser is taken as the right front side, the molten pool formed by the laser beams emitted by the semiconductor laser on the metal powder and the substrate is circular, the three chilled copper pipes face to the right left side, right side and right back side of the scanning direction, and the three chilled copper pipes all aim at the edge of the molten pool to blow out cold air, so that a chilled environment is formed at the edge of the molten pool. The additive can be rapidly solidified at the edge of the molten pool so as to cover the periphery of the molten pool and the formed part of the same layer. The scan direction is such that chilled copper tubes cannot be set, which would affect the continued formation of the molten pool.

Further, the gas provided by the gas bottle group is inert gas, and the chilling copper pipe is used for cooling and dehumidifying the inert gas.

Further, the inert gas includes argon, nitrogen, helium and a combination of two or more of the above three gases.

Furthermore, the three chilling copper pipes of the synchronous suppression device are made of copper with good heat conduction performance. The three chilled copper tubes may also be made of other heat conducting materials, but cannot be affected by the hot environment of the molten bath and the cold environment of the cold gas.

The invention has the beneficial effects that: in the laser additive manufacturing or remanufacturing process of the nickel-based superalloy, the laser source is added around the liquid state of the molten pool, so that the redistribution of a temperature field in the molten pool can be realized, and the temperature gradient at the front edge of a solid-liquid interface is increased; the solidification speed of a molten pool is accelerated, the aggregation of segregation elements such as Nb, Al and Ti among dendrites is effectively reduced, so that the size and the volume fraction of Laves brittle phases among the dendrites are reduced, the solid solution effect of alloy elements such as the strengthening element Nb in a dendrite dry gamma phase is promoted, and the precipitation of the strengthening phase in the subsequent aging heat treatment process is guaranteed.

Drawings

FIG. 1 is a schematic overall structure diagram of equipment used in the method for inhibiting Laves phase precipitation in the process of laser additive manufacturing of the nickel-based alloy. In the figure, 1-cooling device, 2-substrate, 3-laser processing head, 4-circulating liquid cooling device, 5-gas cylinder group, 6-gas cooling valve and 7-nozzle gas cooling device.

FIG. 2 is a cross-sectional structure diagram of a laser cladding additive manufactured by the method for inhibiting Laves phase precipitation in the process of manufacturing a nickel-based alloy by using the laser additive under a scanning electron microscope.

Fig. 3 is a cross-sectional texture view under a scanning electron microscope of a laser-clad additive manufactured by a conventional method.

Detailed Description

The invention will be further described with reference to the accompanying drawings in which:

as shown in figures 1-3, the adopted device comprises a cooling device 1, a semiconductor laser, a boiling type powder feeder and a synchronous suppression device, a base material made of the nickel-based superalloy is placed on a workbench with the cooling device 1 as a sample, and the cooling device 1 cools the lower end of a base body 2, so that the heat accumulation in the initial laser forming manufacturing process is relieved to the greatest extent. The cooling device 1 is evenly paved below the whole matrix 2, and the cooling medium used by the cooling device 1 is ice water or liquid nitrogen.

The synchronous suppression device comprises a gas cylinder group 5, a circulating liquid cooling device 4, a gas cooling valve 6 and a nozzle gas cooling device 7, wherein the gas cylinder group 5 is connected with the circulating liquid cooling device 4 through a pipeline and supplies gas to the circulating liquid cooling device 4, the circulating liquid cooling device 4 is connected with the nozzle gas cooling device 7 through a pipeline, the circulating liquid cooling device 4 supplies cooling gas to the nozzle gas cooling device 7, the gas cooling valve 6 is arranged at the outlet of the circulating liquid cooling device 4 and controls the flow of the cooling gas, the nozzle cooling device 1 is a chilling copper pipe which is arranged on a laser processing head 3 and moves along with the laser processing head 3, the number of the chilling copper pipes is three, and the three chilling copper pipes are respectively aligned to the edge position of a molten pool formed by metal powder, a laser beam and a base body 2.

The gas provided by the gas bottle group 5 is inert gas, and the chilling copper pipe is used for cooling and dehumidifying the inert gas; the inert gas comprises argon, nitrogen, helium and the combination of two or more of the three gases; the three chilling copper pipes of the synchronous suppression device are made of copper with good heat conduction performance.

The laser processing head 3 of the semiconductor laser is over against the substrate 2, the powder feeding head of the boiling type powder feeder is over against the scanning position of the laser processing head on the substrate 2, the laser processing head 3 of the semiconductor laser and the powder feeding head of the boiling type powder feeder are arranged at the movable end of the same moving mechanism, the laser processing head 3 of the semiconductor laser and the powder feeding head of the boiling type powder feeder move synchronously, and the semiconductor laser carries out cladding on metal powder on the substrate 2; the power of the semiconductor laser is 900-2000W, the diameter of a light spot of an emitted laser beam irradiated on the substrate 2 is 4mm, the scanning speed is 360-420 mm/s, the powder feeding amount of the boiling type powder feeder is 10-15g/min, and the flow rate of protective gas and carrier gas is 10-20L/min; the metal powder enters the molten pool in a coaxial powder feeding mode or a lateral powder feeding mode.

In the process of cladding metal powder on a substrate 2 by a semiconductor laser, the metal powder, a laser beam and the substrate 2 form a molten pool, after the forming position of the molten pool is determined, the positions of three chilled copper pipes of a synchronous suppression device are adjusted, the three chilled copper pipes face to the left, the right and the rear in the scanning direction, the heights of the three chilled copper pipes are 5-10 mm higher than the thickness of a single layer of a formed cladding layer, an air cooling valve 6 of the synchronous suppression device is opened, and the flow of cold air is adjusted to be 3-20L/min until the material increasing process of a sample is completed; the scanning direction of the semiconductor laser is used as the right front, a molten pool formed by laser beams emitted by the semiconductor laser on metal powder and the substrate 2 is circular, the three chilling copper pipes face to the right left, right and right of the scanning direction, and the three chilling copper pipes all aim at the edge of the molten pool to blow out cold air, so that a chilling environment is formed at the edge of the molten pool.

After the material increase process is finished, closing the laser processing head 3 of the semiconductor laser and the powder feeding head of the boiling type powder feeder, moving to the initial positions, and taking down a sample after material increase; and then, cutting, inlaying, roughly grinding, finely polishing and corroding the sample, and observing the tissue condition of the cross section by using a scanning electron microscope.

The present application is further described below with reference to specific examples.

Example 1:

1) the Inconel718 high-temperature alloy is selected as the matrix 2, the surface of the matrix is polished by sand paper, and oil stains are removed by using an alcohol solution. And (3) putting the prepared special powder into an oven for half an hour to remove moisture, drying, putting into a boiling type powder feeder, and adopting a coaxial powder feeding mode.

2) Carrying out a cladding experiment by using a 2000W semiconductor laser, wherein the spot diameter of a laser beam emitted by a laser processing head 3 of the semiconductor laser is 4 mm; the selected process comprises the following steps: the laser power is 900W, the scanning speed is 360mm/s, and the powder feeding amount is 10 g/min. The flow rates of the shielding gas and the carrier gas are 15L/min.

3) The cooling device 1 of the base body 2 with the cooling medium of liquid nitrogen cools the bottom of the base material, and reduces heat accumulation in the forming process.

4) Determining a forming position, adjusting the positions and the directions of three chilling copper pipes in the synchronous suppression device, and opening an air cooling valve; and adjusting the flow rate to be 3L/min until the additive process is finished.

FIG. 3 is a typical texture obtained by laser additive manufacturing after chilling.

Example 2:

1) the Inconel 625 is selected as the substrate 2, the surface is polished by sand paper, and then the oil stain is removed by using alcohol solution.

2) And (3) putting the prepared special powder into an oven for half an hour to remove moisture, drying, putting into a scraper type powder feeder, and adopting a coaxial powder feeding mode.

3) Cladding by using a 2000W semiconductor laser, wherein the diameter of a light spot of a laser beam emitted by a laser processing head 3 of the semiconductor laser is 4 mm; the selected process comprises the following steps: laser power 1600W, scanning speed 420mm/s, powder feeding amount 10 g/min.

4) Determining a forming position, adjusting the positions and the directions of three chilling copper pipes in the synchronous suppression device, and opening an air cooling valve; and adjusting the flow rate to be 3L/min until the additive process is finished.

5) After molding, the samples were subjected to a series of processes such as wire cutting, inlaying, rough grinding, fine grinding, polishing and etching, and then the texture was observed.

Example 3:

1) the Inconel 939 is selected as the substrate 2, the surface of the substrate is polished by sand paper, and oil stains are removed by using an alcohol solution.

2) And (3) putting the prepared special powder into a dryer for half an hour to remove moisture, drying, putting the powder into a scraper type powder feeder, and adopting a coaxial powder feeding mode.

3) Cladding by using a 2000W semiconductor laser, wherein the diameter of a light spot of a laser beam emitted by a laser processing head 3 of the semiconductor laser is 4 mm; the selected process comprises the following steps: laser power 1800W, scanning speed 420mm/s, powder feeding amount 15 g/min.

4) Determining a forming position, adjusting the positions and the directions of three chilling copper pipes in the synchronous suppression device, and opening an air cooling valve; and adjusting the flow rate to be 20L/min until the additive process is finished.

5) After forming, the samples were subjected to a series of processes such as wire cutting, inlaying, rough grinding, fine grinding, polishing and etching, and then the texture was observed.

The above embodiments are only preferred embodiments of the present invention, and are not intended to limit the technical solutions of the present invention, so long as the technical solutions can be realized on the basis of the above embodiments without creative efforts, which should be considered to fall within the protection scope of the patent of the present invention.