Method for preparing large-size high-density wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic by laser directional energy deposition technology

Abstract

The invention provides a method for preparing large-size and high-density wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic by a laser directional energy deposition technology. A laser beam is adopted as a heat source to rapidly melt eutectic component ceramic powder, high-density and large-size wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic is directly formed in a near-net mode through layer-by-layer deposition, rapid and high-quality preparation of large-size oxide ceramic is achieved, and high-temperature sintering is not needed; by regulating and controlling the swing of the laser beam in a local range, the effective energy input can be improved, the uniform distribution of the temperature in the molten pool can be ensured, the existence time of the molten pool can be effectively prolonged, the stress accumulation in the ceramic sample piece can be obviously reduced, and the macroscopic crack and pore defects can be effectively inhibited; a wider forming process window is provided, the laser scanning speed capable of being used is higher, the thickness of a deposition layer is larger, the wall-shaped eutectic ceramic forming speed is higher, and follow-up machining is not needed; the microstructure of the prepared wall-like Al2O3-GdAlO3-ZrO2 eutectic ceramic is fine and compact, and the wall-like Al2O3-GdAlO3-ZrO2 eutectic ceramic presents a uniform lamellar eutectic structure.

Description

Technical Field

[0001] The invention relates to the field of laser additive manufacturing of ceramic materials, and in particular to a method for preparing large-size, high-density wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramics using laser directional energy deposition technology. Background Art

[0002] With the rapid development of the aerospace field, aircraft engines tend to pursue higher thrust-to-weight ratios and longer service life, which requires high-temperature structural materials to be lightweight, high-strength, and able to have as long a service life as possible in ultra-high temperature oxidative environments. Therefore, the research and development of new ultra-high temperature structural materials and preparation technologies are key issues that need to be urgently addressed in the aerospace field. Melt-grown Al2O3-GdAlO3-ZrO2 eutectic ceramics are expected to be used in high-temperature hot end components such as aircraft engine turbine guide blades and combustion chamber liners due to their excellent high-temperature strength, oxidation resistance, creep resistance, and high-temperature structural stability. They are considered to be new high-temperature structural materials that can serve for a long time in ultra-high temperature oxidative environments.

[0003] Laser Directed Energy Deposition technology is a laser additive manufacturing technology based on coaxial powder feeding, with a temperature gradient of up to 10 4 K / cm, with the characteristics of high forming efficiency, fast solidification speed, and no restrictions on sample size and shape. Therefore, if the laser directional energy deposition technology can be used to prepare Al2O3-GdAlO3-ZrO2 eutectic ceramics, it is expected to break through the bottleneck problem that traditional directional solidification technology is difficult to prepare complex structure samples and cannot take into account the macroscopic size and microstructural scale of the sample, promote the industrial application process of the material and broaden its application range.

[0004] Patent CN102557596B discloses a method for preparing alumina-based eutectic ceramics by laser powder feeding. This method uses a surface atmosphere heating furnace to heat the powder raw materials to reduce the thermal stress during the zone melting process, inhibit the formation of macroscopic cracks, and assist in the forming of large-sized eutectic ceramics. However, the eutectic ceramics prepared by this method have irregular shapes and poor forming quality; the laser scanning speed is 0.2 - 6 mm / min, and the powder feeding speed of the powder feeder is 0.6 - 2.0 g / min, resulting in a low forming rate. Patent CN109761587B discloses a method for preparing Al2O3-GdAlO3-ZrO2 ternary eutectic ceramics. This method uses laser near-net shaping to manufacture layer by layer, and reciprocally scans the upper surface of the specimen by gradually reducing the laser power to slow down the cooling rate, reduce the thermal stress during the cooling process, and inhibit the formation of macroscopic cracks; however, the diameter or width of the eutectic ceramic sample prepared by this method is only about 5 mm, which is only suitable for preparing eutectic ceramic components with a high aspect ratio such as rods. Patent CN109760173B discloses a laser melting forming method for wall-shaped Al2O3-GdAlO3-ZrO2 ternary eutectic ceramics. This method also uses laser near-net shaping technology combined with laser gradual cooling to prepare wall-shaped Al2O3-GdAlO3-ZrO2 ternary eutectic ceramics with a uniform lamellar eutectic structure; however, the height and width of the wall-shaped specimen prepared by this method cannot reach large sizes simultaneously, and the maximum deposition height of a wall-shaped specimen with a width of 20 mm is only 5 mm. The literature "Haijun Su, Haifang Liu, Hao Jiang, Zhonglin Shen, Qian Chen, Minghui Yu, Di Zhao, Xiang Li, Dong Dong, Zhuo Zhang, One-step preparation of melt-grown Al2O3 / GdAlO3 / ZrO2 eutectic ceramics with large size and irregular shape by directed energy deposition[J]. Additive Manufacturing, 2023, 70:103563." uses laser directed energy deposition technology to prepare wall-shaped Al2O3 / GdAlO3 / ZrO2 eutectic ceramics with different widths, and finds that as the deposition height and wall width increase, the macroscopic cracks in the obtained eutectic ceramic samples are more. A wall-shaped specimen without macroscopic cracks and with a large deposition height can only be prepared by shortening the single-layer scanning length to 5 mm. At this time, the width of the wall-shaped specimen is almost the same as the diameter of the rod-shaped specimen with a high aspect ratio, which does not meet the goal of preparing wall-shaped specimens with a large width-thickness ratio.

[0005] At present, the forming process of the wall-like Al2O3-GdAlO3-ZrO2 eutectic ceramics can only prepare small-sized samples without cracks. Increasing the wall width or deposition height will result in a large number of macroscopic cracks and even lead to forming failure. To overcome this bottleneck problem, the present invention proposes a new method for preparing large-sized and highly dense wall-like Al2O3-GdAlO3-ZrO2 eutectic ceramics by laser directed energy deposition technology. Summary of the Invention

[0006] The present invention provides a method for preparing large-sized and highly dense wall-like Al2O3-GdAlO3-ZrO2 eutectic ceramics by laser directed energy deposition technology. The method provided by the present invention can achieve high-quality 3D printing and rapid near-net forming of larger-sized wall-like eutectic ceramic samples, inhibit solidification defects such as macroscopic cracks and pores, and improve the density of the wall-like eutectic ceramic samples.

[0007] The method for preparing large-sized and highly dense wall-like Al2O3-GdAlO3-ZrO2 eutectic ceramics by laser directed energy deposition technology provided by the present invention comprises the following steps:

[0008] Step 1: Prepare spherical eutectic powder of Al2O3-Gd2O3-ZrO2; the particle size of the spherical eutectic powder is 20-80 μm;

[0009] Step 2: Set the laser scanning path; set the laser scanning path according to the required size of the wall-like eutectic ceramics. The scanning path is composed of specific swinging paths in a number of local areas connected end to end. The scanning path takes the specific swinging path in the local area as the basic unit. In each local area, the laser beam moves clockwise or counterclockwise according to the set path, and the swinging range in the Y-axis direction is 2-6 mm; in adjacent local areas, the swinging range of the laser beam in the X-axis direction is 0.2-0.4 times of its swinging range in the Y-axis direction;

[0010] Connecting the specific swinging paths in a number of local areas end to end forms the entire scanning path of the laser beam movement within a single deposition layer. After completing the entire scanning path of the nth layer, set the laser nozzle to lift by the height of a single deposition layer in the Z-axis direction to prepare for printing the (n + 1)th layer; the entire scanning path within the (n + 1)th layer is composed of the specific swinging paths in the same local areas connected end to end, but the moving direction of the laser beam in the X-axis direction is opposite to that of the nth layer; after completing the entire scanning path of the (n + 1)th layer, set the laser nozzle to lift by the height of a single deposition layer in the Z-axis direction to prepare for printing the (n + 2)th layer; according to the height of the required wall-like eutectic ceramics and the thickness of a single deposition layer, set the entire scanning paths of the nth layer and the (n + 1)th layer to be repeated a number of times, that is, complete the setting of the laser scanning path;

[0011] Step 3: Set the laser scanning parameters; set the laser power and laser scanning speed used in the eutectic ceramic forming process; the laser power is 200 - 600 W, and the scanning rate is 120 - 840 mm / min;

[0012] Step 4: Conduct a laser directed energy deposition experiment; using the laser directed energy deposition method, melt the spherical eutectic powder prepared in Step 1 through a laser beam, and layer by layer deposit and form a wall-like Al2O3-GdAlO3-ZrO2 eutectic ceramic along the laser scanning path set in Step 2 according to the laser scanning parameters set in Step 3.

[0013] Further, in Step 1, during the process of preparing the Al2O3-Gd2O3-ZrO2 spherical eutectic powder, mix the Al2O3 ceramic powder, Gd2O3 ceramic powder, and ZrO2 ceramic powder evenly according to a molar ratio of 58:19:23, add alcohol and an aqueous solution of polyvinyl alcohol, mix evenly and perform spray granulation. Screen the spherical eutectic powder with a particle size of 20 - 100 μm, dry it in an oven for 3 - 6 hours, and then sinter it at a temperature of 1200 - 1600 °C for 2 - 5 hours; continue with plasma spheroidization treatment, screen the spherical eutectic powder with a particle size of 20 - 80 μm, and obtain the Al2O3-Gd2O3-ZrO2 spherical eutectic powder after drying.

[0014] Further, the mass of the alcohol accounts for 7 - 12 wt.% of the total mass of the Al2O3 ceramic powder, Gd2O3 ceramic powder, and ZrO2 ceramic powder, and the mass of the aqueous solution of polyvinyl alcohol accounts for 3 - 6 wt.% of the total mass of the Al2O3 ceramic powder, Gd2O3 ceramic powder, and ZrO2 ceramic powder.

[0015] Further, in Step 2, the specific swinging path is one of a circular swinging path, an equilateral triangle swinging path, a rectangular swinging path, or a sine swinging path. When the specific swinging path is a circular swing, the diameter of the circular swinging path is 2 - 6 mm, and the distance between adjacent circular swinging paths is 0.2 - 0.4 times the diameter of the circular swinging path; when the specific swinging path is an equilateral triangle swing, the side length of the equilateral triangle swinging path is 2 - 6 mm, and the distance between adjacent equilateral triangle swinging paths is 0.2 - 0.4 times the side length of the equilateral triangle swinging path. The moving speed of the laser beam on the three sides of the equilateral triangle is the same, and the residence time at each vertex is 0.1 - 0.5 seconds.

[0016] Further, in Step 2, the height by which the laser nozzle is lifted in the Z-axis direction between adjacent deposition layers does not exceed the thickness of a single deposition layer.

[0017] Further, in step 3, the laser scanning parameters further include that the single-layer scanning distance in the X-axis direction is 5-40 mm, the single-layer lifting height of the laser nozzle is 0.1-2 mm, and the number of processing layers is 10-50 layers.

[0018] Further, in step 4, the process of depositing and forming the wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic is as follows:

[0019] First step, horizontally place the Al2O3 ceramic substrate; the vertical distance between the upper surface of the ceramic substrate and the lower surface of the laser nozzle is 10-20 mm, and the laser spot diameter is 1-3 mm;

[0020] Second step, preheat the Al2O3 ceramic substrate to form a stable molten pool;

[0021] Third step, turn on the powder feeder to convey spherical eutectic powder;

[0022] Fourth step, the laser beam heats and melts the spherical eutectic powder obtained in the first step along the laser scanning path set in step 2 according to the laser scanning parameters set in step 3, and the spherical eutectic powder enters the stable molten pool; and continuously deposits on the surface of the Al2O3 ceramic substrate as the laser nozzle moves; when the laser beam leaves, the temperature drops and the molten pool rapidly solidifies; when the laser beam completes all the scanning paths set in step 2, the deposition and forming of the wall-shaped Al2O3-Gd2O3-ZrO2 eutectic ceramic is completed;

[0023] Fifth step, the deposited wall-shaped eutectic ceramic and the Al2O3 substrate are naturally cooled to room temperature to obtain the formed wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic.

[0024] Further, the process of depositing and forming the wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic is carried out in a glove box with good airtightness and a high-purity argon atmosphere. The high-purity argon circulates in the glove box through a circulation fan. The box pressure of the glove box is 1-6 mbar, the rotation speed of the circulation fan is 30 Hz, and the purity of the high-purity argon is 99.999%.

[0025] Further, the Al2O3 ceramic substrate is prepared by sintering, and the purity is 95%.

[0026] Further, the powder feeding rate of the powder feeder is 2-12 g / min, the powder feeding gas is high-purity argon, the purity is 99.999%, and the gas flow rate is 6-12 L / min.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] By adopting the method of oscillating and scanning cladding with a laser beam in each local area, the present invention increases the volume and existence time of the molten pool during the forming process, can reduce the cooling rate of the specimen, provides a longer time for gas bubbles to escape from the molten pool, and at the same time slows down the thermal stress during the cooling process and inhibits the formation of macroscopic cracks.

[0029] The Al2O3-GdAlO3-ZrO2 eutectic ceramic prepared by the present invention has a fast forming speed; the faster the scanning speed of the laser, the faster the solidification speed inside the prepared Al2O3-GdAlO3-ZrO2 eutectic ceramic and the faster the hot and cold cycle at the same position, which is more likely to cause stress accumulation and form cracks; thanks to the oscillation of the laser within a local range, while increasing the volume of the molten pool, it also ensures a more uniform temperature distribution in the molten pool, reducing the instantaneous magnitude of local stress and the cumulative peak value of cyclic stress; the forming scanning speed of the Al2O3-GdAlO3-ZrO2 eutectic ceramic in the present invention can reach 840 mm / min; while when preparing the Al2O3-GdAlO3-ZrO2 eutectic ceramic by the prior art, the fastest reported scanning speed is 240 mm / min.

[0030] The present invention can greatly improve the forming quality and size of the wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic specimen prepared by the prior art; due to the oscillating scan of the laser within a local range, the volume and existence time of the molten pool are increased, which is beneficial to the escape of gas bubbles and reduces pore defects; at the same time, the temperature is kept uniform in a larger range, the instantaneous stress is significantly reduced, the stress accumulation is reduced, and the formation of crack defects is inhibited; the present invention can simultaneously reduce the number of two solidification defects, namely macroscopic cracks and pores, thereby improving the forming quality and forming size of the Al2O3-GdAlO3-ZrO2 eutectic ceramic; currently, by adjusting the single-layer scanning distance and the number of processing layers, a wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic specimen with a size of 23×20×4 mm 3 can be prepared, as Figure 2 shown; through subsequent process optimization, it is expected to prepare Al2O3-GdAlO3-ZrO2 eutectic ceramic specimens with more complex structures and larger sizes, accelerating the industrial application process of this type of material.

[0031] The solidification structure of the Al2O3-GdAlO3-ZrO2 eutectic ceramic currently prepared by the present invention is fine, and the eutectic lamellar spacing can reach 190 nm, as Figure 3As shown, the microstructure of the sample obtained by the Bridgman method is refined by more than 25 times, and is at the same level as the microstructure size of the ceramic sample prepared by the existing publicly disclosed laser additive manufacturing technology. Therefore, the Al2O3-GdAlO3-ZrO2 eutectic ceramic prepared by the present invention is expected to achieve both the macro-size enlargement and the microstructure refinement, significantly improve the formable size while maintaining high mechanical properties, and broaden the application range of this type of material. Brief Description of the Drawings

[0032] Figure 1 is a flow chart of the preparation of large-size and high-density wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramics by the laser directed energy deposition technology provided by the present invention.

[0033] Figure 2 is a schematic diagram of the local oscillating scanning strategy within a single deposition layer provided by the present invention, where (a) is a circular oscillating scanning strategy and (b) is an equilateral triangle oscillating scanning strategy.

[0034] Figure 3 is a wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic sample prepared according to an embodiment of the present invention.

[0035] Figure 4 is the microstructure morphology of the wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic prepared according to an embodiment of the present invention. Detailed Embodiments

[0036] In order to make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of the present disclosure without creative efforts also fall within the scope of protection of the present disclosure.

[0037] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the subject matter of the present disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the specification and the relevant art, and will not be interpreted in an idealized or overly formal manner unless expressly defined herein otherwise.

[0038] As used herein, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of the present application. The phrase "embodiment" appearing at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0039] As Figure 1 shown, a method for preparing a large-sized and highly dense wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic by a laser directed energy deposition technique provided by the present invention specifically includes the following steps:

[0040] Step 1: Prepare Al2O3-Gd2O3-ZrO2 spherical eutectic powder; the particle size of the spherical eutectic powder is preferably 20 - 80 μm, for example, it can be 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm;

[0041] During the process of preparing the Al2O3-Gd2O3-ZrO2 spherical eutectic powder, mix the Al2O3 ceramic powder, Gd2O3 ceramic powder, and ZrO2 ceramic powder evenly according to a molar ratio of 58:19:23, add alcohol and an aqueous solution of polyvinyl alcohol and mix evenly, and perform spray granulation. After screening spherical eutectic powder with a particle size of 20 - 100 μm and drying it in an oven for 3 - 6 hours, sinter it at a temperature of 1200 - 1600 °C for 2 - 5 hours; continue with plasma spheroidization treatment, screen spherical eutectic powder with a particle size of 20 - 80 μm, and after drying, obtain spherical composite powder with high sphericity, good fluidity, high bonding strength, suitable for laser directed energy deposition technology, and having a eutectic component of Al2O3-Gd2O3-ZrO2;

[0042] Step 2: Set the laser scanning path; set the laser scanning path according to the size of the wall-shaped eutectic ceramic. The scanning path is composed of a combination of specific swinging paths in several local areas connected end to end; within each local area, the laser beam moves clockwise or counterclockwise according to the set scanning parameters, and its swinging range in the Y-axis direction is preferably 2 - 6 mm, for example, it can be 2 mm, 3 mm, 4 mm, 5 mm, 6 mm; in adjacent local areas, the swinging range of the laser beam in the X-axis direction is 0.2 - 0.4 times its swinging range in the Y-axis direction, for example, it can be 0.2, 0.3, 0.4;

[0043] As Figure 2As shown, the scanning path takes a specific swinging path within a local area as the basic unit, and the specific swinging path is one of a circular swinging path, an equilateral triangle swinging path, a rectangular swinging path, or a sine swinging path; connecting the swinging paths in several local areas end to end forms all the scanning paths of the laser beam movement within a single deposition layer; after completing all the scanning paths of the nth layer, the laser nozzle is lifted by the height of a single deposition layer in the Z-axis direction to prepare for printing the (n + 1)th layer; all the scanning paths within the (n + 1)th layer are formed by connecting the specific swinging paths in the same local area end to end, but the moving direction of the laser beam in the X-axis direction is opposite to that of the nth layer; after completing all the scanning paths of the (n + 1)th layer, the laser nozzle is lifted by the height of a single deposition layer in the Z-axis direction to prepare for printing the (n + 2)th layer; according to the height of the desired wall-like eutectic ceramic and the thickness of a single deposition layer, set the scanning paths of all the nth layer and the (n + 1)th layer to be repeated several times, and the setting of the laser scanning path is completed.

[0044] When the specific swinging path is a circular swing, the diameter of the circular swinging path is 2 - 6 mm, and the distance between adjacent circular swinging paths is 0.2 - 0.4 times the diameter of the circular swinging path; when the specific swinging path is an equilateral triangle swing, the side length of the equilateral triangle swinging path is 2 - 6 mm, and the distance between adjacent equilateral triangle swinging paths is 0.2 - 0.4 times the side length of the equilateral triangle swinging path. The moving speed of the laser beam on the three sides of the equilateral triangle is the same, and the residence time at each vertex is 0.1 - 0.5 seconds.

[0045] Step 3: Set the laser scanning parameters; set the laser power and laser scanning speed used in the eutectic ceramic forming process; the laser power is preferably 200 - 600 W, for example, it can be 200 W, 300 W, 350 W, 400 W, 500 W, 600 W, etc., and the scanning rate is preferably 120 - 840 mm / min, for example, it can be 120 mm / min, 240 mm / min, 300 mm / min, 360 mm / min, 420 mm / min, 560 mm / min, 640 mm / min, 750 mm / min, 840 mm / min, etc.; the single-layer scanning distance along the X-axis direction is preferably 5 - 40 mm, for example, it can be 5 mm, 15 mm, 20 mm, 30 mm, 40 mm, etc., the single-layer lifting height of the laser nozzle is preferably 0.1 - 2 mm, for example, it can be 0.1 mm, 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, etc., and the number of processing layers is preferably 10 - 50 layers, for example, it can be 10 layers, 15 layers, 20 layers, 30 layers, 35 layers, 40 layers, 45 layers, 50 layers, etc.

[0046] Step 4: Conduct laser directed energy deposition experiments; using the laser directed energy deposition method, melt the spherical eutectic powder prepared in Step 1 by a laser beam, and layer by layer deposit and form a wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic along the laser scanning path set in Step 2 according to the laser scanning parameters set in Step 3; the specific process is as follows:

[0047] First step, place the Al2O3 ceramic substrate;

[0048] Horizontally and stably place the Al2O3 ceramic substrate so that the vertical distance between the upper surface of the ceramic substrate and the lower surface of the laser nozzle is preferably 10-20 mm. For example, it can be 10 mm, 12 mm, 15 mm, 17 mm, 18 mm, 20 mm, ensuring that the laser spot diameter is 1-3 mm; the Al2O3 ceramic substrate is prepared by sintering and has a purity of 95%.

[0049] Second step, preheat the ceramic substrate to form a stable molten pool;

[0050] Turn on the laser so that the laser beam heats and melts the Al2O3 ceramic substrate along the scanning path set in Step 3 according to the scanning parameters set in Step 2 to form a stable molten pool;

[0051] Third step, open the powder feeder to convey the spherical eutectic powder;

[0052] The powder feeding rate of the powder feeder is preferably 2-12 g / min. For example, it can be 2 g / min, 2.5 g / min, 3 g / min, 3.6 g / min, 4 g / min, 5 g / min, 6 g / min, 7 g / min, 8 g / min, 9 g / min, 10 g / min, 11 g / min, 12 g / min; the powder feeding gas is high-purity argon with a purity of 99.999%, and the gas flow rate is preferably 6-12 L / min. For example, it can be 6 L / min, 7 L / min, 8 L / min, 9 L / min, 10 L / min, 11 L / min, 12 L / min;

[0053] Fourth step, the laser beam heats and melts the eutectic powder obtained in Step 1 along the scanning path set in Step 3 according to the scanning parameters set in Step 2 and enters the stable molten pool; and continuously deposits on the surface of the Al2O3 ceramic substrate as the laser nozzle moves; at the position where the laser beam leaves, the temperature drops, resulting in rapid solidification of the molten pool; when the laser beam completes the scanning paths of all the deposited layers set in Step 2, the deposition and forming of the wall-shaped eutectic ceramic sample is completed;

[0054] Step 5: The laser beam is automatically turned off, the powder feeder is closed, and the laser nozzle is lifted away from the wall-shaped eutectic ceramic sample; the deposited wall-shaped eutectic ceramic and the Al2O3 substrate are naturally cooled to room temperature to obtain the formed wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic.

[0055] In the present invention, the process of depositing and forming the wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic is carried out in a glove box with good airtightness and a high-purity argon atmosphere. The high-purity argon circulates in the glove box through a circulation fan. The box pressure of the glove box is 1 - 6 mbar, the rotation speed of the circulation fan is 30 Hz, and the purity of the high-purity argon is 99.999%.

[0056] The present invention will be further described below through specific examples.

[0057] Example 1

[0058] Step 1: Prepare spherical Al2O3-Gd2O3-ZrO2 powder with eutectic composition;

[0059] When preparing the spherical mixed powder material of Al2O3-Gd2O3-ZrO2 with eutectic components, weigh Al2O3, Gd2O3, and ZrO2 powders with a total mass of 1000 g; the ratio of the Al2O3 powder, Gd2O3 powder, and ZrO2 powder is the eutectic molar ratio Al2O3:Gd2O3:ZrO2 = 58:19:23;

[0060] After uniformly mixing the accurately weighed Al2O3, Gd2O3, and ZrO2 powders, add analytical pure alcohol and polyvinyl alcohol aqueous solution, load them into a ball mill tank, and place them in a planetary ball mill for ball milling for 4 hours at a rotation speed of 500 rpm to obtain a mixture; the dosage of analytical pure alcohol is 10 wt.% of the total mass of the three powders of Al2O3, Gd2O3, and ZrO2, and the dosage of the polyvinyl alcohol aqueous solution is 5 wt.% of the total mass of the three powders of Al2O3, Gd2O3, and ZrO2;

[0061] Use the conventional spray granulation method to spray granulate the above mixture. During spray granulation, the inlet air temperature is 300 °C, the outlet air temperature is 150 °C, the rotation frequency of the nozzle is 30 Hz, the feeding rotation speed is 20 rpm. After spray granulation, screen to obtain spherical eutectic powder with a particle size distribution of 20 - 100 μm, and place it in an oven at 80 °C for drying for 4 hours.

[0062] To improve fluidity and bonding strength, the selected spherical eutectic powder is sintered at a high temperature in the range of 1200 - 1600 °C for 3 hours, so that the powder particles prepared by spray granulation have a certain bonding strength; perform plasma spheroidization treatment, screen the spherical eutectic powder with a particle size distribution of 20 - 80 μm, and after drying, obtain Al2O3-Gd2O3-ZrO2 spherical eutectic powder with high sphericity, good fluidity, high bonding strength, and suitable for laser directed energy deposition technology.

[0063] Step 2: Set the laser scanning path;

[0064] Set the laser scanning path according to the size of the required wall-shaped eutectic ceramic sample. The scanning path is composed of multiple circular swinging micro-regions. In each micro-region, the laser beam moves clockwise (or counterclockwise) according to the set scanning parameters. The diameter of the circular swinging micro-region is 2 - 6 mm.

[0065] The process of setting the laser scanning path (taking the circular swinging strategy as an example, such as Figure 2 (a)) is as follows:

[0066] Ⅰ Set the scanning path of the first deposition layer as: taking the origin of processing as the diameter endpoint of the circle, the laser beam moves clockwise (or counterclockwise) along a complete circular path, that is, complete the circular swinging cladding in the first micro-region and return to the origin of processing; move 0.8 - 1.25 mm along the circular diameter direction into the circle to reach the origin of processing of the second circular micro-region, repeat the circular swinging cladding process in the first micro-region, and continue to move 0.8 - 1.25 mm along the circular diameter direction into the circle to reach the origin of processing of the third circular micro-region. Continuously repeat the above process to complete the circular swinging cladding in several micro-regions until the length of the first deposition layer reaches the set value. Move the length of the circular diameter along the circular diameter direction to move the laser beam to the endpoint of the first deposition layer.

[0067] Ⅱ Set the scanning path of the second deposition layer as follows: The laser nozzle is lifted by the required height along the Z-axis direction, and the position where the laser beam is located at this time is taken as the processing origin of the second deposition layer. Taking the processing origin as the end points of the diameter of a circle, the laser beam moves counterclockwise (or clockwise) along a complete circular path, that is, the circular oscillatory cladding in the first micro-region is completed, and it returns to the processing origin; it moves 0.8 - 1.25 mm inward along the circular diameter direction to reach the processing origin of the second circular micro-region, repeats the circular oscillatory cladding process in the first micro-region, and continues to move 0.8 - 1.25 mm inward along the circular diameter direction to reach the processing origin of the third circular micro-region. Continuously repeat the above process to complete the circular oscillatory cladding in several micro-regions until the length of the second deposition layer reaches the set value. Along the circular diameter direction, move the length of the circular diameter inward so that the laser beam moves to the end point of the second deposition layer, and then the laser nozzle is lifted by the required height along the Z-axis direction.

[0068] Ⅲ Repeat the steps of I and II to complete the setting of the scanning paths of the subsequent deposition layers.

[0069] Step 3: Set the laser scanning parameters;

[0070] Set the laser power and laser scanning speed used during the forming process; the laser power is 200 W, the scanning rate is 600 mm / min, the single-layer scanning distance in the X-axis direction is 15 mm, the single-layer lifting height of the laser nozzle is 0.5 mm, and the number of processing layers is 15 layers.

[0071] Step 4: Conduct the laser directed energy deposition experiment

[0072] Using the laser directed energy deposition method, the high-energy laser beam melts the spherical eutectic powder, and deposits layer by layer to form a wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic. The specific preparation process is as follows:

[0073] The first step is that the high-energy laser beam heats and melts the Al2O3 ceramic substrate along the established scanning path according to the set scanning parameters to form a stable molten pool. The Al2O3 ceramic substrate is prepared by sintering, with a purity of 95%, and the size is 100×100×10 mm 3 ; the vertical distance between the lower surface of the laser nozzle and the upper surface of the Al2O3 ceramic substrate is 10 - 20 mm to ensure that the laser spot diameter is 1 - 3 mm.

[0074] Step 2: Open the powder feeder and adjust the appropriate powder feeding rate so that the spherical eutectic powder is transported to the laser nozzle by an inert gas, forming a conical converging powder beam coaxial with the laser beam; the powder feeding rate is 2 g / min, the powder feeding gas is high-purity argon, and the gas flow rate is 10 L / min; the laser directed energy deposition forming process is completed in a glove box under a high-purity argon atmosphere. During the forming process, the oxygen content is less than 200 ppm, the box pressure is set to 1 - 6 mbar, and the high-purity argon in the glove box is kept circulating throughout the process. The purity of the above high-purity argon is 99.999%.

[0075] Step 3: After the powder is heated and melted by the high-energy laser beam, it enters the molten pool on the Al2O3 ceramic substrate and is continuously deposited on the surface of the Al2O3 ceramic substrate as the laser nozzle moves; at the position where the laser leaves, the temperature drops, causing the molten pool to solidify rapidly. As the laser beam completes the first scanning path, the first deposition layer of the wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic sample is formed; after the laser nozzle is lifted by the height of a single deposition layer under the control of the CNC machine tool program, it continues to scan along the scanning path to complete the deposition of the second layer.

[0076] Repeat the above process of preparing the first and second layers of Al2O3-GdAlO3-ZrO2 eutectic ceramics until the designed number of deposition layers is completed to obtain the Al2O3-GdAlO3-ZrO2 eutectic ceramic sample;

[0077] Step 5: After the forming program runs to completion, the laser beam is automatically turned off, the laser nozzle moves up at a speed of 1000 mm / min by 30 mm, away from the wall-shaped eutectic ceramic sample, and the powder feeder is turned off.

[0078] The deposited ceramic sample and the Al2O3 substrate are naturally cooled to room temperature to obtain the required Al2O3-GdAlO3-ZrO2 eutectic ceramic sample. As shown in Figure 2 and Figure 3 the size of the prepared wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic sample reaches 23×20×4 mm 3 , and the solidification structure of the prepared Al2O3-GdAlO3-ZrO2 eutectic ceramic is fine, and the eutectic lamellar spacing can reach 190 nm.

[0079] The specific process of the present invention is described in detail through five embodiments. The implementation processes of each embodiment are the same, and the differences lie in the process parameters of each embodiment.

[0080] Table 1: Process parameters of the embodiments

[0081] Example Laser power Scanning rate Powder feeding rate Single layer thickness Scanning length Number of processing layers 1 200W 600 mm / min 2 g / min 0.5 15 15 2 300W 300 mm / min 2 g / min 0.5 15 20 3 350W 240 mm / min 2.5 g / min 1 20 20 4 400W 300 mm / min 3 g / min 1 20 20 5 500W 360 mm / min 3.6 g / min 2 30 15

[0082] By adjusting the combination of various process parameters, it is ensured that the ceramic powder fed into the molten pool during the forming process is completely melted, and the distance between the laser nozzle and the upper surface of the ceramic sample is always maintained at 10 - 20 mm to obtain a sample with good forming quality.

[0083] Example 6

[0084] An equilateral triangle swing scanning strategy is adopted to prepare a wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic sample. Steps 1, 3 - 5 are the same as those in Example 1;

[0085] Step 2: The scanning path is composed of a combination of multiple equilateral triangle swing micro-regions. In each micro-region, the laser beam moves clockwise (or counterclockwise) according to the set scanning parameters. The diameter of the equilateral triangle swing micro-region is 2 - 6 mm.

[0086] The setting of the laser scanning path (such as Figure 2 (b)) is specifically as follows:

[0087] Ⅰ Set the scanning path of the first deposition layer as: taking the processing origin as the midpoint of one side of the equilateral triangle, the laser beam moves clockwise (or counterclockwise) along a complete equilateral triangle path, that is, the equilateral triangle swing cladding in the first micro-region is completed and returns to the processing origin; the moving speed of the laser beam on the three sides of the equilateral triangle is the same, and the residence time at each vertex is 0.1 - 0.5 seconds; move 0.8 - 1.25 mm along the median line direction of the equilateral triangle towards the center of the equilateral triangle to reach the processing origin of the second equilateral triangle micro-region, repeat the swing cladding process in the first micro-region, and continue to move 0.8 - 1.25 mm along the median line direction of the equilateral triangle towards the center of the equilateral triangle to reach the processing origin of the third equilateral triangle micro-region. Continuously repeat the above process to complete the equilateral triangle swing cladding in several micro-regions until the length of the first deposition layer reaches the set value. Along the median line direction of the equilateral triangle, move the length of the median line of the equilateral triangle into the equilateral triangle to make the laser beam move to the end point of the first deposition layer.

[0088] Ⅱ Set the scanning path of the second deposition layer as follows: The laser nozzle lifts to the required height along the Z-axis direction, and the position where the laser beam is located at this time is the processing origin of the second deposition layer. Taking the processing origin as the midpoint of one side of an equilateral triangle, the laser beam moves counterclockwise (or clockwise) along a complete equilateral triangle path, thus completing the oscillatory cladding in the first micro-region and returning to the processing origin; the moving speed of the laser beam on the three sides of the equilateral triangle is the same, and the residence time at each vertex is 0.1 - 0.5 seconds; move 0.8 - 1.25 mm inward along the median line direction of the equilateral triangle to reach the processing origin of the second equilateral triangle micro-region, repeat the oscillatory cladding process in the first micro-region, and continue to move 0.8 - 1.25 mm inward along the median line direction of the equilateral triangle to reach the processing origin of the third equilateral triangle micro-region. Continuously repeat the above process to complete the oscillatory cladding of equilateral triangles in several micro-regions until the length of the second deposition layer reaches the set value. Move inward along the median line direction of the equilateral triangle by the length of the median line of the equilateral triangle to move the laser beam to the end point of the second deposition layer, and then the laser nozzle lifts to the required height along the Z-axis direction.

[0089] Ⅲ Repeat the steps in I and II to complete the setting of the scanning paths of subsequent deposition layers.

[0090] The embodiments given above are the preferred examples for implementing the present invention, and the present invention is not limited to the above embodiments. Any non-essential addition or replacement made by those skilled in the art based on the technical features of the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing large-size, high-density wall-shaped Al2O3-Gd2O3-ZrO2 eutectic ceramics by laser directed energy deposition technology, characterized in that: The method comprises the following steps: Step 1: Prepare Al2O3-Gd2O3-ZrO2 spherical eutectic powder; the particle size of the spherical eutectic powder is 20-80 μm; Step 2: Setting a laser scanning path; Setting a laser scanning path according to the size of the required wall-shaped eutectic ceramic, the scanning path is composed of a combination of specific swing paths in a number of local areas connected end to end; the scanning path takes the specific swing path in the local area as a basic unit, and in each local area, the laser beam moves clockwise or counterclockwise according to the set path, and the swing range in the Y-axis direction is 2-6 mm; in adjacent local areas, the swing range of the laser beam in the X-axis direction is 0.2-0.4 times its swing range in the Y-axis direction; The specific swing paths in several local areas are connected end to end to form a complete scanning path for the movement of the laser beam in a single deposition layer. After completing the complete scanning path of the nth layer, the laser nozzle is set to lift the height of the single deposition layer in the Z-axis direction to prepare for printing the n+1th layer; the complete scanning path in the n+1th layer is formed by connecting the specific swing paths in the same local area end to end, but the movement direction of the laser beam in the X-axis direction is opposite to that of the nth layer; after completing the complete scanning path of the n+1th layer, the laser nozzle is set to lift the height of the single deposition layer in the Z-axis direction to prepare for printing the n+2th layer; according to the required height of the wall-like eutectic ceramic and the thickness of the single deposition layer, the complete scanning path of the nth layer and the n+1th layer is set to be repeated several times, so as to complete the setting of the laser scanning path; Step 3: Set the laser scanning parameters; set the laser power and laser scanning speed used in the eutectic ceramic forming process; the laser power is 200-600W, and the scanning rate is 120-840mm / min; Step 4: Conduct a laser directed energy deposition experiment; utilize the laser directed energy deposition method to melt the spherical eutectic powder prepared in step 1 through a laser beam, and deposit layer by layer along the laser scanning path set in step 2 according to the laser scanning parameters set in step 3 to form a wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic.

2. The method for preparing large-size, high-density wall-shaped Al2O3-Gd2O3-ZrO2 eutectic ceramics by laser directed energy deposition technology according to claim 1, characterized in that: In step 1, in the process of preparing Al2O3-Gd2O3-ZrO2 spherical eutectic powder, Al2O3 ceramic powder, Gd2O3 ceramic powder and ZrO2 ceramic powder are evenly mixed in a molar ratio of 58:19:23, alcohol and polyvinyl alcohol aqueous solution are added to mix evenly and spray granulation is performed, and the spherical eutectic powder with a particle size of 20-100 μm is screened and dried in an oven for 3-6 hours, and then sintered at 1200-1600°C for 2-5 hours; plasma spheroidization treatment is continued, spherical eutectic powder with a particle size of 20-80 μm is screened, and Al2O3-Gd2O3-ZrO2 spherical eutectic powder is obtained after drying.

3. The method for preparing large-size, high-density wall-shaped Al2O3-Gd2O3-ZrO2 eutectic ceramics by laser directed energy deposition technology according to claim 2, characterized in that: The mass of the alcohol accounts for 7-12 wt.% of the total mass of the Al2O3 ceramic powder, Gd2O3 ceramic powder and ZrO2 ceramic powder, and the mass of the polyvinyl alcohol aqueous solution accounts for 3-6 wt.% of the total mass of the Al2O3 ceramic powder, Gd2O3 ceramic powder and ZrO2 ceramic powder.

4. The method for preparing large-size, high-density wall-shaped Al2O3-Gd2O3-ZrO2 eutectic ceramics by laser directed energy deposition technology according to claim 1, characterized in that: In step 2, the specific swing path is one of a circular swing path, an equilateral triangle swing path, a rectangular swing path or a sinusoidal swing path. When the specific swing path is a circular swing, the diameter of the circular swing path is 2-6 mm, and the distance between adjacent circular swing paths is 0.2-0.4 times the diameter of the circular swing path; when the specific swing path is an equilateral triangle swing, the side length of the equilateral triangle swing path is 2-6 mm, and the distance between adjacent equilateral triangle swing paths is 0.2-0.4 times the side length of the equilateral triangle swing path. The laser beam moves at the same speed on the three sides of the equilateral triangle, and stays at each vertex for 0.1-0.5 seconds.

5. The method for preparing large-size, high-density wall-shaped Al2O3-Gd2O3-ZrO2 eutectic ceramics by laser directed energy deposition technology according to claim 1, characterized in that: In step 2, the height of the laser nozzle raised along the Z-axis direction between two adjacent deposition layers does not exceed the thickness of a single deposition layer.

6. The method for preparing large-size, high-density wall-shaped Al2O3-Gd2O3-ZrO2 eutectic ceramics by laser directed energy deposition technology according to claim 1, characterized in that: In step 3, the laser scanning parameters also include: a single-layer scanning distance of 5-40 mm along the X-axis direction, a single-layer lifting height of the laser nozzle of 0.1-2 mm, and a processing number of 10-50 layers.

7. The method for preparing large-size, high-density wall-shaped Al2O3-Gd2O3-ZrO2 eutectic ceramics by laser directed energy deposition technology according to claim 1, characterized in that: In step 4, the process of depositing and forming wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramics is as follows: The first step is to place the Al2O3 ceramic substrate horizontally; the vertical distance between the upper surface of the ceramic substrate and the lower surface of the laser nozzle is maintained at 10-20mm, and the laser spot diameter is 1-3mm; The second step is to preheat the Al2O3 ceramic substrate to form a stable molten pool; The third step is to open the powder feeder to deliver the spherical eutectic powder; In the fourth step, the laser beam heats and melts the spherical eutectic powder obtained in step 1 along the laser scanning path set in step 2 according to the laser scanning parameters set in step 3, and the spherical eutectic powder enters a stable molten pool; and is continuously deposited on the surface of the Al2O3 ceramic substrate as the laser nozzle moves; the laser beam leaves, the temperature drops, and the molten pool solidifies rapidly; when the laser beam completes all scanning paths set in step 2, the deposition and forming of the wall-shaped Al2O3-Gd2O3-ZrO2 eutectic ceramic is completed; In the fifth step, the deposited wall-shaped eutectic ceramic and the Al2O3 substrate are naturally cooled to room temperature to obtain a formed wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramic.

8. The method for preparing large-size, high-density wall-shaped Al2O3-Gd2O3-ZrO2 eutectic ceramics by laser directed energy deposition technology according to claim 1, characterized in that: The process of depositing and forming wall-shaped Al2O3-GdAlO3-ZrO2 eutectic ceramics is carried out in a glove box with good sealing and high-purity argon atmosphere. The high-purity argon circulates in the glove box through a circulating fan. The box pressure of the glove box is 1-6mbar, the speed of the circulating fan is 30Hz, and the purity of the high-purity argon is 99.999%.

9. The method for preparing large-size, high-density wall-shaped Al2O3-Gd2O3-ZrO2 eutectic ceramics by laser directed energy deposition technology according to claim 7, characterized in that: The Al2O3 ceramic substrate is prepared by sintering and has a purity of 95%.

10. The method for preparing large-size, high-density wall-shaped Al2O3-Gd2O3-ZrO2 eutectic ceramics by laser directed energy deposition technology according to claim 7, characterized in that: The powder feeding rate of the powder feeder is 2-12 g / min, the powder feeding gas is high-purity argon gas with a purity of 99.999%, and the gas flow rate is 6-12 L / min.

Images