A medium-entropy shell for casting titanium alloy and a preparation method and use thereof
By using medium-entropy zirconate powder and a freeze-vacuum drying process, the heat resistance and drying process problems of titanium alloy investment casting shells were solved, resulting in a highly stable shell that improves the surface quality and precision of the castings.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WUHAN UNIV OF SCI & TECH
- Filing Date
- 2026-03-12
- Publication Date
- 2026-06-05
Smart Images
Figure CN122142237A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of titanium alloy investment casting technology, and specifically relates to a medium-entropy shell for titanium alloy casting, its preparation method and application. Background Technology
[0002] Titanium alloys possess excellent properties, high strength, and low density, making them widely used in aerospace, marine valve bodies, and medical devices. Investment casting is a near-net-shape forming process with advantages such as short production cycles, mass production capability, and low cost. The performance of titanium alloy castings produced by investment casting is directly related to the performance of the mold shell, and the key to the mold shell's performance lies in its ability to resist the erosion of high-temperature molten titanium and maintain precise cavity dimensions. However, existing technologies have significant shortcomings in both mold shell materials and manufacturing processes.
[0003] In terms of materials, mainstream refractory fillers each have fatal flaws. Yttrium oxide has poor thermal shock resistance, zirconium oxide suffers from crystal transformation issues, and calcium oxide is prone to hydration and difficult to store; none of these are ideal materials for titanium alloy investment casting shells. Graphite, nitrides, and carbides, on the other hand, suffer from excessively high thermal conductivity, nitrogen addition to titanium alloys, and high cost, respectively. Currently, the better-performing fillers include zirconate materials such as calcium zirconate and barium zirconate. However, these materials still react with titanium alloys, and the high density of zirconates causes the resulting coatings to settle easily. During the drying process, flow marks in the coating can lead to an uneven surface on the shell, further affecting the performance of the casting.
[0004] In terms of shell-making processes, especially the drying stage, the commonly used fully enclosed central air conditioning temperature and humidity control system operates year-round. This not only results in long drying times and significant resource consumption but also cannot prevent flow marks in zirconate coatings. The resulting component segregation, deformation, and cracking directly lead to a loss of shell precision control. Therefore, developing a new process that can replace traditional drying and ensure uniform curing and shaping of the shell is also an important technical requirement in this field. Summary of the Invention
[0005] To address the shortcomings of the existing technology, the present invention aims to provide a medium-entropy mold shell for titanium alloy casting, its preparation method, and its applications. The mold shell prepared by this method effectively solves the problems of violent reaction between the mold shell and molten titanium, easy cracking, and low precision of the existing mold shell by using a novel medium-entropy refractory filler and combining it with an innovative freeze-vacuum drying process.
[0006] To solve the above-mentioned technical problems, this invention provides a medium-entropy shell for titanium alloy casting and its preparation method, comprising the following steps: Barium salt, calcium salt, and strontium salt are mixed with zirconium oxide in equimolar ratios. The resulting mixture is then mixed with water, dried, pulverized, and calcined at 1100℃~1200℃. The calcined product is cooled and sieved to obtain a shell-type surface packing. The molar ratio of barium salt, calcium salt, and strontium salt to zirconium oxide is 1:1:1:3, and the mass ratio of the mixture to water is 1:1~1.5. The medium-entropy design of this shell-type surface packing significantly improves thermodynamic stability and chemical inertness, enabling it to more effectively resist the erosion of high-temperature titanium liquid and prevent excessively thick interfacial reaction layers.
[0007] The surface layer filler is mixed with yttrium sol binder, wetting agent and defoamer to obtain the surface layer slurry; Mullite is mixed with silica sol binder, wetting agent and defoamer to obtain back layer slurry; The surface layer slurry is evenly applied to the surface of the wax model, and then sprinkled with yttrium oxide powder and frozen for 0.5h to 2h until it is cured and set. The application, sprinkling, and freezing are repeated 1 to 2 times to obtain the surface layer. The back layer slurry is then evenly applied to the surface layer, and then sprinkled with mullite powder and frozen for 0.5h to 2h until it is cured and set. The application, sprinkling, and freezing are repeated 2 to 4 times to obtain the back layer. The model is then dried at a temperature of -40°C to -60°C and a vacuum of 10Pa to 50Pa for 48h to 72h. The dried model is then dewaxed and sintered to obtain the finished model.
[0008] The finished shell consists of a surface layer and a back layer from the inside out; the surface layer is made of a surface coating containing perovskite-type medium-entropy zirconate powder, wherein the perovskite-type medium-entropy zirconate powder is made of Ba 2+ Ca 2+ 、Sr 2+ Three cations occupy the A site in an equimolar ratio, Zr 4+ It occupies the B site and has the general chemical formula (Ba). x Ca x Sr x ZrO3, of which x =1 / 3.
[0009] Preferably, the shell surface filler and yttrium sol binder are mixed at a weight ratio of 3-5:1, and 0.1%-0.5% of a wetting agent and 0.1%-0.2% of a defoamer by weight of the total mixture are added, followed by stirring to obtain the surface slurry. This is because mixing the shell surface filler (medium-entropy zirconate powder) with the yttrium sol binder at this weight ratio further improves the compatibility between the shell surface filler (medium-entropy zirconate powder) and the yttrium sol binder, which is more conducive to obtaining a surface slurry with high stability and good coating properties, and helps to reduce the risk of deformation and cracking of the shell during the drying stage.
[0010] Preferably, the mullite and silica sol binder are mixed at a weight ratio of 1.5 to 2:1, and 0.1% to 0.5% of a wetting agent and 0.1% to 0.2% of a defoamer by weight of the total mixture are added, followed by stirring to obtain the backing slurry. This is because the viscosity of the backing slurry prepared by mixing mullite and silica sol binder at this weight ratio better meets the requirements for backing slurries used in investment casting, which helps to reduce the risk of deformation and cracking of the mold shell during the drying stage.
[0011] Preferably, the particle size of the shell surface filler is 200 mesh to 325 mesh. The reason for limiting the particle size of the shell surface filler to 200 mesh to 325 mesh is that if the particle size of the shell surface filler is coarser than 200 mesh, it will cause the shell surface slurry to settle easily, and it will also increase the surface roughness of the final shell. If the particle size is finer than 325 mesh, it will cause the powder-to-liquid ratio of the slurry to be too low, resulting in insufficient air permeability of the shell surface layer and causing more defects such as pores on the surface of the casting.
[0012] Preferably, the heating rate during calcination is 3℃ / min to 5℃ / min. The reason for limiting the heating rate to 3℃ / min to 5℃ / min within the calcination temperature range of 1100℃ to 1200℃ is that an excessively rapid heating rate may lead to incomplete chemical reactions in the mixture, affecting the chemical purity, phase purity, and structural density of the final shell-surface filler, while also controlling thermal stress to prevent cracking.
[0013] Preferably, the dried shell is dewaxed by high-pressure steam, solvent dewaxing, or microwave dewaxing to obtain an empty shell; the empty shell is then calcined at 1150℃~1250℃ for 2h~4h and cooled in the furnace to obtain the finished shell.
[0014] Preferably, the particle size of the yttrium oxide powder used for sanding is 50 mesh to 150 mesh; the particle size of the mullite powder used for sanding is 50 mesh to 100 mesh.
[0015] This invention provides a method for preparing a medium-entropy shell for titanium alloy casting.
[0016] This invention provides an application of a medium-entropy shell for titanium alloy casting in the precision casting of titanium and titanium alloys.
[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses Ba 2+ Ca 2+ 、Sr 2+A perovskite-type medium-entropy zirconate, composed of three ions in an equimolar ratio and calcined with zirconium oxide, is used as the shell surface layer filler. The medium-entropy design of this shell surface layer filler significantly improves thermodynamic stability and chemical inertness, effectively resisting the erosion of high-temperature titanium liquid and preventing excessively thick interfacial reaction layers. Furthermore, this shell surface layer filler (medium-entropy zirconate powder) exhibits good compatibility with yttrium sol binder, resulting in a surface layer slurry with high stability and good coating properties. During subsequent calcination, the yttrium oxide binder phase formed by the yttrium sol firmly binds the medium-entropy zirconate filler particles, thereby enhancing the sintering performance of the shell and ultimately obtaining a smooth, flat, and more erosion-resistant shell surface layer. Moreover, this invention innovatively introduces a combination of freezing and vacuum freeze-drying processes. First, freezing rapidly fixes the coating structure, preventing the sand layer from shifting under gravity. The subsequent vacuum freeze drying removes moisture through the principle of ice crystal sublimation, reducing the risk of deformation and cracking of the shell during the drying stage. This ensures that the shell has uniform pores and a complete structure, making it particularly suitable for the production of castings with extremely high precision requirements. Attached Figure Description
[0018] Figure 1 The image shows the X-ray diffraction pattern of the shell surface packing prepared in Example 1.
[0019] Figure 2 A macroscopic photograph of the medium-entropy shell obtained in Example 1.
[0020] Figure 3 This is a SEM image of the interface between the medium-entropy shell and the casting obtained in Example 1. Detailed Implementation
[0021] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.
[0022] It should be noted that when numerical ranges are involved in this invention, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in Examples 1 to 4, preferred embodiments are described in this invention to avoid redundancy. However, this invention is not limited to these, but can be implemented in other ways within the scope of the technical solutions defined in the appended claims. All raw materials, reagents, instruments, and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.
[0023] The following detailed description, in conjunction with embodiments of the present invention and accompanying drawings, provides a clear and complete illustration of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0024] The following are specific examples of preparing medium-entropy shells for titanium alloy casting.
[0025] The barium salt, calcium salt, and strontium salt can be any inorganic barium salt, inorganic calcium salt, and inorganic strontium salt. Barium carbonate, calcium carbonate, and strontium carbonate are preferred in the following examples.
[0026] Example 1: A method for preparing a medium-entropy shell for titanium alloy casting includes the following steps: (1) Preparation of intermediate entropy zirconate surface filler: Weigh barium carbonate, calcium carbonate, strontium carbonate and zirconium oxide, and prepare them according to Ba 2+ :Ca 2+ :Sr 2+ :Zr 4+ The mixture was prepared by mixing the components in a molar ratio of 1:1:1:3. The mixture was then ball-milled with water at a mass ratio of 1:1, dried, and pulverized. The pulverized powder was then calcined at 1150℃ for 4 hours at a calcination heating rate of 4℃ / min. After cooling, the powder was passed through a 300-mesh sieve to obtain perovskite-type medium-entropy zirconate powder.
[0027] (2) Slurry preparation: The perovskite-type medium-entropy zirconate powder prepared above was mixed with yttrium sol at a weight ratio of 4:1. A wetting agent of 0.3% and a defoamer of 0.15% of the total weight of the mixture were added, and the mixture was stirred for 8 hours to obtain a uniform surface slurry. Mullite powder and silica sol were mixed at a weight ratio of 1.8:1. A wetting agent of 0.3% and a defoamer of 0.15% of the total weight of the mixture were added, and the mixture was stirred for 8 hours to obtain a back layer slurry.
[0028] (3) Preparation of the mold shell: Immerse the wax model in the surface layer slurry, remove it, and then sprinkle it with 100-mesh yttrium oxide powder. Immediately afterwards, place the mold in a -30°C environment for rapid freezing treatment for 1 hour to cure the coating. Repeat this process once. On the cured surface layer, apply the back layer slurry, sprinkle it with 100-mesh mullite powder, and then rapidly freeze it at -30°C for 1 hour. Repeat this process 3 times. Then place the mold shell in a vacuum freeze-drying oven and dry it at -50°C and a vacuum degree of 30 Pa for 60 hours until the mold shell reaches a constant weight.
[0029] (4) Dewaxing and firing of the shell: Dewaxing is carried out by high-pressure steam dewaxing to obtain an empty shell. The empty shell is fired at 1200℃ for 3 hours and cooled in the furnace to obtain the finished shell.
[0030] The prepared shell was subjected to alloy casting experiments. The resulting titanium alloy TC4 casting had a smooth surface, no obvious contamination layer, and good casting performance.
[0031] Example 2: A method for preparing a medium-entropy shell for titanium alloy casting includes the following steps: (1) Preparation of intermediate entropy zirconate surface filler: Weigh barium carbonate, calcium carbonate, strontium carbonate and zirconium oxide, and prepare them according to Ba 2+ :Ca 2+ :Sr 2+ :Zr 4+ The mixture was prepared by mixing the components in a molar ratio of 1:1:1:3. The mixture was then ball-milled with water at a mass ratio of 1:1.2, dried, and pulverized. The pulverized powder was calcined at 1100℃ for 5 hours at a calcination heating rate of 3℃ / min. After cooling, the powder was passed through a 200-mesh sieve to obtain perovskite-type medium-entropy zirconate powder.
[0032] (2) Slurry preparation: The perovskite-type medium-entropy zirconate powder prepared above is mixed with yttrium sol at a weight ratio of 3:1. Wetting agent and defoamer accounting for 0.1% of the total weight of the mixture are added, and the mixture is stirred for 12 hours to obtain the surface layer slurry. Mullite powder and silica sol are mixed at a weight ratio of 1.5:1. Wetting agent and defoamer accounting for 0.1% of the total weight of the mixture are added, and the mixture is stirred for 12 hours to obtain the back layer slurry.
[0033] (3) Preparation of the mold shell: The wax mold is immersed in the surface layer slurry, and after removal, it is sanded with 50-mesh yttrium oxide powder. Then, the mold is immediately placed in a -20℃ environment for rapid freezing treatment for 2 hours to cure the coating. This process is repeated twice. On the cured surface layer, the back layer coating is applied, and 50-mesh mullite powder is sanded, and it is also rapidly frozen at -20℃ for 2 hours. This process is repeated 4 times. Afterwards, the mold shell is placed in a vacuum freeze-drying oven and dried at -40℃ and a vacuum degree of 50Pa for 72 hours until the mold shell has a constant weight.
[0034] (4) Dewaxing and firing of the shell: Dewaxing was carried out by solvent dewaxing to obtain an empty shell. The empty shell was fired at 1150℃ for 4 hours and cooled in the furnace to obtain the finished shell.
[0035] The prepared shell was subjected to alloy casting experiments. The surface of the prepared titanium alloy TC4 casting was free of obvious contamination layer and the surface of the casting was relatively smooth.
[0036] Example 3: A method for preparing a medium-entropy shell for titanium alloy casting includes the following steps: (1) Preparation of intermediate entropy zirconate surface filler: Weigh barium carbonate, calcium carbonate, strontium carbonate and zirconium oxide, and prepare them according to Ba 2+ :Ca 2+ :Sr 2+ :Zr 4+ The mixture was prepared by mixing the components in a molar ratio of 1:1:1:3. The mixture was then ball-milled with water at a mass ratio of 1:1.5, dried, and pulverized. The pulverized powder was then calcined at 1200℃ for 3 hours at a calcination heating rate of 5℃ / min. After cooling, the powder was passed through a 325-mesh sieve to obtain perovskite-type medium-entropy zirconate powder.
[0037] (2) Slurry preparation: Perovskite-type medium-entropy zirconate powder and yttrium sol were mixed at a weight ratio of 5:1. Wetting agent and defoamer accounting for 0.5% of the total weight of the mixture were added, and the mixture was stirred for 6 hours to obtain the surface layer slurry. Mullite powder and silica sol were mixed at a weight ratio of 2:1. Wetting agent and defoamer accounting for 0.5% of the total weight of the mixture were added, and the mixture was stirred for 6 hours to obtain the back layer slurry.
[0038] (3) Preparation of the mold shell: The wax model was immersed in the surface layer slurry, and after removal, it was sanded with 150-mesh yttrium oxide powder. The mold was then immediately placed in a -50℃ environment for rapid freezing treatment for 0.5 hours to cure the coating. This process was repeated once. On the cured surface layer, a back layer coating was applied, and 100-mesh mullite powder was sanded, and it was also rapidly frozen at -50℃ for 0.5 hours. This process was repeated twice. Afterwards, the mold shell was placed in a vacuum freeze-drying oven and dried at -60℃ and a vacuum degree of 10Pa for 48 hours until the mold shell reached a constant weight.
[0039] (4) Dewaxing and firing of the shell: Dewaxing was carried out by microwave dewaxing to obtain an empty shell. The empty shell was fired at 1250℃ for 2 hours and cooled in the furnace to obtain the finished shell.
[0040] The prepared shell was subjected to alloy casting experiments. The resulting titanium alloy TC4 casting had a smooth surface and no obvious contamination layer.
[0041] Example 4: A method for preparing a medium-entropy shell for titanium alloy casting includes the following steps: (1) Preparation of intermediate entropy zirconate surface filler: Weigh barium carbonate, calcium carbonate, strontium carbonate and zirconium oxide, and prepare them according to Ba 2+ :Ca 2+ :Sr 2+ :Zr 4+The mixture was prepared by mixing the components in a molar ratio of 1:1:1:3. The mixture was then ball-milled with water at a mass ratio of 1:1.5. The crushed powder was then calcined at 1175℃ for 4.5 hours at a calcination heating rate of 4℃ / min. After cooling, the powder was passed through a 250-mesh sieve to obtain perovskite-type medium-entropy zirconate powder.
[0042] (2) Slurry preparation: Perovskite-type medium-entropy zirconate powder and yttrium sol were mixed at a weight ratio of 4.5:1. Wetting agent and defoamer accounting for 0.4% of the total weight of the mixture were added, and the mixture was stirred for 10 hours to obtain the surface layer slurry. Mullite powder and silica sol were mixed at a weight ratio of 1.7:1. Wetting agent and defoamer accounting for 0.4% of the total weight of the mixture were added, and the mixture was stirred for 10 hours to obtain the back layer slurry.
[0043] (3) Preparation of the mold shell: The wax model was immersed in the surface layer slurry, and after removal, it was sanded with 120-mesh yttrium oxide powder. The mold was then immediately placed in a -40℃ environment for rapid freezing treatment for 1.5 hours to cure the coating. This process was repeated once. On the cured surface layer, a back layer coating was applied, and 80-mesh mullite powder was sanded, and it was also rapidly frozen at -40℃ for 1.5 hours. This process was repeated 3 times. Afterwards, the mold shell was placed in a vacuum freeze-drying oven and dried at -55℃ and a vacuum degree of 20Pa for 66 hours until the mold shell reached a constant weight.
[0044] (4) Dewaxing and firing of the shell: Dewaxing is carried out by high-pressure steam dewaxing to obtain an empty shell. The empty shell is fired at 1225℃ for 2.5 hours and cooled in the furnace to obtain the finished shell.
[0045] The prepared shell was subjected to alloy casting experiments. The resulting titanium alloy TC4 casting had no obvious contamination layer on the surface and the casting performance was good.
[0046] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that rapid cooling and freeze-drying were not performed during the preparation of the shell.
[0047] A method for preparing a medium-entropy shell for titanium alloy casting includes the following steps: (1) Preparation of intermediate entropy zirconate surface filler: Weigh barium carbonate, calcium carbonate, strontium carbonate and zirconium oxide, and prepare them according to Ba 2+ :Ca 2+ :Sr 2+ :Zr 4+ The mixture was prepared by mixing the components in a molar ratio of 1:1:1:3. The mixture was then ball-milled with water at a mass ratio of 1:1, dried, and pulverized. The pulverized powder was then calcined at 1150℃ for 4 hours at a calcination heating rate of 4℃ / min. After cooling, the powder was passed through a 300-mesh sieve to obtain perovskite-type medium-entropy zirconate powder.
[0048] (2) Slurry preparation: The perovskite-type medium-entropy zirconate powder prepared above was mixed with yttrium sol at a weight ratio of 4:1. A wetting agent of 0.3% and a defoamer of 0.15% of the total weight of the mixture were added, and the mixture was stirred for 8 hours to obtain a uniform surface slurry. Mullite powder and silica sol were mixed at a weight ratio of 1.8:1. A wetting agent of 0.3% and a defoamer of 0.15% of the total weight of the mixture were added, and the mixture was stirred for 8 hours to obtain a back layer slurry.
[0049] (3) Preparation of the mold shell: Immerse the wax model in the surface layer slurry, remove it, and then sprinkle it with 100-mesh yttrium oxide powder to cure the coating. Repeat this process once. Apply the back layer slurry to the cured surface layer, and then sprinkle it with 100-mesh mullite powder to cure the coating. Repeat this process three times. Afterward, place the mold shell in a drying oven to dry for 60 hours until the mold shell reaches a constant weight.
[0050] (4) Dewaxing and firing of the shell: Dewaxing is carried out by high-pressure steam dewaxing to obtain an empty shell. The empty shell is fired at 1200℃ for 3 hours and cooled in the furnace to obtain the finished shell.
[0051] The prepared shell was subjected to alloy casting experiments. The resulting titanium alloy TC4 casting had a rough surface and exhibited defects such as cold shuts and flow marks.
[0052] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that rapid cooling was not performed during the preparation of the shell.
[0053] A method for preparing a medium-entropy shell for titanium alloy casting includes the following steps: (1) Preparation of intermediate entropy zirconate surface filler: Weigh barium carbonate, calcium carbonate, strontium carbonate and zirconium oxide, and prepare them according to Ba 2+ :Ca 2+ :Sr 2+ :Zr 4+ The mixture was prepared by mixing the components in a molar ratio of 1:1:1:3. The mixture was then ball-milled with water at a mass ratio of 1:1, dried, and pulverized. The pulverized powder was then calcined at 1150℃ for 4 hours at a calcination heating rate of 4℃ / min. After cooling, the powder was passed through a 300-mesh sieve to obtain perovskite-type medium-entropy zirconate powder.
[0054] (2) Slurry preparation: The perovskite-type medium-entropy zirconate powder prepared above was mixed with yttrium sol at a weight ratio of 4:1. A wetting agent of 0.3% and a defoamer of 0.15% of the total weight of the mixture were added, and the mixture was stirred for 8 hours to obtain a uniform surface slurry. Mullite powder and silica sol were mixed at a weight ratio of 1.8:1. A wetting agent of 0.3% and a defoamer of 0.15% of the total weight of the mixture were added, and the mixture was stirred for 8 hours to obtain a back layer slurry.
[0055] (3) Preparation of the mold shell: Immerse the wax model in the surface layer slurry, remove it, and then sprinkle it with 100-mesh yttrium oxide powder to cure the coating. Repeat this process once. Apply the back layer slurry to the cured surface layer and sprinkle it with 100-mesh mullite powder. Repeat this process three times. Then place the mold shell in a fully enclosed central air conditioning system for drying. Dry it for 60 hours at -50℃ and a vacuum of 30Pa until the mold shell reaches a constant weight.
[0056] (4) Dewaxing and firing of the shell: Dewaxing is carried out by high-pressure steam dewaxing to obtain an empty shell. The empty shell is fired at 1200℃ for 3 hours and cooled in the furnace to obtain the finished shell.
[0057] The prepared shell was subjected to alloy casting experiments, and the surface of the resulting titanium alloy TC4 casting had a small number of porosity defects.
[0058] Comparative Example 3 The difference between Comparative Example 3 and Example 1 lies in the preparation of the medium-entropy zirconate surface filler.
[0059] (1) Preparation of intermediate entropy zirconate surface filler: Weigh barium carbonate, calcium carbonate, strontium carbonate and zirconium oxide, and prepare them according to Ba 2+ :Ca 2+ :Sr 2+ :Zr 4+ The mixture was prepared by mixing the components in a molar ratio of 3:3:3:3. The mixture was then ball-milled with water at a mass ratio of 1:1, dried, and pulverized. The pulverized powder was then calcined at 1150℃ for 4 hours at a calcination heating rate of 4℃ / min. After cooling, the powder was passed through a 300-mesh sieve to obtain perovskite-type medium-entropy zirconate powder.
[0060] (2) Slurry preparation: The perovskite-type medium-entropy zirconate powder prepared above was mixed with yttrium sol at a weight ratio of 4:1. A wetting agent of 0.3% and a defoamer of 0.15% of the total weight of the mixture were added, and the mixture was stirred for 8 hours to obtain a uniform surface slurry. Mullite powder and silica sol were mixed at a weight ratio of 1.8:1. A wetting agent of 0.3% and a defoamer of 0.15% of the total weight of the mixture were added, and the mixture was stirred for 8 hours to obtain a back layer slurry.
[0061] (3) Preparation of the mold shell: Immerse the wax model in the surface layer slurry, remove it, and then sprinkle it with 100-mesh yttrium oxide powder. Immediately afterwards, place the mold in a -30°C environment for rapid freezing treatment for 1 hour to cure the coating. Repeat this process once. On the cured surface layer, apply the back layer slurry, sprinkle it with 100-mesh mullite powder, and then rapidly freeze it at -30°C for 1 hour. Repeat this process 3 times. Then place the mold shell in a vacuum freeze-drying oven and dry it at -50°C and a vacuum degree of 30 Pa for 60 hours until the mold shell reaches a constant weight.
[0062] (4) Dewaxing and firing of the shell: Dewaxing is carried out by high-pressure steam dewaxing to obtain an empty shell. The empty shell is fired at 1200℃ for 3 hours and cooled in the furnace to obtain the finished shell.
[0063] The prepared shell was subjected to alloy casting experiments, and the surface of the resulting titanium alloy TC4 casting had sand holes and inclusions.
[0064] Comparative Example 4 The difference between Comparative Example 4 and Example 1 lies in the preparation of the medium-entropy zirconate surface filler.
[0065] (1) Preparation of intermediate entropy zirconate surface filler: Weigh barium carbonate, calcium carbonate and zirconium oxide, and prepare them according to Ba 2+ :Ca 2+ :Zr 4+ The mixture was prepared by mixing the components in a molar ratio of 1:1:3. The mixture was then ball-milled with water at a mass ratio of 1:1, dried, and pulverized. The pulverized powder was then calcined at 1150℃ for 4 hours at a calcination heating rate of 4℃ / min. After cooling, the powder was passed through a 300-mesh sieve to obtain perovskite-type medium-entropy zirconate powder.
[0066] (2) Slurry preparation: The perovskite-type medium-entropy zirconate powder prepared above was mixed with yttrium sol at a weight ratio of 4:1. A wetting agent of 0.3% and a defoamer of 0.15% of the total weight of the mixture were added, and the mixture was stirred for 8 hours to obtain a uniform surface slurry. Mullite powder and silica sol were mixed at a weight ratio of 1.8:1. A wetting agent of 0.3% and a defoamer of 0.15% of the total weight of the mixture were added, and the mixture was stirred for 8 hours to obtain a back layer slurry.
[0067] (3) Preparation of the mold shell: Immerse the wax model in the surface layer slurry, remove it, and then sprinkle it with 100-mesh yttrium oxide powder. Immediately afterwards, place the mold in a -30°C environment for rapid freezing treatment for 1 hour to cure the coating. Repeat this process once. On the cured surface layer, apply the back layer slurry, sprinkle it with 100-mesh mullite powder, and then rapidly freeze it at -30°C for 1 hour. Repeat this process 3 times. Then place the mold shell in a vacuum freeze-drying oven and dry it at -50°C and a vacuum degree of 30 Pa for 60 hours until the mold shell reaches a constant weight.
[0068] (4) Dewaxing and firing of the shell: Dewaxing is carried out by high-pressure steam dewaxing to obtain an empty shell. The empty shell is fired at 1200℃ for 3 hours and cooled in the furnace to obtain the finished shell.
[0069] The prepared shell was subjected to alloy casting experiments, and a large amount of sand adhered to the surface of the resulting titanium alloy TC4 casting.
[0070] Comparative Example 5 Comparative Example 5 is a medium-entropy shell for titanium alloy casting prepared by CN117483644A. Alloy casting experiments were conducted using this medium-entropy shell for titanium alloy casting, and the resulting titanium alloy TC4 castings had smooth surfaces and no obvious defects.
[0071] All of the above Examples 1 to 4 were able to prepare medium-entropy shells for titanium alloy casting. The effectiveness of the medium-entropy shell for titanium alloy casting prepared in Example 1 was then verified.
[0072] Experimental verification (a) Structural confirmation Figure 1 The XRD pattern of the medium-entropy shell-face layer filler (powder) for titanium alloy casting prepared in Example 1. From... Figure 1 It can be seen that the shell surface layer filler is composed of a single pure phase medium entropy zirconate.
[0073] (II) Performance Analysis The shell obtained in Example 1 has a dense, crack-free surface and exhibits reactive inertness with the molten alloy, resulting in a casting with excellent surface quality. Figure 2 This is a physical image of the intermediate-entropy type of titanium alloy prepared for casting in Example 1. Figure 2 It can be seen that the surface of the molded shell is free of defects such as cracks.
[0074] Figure 3 This is a SEM image of the interface between the medium-entropy shell and the casting obtained in Example 1. Figure 3 It can be seen that the shell material and the alloy liquid did not react at all.
[0075] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.
Claims
1. A method for preparing a medium-entropy shell for titanium alloy casting, characterized in that, Includes the following steps: Barium salt, calcium salt and strontium salt are mixed with zirconium oxide in an equimolar ratio. The resulting mixture is then mixed with water, dried and pulverized, and calcined at 1100℃~1200℃. The calcined product is cooled and sieved to obtain the shell surface filler. The molar ratio of barium salt, calcium salt and strontium salt to zirconium oxide is 1:1:1:3, and the mass ratio of the mixture to water is 1:1~1.
5. The surface layer filler is mixed with yttrium sol binder, wetting agent and defoamer to obtain the surface layer slurry; Mullite is mixed with silica sol binder, wetting agent and defoamer to obtain back layer slurry; The surface layer slurry is evenly applied to the surface of the wax model, sprinkled with yttrium oxide powder, and then frozen until solidified. This process of applying, sprinkling, and freezing is repeated 1 to 2 times to obtain the surface layer. The back layer slurry is then evenly applied to the surface layer, sprinkled with mullite powder, and then frozen until solidified. This process of applying, sprinkling, and freezing is repeated 2 to 4 times to obtain the back layer. The model is then dried at a temperature of -40°C to -60°C and a vacuum of 10 Pa to 50 Pa. Finally, the dried model shell is dewaxed and sintered to obtain the finished model shell.
2. The method for preparing a medium-entropy shell for titanium alloy casting according to claim 1, characterized in that, The shell surface filler and yttrium sol binder are mixed at a weight ratio of 3 to 5:1, and 0.1% to 0.5% of the total weight of the mixture of wetting agent and 0.1% to 0.2% of the total weight of the mixture of defoamer are added and stirred to obtain the surface slurry.
3. The method for preparing a medium-entropy shell for titanium alloy casting according to claim 1, characterized in that, The mullite and silica sol binder are mixed at a weight ratio of 1.5 to 2:1, and 0.1% to 0.5% of the total weight of the mixture of wetting agent and 0.1% to 0.2% of the total weight of the mixture of defoamer are added and stirred to obtain the backing slurry.
4. The method for preparing a medium-entropy shell for titanium alloy casting according to claim 1, characterized in that, The particle size of the shell surface filler is 200 mesh to 325 mesh.
5. The method for preparing a medium-entropy shell for titanium alloy casting according to claim 1, characterized in that, The heating rate for calcination is 3℃ / min to 5℃ / min.
6. The method for preparing a medium-entropy shell for titanium alloy casting according to claim 1, characterized in that, The dried shell is dewaxed by high-pressure steam, solvent dewaxing, or microwave dewaxing to obtain an empty shell; the empty shell is then calcined at 1150℃~1250℃ for 2h~4h and cooled in the furnace to obtain the finished shell.
7. The method for preparing a medium-entropy shell for titanium alloy casting according to claim 1, characterized in that, The particle size of the yttrium oxide powder with sand is 50-150 mesh; the particle size of the mullite powder with sand is 50-100 mesh.
8. The method for preparing a medium-entropy shell for titanium alloy casting according to claims 1 to 7 yields a medium-entropy shell for titanium alloy casting.
9. The application of the intermediate entropy shell for titanium alloy casting according to claim 8 in the precision casting of titanium and titanium alloys.