A composite rare earth oxide modified inert coating and preparation method thereof

Abstract

The present invention provides a method for preparing a composite rare earth oxide-modified inert coating, comprising the following steps: mixing polyvinyl alcohol, a solvent, Yb2O3, and CeO2 to obtain a rare earth ceramic slurry; applying the rare earth ceramic slurry to a ceramic substrate to obtain a coating; and sequentially debinding and calcining the coating to obtain the composite rare earth oxide-modified inert coating. Yb2O3 in the present invention has a relatively high melting point and chemical stability, excellent heat resistance, corrosion resistance, and high-temperature stability, and can improve chemical compatibility with the melt. CeO2 belongs to the cubic crystal system and, as a sintering aid, easily forms a eutectic liquid phase with the ceramic material, facilitating low-temperature densification. Furthermore, the coating is not easily detached, and defects such as mechanical sand adhesion and inclusions can be eliminated.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, in particular to a composite rare earth oxide modified inert coating and a preparation method thereof. Background Art

[0002] High-temperature alloy investment casting technology is primarily used in the production of key hot-end components for aerospace turbine engines, such as turbine blades, integral turbine disks, guide vanes, casings, and combustion chambers. However, in actual production, the high-temperature alloy melt is exposed to high temperatures for extended periods of time with various ceramic materials, including the mold shell, core, and crucible. Highly reactive elements in the alloy (such as Ti, Cr, Hf, Y, and C) readily react with the ceramic at the interface. Furthermore, if the ceramic surface is not sintered densely and exhibits significant porosity, it is susceptible to severe mechanical penetration and physical and chemical reactions. This results in chemical composition differences between the surface and interior of the turbine blade, leading to casting defects such as sand sticking and inclusions, and deteriorating the surface quality and dimensional accuracy of the casting. Mechanical polishing, coupled with stress, can cause directional recrystallization of the high-temperature alloy blade, reducing the mechanical properties of the casting. With the development of new generations of high-temperature alloys, the content of these reactive elements is expected to increase further. Consequently, interfacial compatibility between the high-temperature alloy melt and ceramic materials has become a major technical bottleneck affecting the yield of precision castings, severely restricting the development and mass production of high-performance aerospace engines.

[0003] From a metallurgical thermodynamics perspective, reducing the alloy melting temperature or the contact time with the ceramic material can improve interfacial compatibility. However, these measures can reduce the alloy's flow behavior, hindering the precision forming of high-temperature alloy castings. Modifying the ceramic material composition or components, such as using a silica-free binder or adding chromium oxide (Cr2O3) powder to the mold shell, can improve the mold shell's chemical stability and mitigate surface sand sticking. However, due to the complex mold shell components and the limited amount of additives, interfacial reactions cannot be completely eliminated. In recent years, Y2O3 and perovskite-structured zirconates (CaZrO3, SrZrO3, and BaZrO3) have been used in precision casting of active metals such as titanium alloys. While these materials exhibit excellent chemical stability and help suppress chemical sand sticking, their high melting points and demanding sintering equipment result in poor porcelain-forming properties. Their low density and high-temperature strength make them susceptible to mechanical penetration, leading to physical sand sticking defects. This still fails to significantly improve the surface accuracy of the casting.

[0004] Therefore, how to solve the problem of interfacial reaction between alloy melt and ceramic material in the existing technology, and the large porosity of the surface of ceramic material, which is very prone to serious mechanical penetration and physical and chemical reactions, resulting in sand sticking and inclusion casting defects, has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] The present invention provides a composite rare earth oxide-modified inert coating and a method for preparing the same. The composite rare earth oxide-modified inert coating, when applied to a ceramic surface, exhibits excellent surface finish, chemical stability, and low porosity, effectively eliminating both chemical and physical sand adhesion.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a composite rare earth oxide modified inert coating, comprising the following steps:

[0008] (1) mixing polyvinyl alcohol, a solvent, Yb2O3 and CeO2 to obtain a rare earth ceramic slurry;

[0009] (2) applying the rare earth ceramic slurry obtained in step (1) onto a ceramic substrate to obtain a coating;

[0010] (3) The coating obtained in step (2) is subjected to debinding and calcination in sequence to obtain a composite rare earth oxide modified inert coating.

[0011] Preferably, the operation of mixing polyvinyl alcohol, solvent, Yb2O3 and CeO2 in step (1) comprises the following steps:

[0012] 1) mixing polyvinyl alcohol and a solvent to obtain a binder solution;

[0013] 2) Mixing the binder solution obtained in step 1), Yb2O3 and CeO2.

[0014] Preferably, the mixing temperature in step 1) is 70-80° C., and the mixing time is 30-60 min.

[0015] Preferably, the mixing in step 1) is carried out under stirring conditions, and the stirring speed is 70 to 80 r / min.

[0016] Preferably, in step 2), the total volume of Yb2O3 and CeO2 accounts for 25-40% of the volume of the binder solution.

[0017] Preferably, in step (1), the particle size of Yb2O3 is 1 to 10 μm, and the particle size of CeO2 is 20 to 100 nm.

[0018] Preferably, the mass of CeO2 in step (1) accounts for 0.2-1% of the total mass of Yb2O3 and CeO2.

[0019] Preferably, the thickness of the coating in step (2) is 100 to 800 μm.

[0020] Preferably, the calcination temperature in step (3) is 1400-1550° C., the rate of heating to the calcination temperature is 4-8° C. / min, and the calcination holding time is 2-6 h.

[0021] The present invention also provides a composite rare earth oxide modified inert coating prepared by the preparation method described in the above technical solution.

[0022] The present invention provides a method for preparing a composite rare earth oxide-modified inert coating, comprising the following steps: mixing polyvinyl alcohol, a solvent, Yb2O3, and CeO2 to obtain a rare earth ceramic slurry; applying the rare earth ceramic slurry to a ceramic substrate to obtain a coating; and sequentially debinding and calcining the coating to obtain the composite rare earth oxide-modified inert coating. Yb2O3 in the present invention has a relatively high melting point and chemical stability, excellent heat resistance, corrosion resistance, and high-temperature stability, and can improve chemical compatibility with the melt. CeO2 belongs to the cubic crystal system and, as a sintering aid, easily forms a eutectic liquid phase with the ceramic material, facilitating low-temperature densification. The coating is also non-detachable, eliminating mechanical sand adhesion and inclusion defects. By uniformly applying the coating to the substrate surface and calcining it, an ideal inert coating can be prepared. This inert coating, due to its good surface finish and chemical stability, can effectively eliminate both chemical and physical sand adhesion, and has broad application prospects in the production of high-temperature alloy precision castings. Experimental results show that the ceramic particles in the coating prepared by the present invention have a high degree of solid solubility and reduced porosity; the SiO2 crucible coated with the coating prepared by the present invention is used to smelt DZ22B alloy at a melting temperature of 1500°C and a holding time of 15 minutes. No interfacial reaction occurs between the SiO2 crucible and the DZ22B alloy melt, and the surface of the casting is smooth, indicating that the composite rare earth oxide-modified inert coating can effectively eliminate interfacial reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a microscopic morphology of the rare earth oxide modified inert coating prepared in Comparative Example 1;

[0024] Figure 2 This is a microscopic morphology of the composite rare earth oxide modified inert coating prepared in Example 1;

[0025] Figure 3 This is the microscopic morphology of the cross section of DZ22B alloy after smelting in Al2O3 crucible;

[0026] Figure 4 This is a microscopic morphology of the cross section of the DZ22B alloy after smelting the DZ22B alloy in an Al2O3 crucible coated with the composite rare earth oxide modified inert coating of Example 1;

[0027] Figure 5 This is a microscopic morphology of the rare earth oxide modified inert coating prepared in Comparative Example 2;

[0028] Figure 6 This is a microscopic morphology of the composite rare earth oxide modified inert coating prepared in Example 2;

[0029] Figure 7 This is the microscopic morphology of the cross section of DZ22B alloy after smelting in ZrO2 crucible;

[0030] Figure 8 This is a microscopic morphology of a cross section of a DZ22B alloy after smelting the DZ22B alloy in a ZrO2 crucible coated with the composite rare earth oxide modified inert coating of Example 2;

[0031] Figure 9 This is a microscopic morphology of the rare earth oxide modified inert coating prepared in Comparative Example 3;

[0032] Figure 10 This is a microscopic morphology of the composite rare earth oxide modified inert coating prepared in Example 3;

[0033] Figure 11 This is the microscopic morphology of the cross section of DZ22B alloy after melting in SiO2 crucible;

[0034] Figure 12 This is a microscopic morphology of the cross section of the DZ22B alloy after the DZ22B alloy is smelted in a SiO2 crucible coated with the composite rare earth oxide modified inert coating of Example 3. DETAILED DESCRIPTION

[0035] The present invention provides a method for preparing a composite rare earth oxide modified inert coating, comprising the following steps:

[0036] (1) mixing polyvinyl alcohol, a solvent, Yb2O3 and CeO2 to obtain a rare earth ceramic slurry;

[0037] (2) applying the rare earth ceramic slurry obtained in step (1) onto a ceramic substrate to obtain a coating;

[0038] (3) The coating obtained in step (2) is subjected to debinding and calcination in sequence to obtain a composite rare earth oxide modified inert coating.

[0039] The present invention has no particular limitation on the sources of the raw materials, and the raw materials can be prepared using commercially available products or well-known preparation methods known to those skilled in the art.

[0040] The invention mixes polyvinyl alcohol, solvent, Yb2O3 and CeO2 to obtain rare earth ceramic slurry.

[0041] In the present invention, the solvent is preferably water.

[0042] In the present invention, the particle size of the Yb2O3 is preferably 1 to 10 μm; the particle size of the CeO2 is preferably 20 to 100 nm, more preferably 50 nm; and the purity of the Yb2O3 and CeO2 is preferably independently 99.99%.

[0043] In the present invention, the mass of the CeO2 preferably accounts for 0.2-1% of the total mass of the Yb2O3 and CeO2, and more preferably 0.5-0.8%. By controlling the composition and ratio of the rare earth oxides, the present invention prepares a ceramic slurry with good coating properties. By uniformly coating the slurry on the surface of the substrate and calcining it, an ideal inert coating can be prepared.

[0044] In the present invention, the operation of mixing the polyvinyl alcohol, solvent, Yb2O3 and CeO2 preferably includes the following steps:

[0045] 1) mixing polyvinyl alcohol and a solvent to obtain a binder solution;

[0046] 2) Mixing the binder solution obtained in step 1), Yb2O3 and CeO2.

[0047] In the present invention, polyvinyl alcohol and a solvent are preferably mixed to obtain a binder solution.

[0048] In the present invention, the ratio of the mass of the polyvinyl alcohol to the volume of the solvent is preferably (3-6) g:100 mL, more preferably (4-5) g:100 mL. In the present invention, the polyvinyl alcohol is a binder.

[0049] In the present invention, the mixing of the polyvinyl alcohol and the solvent is preferably carried out under magnetic stirring; the speed of the magnetic stirring is preferably 70 to 80 r / min. In the present invention, the mixing temperature is preferably 70 to 80°C, more preferably 75°C; and the mixing time is preferably 30 to 60 minutes, more preferably 30 to 40 minutes.

[0050] After obtaining the binder solution, the present invention mixes the binder solution, Yb2O3 and CeO2.

[0051] In the present invention, the total volume of the Yb2O3 and CeO2 preferably accounts for 25-40% of the volume of the binder solution, and more preferably 30-35%.

[0052] In the present invention, the Yb2O3 and CeO2 are preferably dried and calcined separately before use. The present invention can remove moisture and impurities by drying and calcining Yb2O3 and CeO2 separately, thereby avoiding affecting the performance of the coating in the later stage.

[0053] In the present invention, the drying temperature is preferably 180-240° C., more preferably 200° C.; the drying time is preferably 3-5 hours, more preferably 3-4 hours.

[0054] In the present invention, the calcination temperature is preferably 700-900° C., more preferably 800° C.; the calcination time is preferably 8-10 h, more preferably 8-9 h.

[0055] In the present invention, the operation of mixing the binder solution, Yb2O3 and CeO2 is preferably to mix Yb2O3 and CeO2 and then add them into the binder solution for mixing.

[0056] The present invention has no special limitation on the operation of mixing Yb2O3 and CeO2, and the technical scheme for preparing the mixed material well known to those skilled in the art can be adopted.

[0057] In the present invention, the mixing step of adding the raw materials to the binder solution is preferably performed under magnetic stirring conditions; the magnetic stirring speed is preferably 80 to 100 r / min; the mixing temperature is preferably 70 to 80°C, more preferably 75°C; and the mixing time is preferably 120 to 180 minutes, more preferably 120 to 150 minutes. By controlling the mixing process parameters, the present invention can further uniformly mix the raw materials, thereby obtaining a uniformly suspended and distributed ceramic slurry.

[0058] After obtaining the rare earth ceramic slurry, the present invention applies the rare earth ceramic slurry on a ceramic substrate to obtain a coating.

[0059] In the present invention, the coating method is preferably brushing, and the number of coating times is preferably 4 to 6. The present invention has no special limitation on the brushing operation, and any operation well known to those skilled in the art can be used.

[0060] After coating is completed, the present invention preferably air-dries the coated product to obtain a coating.

[0061] In the present invention, the natural air-drying time is preferably 12 to 15 hours.

[0062] In the present invention, the thickness of the coating layer is preferably 100 to 800 μm, more preferably 300 to 500 μm.

[0063] After the coating is obtained, the coating is sequentially subjected to debinding and calcination to obtain a composite rare earth oxide modified inert coating.

[0064] In the present invention, the binder removal temperature is preferably 600-800°C, more preferably 600-700°C, and even more preferably 600-650°C; the rate of heating to the binder removal temperature is preferably 2-4°C / min; and the binder removal time is preferably 4-8 hours, more preferably 6-8 hours. The binder removal process of the present invention can remove the binder.

[0065] In the present invention, the calcination temperature is preferably 1400-1550°C, more preferably 1450-1500°C; the calcination time is preferably 2-6 hours, more preferably 2-3 hours; and the rate of heating to the calcination temperature is preferably 4-8°C / min, more preferably 5-6°C / min. By controlling the calcination process parameters, the present invention can achieve sufficient solid solution sintering of the components to form porcelain, thereby improving surface smoothness and strength.

[0066] After the calcination is completed, the present invention preferably cools the calcined product along with the furnace to obtain a composite rare earth oxide modified inert coating.

[0067] The present invention has no special limitation on the operation of furnace cooling, and cooling to room temperature can be performed using operations well known to those skilled in the art.

[0068] This invention utilizes a high-temperature sintering method to optimize the composition and ratio of different rare earth oxides to produce a ceramic slurry with excellent coating properties. This slurry is then uniformly applied to the substrate surface and sintered at high temperature to create an ideal inert coating. This technology offers the advantages of simple equipment, ease of operation, and a wide range of controllable coating composition, making it suitable for large-scale production. The resulting inert coating exhibits excellent surface finish and chemical stability, effectively eliminating both chemical and physical sand adhesion, and has broad application prospects in the production of high-temperature alloy precision castings.

[0069] The present invention also provides a composite rare earth oxide modified inert coating prepared by the preparation method described in the above technical solution.

[0070] The composite rare earth oxide modified inert coating provided by the present invention has high density and can effectively eliminate chemical sand adhesion and physical sand adhesion.

[0071] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0072] Example 1

[0073] A method for preparing a composite rare earth oxide modified inert coating comprises the following steps:

[0074] (1) 200 g of Yb2O3 with a particle size of 5 μm and a purity of 99.99% and 20 g of CeO2 with a particle size of 50 nm and a purity of 99.99% were placed in an oven and dried at 200°C for 3 h, and then calcined at 800°C for 8 h to obtain pretreated Yb2O3 and CeO2;

[0075] (2) adding 15 g of polyvinyl alcohol powder to 500 mL of water and subjecting the mixture to magnetic stirring under heating in a water bath to obtain a binder solution; wherein the water bath heating temperature is 75° C., the heating time is 30 min, and the magnetic stirring speed is 70 r / min;

[0076] (3) mixing the pretreated Yb2O3 and CeO2 obtained in step (1), pouring the mixture into the binder solution obtained in step (2), and subjecting the mixture to magnetic stirring for 120 minutes under the condition of water bath heating to obtain a rare earth ceramic slurry; wherein the mass of CeO2 accounts for 0.5% of the total mass of Yb2O3 and CeO2; the total volume of Yb2O3 and CeO2 accounts for 30% of the volume of the binder solution; the water bath heating temperature is 75°C; and the magnetic stirring speed is 80 r / min;

[0077] (4) applying the rare earth ceramic slurry obtained in step (3) on an Al2O3 crucible and drying the slurry naturally to obtain a coating with a thickness of 300±30 μm; wherein the coating is applied four times;

[0078] (5) The coating obtained in step (4) is sequentially debinded and calcined, and then cooled in the furnace to obtain a composite rare earth oxide modified inert coating; wherein the debinding temperature is 600°C, the debinding time is 6 hours, and the heating rate to the debinding temperature is 4°C / min; the calcination temperature is 1500°C, the calcination time is 2 hours, and the heating rate to the calcination temperature is 4°C / min.

[0079] Comparative Example 1

[0080] The preparation method of the rare earth oxide modified inert coating comprises the following steps:

[0081] (1) 200 g of Yb2O3 with a particle size of 5 μm and a purity of 99.99% was placed in an oven and dried at 200°C for 3 h, and then calcined at 800°C for 8 h to obtain pretreated Yb2O3;

[0082] (2) adding 15 g of polyvinyl alcohol powder to 500 mL of water and subjecting the mixture to magnetic stirring under heating in a water bath to obtain a binder solution; wherein the water bath heating temperature is 75° C., the heating time is 30 min, and the magnetic stirring speed is 70 r / min;

[0083] (3) Pour the pretreated Yb2O3 obtained in step (1) into the binder solution obtained in step (2) and perform magnetic stirring for 120 minutes under the condition of water bath heating to obtain a rare earth ceramic slurry; the total volume of Yb2O3 accounts for 30% of the volume of the binder solution; the water bath heating temperature is 75°C; and the magnetic stirring speed is 80 r / min;

[0084] (4) applying the rare earth ceramic slurry obtained in step (3) on an Al2O3 crucible and drying the slurry naturally to obtain a coating with a thickness of 300±30 μm; wherein the coating is applied four times;

[0085] (5) The coating obtained in step (4) is sequentially debinded and calcined, and then cooled in the furnace to obtain a rare earth oxide modified inert coating; wherein the debinding temperature is 600°C, the debinding time is 6 hours, and the heating rate to the debinding temperature is 4°C / min; the calcination temperature is 1500°C, the calcination time is 2 hours, and the heating rate to the calcination temperature is 4°C / min.

[0086] The Yb2O3 rare earth oxide modified inert coating prepared in Comparative Example 1 was analyzed for its tissue density using a scanning electron microscope. The microscopic morphology is shown in FIG. Figure 1 As shown. Figure 1 It can be seen that the Yb2O3 rare earth coating without CeO2 addition has poor surface density and high porosity.

[0087] The composite rare earth oxide modified inert coating prepared in Example 1 was analyzed for its tissue density using a scanning electron microscope. The microscopic morphology is shown in FIG. Figure 2 As shown. Figure 2 It can be seen that the CeO2-added Yb2O3 composite rare earth coating prepared by the present invention has a high degree of solid solution of ceramic particles and a reduced porosity.

[0088] The DZ22B alloy was smelted in an Al2O3 crucible at a melting temperature of 1600°C and a holding time of 15 min. The alloy casting was cut transversely by electrospark machining to obtain a cross section. After being inlaid with bakelite powder, the degree of interfacial reaction was analyzed by scanning electron microscopy. The micromorphology of the cross section of the DZ22B alloy is shown in Figure 2. Figure 3 As shown. Figure 3 It can be seen that the interface reaction occurred between the Al2O3 crucible and the DZ22B alloy melt.

[0089] The DZ22B alloy was smelted in an Al2O3 crucible coated with the composite rare earth oxide modified inert coating of Example 1 at a melting temperature of 1600°C for 15 min. The alloy casting was cut transversely by electrospark machining to obtain a cross section. After inlaying with bakelite powder, the degree of interfacial reaction was analyzed by scanning electron microscopy. The micromorphology of the cross section of the DZ22B alloy is shown in FIG. Figure 4 As shown. Figure 4 It can be seen that no interfacial reaction occurs between the Al2O3 crucible and the DZ22B alloy melt, and the casting surface is smooth, indicating that the composite rare earth oxide modified inert coating can effectively eliminate the interfacial reaction.

[0090] Example 2

[0091] A method for preparing a composite rare earth oxide modified inert coating comprises the following steps:

[0092] (1) 200 g of Yb2O3 with a particle size of 10 μm and a purity of 99.99% and 20 g of CeO2 with a particle size of 100 nm and a purity of 99.99% were placed in an oven and dried at 200°C for 4 h, and then calcined at 800°C for 8 h to obtain pretreated Yb2O3 and CeO2;

[0093] (2) adding 15 g of polyvinyl alcohol powder to 500 mL of water and subjecting the mixture to magnetic stirring under heating in a water bath to obtain a binder solution; wherein the water bath heating temperature is 75° C., the heating time is 40 min, and the magnetic stirring speed is 80 rpm;

[0094] (3) mixing the pretreated Yb2O3 and CeO2 obtained in step (1) and then pouring the mixture into the binder solution obtained in step (2), and magnetically stirring the mixture for 120 minutes under the condition of heating in a water bath to obtain a rare earth ceramic slurry; wherein the total volume of Yb2O3 and CeO2 accounts for 35% of the volume of the binder solution; the water bath heating temperature is 75°C; and the magnetic stirring speed is 90 r / min;

[0095] (4) applying the rare earth ceramic slurry obtained in step (3) on a ZrO2 crucible and drying the mixture naturally to obtain a coating having a thickness of 400±30 μm; the coating is applied five times;

[0096] (5) The coating obtained in step (4) is sequentially debinded and calcined, and then cooled in the furnace to obtain a composite rare earth oxide modified inert coating; wherein the debinding temperature is 700°C, the debinding time is 8 hours, and the heating rate to the debinding temperature is 4°C / min; the calcination temperature is 1550°C, the calcination time is 2 hours, and the heating rate to the calcination temperature is 4°C / min.

[0097] Comparative Example 2

[0098] Compared with Example 2, the addition of CeO2 was omitted, and other conditions remained unchanged to obtain a rare earth oxide modified inert coating.

[0099] The rare earth oxide modified inert coating prepared in Comparative Example 2 was analyzed for its tissue density using a scanning electron microscope. The microscopic morphology is shown in FIG. Figure 5 As shown. Figure 5 It can be seen that the Yb2O3 rare earth coating without CeO2 addition has poor surface density and high porosity.

[0100] The composite rare earth oxide modified inert coating prepared in Example 2 was subjected to tissue density analysis using a scanning electron microscope. The microscopic morphology is shown in FIG. Figure 6 As shown. Figure 6 It can be seen that the coating prepared by the present invention has a high degree of solid solution of ceramic particles and a reduced porosity.

[0101] The DZ22B alloy was smelted in a ZrO2 crucible at a melting temperature of 1600°C and a holding time of 45 min. The alloy casting was cut transversely by electrospark machining to obtain a cross section. After being inlaid with bakelite powder, the degree of interfacial reaction was analyzed by scanning electron microscopy. The micromorphology of the cross section of the DZ22B alloy is shown in Figure 2. Figure 7 As shown. Figure 7 It can be seen that the ZrO2 crucible and the DZ22B alloy melt undergo an interfacial reaction.

[0102] The DZ22B alloy was smelted in a ZrO2 crucible coated with the composite rare earth oxide modified inert coating of Example 2 at a melting temperature of 1600°C for 45 min. The alloy casting was cut transversely by electrospark machining to obtain a cross section. After inlaying with bakelite powder, the degree of interfacial reaction was analyzed by scanning electron microscopy. The micromorphology of the cross section of the DZ22B alloy is shown in FIG. Figure 8 As shown. Figure 8 It can be seen that no interfacial reaction occurs between the ZrO2 crucible and the DZ22B alloy melt, and the casting surface is smooth, indicating that the composite rare earth oxide modified inert coating can effectively eliminate the interfacial reaction.

[0103] Example 3

[0104] A method for preparing a composite rare earth oxide modified inert coating comprises the following steps:

[0105] (1) 200 g of Yb2O3 with a particle size of 1 μm and a purity of 99.99% and 20 g of CeO2 with a particle size of 20 nm and a purity of 99.99% were placed in an oven and dried at 200°C for 3 h, and then calcined at 800°C for 8 h to obtain pretreated Yb2O3 and CeO2;

[0106] (2) adding 15 g of polyvinyl alcohol powder to 500 mL of water and subjecting the mixture to magnetic stirring under heating in a water bath to obtain a binder solution; wherein the water bath heating temperature is 75° C., the heating time is 30 min, and the magnetic stirring speed is 70 r / min;

[0107] (3) mixing the pretreated Yb2O3 and CeO2 obtained in step (1) and then pouring the mixture into the binder solution obtained in step (2), and magnetically stirring the mixture for 120 minutes under the condition of water bath heating to obtain a rare earth ceramic slurry; wherein the total volume of Yb2O3 and CeO2 accounts for 30% of the volume of the binder solution; the water bath heating temperature is 75°C; and the magnetic stirring speed is 80 r / min;

[0108] (4) applying the rare earth ceramic slurry obtained in step (3) on a SiO2 crucible and drying the slurry naturally to obtain a coating with a thickness of 300±30 μm; wherein the coating is applied four times;

[0109] (5) The coating obtained in step (4) is sequentially debinded and calcined, and then cooled in the furnace to obtain a composite rare earth oxide modified inert coating; wherein the debinding temperature is 600°C, the debinding time is 6 hours, and the heating rate to the debinding temperature is 4°C / min; the calcination temperature is 1500°C, the calcination time is 2 hours, and the heating rate to the calcination temperature is 4°C / min.

[0110] Comparative Example 3

[0111] Compared with Example 3, the addition of CeO2 was omitted, and other conditions remained unchanged to obtain a rare earth oxide modified inert coating.

[0112] The rare earth oxide modified inert coating prepared in Comparative Example 3 was analyzed for its tissue density using a scanning electron microscope. The microscopic morphology is shown in FIG. Figure 9 As shown. Figure 9 It can be seen that the Yb2O3 rare earth coating without CeO2 addition has poor surface density and high porosity.

[0113] The composite rare earth oxide modified inert coating prepared in Example 3 was analyzed for its tissue density using a scanning electron microscope. The microscopic morphology is shown in FIG. Figure 10 As shown. Figure 10 It can be seen that the coating prepared by the present invention has a high degree of solid solution of ceramic particles and a reduced porosity.

[0114] The DZ22B alloy was smelted in a SiO2 crucible at a melting temperature of 1500°C and a holding time of 15 min. The alloy casting was cut transversely by electrospark machining to obtain a cross section. After being inlaid with bakelite powder, the degree of interfacial reaction was analyzed by scanning electron microscopy. The micromorphology of the cross section of the DZ22B alloy is shown in Figure 2. Figure 11 As shown. Figure 11 It can be seen that the interface reaction occurred between the SiO2 crucible and the DZ22B alloy melt.

[0115] The DZ22B alloy was smelted in a SiO2 crucible coated with the composite rare earth oxide modified inert coating of Example 3 at a melting temperature of 1500°C for 15 min. The alloy casting was cut transversely by electrospark machining to obtain a cross section. After being inlaid with bakelite powder, the degree of interfacial reaction was analyzed by scanning electron microscopy. The micromorphology of the cross section of the DZ22B alloy is shown in FIG. Figure 12 As shown. Figure 12 It can be seen that no interfacial reaction occurs between the SiO2 crucible and the DZ22B alloy melt, and the casting surface is smooth, indicating that the composite rare earth oxide modified inert coating can effectively eliminate the interfacial reaction.

[0116] It can be seen from the above embodiments and comparative examples that the composite rare earth oxide modified inert coating prepared by the present invention is applied to the surface of ceramic materials, which has good surface finish, chemical stability and low porosity, and can effectively eliminate chemical and physical sand adhesion.

[0117] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a composite rare earth oxide modified inert coating, comprising the following steps: (1) polyvinyl alcohol, a solvent, Yb2O3 and CeO2 are mixed to obtain a rare earth ceramic slurry; the Yb2O3 and CeO2 are dried and calcined in sequence before use; (2) coating the rare earth ceramic slurry obtained in step (1) on a ceramic substrate, and after coating, naturally air-drying the coated product to obtain a coating; (3) Debinding and calcining the coating obtained in step (2) in sequence. After the calcination is completed, the calcined product is cooled in the furnace to obtain a composite rare earth oxide modified inert coating; The calcination temperature in step (3) is 1400-1550°C, the rate of heating to the calcination temperature is 4-8°C / min, and the calcination holding time is 2-6h; In the step (1), the particle size of Yb2O3 is 1-10 μm, and the particle size of CeO2 is 20-100 nm; The mass of CeO2 in step (1) accounts for 0.2-1% of the total mass of Yb2O3 and CeO2.

2. The preparation method according to claim 1, characterized in that The operation of mixing polyvinyl alcohol, solvent, Yb2O3 and CeO2 in step (1) comprises the following steps: 1) mixing polyvinyl alcohol and a solvent to obtain a binder solution; 2) Mixing the binder solution obtained in step 1), Yb2O3 and CeO2.

3. The preparation method according to claim 2, characterized in that The mixing temperature in step 1) is 70-80° C., and the mixing time is 30-60 min.

4. The preparation method according to claim 2 or 3, characterized in that The mixing in step 1) is performed under stirring conditions, and the stirring speed is 70-80 r / min.

5. The preparation method according to claim 2, characterized in that In the step 2), the total volume of Yb2O3 and CeO2 accounts for 25-40% of the volume of the binder solution.

6. The preparation method according to claim 1, characterized in that The thickness of the coating in step (2) is 100-800 μm.

7. The composite rare earth oxide modified inert coating prepared by the preparation method according to any one of claims 1 to 6.

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