A high-temperature alloy smelting crucible with a gradient structure and a preparation method thereof

Abstract

The present application relates to the technical field of high-temperature structural ceramics, and in particular to a high-temperature alloy smelting crucible with a gradient structure and a preparation method thereof. The crucible prepared by the method comprises, from inside to outside, a rare earth oxide inner layer, a rare earth oxide-zirconia solid solution intermediate layer and a zirconia outer layer. The inner layer is selected from rare earth oxides such as CeO2 and Y2O3, and provides excellent high-temperature corrosion resistance; the intermediate layer is a continuous solid solution structure formed by rare earth oxides and zirconia, which realizes the gradient transition of composition and crystal lattice structure and relieves the interface thermal stress; and the outer layer is a dense zirconia skeleton, which provides excellent mechanical properties. The crucible adopts a process route of layered pressing and high-temperature sintering, and during the sintering process, rare earth ions diffuse from the inside to the outside, thereby constructing a multilayer ceramic system with stable structure and continuous interface transition. The prepared ceramic crucible has high density, excellent corrosion resistance, thermal shock resistance and mechanical properties, and can meet the use requirements of high-temperature alloy smelting.

Description

Technical Field

[0001] This invention relates to the field of high-temperature structural ceramics technology, specifically a high-temperature alloy melting crucible with a gradient structure and its preparation method. Background Technology

[0002] High-temperature alloys are widely used in extreme high-temperature environments such as turbine blades for aero-engines, combustion chambers for gas turbines, and fuel cladding for nuclear reactors. Vacuum induction melting is the main production method for high-temperature alloys, but it suffers from the problem of reaction between the alloy melt and the crucible, leading to the formation of refractory inclusions in the high-temperature alloy, which affects its purity and performance. Therefore, selecting appropriate crucible materials is of great significance for improving the purity of high-temperature alloys.

[0003] Zirconia (ZrO2) has broad application prospects in the field of high-temperature ceramic crucibles due to its high melting point, excellent thermal shock resistance, and chemical stability. However, pure ZrO2 ceramics undergo a crystal transformation during high-temperature sintering, resulting in volume changes that may lead to cracking and damage of the ceramic crucible. Furthermore, ZrO2 ceramic crucibles may be reduced by hafnium (Hf) in the melt under certain circumstances. Yttrium oxide (Y2O3) ceramic crucibles exhibit good chemical stability, low thermal conductivity, and good corrosion resistance. However, yttrium oxide raw materials are expensive, and its thermal shock resistance and sinterability are poor.

[0004] Rare earth oxides, such as Y2O3 and cerium oxide (CeO2), are widely used to stabilize the ZrO2 crystal phase and form materials such as Y-stabilized zirconia (YSZ) and Ce-stabilized zirconia (CSZ). However, their sintering temperature ranges vary greatly, and traditional homogeneous doping methods often lead to problems such as structural inhomogeneity, weak interfacial bonding, and difficulty in controlling density.

[0005] Therefore, there is an urgent need for a high-temperature alloy melting ceramic crucible with optimized structure, stable interface, easy-to-control sintering process, and scalable preparation, in order to meet the requirements of high-temperature alloys for crucible material's resistance to erosion, thermal shock and mechanical properties. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a high-temperature alloy melting crucible with a gradient structure and its preparation method. This high-temperature alloy melting ceramic crucible exhibits strong interfacial transition zone bonding, dense sintering, and strong resistance to high-temperature alloy erosion. Through the layered composite design and diffusion bonding mechanism of rare earth oxides (CeO2 or Y2O3) and ZrO2, combined with an optimized sintering process, the crucible achieves improved high-temperature erosion resistance and thermal shock stability while ensuring structural stability, thus meeting the application requirements of high-temperature alloy smelting.

[0007] The innovation of this technology lies in its first-ever introduction of a gradient structure. Through the design of different functional layers (inner rare earth oxide, outer ZrO2), the overall thermal stability and interfacial bonding strength of the crucible are enhanced. Simultaneously, a diffusion bonding zone is constructed, allowing rare earth ions to diffuse into the ZrO2 matrix during sintering, forming a stable solid solution and achieving a gradient transition structure. The inner rare earth oxide layer resists the corrosion of high-temperature alloys, the outer ZrO2 layer imparts excellent mechanical properties to the material, and the transition layer alleviates interfacial thermal stress, improving the thermal shock resistance of the ceramic crucible.

[0008] The present invention provides a method for preparing a high-temperature alloy melting crucible with a gradient structure, which specifically includes the following steps:

[0009] (1) Select rare earth oxides, add binders, mix evenly to obtain mixture A; select zirconium oxide, add binders, mix evenly to obtain mixture B, and then process mixtures A and B separately.

[0010] (2) Weigh the mixture A and B after the material is trapped according to a certain ratio, and press the powder into a blank by layer pressing.

[0011] (3) Place the shaped blank into a drying oven;

[0012] (4) Place the dried billet into an electric furnace for calcination. The heating rate is 2-8℃ / min, the calcination temperature is 1600-1700℃, and the holding time is 2-5h. After the holding time is completed, let it cool naturally to room temperature to obtain a high-temperature alloy melting crucible.

[0013] Furthermore, the rare earth oxide mentioned in step (1) is one or more of Y2O3, CeO2 and La2O3, with a particle size ≤0.075mm.

[0014] Furthermore, in step (1), when the rare earth oxide is multiple of Y2O3, CeO2 and La2O3, the raw materials that make up the rare earth oxide are first premixed, and then a binder is added and mixed evenly to obtain mixture A.

[0015] Furthermore, in the chemical composition of the zirconium oxide described in step (1), ZrO2 > 99.5 wt% and particle size ≤ 0.044 mm.

[0016] Furthermore, the binder in step (1) is a polyvinyl alcohol (PVA) solution with a concentration of 2wt%-5wt%, and the amount of binder added to mixture A or mixture B is 4wt%-8wt%.

[0017] Furthermore, in step (1), mixtures A and B are respectively conditioned at 25°C for 24 hours.

[0018] Furthermore, in step (1), the mixture is uniformly mixed in a ball mill.

[0019] Furthermore, in step (2), the mass ratio of the mixture A and the mixture B after acclimation is 1:1 to 1:5, and the mixtures A and B after acclimation are powders.

[0020] Furthermore, in step (2), a layered pressing method is adopted. First, the mixture A after the material is trapped is added to the mold, and then the mixture B after the material is trapped is added. That is, the mixture B after the material is trapped is placed on top of the mixture A after the material is trapped, and it is pressed into a blank at 120-180MPa.

[0021] Furthermore, in step (3), the shaped blank is placed in a drying oven, and the blank is first dried at 60°C for 6-12 hours, and then dried at 110-120°C for 6-12 hours.

[0022] The present invention also provides a high-temperature alloy melting crucible obtained according to the above preparation method.

[0023] Furthermore, the high-temperature alloy melting crucible comprises, from the inside out, a rare earth oxide inner layer, a rare earth oxide-zirconia solid solution intermediate layer, and a zirconia outer layer. The inner layer uses rare earth oxides such as CeO2 and Y2O3, providing excellent high-temperature corrosion resistance; the intermediate layer is a continuous solid solution structure formed by rare earth oxides and zirconia, achieving a gradient transition in composition and crystal structure, and alleviating interfacial thermal stress; the outer layer is a dense zirconia framework, providing excellent mechanical properties. During sintering, rare earth ions diffuse from the inside out, constructing a structurally stable, continuously transitioning multilayer ceramic system.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) Improve thermal shock resistance and thermal stability: Through the rational design of inner and outer functional layers, a gradient transition structure is formed to alleviate the interface stress concentration caused by the difference in thermal expansion coefficient, thereby improving the thermal shock stability and service life of ceramic crucibles under high temperature and rapid cooling and heating conditions.

[0026] (2) Enhance the bonding strength of the interface: During the sintering process, rare earth ions in rare earth oxides diffuse into the ZrO2 matrix to form a stable solid solution structure, thereby constructing a stable diffusion bonding zone, realizing high-strength bonding between interfaces, and avoiding delamination and peeling.

[0027] (3) Enhanced corrosion resistance: The inner rare earth oxides (such as CeO2 and Y2O3) have good chemical stability and corrosion resistance to high-temperature alloys, which can effectively prevent the alloy melt from corroding the crucible and ensure the purity of the alloy during the smelting process.

[0028] (4) Excellent mechanical properties: The outer ZrO2 layer has good high-temperature strength and fracture toughness, which gives the crucible excellent mechanical properties and enhances its ability to resist thermomechanical shock. Attached Figure Description

[0029] Figure 1 This is a scanning electron microscope image of the high-temperature alloy melting crucible prepared in Example 2;

[0030] Figure 2 yes Figure 1 Distribution diagram of Y element in surface scan analysis;

[0031] Figure 3 yes Figure 1 Distribution map of Zr elements in surface scan analysis. Detailed Implementation

[0032] To better understand the content of this invention, it will be further described below with reference to specific embodiments and accompanying drawings. The following embodiments are based on the technology of this invention and provide detailed implementation methods and operating steps, but the scope of protection of this invention is not limited to the following embodiments.

[0033] In all the examples and comparative examples below, the testing methods for the samples were consistent. The room temperature compressive strength and thermal shock stability of the samples were tested according to national standards GB / T5072-2023 and GB / T 30873-2014, respectively. The corrosion resistance of the samples was tested using K417 high-temperature alloy.

[0034] In the following examples and comparative examples, the chemical composition of the zirconium oxide powder is ZrO2 > 99.5 wt% and the particle size is ≤ 0.044 mm; in the cerium oxide and yttrium oxide powders, the particle size of Y2O3 and CeO2 is ≤ 0.075 mm.

[0035] Example 1:

[0036] (1) Select cerium oxide powder, add a 2wt% PVA solution, mix evenly in a ball mill to obtain mixture A, the amount of PVA solution added accounts for 5wt% of the mass fraction of mixture A; select zirconia powder, add a 2wt% PVA solution, mix evenly in a ball mill to obtain mixture B, the amount of PVA solution added accounts for 5wt% of the mass fraction of mixture B; caking mixture A and mixture B at 25℃ for 24h respectively;

[0037] (2) Weigh the mixture A and mixture B after tamping according to a mass ratio of 1:2. Using a layered pressing method, first add the mixture A after tamping to the mold, then add the mixture B after tamping. Press the powder into a blank at 150MPa. Then, mixture A is located in the inner layer and mixture B is located in the outer layer.

[0038] (3) Place the molded blank in a drying oven and dry it at 60°C for 6 hours, and then at 110°C for 12 hours;

[0039] (4) Place the dried billet into an electric furnace for calcination. The heating rate is 5℃ / min, the calcination temperature is 1650℃, and the holding time is 3h. After the holding time is completed, let it cool naturally to room temperature to obtain a high-temperature alloy melting crucible.

[0040] In this embodiment, the compressive strength of the obtained high-temperature alloy melting crucible sample is 203 MPa, the strength retention rate after thermal shock is 89.7%, and after the K417G alloy erosion test, there is no metal penetration phenomenon at the interface, and the erosion depth of the alloy on the sample is about 18 μm.

[0041] Example 2:

[0042] (1) Select yttrium oxide powder, add a 2wt% PVA solution, mix evenly in a ball mill to obtain mixture A, the amount of PVA solution added accounts for 5wt% of the mass fraction of mixture A; select zirconium oxide powder, add a 2wt% PVA solution, mix evenly in a ball mill to obtain mixture B, the amount of PVA solution added accounts for 5wt% of the mass fraction of mixture B; caking mixture A and mixture B at 25℃ for 24h respectively;

[0043] (2) Weigh the mixture A and mixture B after tamping according to a mass ratio of 1:3. Using a layered pressing method, first add the mixture A after tamping to the mold, then add the mixture B after tamping. Press the powder into a blank at 150MPa. Then, mixture A is located in the inner layer and mixture B is located in the outer layer.

[0044] (3) Place the molded blank in a drying oven and dry it at 60°C for 6 hours, and then at 110°C for 12 hours;

[0045] (4) Place the dried billet into an electric furnace for calcination. The heating rate is 5℃ / min, the calcination temperature is 1650℃, and the holding time is 3h. After the holding time is completed, let it cool naturally to room temperature to obtain a high-temperature alloy melting crucible.

[0046] In this embodiment, the compressive strength of the obtained high-temperature alloy melting crucible sample is 223 MPa, the strength retention rate after thermal shock is 91.7%, and after the K417G alloy erosion test, there is no metal penetration phenomenon at the interface, and the erosion depth of the alloy on the sample is about 15 μm.

[0047] Example 3:

[0048] (1) Weigh cerium oxide and yttrium oxide powders at a mass ratio of 1:1 and premix them. Then add a 2wt% PVA solution and mix them evenly in a ball mill to obtain mixture A. The amount of PVA solution added accounts for 5wt% of the mass fraction of mixture A. Select zirconium oxide powder, add a 2wt% PVA solution and mix them evenly in a ball mill to obtain mixture B. The amount of PVA solution added accounts for 5wt% of the mass fraction of mixture B. Let mixture A and mixture B rest at 25℃ for 24h respectively.

[0049] (2) Weigh the mixture A and mixture B after tamping according to a mass ratio of 1:2. Using a layered pressing method, first add the mixture A after tamping to the mold, then add the mixture B after tamping. Press the powder into a blank at 150MPa. Then, mixture A is located in the inner layer and mixture B is located in the outer layer.

[0050] (3) Place the molded blank in a drying oven and dry it at 60°C for 6 hours, and then at 110°C for 12 hours;

[0051] (4) Place the dried billet into an electric furnace for calcination. The heating rate is 5℃ / min, the calcination temperature is 1650℃, and the holding time is 3h. After the holding time is completed, let it cool naturally to room temperature to obtain a high-temperature alloy melting crucible.

[0052] In this embodiment, the compressive strength of the obtained high-temperature alloy melting crucible sample is 256 MPa, the strength retention rate after thermal shock is 93.1%, and after the K417G alloy erosion test, there is no metal penetration phenomenon at the interface, and the erosion depth of the alloy on the sample is about 10 μm.

[0053] Example 4:

[0054] (1) Select cerium oxide powder, add a 5wt% PVA solution, mix evenly in a ball mill to obtain mixture A, the amount of PVA solution added accounts for 4wt% of the mass fraction of mixture A; select zirconia powder, add a 3wt% PVA solution, mix evenly in a ball mill to obtain mixture B, the amount of PVA solution added accounts for 7wt% of the mass fraction of mixture B; caking mixture A and mixture B at 25℃ for 24h respectively;

[0055] (2) Weigh the mixture A and mixture B after tamping according to a mass ratio of 1:2. Using a layered pressing method, first add the mixture A after tamping to the mold, then add the mixture B after tamping. Press the powder into a blank at 170MPa. Then, mixture A is located in the inner layer and mixture B is located in the outer layer.

[0056] (3) Place the molded blank in a drying oven and dry it at 60°C for 10 hours, and then at 110°C for 7 hours;

[0057] (4) Place the dried billet into an electric furnace for calcination. The heating rate is 8℃ / min, the calcination temperature is 1700℃, and the holding time is 2h. After the holding time is completed, let it cool naturally to room temperature to obtain a high-temperature alloy melting crucible.

[0058] In this embodiment, the compressive strength of the obtained high-temperature alloy melting crucible sample is 214 MPa, the strength retention rate after thermal shock is 91.5%, and after the K417G alloy erosion test, there is no obvious cracking and penetration phenomenon at the interface, and the erosion depth of the alloy on the sample is about 17 μm.

[0059] Example 5:

[0060] (1) Select yttrium oxide powder, add a 3wt% PVA solution, mix evenly in a ball mill to obtain mixture A, the amount of PVA solution added accounts for 8wt% of the mass fraction of mixture A; select zirconium oxide powder, add a 5wt% PVA solution, mix evenly in a ball mill to obtain mixture B, the amount of PVA solution added accounts for 4wt% of the mass fraction of mixture B, and conditioned mixture A and mixture B at 25℃ for 24h respectively;

[0061] (2) Weigh the mixture A and mixture B after tamping according to a mass ratio of 1:3. Using a layered pressing method, first add the mixture A after tamping to the mold, then add the mixture B after tamping. Press the powder into a blank at 120MPa. Then, mixture A is located in the inner layer and mixture B is located in the outer layer.

[0062] (3) Place the molded blank in a drying oven and dry it at 60°C for 12 hours, and then at 120°C for 8 hours;

[0063] (4) Place the dried billet into an electric furnace for calcination. The heating rate is 2℃ / min, the calcination temperature is 1600℃, and the holding time is 5h. After the holding time is completed, let it cool naturally to room temperature to obtain a high-temperature alloy melting crucible.

[0064] In this embodiment, the compressive strength of the obtained high-temperature alloy melting crucible sample was 241 MPa, and the strength retention rate after thermal shock was 92.4%. After the K417G alloy erosion test, there was no bursting metal penetration at the interface, and the alloy erosion depth of the sample was about 12 μm.

[0065] Comparative Example 1

[0066] (1) Select zirconium oxide powder, add a 2wt% PVA solution, mix evenly in a ball mill to obtain a mixture. The amount of PVA solution added accounts for 5wt% of the mass fraction of the mixture. The mixture is then left to stand at 25°C for 24 hours.

[0067] (2) Add the mixture after the material has been trapped into the mold and press it into a blank at 150MPa;

[0068] (3) Place the molded blank in a drying oven and dry it at 60°C for 6 hours, and then at 110°C for 12 hours;

[0069] (4) The dried blank is placed in an electric furnace for calcination. The heating rate is 5℃ / min, the calcination temperature is 1650℃, and the holding time is 3h. After the holding time is completed, it is naturally cooled to room temperature to obtain a crucible.

[0070] In this comparative example, the compressive strength of the obtained crucible sample was 205 MPa, and the strength retention rate after thermal shock was 86.2%. After the K417G alloy erosion test, local metal penetration and microcracks appeared at the interface, and the alloy erosion depth of the sample was about 41 μm. This indicates that the crucible made of zirconia alone has decent thermal shock resistance, but insufficient resistance to alloy erosion / penetration, and its overall performance is not as good as the gradient structure crucible of this invention.

[0071] Comparative Example 2

[0072] (1) Select yttrium oxide powder, add a 2wt% PVA solution, mix evenly in a ball mill to obtain a mixture. The amount of PVA solution added accounts for 5wt% of the mass fraction of the mixture. The mixture is then left to stand at 25°C for 24 hours.

[0073] (2) Add the mixture after the material has been trapped into the mold and press it into a blank at 150MPa;

[0074] (3) Place the molded blank in a drying oven and dry it at 60°C for 6 hours, and then at 110°C for 12 hours;

[0075] (4) The dried blank is placed in an electric furnace for calcination. The heating rate is 5℃ / min, the calcination temperature is 1650℃, and the holding time is 3h. After the holding time is completed, it is naturally cooled to room temperature to obtain a crucible.

[0076] In this comparative example, the compressive strength of the obtained crucible sample was 190 MPa, and the strength retention rate after thermal shock was 64.7%. After thermal shock, through-cracks or edge chipping appeared on the sample surface. After the K417G alloy erosion test, there was no obvious bursting or penetration phenomenon overall, and the alloy erosion depth of the sample was approximately 18 μm. This indicates that only the yttrium oxide crucible has good resistance to alloy erosion, but its thermal shock resistance is poor, and its strength retention rate after thermal shock is low. It is difficult to handle the rapid temperature change conditions during high-temperature melting, and its overall performance is inferior to that of this invention.

[0077] Please see Figure 1 This is a scanning electron microscope (SEM) image of the high-temperature alloy melting crucible prepared in Example 2 of this invention. Figure 1 It can be seen that a gradient structure ceramic crucible was successfully prepared, and the interface bonding is strong.

[0078] Please see Figure 2 and Figure 3 , respectively Figure 1 Distribution maps of Y and Zr elements in surface scan analysis. From Figure 2 and Figure 3 It can be seen that, Figure 1 The left side shows a zirconium oxide layer, and the right side shows a yttrium oxide layer. The yttrium oxide layer has a dense structure and can resist alloy corrosion, while the zirconium oxide layer can give the material excellent thermal shock resistance. In addition, it can be seen that Y element diffuses into the zirconium oxide layer and Zr element diffuses into the yttrium oxide layer, indicating the formation of a stable solid solution structure.

[0079] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any way. The present invention can also have other embodiments based on the above structure and function, which will not be listed hereafter. Therefore, any simple modifications, equivalent changes, and alterations made by those skilled in the art to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a high-temperature alloy melting crucible with a gradient structure, characterized in that, Specifically, the following steps are included: (1) Select rare earth oxides, add binders, mix evenly to obtain mixture A; select zirconium oxide, add binders, mix evenly to obtain mixture B, and then process mixtures A and B separately. (2) Weigh out the mixture A and B after the material is trapped according to a certain ratio, and press them in layers. First, add the mixture A after the material is trapped into the mold, and then add the mixture B after the material is trapped. That is, place the mixture B after the material is trapped on top of the mixture A after the material is trapped, and press it into a blank at 120-180MPa. (3) Place the shaped blank into a drying oven; (4) Place the dried billet into an electric furnace for calcination. The heating rate is 2-8℃ / min, the calcination temperature is 1600-1700℃, and the holding time is 2-5h. After the holding time is completed, let it cool naturally to room temperature to obtain a high-temperature alloy melting crucible.

2. The method for preparing a high-temperature alloy melting crucible with a gradient structure as described in claim 1, characterized in that, The rare earth oxide mentioned in step (1) is one or more of Y2O3, CeO2 and La2O3, with a particle size ≤0.075mm; in the chemical composition of the zirconium oxide, ZrO2>99.5wt% and particle size ≤0.044mm.

3. The method for preparing a high-temperature alloy melting crucible with a gradient structure as described in claim 2, characterized in that, In step (1), when the rare earth oxide is multiple of Y2O3, CeO2 and La2O3, the raw materials that make up the rare earth oxide are first premixed, and then a binder is added and mixed evenly to obtain mixture A.

4. The method for preparing a high-temperature alloy melting crucible with a gradient structure as described in claim 1, characterized in that, The binder mentioned in step (1) is a polyvinyl alcohol solution with a concentration of 2wt%-5wt%, and its addition amount in mixture A or mixture B is 4wt%-8wt%.

5. The method for preparing a high-temperature alloy melting crucible with a gradient structure as described in claim 1, characterized in that, In step (1), the mixtures were mixed evenly in a ball mill; mixtures A and B were then conditioned at 25°C for 24 hours.

6. The method for preparing a high-temperature alloy melting crucible with a gradient structure as described in claim 1, characterized in that, In step (2), the mass ratio of mixture A and mixture B after the material is trapped is 1:1 to 1:

5.

7. The method for preparing a high-temperature alloy melting crucible with a gradient structure as described in claim 1, characterized in that, In step (3), the shaped blank is placed in a drying oven and dried at 60°C for 6-12 hours, and then dried at 110-120°C for 6-12 hours.

8. The high-temperature alloy melting crucible obtained by any one of the preparation methods described in claims 1 to 7.

9. The high-temperature alloy melting crucible as described in claim 8, characterized in that, From the inside out, it consists of an inner layer of rare earth oxides, an intermediate layer of rare earth oxides-zirconia solid solution, and an outer layer of zirconia.

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