An erosion resistant, infiltrated yttria refractory material, method of making and use

Abstract

The application discloses an anti-erosion yttrium oxide infiltrated refractory material, a preparation method and application. The method is characterized by adding a small amount of sintering aid powder into Y2O3 powder to reduce the sintering temperature, and meanwhile, the particle size of the powder, the cold isostatic pressing parameter and the sintering process are adjusted to prepare the Y2O3 refractory material with high density, large size grain and no second phase. The method is suitable for preparing the Y2O3 crucible powder and the cold isostatic pressing Y2O3 crucible, and can effectively improve the anti-erosion infiltration capacity of the crucible to the titanium-aluminum alloy melt.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials, specifically relating to an erosion-resistant and penetrating yttrium oxide refractory material, its preparation method, and its uses. Background Technology

[0002] Oxide crucibles, replacing water-cooled copper crucibles in titanium-aluminum alloy smelting, can increase the melt superheating temperature and reduce energy consumption. Compared with refractories such as alumina, magnesia, and zirconium oxide, yttrium oxide (Y₂O₃) has high thermodynamic stability and high chemical inertness towards titanium-aluminum alloys. Using Y₂O₃ crucibles can reduce oxygen contamination of the ingot. Besides thermodynamic factors, the density of Y₂O₃ refractories affects the degree of interfacial reaction between the alloy melt and the refractory material. When the Y₂O₃ refractories have fine grains and a loose, porous structure, melt intrusion can lead to grain melting, increasing the number of inclusions and oxygen content within the alloy. Increasing the density of the refractory material helps inhibit melt diffusion into the refractory material, reducing the contact area between the melt and the oxide, and mitigating the interaction.

[0003] However, Y₂O₃ has a melting point greater than 2400℃, requiring a high sintering temperature (not less than 1700℃) to achieve high density, which increases manufacturing costs and performance requirements for production equipment. Chinese patent application CN202210099193.5 discloses a method and crucible for preparing yttrium oxide refractory products using gel casting molding. The crucible is prepared using pure yttrium oxide powder, and the required sintering temperature for the green body is 1750℃~1850℃, placing high demands on equipment. To lower the sintering temperature and improve the density of Y₂O₃ refractory materials, a second phase can be added (Li H, Liu Y, Yang J, et al. Preparation and application evaluation of La₂O₃-doped Y₂O₃ crucible materials for melting TiAlalloys. Ceram Int. 2022;48:15762-15769.). The patented technology, "A Method for Low-Temperature Sintering of Yttrium Oxide Ceramic Crucibles" (202110388155.7), uses magnesium oxide powder and titanium oxide powder as sintering aids to lower the sintering temperature of yttrium oxide ceramics. However, this method results in a large number of second phases in the microstructure. The presence of numerous second phases with low thermodynamic stability exacerbates the interaction between the material and the alloy. Therefore, it is necessary to select appropriate element types and control the amount of elements added. Summary of the Invention

[0004] The purpose of this invention is to provide a method for reducing the sintering temperature of Y2O3 and increasing the density of Y2O3 refractory materials by adding sintering aids. The preparation method is simple and applicable to the preparation of Y2O3 crucible powder and cold isostatic pressing of Y2O3 crucibles, which can effectively improve the crucible's resistance to erosion and penetration.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing an erosion-resistant and permeable yttrium oxide refractory material, comprising the following steps:

[0007] (1) Powder pretreatment: Y2O3 powder and sintering aid powder are mixed in proportion, and an equal mass of anhydrous ethanol is added to the mixture for ball milling. Then, the mixture is dried and solid-phase sintered to obtain Y2O3 powder with doped element solid solution and then ball milled again. The sintering aid powder is one of TiO2, SrO and CaO.

[0008] (2) Green blank forming: PVA aqueous solution is added to the powder obtained after ball milling, and after mixing evenly, it is granulated; the granulated powder is dry-pressed into discs at 4~6 MPa, and then the discs are heated to 400~800℃ and kept at 3~5h to decompose PVA; finally, the discs are subjected to cold isostatic pressing at 180~200 MPa;

[0009] (3) Sintering: The circular blank is placed in a muffle furnace for high-temperature sintering to obtain the Y2O3 refractory material.

[0010] Furthermore, the purity of the Y2O3 and sintering aid powder is 99.99%, and the particle size range is 1~3μm.

[0011] Furthermore, the molar ratio of Y2O3 to sintering aid powder is 100:1 to 5, preferably 100:1.

[0012] Furthermore, in step (1), the ball milling time is 12~24 h and the rotation speed is 190~220 r / min.

[0013] Furthermore, in step (1), solid-state sintering refers to heating the furnace to 1300~1350℃ at a rate of 3~5℃ / min, holding the temperature for 10~12h, and then cooling it with the furnace.

[0014] Furthermore, in step (2), the amount of PVA aqueous solution used is 6-10% of the powder mass, and the concentration of PVA aqueous solution is 5-10 wt.%.

[0015] Furthermore, in step (2), the particle size of the powder obtained by granulation is 120~200 mesh.

[0016] Furthermore, in step (2), the holding time for cold isostatic pressing is 1000~1800 s.

[0017] Furthermore, in step (3), the sintering temperature is 1650℃~1700℃, the holding time is 8~16 h, and the heating rate is 2~5℃ / min.

[0018] In a second aspect, the present invention provides an erosion-resistant and permeable yttrium oxide refractory material prepared by the method described in the first aspect.

[0019] Thirdly, the present invention provides a crucible material, which is an erosion-resistant and permeable yttrium oxide refractory material prepared by the method described in the first aspect.

[0020] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0021] This invention selects raw materials with a purity of 99.99% for preparation to avoid excessive impurities that could lead to the formation of a second phase. A small amount of sintering aid is uniformly mixed with Y₂O₃ powder through ball milling, and the sintering aid is fully dissolved into the Y₂O₃ through solid-state sintering. Simultaneously, by controlling the particle size of the powder and the cold isostatic pressing parameters, a green body with high bulk density is obtained. The green body can form a high-density, large-grained refractory material without second-phase precipitation at a relatively low sintering temperature. The method of this invention can significantly reduce the diffusion depth of alloy melts (e.g., titanium-aluminum alloys) in refractory materials and reduce the contact area between the melt and the refractory material. Attached Figure Description

[0022] Figure 1 These are SEM images of refractory material cross-sections obtained from the embodiments and comparative examples of the present invention: (a): Example 1, (b): Example 2, (c): Example 3, (d): Comparative Example 1.

[0023] Figure 2 The microstructure (a) and elemental distribution (b) of the interface after the reaction between the refractory material obtained in Example 1 and the TiAl alloy melt are shown.

[0024] Figure 3 The microstructure (a) and elemental distribution (b) of the interface after the refractory material obtained in Example 2 reacts with the TiAl alloy melt are shown.

[0025] Figure 4 The microstructure (a) and elemental distribution (b) of the interface after the reaction between the refractory material obtained in Example 3 and the TiAl alloy melt are shown.

[0026] Figure 5 The microstructure (a) and elemental distribution (b) of the interface after the reaction of the refractory material obtained in Comparative Example 1 with the TiAl alloy melt are shown. Detailed Implementation

[0027] The present invention will be further described in detail below through specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are still within the scope of protection of the present invention.

[0028] It should be noted that terms such as "upper", "lower", "left", "right", and "middle" used in this specification are only for clarity of description and are not intended to limit the scope of implementation. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as within the scope of this application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0030] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0031] As used herein, the term “about” is used to provide for the flexibility and imprecision associated with a given term, measure, or value. Those skilled in the art can readily determine the degree of flexibility for a particular variable.

[0032] As used herein, the term “at least one of…” is intended to be synonymous with “one or more of…”. For example, “at least one of A, B, and C” explicitly includes only A, only B, only C, and combinations thereof.

[0033] This application provides a carborane sulfide compound and its preparation method. Detailed descriptions follow. It should be noted that the order of description in the following embodiments is not intended to limit the preferred order of embodiments. Furthermore, in the description of this application, various embodiments of the invention may be presented in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 5, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0034] Example 1

[0035] (1) Powder pretreatment: Y2O3 powder and TiO2 were mixed at a molar ratio of 100:1. An equal mass of anhydrous ethanol was added to the resulting mixture and ball-milled for 24 h at a speed of 220 r / min. The mixture was then dried and solid-state sintered in a high-temperature muffle furnace, with the temperature increased to 1300℃ at a rate of 5℃ / min and held for 10 h. After sintering, Y2O3 powder with Ti element solid solution was obtained and then ball-milled again.

[0036] (2) Green body forming: 10 wt% PVA aqueous solution (concentration of 10 wt.%) is added dropwise to the powder, mixed evenly and then granulated; the granulated powder is dry-pressed into discs at 4 MPa. The discs are then heated to 600℃ and kept at that temperature for 5 hours to decompose the PVA; finally, they are subjected to cold isostatic pressing at 200 MPa for 1800 s.

[0037] (3) Sintering: The green blank is sintered at a high temperature of 1700℃, and then cooled in the furnace after being held at the sintering temperature for 8 hours to obtain the yttrium oxide refractory material. Its cross-section SEM is shown in Figure 1. Figure 1 As shown in (a) of Table 1, the Ti-containing Y2O3 refractory material is dense with a cross-sectional porosity of 0.02%.

[0038] The obtained refractory material was placed between two TiAl alloy pieces and reacted in an induction vacuum levitation furnace. The specific microstructure of the interface after the reaction between the refractory material and the TiAl alloy melt is as follows: Figure 2As shown, no obvious reaction layer appeared between the refractory material and the melt, and there was no obvious enrichment of Al element inside the refractory material. This indicates that the refractory material can significantly reduce the diffusion depth of titanium-aluminum alloy in the refractory material and reduce the contact area between the melt and the refractory material.

[0039] Example 2

[0040] (1) Powder pretreatment: Y2O3 powder and SrO were mixed in a ratio of 100:1. An equal mass of anhydrous ethanol was added to the mixture and ball-milled for 12 h at a speed of 220 r / min. The mixture was then dried and solid-state sintered in a high-temperature muffle furnace at a rate of 5 °C / min to 1300 °C and held for 10 h. After sintering, Y2O3 powder with Sr element solid solution was obtained and then ball-milled again.

[0041] (2) Green body forming: 10 wt% PVA aqueous solution (concentration of 5 wt.%) is added dropwise to the powder, and after mixing evenly, it is granulated; the granulated powder is dry-pressed into discs at 4 MPa. Then the discs are heated to 600℃ and kept at 5h to decompose PVA; finally, they are subjected to cold isostatic pressing at 200 MPa for 1800 s.

[0042] (3) Sintering: The green blank is sintered at a high temperature of 1650℃, and then cooled in the furnace after being held at the sintering temperature for 12 hours to obtain the yttrium oxide refractory material. Its cross-section SEM is shown in Figure 1. Figure 1 As shown in (b) of the table, the Sr-containing Y2O3 refractory material is dense with a cross-sectional porosity of 0.6%, as shown in Table 1.

[0043] The specific microstructure of the interface after its reaction with TiAl alloy melt is as follows: Figure 3 As shown, no obvious reaction layer appeared between the refractory material and the melt, and there was no obvious enrichment of Al element inside the refractory material.

[0044] Example 3

[0045] (1) Powder pretreatment: Y2O3 powder and CaO were mixed in a ratio of 100:1. An equal mass of anhydrous ethanol was added to the mixture and ball-milled for 18 h at a speed of 200 r / min. The mixture was then dried and solid-state sintered in a high-temperature muffle furnace at a rate of 3 °C / min to 1300 °C and held for 10 h. After sintering, Y2O3 powder with CaO element solid solution was obtained and then ball-milled again.

[0046] (2) Green body forming: 10 wt% PVA aqueous solution (concentration of 8 wt.%) is added dropwise to the powder, and after mixing evenly, it is granulated; the granulated powder is dry-pressed into discs at 4 MPa. Then the discs are heated to 600℃ and kept at 5 h to decompose PVA; finally, they are subjected to cold isostatic pressing at 200 MPa for 1800 s.

[0047] (3) Sintering: The green blank is sintered at a high temperature of 1700℃ and held at the sintering temperature for 8 h before being cooled in the furnace to obtain the yttrium oxide refractory material. Its cross-section SEM is shown in Figure 1. Figure 1 As shown in (c), the CaO-containing Y2O3 refractory material is dense with a cross-sectional porosity of 0.2%, as shown in Table 1.

[0048] The specific microstructure of the interface after its reaction with TiAl alloy melt is as follows: Figure 4 As shown, no obvious reaction layer appeared between the refractory material and the melt, and there was no obvious enrichment of Al element inside the refractory material.

[0049] Comparative Example 1

[0050] The remaining processes are the same as in Example 1, without the addition of sintering aids, to obtain yttrium oxide refractory material, the cross-section of which is shown in the SEM image. Figure 1 As shown in (d) in the figure, the grain size is small and the porosity is high after sintering. The cross-sectional porosity is 8.9%, as shown in the table.

[0051] The specific microstructure of its reaction interface with TiAl alloy is as follows: Figure 5 As shown, there are obvious pores on the side of the ceramic sheet, and the interface between the alloy and the ceramic is clear. Observation of the surface scan reveals that there is Al element infiltration in the crucible, which means that the refractory material has poor resistance to melt erosion and infiltration.

[0052] Table 1

[0053]

[0054] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing an erosion-resistant and permeable yttrium oxide refractory material, characterized in that, Includes the following steps: (1) Powder pretreatment: Y2O3 powder and sintering aid powder are mixed in proportion, and an equal mass of anhydrous ethanol is added to the mixture for ball milling. Then, the mixture is dried and solid-phase sintered to obtain Y2O3 powder with doped element solid solution. The powder is then ball milled again. The sintering aid powder is one of TiO2, SrO, and CaO. The molar ratio of Y2O3 to sintering aid powder is 100:1~5. The purity of Y2O3 powder and sintering aid powder is 99.99%, and the particle size range is 1~3μm. Solid-phase sintering refers to heating to 1300~1350℃ in a muffle furnace at a heating rate of 3~5℃ / min, holding for 10~12h, and then cooling with the furnace. (2) Green body forming: PVA aqueous solution is added to the powder obtained after ball milling and mixed evenly, and then granulated; the granulated powder is dry-pressed into discs at 4~6 MPa, and then the discs are heated to 400~800℃ and kept at 3~5h to decompose PVA; finally, the discs are subjected to cold isostatic pressing at 180~200 MPa, and the particle size of the granulated powder is 120~200 mesh; (3) Sintering: The circular blank is placed in a muffle furnace for high-temperature sintering to obtain the Y2O3 refractory material. The sintering temperature is 1650℃~1700℃, the holding time is 8~16 h, and the heating rate is 2~5℃ / min.

2. The method as described in claim 1, characterized in that, In step (1), the ball milling time is 12~24 h and the rotation speed is 190~220 r / min.

3. The method as described in claim 1, characterized in that, In step (2), the amount of PVA aqueous solution used is 6-10% of the powder mass, and the concentration of PVA aqueous solution is 5-10 wt.%.

4. The method as described in claim 1, characterized in that, In step (2), the holding time for cold isostatic pressing is 1000~1800 s.

5. An erosion-resistant and permeable yttrium oxide refractory material prepared by the method according to any one of claims 1-4.

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