High-purity, high-thermal shock resistance zirconia crucible for superalloys

Abstract

The application belongs to the field of refractory materials, and relates to high-purity and high-thermal shock resistance zirconia crucible for high-temperature alloy and a preparation method thereof. The crucible adopts sintered partially stabilized zirconia particles, fused stabilized zirconia fine powder and monoclinic zirconia fine powder as main raw materials. In the application, calcium oxide and monoclinic zirconia fine powder are fully ball milled, 5-7% concentration polyvinyl alcohol solution is added, a green body is formed by vibration, and then sintering is performed at 1750-1800 DEG C. Subsequently, the sintered partially stabilized zirconia raw material with high monoclinic phase is prepared by crushing. The prepared raw material is added with a binder and machine-pressed into a crucible. Finally, the crucible is composed of the following components by weight ratio: (ZrO2+HfO2): 91.5%-97.5%; CaO: 2-3% or Y2O3: 5-7%. The green body of the crucible is sintered at 1680-1720 DEG C, and finally the high-purity and high-thermal shock resistance zirconia crucible is prepared. The application greatly improves the thermal shock resistance of the zirconia crucible, prolongs the service life, and does not cause pollution to the alloy solution.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of refractory materials, and particularly relates to a high-purity high-thermal-shock-resistance zirconia crucible for high-temperature alloy. BACKGROUND

[0002] High-temperature alloy is an irreplaceable key material for high-temperature parts of aviation industry and gas turbine, and the comprehensive performance of the high-temperature alloy directly restricts the development of aviation and gas turbine. The purity of the master alloy is one of the key factors for the manufacturing level of the high-temperature alloy, and the content of harmful impurities has a significant impact on the alloy performance. At present, vacuum induction melting is the main method for producing high-temperature alloy. The refractory material is used as the container of the alloy, but the alloy is still polluted by the refractory material due to the damage and reaction of the refractory material during high-temperature process, which affects the quality of the alloy and reduces the performance of the alloy.

[0003] At present, the common refractory material crucible mainly uses magnesia-alumina spinel or stabilized zirconia. The former is mainly prepared by the traditional forming method of refractory material, which leads to uneven structure and composition of the crucible, high overall porosity, and poor thermal shock resistance. More importantly, magnesium oxide is more likely to volatilize during use due to its high vapor pressure, and the alloy is more severely penetrated and eroded by the crucible, which causes the cracking and damage of the crucible and cannot meet the smelting requirements of the high-temperature alloy. The latter stabilized zirconia crucible has a wide application prospect. Compared with the magnesia-alumina spinel crucible, it fully guarantees the purity of the refractory material, significantly reduces the pollution of the refractory material to the alloy, and to some extent, improves the use frequency of the crucible. However, the crucible is still damaged and cracked due to poor thermal shock resistance during use, which reduces the service life of the crucible and restricts its development. Both of the above two kinds of crucible materials have the problems of short service life and low reuse frequency. In addition, relevant literature indicates that the thermal expansion coefficient of cubic zirconia is the largest and increases with temperature, so the material mainly composed of cubic zirconia has poor thermal shock resistance. In addition, general research shows that the thermal shock resistance of sintered raw materials is significantly better than that of electrically fused materials. If the related theory is used as a guide, a partially stabilized sintered zirconia raw material mainly composed of monoclinic phase is prepared, and a zirconia crucible product with excellent thermal shock resistance is expected to be developed. Therefore, it is very meaningful to develop a zirconia crucible with uniform structure, high purity and high thermal shock stability for improving the purity and service life of the high-temperature alloy crucible on the basis of the existing high-temperature alloy smelting technology. SUMMARY

[0004] The purpose of the present application is to provide a high-purity high-thermal-shock-resistance zirconia crucible for high-temperature alloy, which has high strength, good high-temperature volume stability and does not pollute the alloy solution during use, thereby significantly improving the service life of the crucible body.

[0005] To solve the above technical problems, the application adopts the following technical solutions:

[0006] A high-purity and high-thermal shock resistance zirconia crucible for high-temperature alloy, raw materials of the zirconia crucible and mass percentage are as follows: sintered partially stabilized zirconia particles 45-60%, fused stabilized zirconia fine powder 35-40%, and monoclinic zirconia micro powder 2-5%; the total mass of the raw materials of the zirconia crucible is 100%, and an organic binder is additionally added, and ZrO2+HfO2+stabilizer in the zirconia crucible product is greater than or equal to 99%.

[0007] The stabilizer of the partially sintered stabilized zirconia and the fused stabilized zirconia fine powder is one of calcium oxide or yttrium oxide.

[0008] The preparation method of the sintered partially stabilized zirconia particles is as follows: the monoclinic zirconia micro powder and the stabilizer are mixed according to the ratio of ZrO2 / CaO or ZrO2 / Y2O3=(95-98) / (2-5), and the two are fully mixed by using a ball mill for 30-60 minutes; then 4.5% of the polyvinyl alcohol binder with a concentration of 5-7% is added, and the mixture is uniformly mixed in a stirring pot, and then the green brick is pressed on a vibration molding machine, dried at 110°C, sintered at 1750-1800°C, and finally the sintered green brick is crushed and sieved to obtain the sintered partially stabilized zirconia particles; the volume density of the prepared particles is greater than or equal to 5 g / cm 3 , and the monoclinic phase content of zirconia is 65-75%.

[0009] The particle size of the sintered partially stabilized zirconia particles is 0.2-1.5 mm, the particle size of the fused stabilized zirconia fine powder is less than or equal to 0.045 mm, the particle size of the monoclinic zirconia is less than or equal to 0.5 μm, the calcium oxide is an analytically pure reagent with a particle size of less than or equal to 0.074 mm, and the yttrium oxide has a particle size of less than or equal to 0.044 mm.

[0010] The purity of the sintered partially stabilized zirconia particles is greater than or equal to 97.5%, the purity of the fused stabilized zirconia fine powder and the monoclinic zirconia is greater than or equal to 99%, the purity of the analytically pure calcium oxide is greater than or equal to 99%, and the purity of the yttrium oxide is greater than or equal to 99%.

[0011] The binder used for the formed crucible is a solution of one or two kinds of phenolic resin, epoxy resin or water-based resin mixed in any ratio, and the addition amount is 3-5% of the total mass of the zirconia crucible raw materials.

[0012] The zirconia crucible is formed by machine pressing under a pressure of 150-200 MPa.

[0013] The preparation method of the high-purity and high-thermal shock resistance zirconia crucible for high-temperature alloy comprises the following steps: uniformly mixing sintered partially stabilized zirconia particles, fused stabilized zirconia fine powder, monoclinic zirconia micro powder and a binder according to a proportion, forming a green body by machine pressing in a mold, drying at a temperature of 40-110 ℃, and then sintering at 1680-1720 ℃ to obtain the zirconia crucible for high-temperature alloy.

[0014] Through the above technical scheme, the product has the following excellent performances and characteristics:

[0015] 1) The raw materials used in the product are mainly high-purity zirconia, and no other impurities are introduced in the preparation process, so that the purity and use temperature of the product are not reduced; the high-purity product ensures the purity of the alloy and does not pollute the product.

[0016] 2) The aggregate used is sintered monoclinic zirconia with a relatively high content of monoclinic zirconia, and the increase of the content of monoclinic zirconia and the use of sintered raw materials can improve the thermal shock stability of the material; the added zirconia micro powder has the characteristics of fine particle size and high activity, which ensures the sintering of the product; the above factors can make the product have the characteristics of high strength and high thermal shock resistance. DETAILED DESCRIPTION

[0017] The application will be described in combination with specific examples:

[0018] Example 1: The process and scheme described in the application are used, the sintered partially CaO stabilized zirconia aggregate with a particle size of 0.2-1.5 mm accounts for 60%, the fused CaO stabilized zirconia fine powder with a particle size of ≤0.045 mm accounts for 38%, the monoclinic zirconia micro powder with a particle size of ≤0.5 μm accounts for 2%, and 4% of epoxy resin binder is added, the above raw materials are uniformly mixed, the crucible green body is formed by machine pressing in a mold, dried at 110 ℃, and then sintered at a high temperature of 1720 ℃, so that the high-purity and high-thermal shock resistance alloy crucible is obtained.

[0019] Example 2: The process and scheme described in the application are used, the sintered partially CaO stabilized zirconia aggregate with a particle size of 0.2-1.5 mm accounts for 55%, the fused CaO stabilized zirconia fine powder with a particle size of ≤0.045 mm accounts for 40%, the monoclinic zirconia micro powder with a particle size of ≤0.5 μm accounts for 5%, and 4% of phenolic resin binder is added, the above raw materials are uniformly mixed, the crucible green body is formed by machine pressing in a mold, dried at 110 ℃, and then sintered at a high temperature of 1720 ℃, so that the high-purity and high-thermal shock resistance alloy crucible is obtained.

[0020] Example 3: Using the process and scheme described in the present application, 65% of sintered CaO stabilized zirconia aggregate with a particle size of 0.2-1.5 mm, 32% of electrically fused CaO stabilized zirconia fine powder with a particle size of ≤0.045 mm, 3% of monoclinic zirconia micropowder with a particle size of ≤0.5 μm, and 4% of water-based resin binder are mixed uniformly, and the mixture is machine-pressed into a crucible blank in a mold, dried at 60°C, and then fired at a high temperature of 1680°C to obtain an alloy crucible with high purity and high thermal shock stability.

[0021] Example 4: Using the process and scheme described in the present application, 60% of sintered CaO stabilized zirconia aggregate with a particle size of 0.2-1.5 mm, 38% of electrically fused CaO stabilized zirconia fine powder with a particle size of ≤0.045 mm, 2% of monoclinic zirconia micropowder with a particle size of ≤0.5 μm, and 4% of phenolic resin binder are mixed uniformly, and the mixture is machine-pressed into a crucible blank in a mold, dried at 110°C, and then fired at a high temperature of 1680°C to obtain an alloy crucible with high purity and high thermal shock stability.

[0022] The alloy zirconia crucible prepared according to the above examples has a higher use temperature and purity than other existing schemes, ZrO2+HfO2+stabilizer ≥99.5%, and the crucible has a good high-temperature stability with a 1100°C air-cooled thermal shock resistance ≥15 times according to relevant national standards.

Claims

1. A high-purity, high-thermal shock resistance zirconia crucible for high-temperature alloys, characterized by: The raw materials and mass percentage used for the zirconia crucible are: 45-60% of sintered partially stabilized zirconia particles, 35-40% of fused stabilized zirconia fine powder, and 2-5% of monoclinic zirconia micro powder; the total mass of the raw materials is 100%, and an organic binder is additionally added; ZrO2+HfO2+stabilizer in the zirconia crucible product is ≥99%; the preparation method of the sintered partially stabilized zirconia particles is: the monoclinic zirconia micro powder and the stabilizer are mixed in a ratio of ZrO2 / CaO or ZrO2 / Y2O3=95-98 / 2-5, and first ground together for 30-60 minutes by using a ball mill to fully mix them; then 4.5% of a polyvinyl alcohol binder with a concentration of 5-7% is added, and the mixture is uniformly mixed in a stirring pot, and then pressed into a brick body on a vibration molding machine, dried at 110°C, sintered at 1750-1800°C, and finally broken and sieved to obtain the sintered partially stabilized zirconia particles; the volume density of the prepared particles is ≥5g / cm 3 , and the monoclinic zirconia content is 65-75%; the preparation method of the zirconia crucible is: the sintered partially stabilized zirconia particles, the fused stabilized zirconia fine powder, the monoclinic zirconia micro powder, and the binder are mixed in a ratio, uniformly formed into a green body by using a die machine, dried at a temperature of 40-110°C, and then sintered at 1680-1720°C to obtain the zirconia crucible for high-temperature alloy.

2. The high purity, high thermal shock resistance zirconia crucible for superalloys according to claim 1, characterized in that: The whole crucible has the following chemical composition in percentage of oxide weight: (ZrO2+HfO2): 91.5%-97.5%; CaO: 2-3% or Y2O3: 5-7%; 0.5% of other trace impurities which are oxides. The stabilizer of the partially stabilized sintered zirconia and the fine electrically fused stabilized zirconia powder is one of CaO or Y2O3.

3. The high purity, high thermal shock resistance zirconia crucible for superalloys of claim 1, wherein: The particle size of the sintered partially stabilized zirconia particles is 0.2-1.5mm, the particle size of the fine electrically fused stabilized zirconia powder is ≤0.045mm, the particle size of the monoclinic zirconia micro powder is ≤0.5μm, the CaO is an analytically pure reagent with a particle size of ≤0.074mm; the particle size of the Y2O3 is ≤0.044mm.

4. The high purity, high thermal shock resistant zirconia crucible for superalloys of claim 1 wherein: The purity of the sintered partially stabilized zirconia particles is ≥97.5%, the purity of the fine electrically fused stabilized zirconia powder and the monoclinic zirconia micro powder is ≥99%, the purity of the analytically pure calcium oxide is ≥99%, and the purity of the yttrium oxide is ≥99%.

5. The high purity, high thermal shock resistant zirconia crucible for superalloys of claim 1 wherein: The binder is one or a mass mixed solution of two of phenolic resin, epoxy resin or water-based resin in any proportion, and the addition amount is 3-5% of the total mass of the zirconia crucible raw materials.

6. The high purity, high thermal shock resistant zirconia crucible for superalloys of claim 1 wherein: The zirconia crucible is formed by machine pressing under a pressure of 150-200MPa.

7. The high purity, high thermal shock resistant zirconia crucible for superalloys of claim 1 wherein: The high-temperature heat treatment temperature of the zirconia crucible is 1680-1720℃.

8. The high purity, high thermal shock resistant zirconia crucible for superalloys of claim 1 wherein: ​