Preparation process of tantalum-based coating material

Abstract

The invention relates to a preparation process of a tantalum-based coating material in the technical field of thermal insulation materials. The preparation process comprises the following steps: S1, pretreating raw materials; drying tantalum oxide and magnesium oxide, and then carrying out mixing, ball milling and screening treatment; s2, blank forming; the screened mixed powder material is pressed and molded into a blank block; s3, calcining and synthesizing; carrying out high-temperature calcination on the pressed and molded briquette to synthesize magnesium tantalate; s4, granulating and refining; carrying out crushing and granulation processing on magnesium tantalate blocks generated by calcination; s5, sintering and ceramization; the magnesium tantalate material obtained through granulation processing is pressed and molded into a green body, glue discharging and high-temperature sintering are carried out, and finally the compact magnesium tantalate ceramic is obtained. The magnesium tantalate ceramic is uniform in component, free of segregation and low in manufacturing cost, the thermal performance index can reach the application standard of ceramic for a thermal barrier coating, the preparation process is simple and efficient, high purity can be guaranteed, the raw material cost is low, and good economical efficiency is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal insulation materials, in particular to a thermal insulation coating material suitable for the surface of an aero-engine blade, and specifically relates to a preparation process of a tantalum-based coating material. Background Art

[0002] As aircraft engines evolve toward higher thrust-to-weight ratios, higher speeds, and higher fuel efficiency, combustion chamber temperatures continue to rise. Research shows that when an aircraft engine's thrust-to-weight ratio reaches 15-20, the combustion chamber flame temperature reaches 2000°C, far exceeding the operating limit of current high-temperature nickel-based alloys (1100°C). Alloy components, such as aircraft engine blades, are subject to prolonged operation in temperatures exceeding 2000°C. The alloy substrate, their primary component, faces this extreme heat, severely impacting the stability of various performance characteristics. Applying a ceramic thermal barrier coating to the alloy surface provides a cooling gradient, lowering the alloy's surface temperature and enabling long-term, effective service at these extreme operating temperatures. As the saying goes, "a new generation of coatings, a new generation of blades," each generation of performance innovation in thermal barrier coating materials represents a significant advancement in aircraft engine service life and performance. Thermal barrier coatings typically consist of a high-temperature alloy substrate, a metallic bond layer, and a surface ceramic layer, from bottom to top. Thermal barrier coating ceramic materials used in high-temperature environments have the characteristics of low thermal conductivity, high thermal expansion coefficient, high hardness and good high-temperature phase stability. As materials covering the surface of engine blades, they can provide excellent heat insulation and impact resistance protection, and can effectively ensure the normal operation of the alloy matrix in high-temperature environments exceeding 2000°C.

[0003] Currently, high-end thermal barrier coatings primarily utilize YSZ ceramics and rare earth tantalate ceramics. However, traditional YSZ tends to undergo phase transitions between monoclinic, cubic, and tetragonal phases. This reduces its performance stability and service life due to a certain degree of volume expansion and phase transitions at high temperatures. This leads to volume expansion and coating flaking, shortening component life and increasingly failing to meet the rapid iteration requirements of aircraft engines. In recent years, emerging rare earth tantalate ceramics have garnered widespread attention in the field of thermal barrier coatings and are considered a promising class of TBCs. However, the development of rare earth tantalates is hampered by the high cost of their raw materials, rare earth oxides, and the scarcity and uneven distribution of rare earth resources worldwide, which hinder their industrialization. For example, Nd2O3, Ho2O3, and Dy2O3 are all very expensive. From an economic perspective, the development of new, high-performance, low-cost coating materials is a strategic priority that urgently needs breakthroughs. Due to the nature of the materials themselves, existing thermal barrier coating ceramics are difficult to balance the advantages of performance and cost-effectiveness. As a result, existing ceramic materials either have poor performance and service life, or are difficult to form large-scale industrialization due to high costs. Therefore, it is necessary to select new ceramic materials with higher thermal performance and lower costs for larger-scale industrial production of thermal barrier coatings. Summary of the Invention

[0004] In response to the above situation, the present invention provides a preparation process for a tantalum-based coating material (magnesium tantalate ceramic coating). Magnesium tantalate also has the basic property advantages of rare earth oxide ceramics, and even has more obvious advantages in some thermal properties.

[0005] In order to achieve the above objectives, the present invention provides a process for preparing a tantalum-based coating material, comprising the following steps:

[0006] S1, raw material pretreatment; drying tantalum oxide and magnesium oxide, then mixing tantalum oxide and magnesium oxide according to a ratio, ball milling, and screening the mixed powder material after ball milling;

[0007] S2, blank forming; pressing the screened tantalum oxide and magnesium oxide mixed powder material into a briquette; S3, calcination synthesis; calcining the pressed tantalum oxide and magnesium oxide mixed material briquette at high temperature to synthesize magnesium tantalate; S4, granulation and refinement; crushing the calcined magnesium tantalate block, and granulating the crushed magnesium tantalate powder material;

[0008] S5. Sintering and ceramicization: the magnesium tantalate material obtained by the granulation process is pressed into a green body, and then the green body is subjected to high-temperature debinding and then sintered again at high temperature to obtain a dense magnesium tantalate ceramic.

[0009] Furthermore, the drying in step S1 is vacuum drying, which is to place the tantalum oxide and magnesium oxide in a vacuum drying oven for vacuum drying until the purity of the tantalum oxide and magnesium oxide is ≥99.9%.

[0010] Furthermore, the mixing in step S1 is to place tantalum oxide and magnesium oxide in a sealed can at a molar ratio of 1:4, and then use an acoustic resonance mixer to mix; preferably, a single mixing duration is 120s, repeated 5 times, and then ball milling mixing is performed using a ball mill.

[0011] Preferably, the screening in step S1 is to use a rotary vibration screen with a 60-mesh screen to screen the mixed powder material after ball milling.

[0012] Furthermore, in step S2, the compact is formed by placing the sieved mixed powder material into a mold, and then using an electric tablet press or cold isostatic pressing equipment to form a compact.

[0013] Furthermore, in step S3, the calcination synthesis is to place the pressed tantalum oxide and magnesium oxide mixture block on a corundum plate, and then place it in a muffle furnace for high-temperature calcination, raising the temperature from room temperature to 1000°C at a rate of 10°C / min, and then raising it to 1260°C at a rate of 5°C / min, and keeping it warm for 10 hours; then naturally cooling it to room temperature in the furnace, taking out the synthetic product, and obtaining magnesium tantalate.

[0014] Preferably, when the magnesium tantalate powder is granulated in step S4, appropriate amounts of polyvinyl alcohol and polyacrylic acid are added to the magnesium tantalate powder to facilitate granulation.

[0015] Furthermore, in step S5, the green body is pressed to form a green body by pressing the magnesium tantalate material obtained by granulation to 100 MPa using a cold isostatic pressing device and maintaining the pressure for 60 seconds; then the green body is placed in a muffle furnace, kept at 1500°C for 2 hours for high-temperature debinding, and then sintered at 1500°C for 6 hours to finally obtain a dense magnesium tantalate (Mg4Ta2O9) ceramic.

[0016] The present invention also includes other components that enable normal use, which are conventional means in the field. In addition, devices or components not limited in the present invention all adopt existing technologies in the field.

[0017] The beneficial effects of the present invention are as follows:

[0018] The present invention provides a preparation process for a tantalum-based coating material (magnesium tantalate ceramic coating). During the reduction of tantalum oxide by magnesium, it is discovered that the intermediate oxide phase of tantalum and magnesium, magnesium tantalate, also possesses the basic property advantages of rare earth oxide ceramics, and even has more significant advantages in certain thermal properties, showing potential for application as a thermal barrier coating ceramic material. In addition, the preparation process of magnesium tantalate is simple and efficient, while also ensuring high purity and low raw material cost, and its economic benefits are becoming increasingly prominent.

[0019] The magnesium tantalate ceramic produced by the present invention uses high-purity tantalum oxide and high-purity magnesium oxide as raw materials, and undergoes the steps of drying, mixing, ball milling, screening, briquetting and calcining synthesis, secondary ball milling and crushing, sintering and densification to synthesize two single magnesium tantalate phase ceramics. The composition is uniform and non-segregated, the production cost is low, and the thermal performance indicators can meet the application standards of ceramics for thermal barrier coatings.

[0020] Compared with the existing technology, the thermal insulation performance of the magnesium tantalate ceramics produced by the present invention is improved. According to the test, within the test temperature range of 0-1000℃, the thermal conductivity of the magnesium tantalate (Mg4Ta2O9) ceramics is (1.94-3.02W·m -1 ·K -1 ), the lowest thermal conductivity is lower than DyTaO4 (1.80-3.45W·m -1 ·K -1 ) and traditional YSZ (2.38-3.02W·m -1 ·K -1 ), the thermal insulation and cooling effect of thermal barrier coating has been improved to a certain extent. Secondly, in terms of thermal expansion coefficient, magnesium tantalate (Mg4Ta2O9) ceramics are 11.1×10 -6 K -1 (1000℃), which is better than some rare earth tantalates ScTaO4 (6.4×10 -6 K -1 ), SmTaO4(10.7×10 -6 K -1 ), and its stability at high temperatures has also been greatly improved. It can be used as a new material in the current thermal barrier ceramic system and can well adapt to the performance and life requirements of thermal barrier coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Flow chart of the preparation process of tantalum-based coating material (magnesium tantalate ceramic coating) in the embodiment. DETAILED DESCRIPTION

[0022] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments.

[0023] Example

[0024] like Figure 1 As shown, the present invention provides a preparation process of a tantalum-based coating material (magnesium tantalate ceramic coating), comprising the following steps:

[0025] S1, raw material pretreatment; drying tantalum oxide and magnesium oxide, then mixing tantalum oxide and magnesium oxide according to a ratio, ball milling, and screening the mixed powder material after ball milling;

[0026] S2, blank forming; pressing the screened tantalum oxide and magnesium oxide mixed powder material into a briquette; S3, calcination synthesis; calcining the pressed tantalum oxide and magnesium oxide mixed material briquette at high temperature to synthesize magnesium tantalate; S4, granulation and refinement; the calcined magnesium tantalate block is subjected to secondary ball milling, and the crushed magnesium tantalate powder material is further granulated;

[0027] S5. Sintering and ceramicization: the magnesium tantalate material obtained by the granulation process is pressed into a green body, and then the green body is subjected to high-temperature debinding and then sintered again at high temperature to obtain a dense magnesium tantalate ceramic.

[0028] Specifically, the drying described in step S1 is vacuum drying, which is to place tantalum oxide and magnesium oxide in a vacuum drying oven for vacuum drying, and then weigh 8.838 g of tantalum oxide (purity ≥99.9%) and 3.224 g of magnesium oxide (purity ≥99.9%), and place them together in a sealed can according to the molar ratio of n(Ta2O5):n(MgO)=1:4, and then use an acoustic resonance mixer to mix the materials. The single mixing duration is 120 s, and it is repeated 5 times; then a planetary ball mill is used for ball milling mixing for 2 hours; then the material is taken out and sieved using a rotary vibrating screen with a 60-mesh screen, and the sieved powder material is taken for subsequent briquetting.

[0029] Specifically, in step S2, the compact is formed by placing the sieved mixed powder material into a mold, and then using an electric tablet press (under a pressure of 50 MPa) or a cold isostatic pressing device (under a pressure of 100 MPa) to press it into a cylindrical compact with a diameter of 12.5 mm and a thickness of about 1 cm.

[0030] Specifically, in step S3, the calcination synthesis is to place the pressed tantalum oxide and magnesium oxide mixture block on a corundum plate, then put it into a muffle furnace, and calcine it at a high temperature from room temperature to 1000°C at a rate of 10°C / min, and then to 1260°C at a rate of 5°C / min, and keep it at that temperature for 10 hours; then cool it with the furnace, and after it cools naturally to room temperature, take out the product to synthesize magnesium tantalate.

[0031] Specifically, in step S4, when the magnesium tantalate powder is granulated, an appropriate amount of polyvinyl alcohol and polyacrylic acid solution are added to the magnesium tantalate powder; wherein the polyvinyl alcohol is used as a dispersant to make the magnesium tantalate powder more evenly dispersed during the ball milling process before spray granulation; the polyacrylic acid solution is used as a binder to facilitate the formation of spherical particles during the spray granulation of the magnesium tantalate powder.

[0032] Specifically, in step S5, the green body is pressed to form a green body by pressing the magnesium tantalate material obtained by granulation to 100 MPa using a cold isostatic pressing device and maintaining the pressure for 60 seconds, and then placing the green body into a muffle furnace, keeping it at 1500 ° C for 2 hours for high-temperature debinding, and then sintering it at 1500 ° C for 6 hours to finally obtain a dense magnesium tantalate (Mg4Ta2O9) ceramic.

[0033] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Without departing from the scope and spirit of the described embodiments, many modifications and changes are obvious to ordinary technicians in this technical field. Any technical deformation made within the spirit and principles of the present invention falls within the scope of protection of the present invention.

Claims

1. A process for preparing a tantalum-based coating material, characterized in that: The following steps are involved: S1, raw material pretreatment; drying tantalum oxide and magnesium oxide, then mixing tantalum oxide and magnesium oxide according to a ratio, ball milling, and screening the mixed powder material obtained after ball milling; S2, blank forming: pressing the mixed powder material obtained after screening into a blank; S3, calcination synthesis; the pressed block is calcined at high temperature to synthesize a magnesium tantalate block; S4, granulation and refinement; crushing the magnesium tantalate block generated by calcination, and granulating the magnesium tantalate powder obtained after crushing; S5. Sintering and ceramicization: the magnesium tantalate material obtained by the granulation process is pressed into a green body, and then the green body is subjected to high-temperature debinding and then sintered again at high temperature to obtain a dense magnesium tantalate ceramic.

2. The process for preparing a tantalum-based coating material according to claim 1, wherein: The drying in step S1 is vacuum drying, which is to place the tantalum oxide and magnesium oxide in a vacuum drying oven for vacuum drying until the purity of the tantalum oxide and magnesium oxide is ≥99.9%.

3. The process for preparing a tantalum-based coating material according to claim 1, wherein: The mixing in step S1 is to place tantalum oxide and magnesium oxide in a sealed can at a molar ratio of 1:4, then use an acoustic resonance mixer to mix the materials, and then use a ball mill to perform ball milling mixing.

4. The process for preparing a tantalum-based coating material according to claim 1, wherein: The screening in step S1 is performed by using a rotary vibrating screen with a 60-mesh screen to screen the mixed powder material obtained after ball milling.

5. The process for preparing a tantalum-based coating material according to claim 1, wherein: The compact is formed by pressing the sieved mixed powder material into a mold and then pressing it into a compact using an electric tablet press or cold isostatic pressing equipment.

6. The process for preparing a tantalum-based coating material according to claim 1, characterized in that: The calcination synthesis in step S3 is to place the pressed tantalum oxide and magnesium oxide mixture block on a corundum plate, and then place it in a muffle furnace for high-temperature calcination, heating from room temperature to 1000°C at a rate of 10°C / min, and then heating to 1260°C at a rate of 5°C / min and keeping it warm for 10 hours, and then naturally cooling, thereby synthesizing magnesium tantalate.

7. The process for preparing a tantalum-based coating material according to claim 1, characterized in that: When the crushed magnesium tantalate powder is granulated in step S4, polyvinyl alcohol and polyacrylic acid are added to the magnesium tantalate powder.

8. The process for preparing a tantalum-based coating material according to claim 1, characterized in that: In step S5, the green body is pressed by pressing the magnesium tantalate material obtained by granulation using a cold isostatic pressing device and maintaining the pressure for 60 seconds to obtain a green body. The green body is then placed in a muffle furnace, kept at 1500°C for 2 hours to remove the binder, and then sintered at 1500°C for 6 hours to finally obtain a dense magnesium tantalate ceramic.

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