Preparation method of molten salt corrosion resistant coating on surface of TiAl alloy

Abstract

The invention discloses a preparation method of a molten salt corrosion resistant coating on the surface of a TiAl alloy, relates to the technical field of surface treatment, and aims to solve the technical problems of low binding force between an existing TiAl alloy matrix and a coating interface and poor corrosion resistance of the coating. The preparation method of the molten salt corrosion resistant coating on the surface of the TiAl alloy comprises the steps that a Zr-Y alloy is infiltrated on the surface of the TiAl alloy through a double glow plasma method, and a Zr-Y infiltrated layer is formed on the surface of the TiAl alloy; the TiAl alloy is subjected to heat preservation for 1-5 hours under the condition that the temperature ranges from 850 DEG C to 900 DEG C; a Zr-Cr-Y alloy is infiltrated on the surface of the TiAl alloy, and a Zr-Y / Zr-Cr-Y infiltrated layer is formed on the surface of the TiAl alloy; the TiAl alloy is subjected to heat preservation for 2-3 hours under the condition that the temperature ranges from 900 DEG C to 950 DEG C, and is oxidized under the condition that the temperature ranges from 860 DEG C to 920 DEG C;

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology, and more specifically, to a method for preparing a molten salt corrosion resistant coating on a TiAl alloy surface. Background Technology

[0002] Titanium-aluminum alloys are widely used in aerospace, nuclear energy, and solar thermal power generation due to their excellent performance characteristics, such as low density, high strength, high modulus, good corrosion resistance, and high temperature resistance. These fields demand extremely high material performance, especially in high-temperature environments where alloys need to possess excellent mechanical properties and corrosion resistance. To improve the high-temperature resistance of alloys, corrosion-resistant coatings, such as pure Ni layers or MCrAlY coatings, are typically applied to their surfaces. However, during long-term high-temperature service, significant interdiffusion of elements occurs between the coating and the substrate, leading to coating degradation and severely affecting the material's mechanical properties and corrosion resistance.

[0003] Currently, researchers are attempting to address interdiffusion problems by adding diffusion barriers between the coating and the substrate. Commonly used diffusion barriers include metallic and ceramic types. While ceramic diffusion barriers effectively prevent element interdiffusion, they can impair the adhesion between the substrate and coating. Metallic diffusion barriers, due to their strong adhesion to both the substrate and coating, are considered a more ideal choice. However, existing metallic diffusion barriers still suffer from insufficient diffusion resistance and are prone to forming voids at the coating-substrate interface, affecting the overall material performance. Therefore, current techniques for adding diffusion barriers between the TiAl alloy substrate and coating result in reduced adhesion at the substrate-coating interface and the formation of voids at the coating-substrate interface due to insufficient diffusion resistance, severely impacting the coating's corrosion resistance. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a molten salt corrosion resistant coating on a TiAl alloy surface. This method addresses the technical problems in existing technologies where adding a diffusion barrier between the TiAl alloy substrate and the coating reduces the bonding strength at the substrate-coating interface, and the insufficient diffusion-blocking performance of the diffusion barrier leads to the formation of porous regions at the coating-substrate interface, resulting in poor corrosion resistance of the coating. Therefore, this invention achieves this through the following solution.

[0005] In a first aspect, the present invention provides a method for preparing a molten salt corrosion resistant coating on a TiAl alloy surface, comprising: Zr-Y alloy was infiltrated onto the surface of TiAl alloy using a double glow plasma method to form a Zr-Y infiltrated layer on the surface of TiAl alloy. The TiAl alloy / Zr-Y diffusion layer was held at 850~900℃ for 1~5 hours; Zr-Cr-Y alloy is infiltrated onto the surface of the TiAl alloy / Zr-Y infiltrated layer to form a Zr-Y / Zr-Cr-Y infiltrated layer on the surface of the TiAl alloy. The TiAl alloy / Zr-Y / Zr-Cr-Y diffusion layer was kept at 900~950℃ for 2~3 hours; The TiAl alloy / Zr-Y / Zr-Cr-Y diffusion layer was oxidized at 860~920℃ for 1~3 hours and then cooled to room temperature.

[0006] Compared with existing technologies, the method for preparing a molten salt corrosion resistant coating on the TiAl alloy surface of the present invention is used to prepare a Zr-Y / Zr-Cr-Y diffusion layer with molten salt corrosion resistance on the surface of TiAl alloy. The preparation of the Zr-Y / Zr-Cr-Y diffusion layer employs a step-by-step diffusion process involving Zr-Y and Zr-Cr-Y alloys. Specifically, after preparing the Zr-Y diffusion layer using double-glow plasma diffusion technology, a first annealing treatment is performed; after preparing the Zr-Y diffusion layer on the Zr-Y diffusion layer surface, a second annealing treatment is performed; and finally, an oxidation treatment is performed. By controlling the parameters of each treatment process within the aforementioned reasonable range, a dense Zr-Y / Zr-Cr-Y diffusion layer with molten salt corrosion resistance can be prepared. Specifically, the Zr (zirconium) element can form a stable (Ti,Zr)Al phase with TiAl, improving the surface thermodynamic stability of the coating, while the Y (yttrium) element can significantly improve the oxide film structure and promote the formation of a dense protective layer. A membrane can be formed by the introduction of Cr (chromium) element. The phase further enhances the coating's resistance to molten salt corrosion. The Zr-Y / Zr-Cr-Y infiltration layer prepared by the above technical solution exhibits a gradient distribution of elements, which is beneficial for enhancing the bonding force with the substrate and the infiltration layer itself. Through the above two heat treatments (i.e., annealing), residual stress can be effectively released, making the microstructure of the infiltration layer more uniform, reducing coarse columnar crystals, eliminating defects such as pores, and further forming an interdiffusion structure, thus improving the bonding force. Furthermore, due to the high solubility of Zr in Ti (titanium), the infiltration layer formed after thermal oxidation is thicker, while the infiltration layer formed by only infiltrating Zr-Cr-Y is thinner after oxidation. It exhibits excellent chemical stability and electrical insulation, and performs exceptionally well in strong acid (HF, HCl) and strong alkali (NaOH) environments; It provides excellent thermal stability and mechanical strength, especially with partial stabilization. (i.e., partially stabilized zirconia ceramics, PSZ) have a phase transformation toughening mechanism; This provides excellent wear resistance and high-temperature oxidation protection. Through the above technical solution, an oxidation treatment is performed on the Zr-Y / Zr-Cr-Y diffusion layer at the end, resulting in a composite structure of these three oxides. The oxides achieve a synergistic protective effect, meeting the corrosion protection requirements in extreme environments. This further enhances the thickness and stability of the oxide layer, forming a denser and more stable surface protective layer, effectively improving the coating's performance (i.e., corrosion resistance) in high-temperature corrosive environments. In one embodiment of the invention, the prepared Zr-Y / Zr-Cr-Y diffusion layer can reach a thickness of 25~40 μm. After 100 hours of molten salt corrosion at 850℃, the diffusion layer did not change color or peel off, exhibiting excellent molten salt corrosion resistance. The above technical solution of the present invention solves the technical problems of existing technologies where adding a diffusion barrier between the TiAl alloy substrate and the coating leads to reduced bonding strength at the substrate-coating interface, and the formation of porous areas at the coating-substrate interface due to insufficient diffusion barrier performance, resulting in poor corrosion resistance of the coating.

[0007] Furthermore, in the method for preparing the molten salt corrosion resistant coating on the TiAl alloy surface of the present invention, the thickness of the Zr-Y diffusion layer and / or the Zr-Y / Zr-Cr-Y diffusion layer is 30~40μm.

[0008] Furthermore, in the method for preparing the molten salt corrosion resistant coating on the TiAl alloy surface of the present invention, the atomic ratio of Zr to Y in the Zr-Y alloy is 75:25; In the Zr-Cr-Y alloy, the atomic ratio of Zr to Cr and Y is 50:40:10.

[0009] Furthermore, in the method for preparing the molten salt corrosion resistant coating on the TiAl alloy surface of the present invention, the process parameters for the double glow plasma metal infiltration during the Zr-Y alloy infiltration process are as follows: The atmospheric pressure is 43~47Pa, the cathode voltage is 400~600V, the source voltage is 700~720V, the holding temperature is 840~860℃, the holding time is 1~5 hours, and the distance between the two electrodes is 14~18mm.

[0010] Furthermore, in the method for preparing the molten salt corrosion resistant coating on the TiAl alloy surface of the present invention, the process parameters for the double glow plasma metal infiltration during the Zr-Cr-Y alloy infiltration process are as follows: The atmospheric pressure is 48~50Pa, the cathode voltage is 500~700V, the source voltage is 810~850V, the holding temperature is 850~890℃, the holding time is 2~7 hours, and the distance between the two electrodes is 14~18mm.

[0011] Furthermore, in the method for preparing the molten salt corrosion resistant coating on the TiAl alloy surface of the present invention, during the process of oxidizing the TiAl alloy / Zr-Y / Zr-Cr-Y diffusion layer at a temperature of 860~920℃ for 1~3 hours and then cooling it to room temperature, the heating rate is 5℃ / min and the cooling rate is 8℃ / min.

[0012] Furthermore, in the method for preparing the molten salt corrosion resistant coating on the TiAl alloy surface of the present invention, before infiltrating the Zr-Y alloy, the method further includes: The TiAl alloy is subjected to surface treatment.

[0013] Furthermore, in the method for preparing the molten salt corrosion resistant coating on the TiAl alloy surface of the present invention, the surface treatment process includes: After polishing the TiAl alloy with 400#, 800# and 1000# sandpaper for 20-30 minutes respectively, it was ultrasonically treated with anhydrous ethanol for 30-90 seconds and then dried. The frequency of the ultrasonic treatment is 25~50kHz.

[0014] In a second aspect, the present invention provides a TiAl alloy with a molten salt corrosion resistant coating, which is prepared by the above-mentioned method for preparing a molten salt corrosion resistant coating on the surface of a TiAl alloy; The molten salt corrosion resistant coating is a Zr-Y / Zr-Cr-Y diffusion layer formed on the surface of the TiAl alloy; the thickness of the Zr-Y / Zr-Cr-Y diffusion layer is 30~40μm.

[0015] Compared with the prior art, the beneficial effects of the TiAl alloy with molten salt corrosion resistant coating of the present invention are the same as the beneficial effects of the preparation method of molten salt corrosion resistant coating on TiAl alloy surface described in the above technical solution, and will not be repeated here. Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 The image shows the surface morphology of the Zr-Y / Zr-Cr-Y composite coating prepared in Example 1 of this invention. Figure 2 The surface morphology of the Zr-Y / Zr-Cr-Y composite coating prepared in Example 2 of this invention after molten salt corrosion at 850°C for 100 hours is shown. Figure 3 The image shows the surface morphology of the Zr-Y / Zr-Cr-Y composite coating prepared in Comparative Example 1 of this invention. Figure 4The surface morphology of the Zr-Y / Zr-Cr-Y composite coating prepared in Comparative Example 1 of this invention after molten salt corrosion at 850℃ for 100 hours is shown. Figure 5 The cross-sectional morphology of the Zr-Cr-Y coating prepared in Comparative Example 2 of this invention after molten salt corrosion at 850℃ for 50 hours is shown. Figure 6 The cross-sectional morphology of the Zr-Y / Zr-Cr-Y composite coating prepared in Comparative Example 3 of this invention after molten salt corrosion at 850℃ for 80 hours is shown. Figure 7 This is a cross-sectional morphology diagram of the TiAl alloy after alloying in Comparative Example 4 of the present invention. Detailed Implementation

[0017] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0018] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0019] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. "Several" means one or more, unless otherwise explicitly specified.

[0020] Currently, researchers are attempting to address interdiffusion problems by adding diffusion barriers between the coating and the substrate. Commonly used diffusion barriers include metallic and ceramic types. While ceramic diffusion barriers effectively prevent element interdiffusion, they can impair the adhesion between the substrate and coating. Metallic diffusion barriers, due to their strong adhesion to both the substrate and coating, are considered a more ideal choice. However, existing metallic diffusion barriers still suffer from insufficient diffusion resistance and are prone to forming voids at the coating-substrate interface, affecting the overall material performance. Therefore, current techniques for adding diffusion barriers between the TiAl alloy substrate and coating result in reduced adhesion at the substrate-coating interface and the formation of voids at the coating-substrate interface due to insufficient diffusion resistance, severely impacting the coating's corrosion resistance.

[0021] To address the aforementioned technical problems, this invention provides a method for preparing a molten salt corrosion-resistant coating on a TiAl alloy surface, comprising: Zr-Y alloy was infiltrated onto the surface of TiAl alloy using a double glow plasma method to form a Zr-Y infiltrated layer on the surface of TiAl alloy. The TiAl alloy / Zr-Y diffusion layer was held at 850~900℃ for 1~5 hours; Zr-Cr-Y alloy is infiltrated onto the surface of the TiAl alloy / Zr-Y infiltrated layer to form a Zr-Y / Zr-Cr-Y infiltrated layer on the surface of the TiAl alloy. The TiAl alloy / Zr-Y / Zr-Cr-Y diffusion layer was kept at 900~950℃ for 2~3 hours; The TiAl alloy / Zr-Y / Zr-Cr-Y diffusion layer was oxidized at 860~920℃ for 1~3 hours and then cooled to room temperature.

[0022] Using the above technical solution, the method for preparing a molten salt corrosion resistant coating on the TiAl alloy surface of the present invention is used to prepare a Zr-Y / Zr-Cr-Y diffusion layer with molten salt corrosion resistance on the surface of TiAl alloy. The preparation of the Zr-Y / Zr-Cr-Y diffusion layer employs a step-by-step diffusion process involving Zr-Y and Zr-Cr-Y alloys. Specifically, after preparing the Zr-Y diffusion layer using double-glow plasma diffusion technology, a first annealing treatment is performed; after preparing the Zr-Y diffusion layer on the Zr-Y diffusion layer surface, a second annealing treatment is performed; and finally, an oxidation treatment is performed. By controlling the parameters of each treatment process within the above-mentioned reasonable range, a dense Zr-Y / Zr-Cr-Y diffusion layer with molten salt corrosion resistance can be prepared. Specifically, the Zr (zirconium) element can form a stable (Ti,Zr)Al phase with TiAl, improving the surface thermodynamic stability of the coating, while the Y (yttrium) element can significantly improve the oxide film structure and promote the formation of a dense protective layer. A membrane can be formed by the introduction of Cr (chromium) element. The phase further enhances the coating's resistance to molten salt corrosion. The Zr-Y / Zr-Cr-Y infiltration layer prepared by the above technical solution exhibits a gradient distribution of elements, which is beneficial for enhancing the bonding force with the substrate and the infiltration layer itself. Through the above two heat treatments (i.e., annealing), residual stress can be effectively released, making the microstructure of the infiltration layer more uniform, reducing coarse columnar crystals, eliminating defects such as pores, and further forming an interdiffusion structure, thus improving the bonding force. Furthermore, due to the high solubility of Zr in Ti (titanium), the infiltration layer formed after thermal oxidation is thicker, while the infiltration layer formed by only infiltrating Zr-Cr-Y is thinner after oxidation. It exhibits excellent chemical stability and electrical insulation, and performs exceptionally well in strong acid (HF, HCl) and strong alkali (NaOH) environments; It provides excellent thermal stability and mechanical strength, especially with partial stabilization. (i.e., partially stabilized zirconia ceramics, PSZ) have a phase transformation toughening mechanism; This provides excellent wear resistance and high-temperature oxidation protection. Through the above technical solution, an oxidation treatment is performed on the Zr-Y / Zr-Cr-Y diffusion layer at the end, resulting in a composite structure of these three oxides. The oxides achieve a synergistic protective effect, meeting the corrosion protection requirements in extreme environments. This further enhances the thickness and stability of the oxide layer, forming a denser and more stable surface protective layer, effectively improving the coating's performance (i.e., corrosion resistance) in high-temperature corrosive environments. In one embodiment of the invention, the prepared Zr-Y / Zr-Cr-Y diffusion layer can reach a thickness of 25~40 μm. After 100 hours of molten salt corrosion at 850℃, the diffusion layer did not change color or peel off, exhibiting excellent molten salt corrosion resistance. The above technical solution of the present invention solves the technical problems of existing technologies where adding a diffusion barrier between the TiAl alloy substrate and the coating leads to reduced bonding strength at the substrate-coating interface, and the formation of porous areas at the coating-substrate interface due to insufficient diffusion barrier performance, resulting in poor corrosion resistance of the coating.

[0023] For example, in the method for preparing the molten salt corrosion resistant coating on the TiAl alloy surface of the present invention, the thickness of the Zr-Y diffusion layer and / or the Zr-Y / Zr-Cr-Y diffusion layer is 30~40μm; in the Zr-Y alloy, the atomic ratio of Zr (zirconium) to Y (yttrium) is 75:25; in the Zr-Cr-Y alloy, the atomic ratio of Zr (zirconium) to Cr (chromium) and Y (yttrium) is 50:40:10; in yet another example, the thickness of the Zr-Y diffusion layer and / or the Zr-Y / Zr-Cr-Y diffusion layer can be 30μm, 35μm or 40μm.

[0024] For example, in the above-mentioned process of infiltrating Zr-Y alloys, the double-glow plasma metal infiltration process parameters are as follows: the gas pressure can be 43~47 Pa, the cathode voltage can be 400~600 V, the source voltage can be 700~720 V, the holding temperature can be 840~860 °C, the holding time can be 1~5 hours, and the distance between the two electrodes can be 14~18 mm; in another example, the gas pressure can be 43 Pa, 45 Pa, or 47 Pa, the cathode voltage can be 400 V, 450 V, 500 V, 550 V, or 600 V, the source voltage can be 700 V, 710 V, or 720 V, the holding temperature can be 840 °C, 850 °C, or 860 °C, the holding time can be 1 hour, 3 hours, or 5 hours, and the distance between the two electrodes can be 14 mm, 16 mm, or 18 mm.

[0025] For example, in the above-mentioned process of infiltrating Zr-Cr-Y alloy, the double glow plasma metal infiltration process parameters are: gas pressure of 48~50Pa, cathode voltage of 500~700V, source voltage of 810~850V, holding temperature of 850~890℃, holding time of 2~7 hours, and distance between the two electrodes of 14~18mm; in another example, the gas pressure is 48Pa, 49Pa or 50Pa, the cathode voltage is 500V, 550V, 600V, 650V or 700V, the source voltage is 810V, 830V or 850V, the holding temperature is 850℃, 870℃ or 890℃, the holding time is 2 hours, 5 hours or 7 hours, and the distance between the two electrodes is 14mm, 16mm or 18mm.

[0026] As one possible implementation, the method for preparing the molten salt corrosion resistant coating on the TiAl alloy surface of the present invention further includes, before infiltrating the Zr-Y alloy: The TiAl alloy is subjected to surface treatment; specifically, the surface treatment process includes: polishing the TiAl alloy with 400#, 800# and 1000# sandpaper for 20 to 30 minutes respectively, ultrasonically treating it with anhydrous ethanol for 30 to 90 seconds, and then blowing it dry; the frequency of the ultrasonic treatment is 25 to 50 kHz.

[0027] When the above technical solution is adopted, a clean TiAl alloy substrate after removing the oxide layer can be obtained by surface treatment of the TiAl alloy; for example, the grinding time can be 20 minutes, 25 minutes or 30 minutes, the ultrasonic treatment time can be 30 seconds, 60 seconds or 90 seconds, and the ultrasonic treatment frequency can be 25 kHz, 40 kHz or 50 kHz.

[0028] To better understand the present invention, the following specific embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0029] Unless otherwise specified, all raw materials used in the following examples are commercially available.

[0030] The TiAl alloy used in the following examples contains 48% Ti, 48% Al, 2% Nb, and 2% Cr.

[0031] Example 1 This embodiment provides a method for preparing a molten salt corrosion resistant coating on the surface of a TiAl alloy, including: Step 1: Use Zr-Y alloy as the target material. The target material has a composition ratio of Zr (75)-Y (25) and a purity of 99.99 wt.% or higher. Perform surface cleaning treatment on the target material to remove surface impurities. Install the cleaned Zr-Y alloy target material in the metal infiltration equipment to ensure stable and reliable installation. Step 2: Polish the TiAl alloy substrate with 400#, 800# and 1000# sandpaper for 10 minutes in sequence, then sonicate it with anhydrous ethanol for 60 seconds at a frequency of 25kHz, and then dry it with cold air for later use. Step 3: Clean and tidy the test equipment, and sandblast the tooling; place the TiAl alloy matrix sample after the pretreatment in Step 2 on the worktable; turn on the cooling water circulation; open the argon valve and introduce argon gas; turn on the power. Step 4: Zr-Y alloy is infiltrated onto the surface of the TiAl alloy using a double-glow plasma method to form a Zr-Y infiltrated layer on the surface of the TiAl alloy; specifically: The process parameters for double-glowing plasma infiltration of Zr-Y alloy are: gas pressure 45Pa, cathode voltage 400V, source voltage 720V, holding temperature 850℃, holding time 1 hour, and distance between the two electrodes 16mm. Step 5: After the equipment reaches the set temperature and duration, stop the argon gas supply, maintain the furnace pressure below 30 Pa, turn off the cathode voltage and source voltage, and use only the auxiliary heating module of the metal diffusion furnace to hold the TiAl alloy at 880℃ in a vacuum environment (for diffusion annealing) for 2 hours; after the holding is completed, wait for the TiAl alloy (sample) to cool, then sonicate it with anhydrous ethanol for 60 seconds, and dry it with cold air for later use; the frequency of the sonication is 25 kHz. Step 6: A Zr-Cr-Y alloy is infiltrated onto the surface of the TiAl alloy to form a Zr-Y / Zr-Cr-Y infiltrated layer; specifically: Zr-Cr-Y alloy was used as the target material, with a composition ratio of Zr:Cr:Y = 50:40:10 and a purity of over 99.99 wt.%. The target material was then surface-cleaned to remove impurities. The cleaned Zr-Cr-Y alloy target material was then installed in the metal infiltration equipment to ensure stable and reliable installation. Step 7: Clean and tidy the test equipment, and sandblast the tooling; place the TiAl alloy (sample) treated with Zr-Y alloying in Step 4 on the worktable; turn on the cooling circulating water; open the argon valve and introduce argon gas; turn on the power; set the double glow plasma process parameters for Zr-Cr-Y alloying as follows: The air pressure is 50Pa, the cathode voltage is 500V, the source voltage is 830V, the holding temperature is 870℃, the holding time is 2 hours, and the distance between the two electrodes is 16mm. Step 8: After the equipment has run to the set temperature for the set time, close the gas valve and allow the sample to cool with the furnace. After completion, continue to place it in a vacuum metallizing furnace and set the temperature to 910℃ for diffusion annealing for 2.5 hours. Maintain a vacuum environment during the annealing process to prevent oxide precipitation. Step 9: After the TiAl alloy (sample) has cooled, check the temperature control accuracy of the pre-oxidation equipment to ensure temperature stability. Place the sample in a muffle furnace at 890℃ to oxidize the Zr-Y / Zr-Cr-Y composite layer for 2 hours. The heating and cooling rates of the oxidation are 5℃ / min and 8℃ / min, respectively.

[0032] The surface morphology of the molten salt corrosion resistant coating (Zr-Y / Zr-Cr-Y composite coating) prepared on the TiAl alloy surface in this embodiment is as follows: Figure 1 As shown, from Figure 1 It can be seen that the Zr-Y / Zr-Cr-Y composite coating has a dense and defect-free surface, and the thickness of the composite coating is 12μm.

[0033] Example 2 This embodiment provides a method for preparing a molten salt corrosion resistant coating on the surface of a TiAl alloy, including: Step 1: Use Zr-Y alloy as the target material. The target material has a composition ratio of Zr (75)-Y (25) and a purity of 99.99 wt.% or higher. Perform surface cleaning treatment on the target material to remove surface impurities. Install the cleaned Zr-Y alloy target material in the metal infiltration equipment to ensure stable and reliable installation. Step 2: Polish the TiAl alloy substrate with 400#, 800# and 1000# sandpaper for 30 minutes in sequence, then sonicate it with anhydrous ethanol for 60 seconds at a frequency of 25kHz, and then dry it with cold air for later use. Step 3: Clean and tidy the test equipment, and sandblast the tooling; place the TiAl alloy matrix sample after the pretreatment in Step 2 on the worktable; turn on the cooling water circulation; open the argon valve and introduce argon gas; turn on the power. Step 4: Zr-Y alloy is infiltrated onto the surface of the TiAl alloy using a double-glow plasma method to form a Zr-Y infiltrated layer on the surface of the TiAl alloy; specifically: The process parameters for dual-glow plasma infiltration of Zr-Y alloy are as follows: gas pressure 45 Pa, cathode voltage 500 V, source voltage 720 V, holding temperature 850 °C, holding time 3 hours, and distance between the two electrodes 16 mm. The process parameters are checked for accuracy to ensure they meet the requirements. The parameters are then optimized to ensure process stability and repeatability. Real-time monitoring of gas flow rate and voltage waveform is conducted to ensure precise process execution. Step 5: After the equipment reaches the set temperature and duration, stop the argon gas supply, maintain the furnace pressure below 30 Pa, turn off the cathode voltage and source voltage, and use only the auxiliary heating module of the metal diffusion furnace to hold the TiAl alloy at 880℃ in a vacuum environment (for diffusion annealing) for 2 hours; after the holding is completed, wait for the TiAl alloy (sample) to cool, then sonicate it with anhydrous ethanol for 60 seconds, and dry it with cold air for later use; the frequency of the sonication is 25 kHz. Step 6: A Zr-Cr-Y alloy is infiltrated onto the surface of the TiAl alloy to form a Zr-Y / Zr-Cr-Y infiltrated layer; specifically: Zr-Cr-Y alloy was used as the target material, with a composition ratio of Zr:Cr:Y = 50:40:10 and a purity of over 99.99 wt.%. The target material was then surface-cleaned to remove impurities. The cleaned Zr-Cr-Y alloy target material was then installed in the metal infiltration equipment to ensure stable and reliable installation. Step 7: Clean and tidy the test equipment, and sandblast the tooling; place the TiAl alloy (sample) treated with Zr-Y alloying in Step 4 on the worktable; turn on the cooling circulating water; open the argon valve and introduce argon gas; turn on the power; set the double glow plasma process parameters for Zr-Cr-Y alloying as follows: The air pressure is 50Pa, the cathode voltage is 650V, the source voltage is 830V, the holding temperature is 870℃, the holding time is 5 hours, and the distance between the two electrodes is 16mm. Step 8: After the equipment has run to the set temperature for the set time, close the gas valve and allow the sample to cool with the furnace. After completion, continue to place it in a vacuum metallizing furnace and set the temperature to 910℃ for diffusion annealing for 2.5 hours. Maintain a vacuum environment during the annealing process to prevent oxide precipitation. Step 9: After the TiAl alloy (sample) has cooled, check the temperature control accuracy of the pre-oxidation equipment to ensure temperature stability. Place the sample in a muffle furnace at 890℃ to oxidize the Zr-Y / Zr-Cr-Y composite layer for 2 hours. The heating and cooling rates of the oxidation are 5℃ / min and 8℃ / min, respectively.

[0034] In this embodiment, the molten salt corrosion resistant coating (Zr-Y / Zr-Cr-Y composite coating) prepared on the TiAl alloy surface is dense, defect-free, and crack-free. The surface morphology of this Zr-Y / Zr-Cr-Y composite coating after molten salt corrosion at 850℃ for 100 hours is as follows: Figure 2 As shown, the oxide particles on the surface of the composite layer are closely arranged, and the thickness of the composite coating is 30 μm.

[0035] Example 3 This embodiment provides a method for preparing a molten salt corrosion resistant coating on the surface of a TiAl alloy, including: Step 1: Use Zr-Y alloy as the target material. The target material has a composition ratio of Zr (75)-Y (25) and a purity of 99.99 wt.% or higher. Perform surface cleaning treatment on the target material to remove surface impurities. Install the cleaned Zr-Y alloy target material in the metal infiltration equipment to ensure stable and reliable installation. Step 2: Polish the TiAl alloy matrix with 400#, 800# and 1000# sandpaper for 20 minutes in sequence, then sonicate it with anhydrous ethanol for 60 seconds at a frequency of 25kHz, and then dry it with cold air for later use. Step 3: Clean and tidy the test equipment, and sandblast the tooling; place the TiAl alloy matrix sample after the pretreatment in Step 2 on the worktable; turn on the cooling water circulation; open the argon valve and introduce argon gas; turn on the power. Step 4: Zr-Y alloy is infiltrated onto the surface of the TiAl alloy using a double-glow plasma method to form a Zr-Y infiltrated layer on the surface of the TiAl alloy; specifically: The process parameters for dual-glow plasma infiltration of Zr-Y alloy are as follows: gas pressure 45 Pa, cathode voltage 600 V, source voltage 720 V, holding temperature 880 °C, holding time 5 hours, and distance between the two electrodes 16 mm. The process parameters are checked for accuracy to ensure they meet the requirements. The process parameters are then optimized to ensure stability and repeatability. Real-time monitoring of the gas flow rate and voltage waveform during the process ensures precise execution. Step 5: After the equipment reaches the set temperature and duration, stop the argon gas supply, maintain the furnace pressure below 30 Pa, turn off the cathode voltage and source voltage, and use only the auxiliary heating module of the metal diffusion furnace to hold the TiAl alloy at 880℃ in a vacuum environment (for diffusion annealing) for 2 hours; after the holding is completed, wait for the TiAl alloy (sample) to cool, then sonicate it with anhydrous ethanol for 60 seconds, and dry it with cold air for later use; the frequency of the sonication is 25 kHz. Step 6: A Zr-Cr-Y alloy is infiltrated onto the surface of the TiAl alloy to form a Zr-Y / Zr-Cr-Y infiltrated layer; specifically: Zr-Cr-Y alloy was used as the target material, with a composition ratio of Zr:Cr:Y = 50:40:10 and a purity of over 99.99 wt.%. The target material was then surface-cleaned to remove impurities. The cleaned Zr-Cr-Y alloy target material was then installed in the metal infiltration equipment to ensure stable and reliable installation. Step 7: Clean and tidy the test equipment, and sandblast the tooling; place the TiAl alloy (sample) treated with Zr-Y alloying in Step 4 on the worktable; turn on the cooling circulating water; open the argon valve and introduce argon gas; turn on the power; set the double glow plasma process parameters for Zr-Cr-Y alloying as follows: The air pressure is 50Pa, the cathode voltage is 750V, the source voltage is 830V, the holding temperature is 870℃, the holding time is 7 hours, and the distance between the two electrodes is 16mm. Step 8: After the equipment has run to the set temperature for the set time, close the gas valve and allow the sample to cool with the furnace. After completion, continue to place it in a vacuum metallizing furnace and set the temperature to 910℃ for diffusion annealing for 2.5 hours. Maintain a vacuum environment during the annealing process to prevent oxide precipitation. Step 9: After the TiAl alloy (sample) has cooled, check the temperature control accuracy of the pre-oxidation equipment to ensure temperature stability. Place the sample in a muffle furnace at 890℃ to oxidize the Zr-Y / Zr-Cr-Y composite layer for 2 hours. The heating and cooling rates of the oxidation are 5℃ / min and 8℃ / min, respectively.

[0036] The molten salt corrosion resistant coating (Zr-Y / Zr-Cr-Y composite coating) prepared on the TiAl alloy surface in this embodiment is dense, defect-free, and crack-free, with a thickness of 30 μm.

[0037] Example 4 This embodiment provides a method for preparing a molten salt corrosion resistant coating on the surface of a TiAl alloy, including: Step 1: Use Zr-Y alloy as the target material. The target material has a composition ratio of Zr (75)-Y (25) and a purity of 99.99 wt.% or higher. Perform surface cleaning treatment on the target material to remove surface impurities. Install the cleaned Zr-Y alloy target material in the metal infiltration equipment to ensure stable and reliable installation. Step 2: Polish the TiAl alloy matrix with 400#, 800# and 1000# sandpaper for 20 minutes in sequence, then sonicate it with anhydrous ethanol for 60 seconds at a frequency of 25kHz, and then dry it with cold air for later use. Step 3: Clean and tidy the test equipment, and sandblast the tooling; place the TiAl alloy matrix sample after the pretreatment in Step 2 on the worktable; turn on the cooling water circulation; open the argon valve and introduce argon gas; turn on the power. Step 4: Zr-Y alloy is infiltrated onto the surface of the TiAl alloy using a double-glow plasma method to form a Zr-Y infiltrated layer on the surface of the TiAl alloy; specifically: The process parameters for dual-glow plasma infiltration of Zr-Y alloy are as follows: gas pressure 45 Pa, cathode voltage 600 V, source voltage 720 V, holding temperature 880 °C, holding time 5 hours, and distance between the two electrodes 16 mm. The process parameters are checked for accuracy to ensure they meet the requirements. The process parameters are then optimized to ensure stability and repeatability. Real-time monitoring of the gas flow rate and voltage waveform during the process ensures precise execution. Step 5: After the equipment reaches the set temperature and duration, stop the argon gas supply, maintain the furnace pressure below 30 Pa, turn off the cathode voltage and source voltage, and use only the auxiliary heating module of the metal diffusion furnace to hold the TiAl alloy at 850℃ in a vacuum environment (for diffusion annealing) for 5 hours; after the holding period, wait for the TiAl alloy (sample) to cool, then sonicate it with anhydrous ethanol for 60 seconds, and dry it with cold air for later use; the frequency of the sonication treatment is 25 kHz. Step 6: A Zr-Cr-Y alloy is infiltrated onto the surface of the TiAl alloy to form a Zr-Y / Zr-Cr-Y infiltrated layer; specifically: Zr-Cr-Y alloy was used as the target material, with a composition ratio of Zr:Cr:Y = 50:40:10 and a purity of over 99.99 wt.%. The target material was then surface-cleaned to remove impurities. The cleaned Zr-Cr-Y alloy target material was then installed in the metal infiltration equipment to ensure stable and reliable installation. Step 7: Clean and tidy the test equipment, and sandblast the tooling; place the TiAl alloy (sample) treated with Zr-Y alloying in Step 4 on the worktable; turn on the cooling circulating water; open the argon valve and introduce argon gas; turn on the power; set the double glow plasma process parameters for Zr-Cr-Y alloying as follows: The air pressure is 50Pa, the cathode voltage is 750V, the source voltage is 830V, the holding temperature is 870℃, the holding time is 7 hours, and the distance between the two electrodes is 16mm. Step 8: After the equipment has run to the set temperature for the set time, close the gas valve and allow the sample to cool with the furnace. After completion, continue to place it in a vacuum metal infiltration furnace and set the temperature to 950℃ for diffusion annealing for 3 hours. Maintain a vacuum environment during the annealing process to prevent oxide precipitation. Step 9: After the TiAl alloy (sample) has cooled, check the temperature control accuracy of the pre-oxidation equipment to ensure temperature stability. Place the sample in a muffle furnace at 890℃ to oxidize the Zr-Y / Zr-Cr-Y composite layer for 2 hours. The heating and cooling rates of the oxidation are 5℃ / min and 8℃ / min, respectively.

[0038] The molten salt corrosion resistant coating (Zr-Y / Zr-Cr-Y composite coating) prepared on the TiAl alloy surface in this embodiment is dense, defect-free, and crack-free, with a thickness of 25 μm.

[0039] Comparative Example 1 The preparation method of the molten salt corrosion resistant coating on the TiAl alloy surface provided in this comparative example is basically the same as that in Example 1. The difference is that the TiAl alloy was not subjected to the heat preservation treatment in steps 5 and 8 of Example 1, that is, the diffusion annealing treatment was not performed.

[0040] Please see Figure 3 and Figure 4 , Figure 3 This is a structural diagram of the Zr-Y / Zr-Cr-Y composite coating (i.e., the diffusion layer) in this comparative example. Figure 4 The image shows the surface morphology of the Zr-Y / Zr-Cr-Y composite coating after molten salt corrosion at 850℃ for 100 hours. It can be seen that a major drawback of dual-glow plasma infiltration is the uneven distribution of elements after infiltration. Elements tend to accumulate during the infiltration process, generating residual stress. After two consecutive infiltrations, the residual stress inside the infiltrated layer becomes too large, leading to cracking.

[0041] Comparative Example 2 The preparation method of the molten salt corrosion resistant coating on the TiAl alloy surface provided in this comparative example is basically the same as that in Example 2. The difference is that the TiAl alloy surface is not subjected to Zr-Y alloy diffusion treatment, that is, steps 1 to 5 of Example 2 are not performed. Instead, the TiAl alloy is directly subjected to Zr-Cr-Y alloy diffusion treatment.

[0042] Please see Figure 5 Because Zr has a large atomic radius, the Cr-Y infiltration layer was not pre-drained to open up the channel for Zr element entry, resulting in an extremely low Zr content in the Zr-Cr-Y infiltrated layer, which is almost undetectable. As a result, the excellent properties of zirconium oxide as an advanced refractory material could not be fully utilized, and corrosion occurred after 50 hours of molten salt corrosion at 850℃.

[0043] Comparative Example 3 The preparation method of the molten salt corrosion resistant coating on the TiAl alloy surface provided in this comparative example is basically the same as that in Example 2. The difference is that the Zr-Y / Zr-Cr-Y composite layer formed in this comparative example was not subjected to the oxidation treatment as in step 9 of Example 2 after diffusion annealing.

[0044] Please see Figure 6The Zr-Y / Zr-Cr-Y composite layer prepared in this comparative example only contains ZrO2, Cr2O3, and Y2O3 at a distance of 1-2 μm from the surface. This is because the oxide layer is relatively thin, and the high-temperature corrosion resistance needs to be improved. The sample in this comparative example corroded after 80 hours of molten salt corrosion at 850℃.

[0045] Comparative Example 4 The preparation method of the molten salt corrosion resistant coating on the TiAl alloy surface provided in this comparative example is basically the same as that in Example 2, except that the dual-glow plasma process parameters in steps 4 and 7 of Example 2 are changed; the changed dual-glow plasma process parameters are as follows: The dual-glow plasma process parameters for step 4 of this comparative example are: gas pressure of 30 Pa, cathode voltage of 650 V, source voltage of 800 V, holding temperature of 800 °C, holding time of 0.5 hours, and distance between the two electrodes of 19 mm.

[0046] The dual-glow plasma process parameters for step 7 of this comparative example are: gas pressure of 52 Pa, cathode voltage of 450 V, source voltage of 900 V, holding temperature of 830 °C, holding time of 1 hour, and distance between the two electrodes of 19 mm.

[0047] Please see Figure 7 It can be seen that after changing the dual-glow plasma process parameters of the Zr-Y alloy and the Zr-Cr-Y alloy, no Zr-Y / Zr-Cr-Y composite layer was formed due to the oxidation of the TiAl alloy surface.

[0048] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0049] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a molten salt corrosion resistant coating on a TiAl alloy surface, characterized in that, include: Zr-Y alloy was infiltrated onto the surface of TiAl alloy using a double glow plasma method to form a Zr-Y infiltrated layer on the surface of TiAl alloy. The TiAl alloy / Zr-Y diffusion layer was held at 850~900℃ for 1~5 hours; Zr-Cr-Y alloy is infiltrated onto the surface of the TiAl alloy / Zr-Y infiltrated layer to form a Zr-Y / Zr-Cr-Y infiltrated layer on the surface of the TiAl alloy. The TiAl alloy / Zr-Y / Zr-Cr-Y diffusion layer was held at 900~950℃ for 2~3 hours; The TiAl alloy / Zr-Y / Zr-Cr-Y diffusion layer was oxidized at 860~920℃ for 1~3 hours and then cooled to room temperature.

2. The method for preparing a molten salt corrosion resistant coating on the TiAl alloy surface according to claim 1, characterized in that, The thickness of the Zr-Y infiltration layer and / or Zr-Y / Zr-Cr-Y infiltration layer is 30~40μm.

3. The method for preparing a molten salt corrosion resistant coating on the TiAl alloy surface according to claim 1, characterized in that, In the Zr-Y alloy, the atomic ratio of Zr to Y is 75:25; In the Zr-Cr-Y alloy, the atomic ratio of Zr to Cr and Y is 50:40:

10.

4. The method for preparing a molten salt corrosion resistant coating on the TiAl alloy surface according to claim 1, characterized in that, During the Zr-Y alloy infiltration process, the parameters for the dual-glow plasma metallization process are as follows: The atmospheric pressure is 43~47Pa, the cathode voltage is 400~600V, the source voltage is 700~720V, the holding temperature is 840~860℃, the holding time is 1~5 hours, and the distance between the two electrodes is 14~18mm.

5. The method for preparing a molten salt corrosion resistant coating on the TiAl alloy surface according to claim 1, characterized in that, During the Zr-Cr-Y alloy infiltration process, the parameters for the dual-glow plasma metal infiltration process are as follows: The atmospheric pressure is 48~50Pa, the cathode voltage is 500~700V, the source voltage is 810~850V, the holding temperature is 850~890℃, the holding time is 2~7 hours, and the distance between the two electrodes is 14~18mm.

6. The method for preparing a molten salt corrosion resistant coating on the TiAl alloy surface according to claim 1, characterized in that, During the process of oxidizing the TiAl alloy / Zr-Y / Zr-Cr-Y diffusion layer at a temperature of 860~920℃ for 1~3 hours and then cooling it to room temperature, the heating rate is 5℃ / min and the cooling rate is 8℃ / min.

7. The method for preparing a molten salt corrosion resistant coating on the TiAl alloy surface according to claim 1, characterized in that, Before performing Zr-Y alloy diffusion, the following steps are also included: The TiAl alloy is subjected to surface treatment.

8. The method for preparing a molten salt corrosion resistant coating on the TiAl alloy surface according to claim 7, characterized in that, The surface treatment process includes: After polishing the TiAl alloy with 400#, 800# and 1000# sandpaper for 20-30 minutes respectively, it was ultrasonically treated with anhydrous ethanol for 30-90 seconds and then dried. The frequency of the ultrasonic treatment is 25~50kHz.

9. A TiAl alloy with a molten salt corrosion resistant coating, characterized in that, The coating was prepared using the method described in any one of claims 1 to 8 for preparing a molten salt corrosion resistant coating on the surface of the TiAl alloy. The molten salt corrosion resistant coating is a Zr-Y / Zr-Cr-Y diffusion layer formed on the surface of TiAl alloy; the thickness of the Zr-Y / Zr-Cr-Y diffusion layer is 30~40μm.

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