Ti al alloy si-hf-ce co-deposition coating and preparation method thereof

Abstract

The application discloses a preparation method of a TiAl alloy Si-Hf-Ce co-permeation coating, and the method comprises the following steps: step one, preheating the TiAl alloy by high-temperature airflow after pretreatment; step two, shot blasting the TiAl alloy under the condition of high-temperature airflow; step three, immersing the TiAl alloy into pickling solution, and then obtaining a substrate by ultrasonic cleaning with distilled water; step four, embedding and permeating the substrate to obtain the Si-Hf-Ce co-permeation coating; and the application further discloses a TiAl alloy Si-Hf-Ce co-permeation coating. The preparation method preheats and shot blasts the TiAl alloy by high-temperature airflow, the plasticity of the TiAl alloy is improved after heating, plastic deformation, grain refinement and a large number of non-equilibrium defects are generated on the surface of the shot blasted TiAl alloy, brittle microcracks are avoided on the surface of the TiAl alloy during shot blasting, and the method is suitable for the technical field of material surface coating and modification.

Description

Technical Field

[0001] The invention belongs to the technical field of material surface coating and modification, and in particular relates to a TiAl alloy Si-Hf-Ce co-penetration coating and a preparation method thereof. Background Art

[0002] Due to its low density, high specific strength, and excellent high-temperature mechanical properties, TiAl alloys have become one of the most competitive high-temperature structural materials among nickel-based superalloys for aircraft engines. However, Al and Ti easily form a mixture of TiO2 and Al2O3 at high temperatures. The loose structure of TiO2 effectively prevents oxygen diffusion, resulting in insufficient oxidation resistance at high temperatures, significantly limiting the application of TiAl alloys.

[0003] Applying a protective coating to the surface of TiAl alloys is the most effective and economical method for improving their resistance to high-temperature oxidation. Si is typically infiltrated onto the surface of TiAl alloys using a powder embedding method to produce a silicide coating. This coating has the advantages of low density, high melting point, and good thermal stability, forming a strong metallurgical bond with the base TiAl alloy. At high temperatures, the silicide coating generates a protective oxide, SiO2, which provides protection for the TiAl alloy. Furthermore, the powder embedding process is simple, low-cost, and imposes few restrictions on the shape and size of the base workpiece, making it suitable for practical production and application.

[0004] However, single silicide coatings are brittle, making them prone to internal cracking. Furthermore, during high-temperature oxidation, the thermal expansion coefficients of the coating and the surface oxide film do not match, causing the oxide film to peel off and lose its protective properties. This requires the addition of other elements to modify the coating. Studies have shown that the active elements Hf and Ce can effectively modify silicide coatings. HfO2 particles generated by Hf oxidation are distributed at the interface between the oxide film and the silicide coating, inhibiting crack propagation caused by vacancy accumulation, thereby improving the adhesion of the oxide film. The rare earth element Ce has a significant effect in improving the density of the coating and reducing the oxidation rate of the alloy.

[0005] However, the atomic radius of Hf and Ce is relatively large, making it difficult for them to diffuse in TiAl alloys. Therefore, it is difficult to prepare Hf and Ce modified silicide coatings on the surface of TiAl alloys using a simple Si-Hf-Ce ternary diffusion co-penetration method. Given that the formation of diffusion-penetrated coatings is based on the diffusion of atoms at high temperatures, pre-shot peening of the alloy can produce surface structural changes such as grain refinement and phase composition transformation, as well as changes in the surface morphology of the alloy, thereby promoting the diffusion of atoms of the infiltrated elements on the surface. Studies have shown that shot peening can promote the growth of diffusion-penetrated coatings on the surfaces of materials such as steel. However, as an intermetallic compound, TiAl alloy has low room temperature plasticity. When TiAl alloy is directly subjected to traditional shot peening at room temperature, the low plasticity of the material is prone to microcracks. During the service life of TiAl alloy workpieces, microcracks will further expand and cause surface cracking, resulting in premature fracture or even scrapping of the workpiece. Summary of the Invention

[0006] The present invention aims to overcome the shortcomings of the prior art by providing a method for preparing a Si-Hf-Ce co-penetrated coating on a TiAl alloy. This method utilizes a high-temperature airflow to preheat and shot-peen the TiAl alloy. This heating enhances the plasticity of the TiAl alloy, leading to plastic deformation on the surface of the shot-peened TiAl alloy, grain refinement, and the formation of numerous non-equilibrium defects such as vacancies, dislocations, and twins. This method addresses the prior art issue of microcracks that are common when direct shot-peening is performed on TiAl alloys.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating, characterized in that the preparation method comprises the following steps:

[0008] Step 1: preheating the TiAl alloy using high-temperature airflow after pretreatment;

[0009] Step 2: Shot peening the TiAl alloy preheated in step 1 under high-temperature airflow conditions;

[0010] Step 3: Immerse the TiAl alloy shot-blasted in step 2 in a pickling solution, and then ultrasonically clean it with distilled water to obtain a substrate;

[0011] Step 4: embedding and infiltrating the substrate obtained in step 3 to obtain a Si-Hf-Ce co-infiltrating coating; the embedding and infiltrating agent consists of Si, Hf, CeO2, NaF, and Al2O3.

[0012] The above-mentioned method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating is characterized in that the pretreatment process in step 1 is: the TiAl alloy is polished step by step using 80-2000 mesh SiC wet sandpaper, and then placed in anhydrous ethanol for ultrasonic cleaning for 15 minutes to 45 minutes and then dried.

[0013] The above-mentioned method for preparing a TiAl alloy Si-Hf-Ce co-diffusion coating is characterized in that the high-temperature airflows in step one and step two are both argon, the temperature of the argon is 450°C to 650°C, and the pressure of the argon is 0.5MPa to 0.8MPa.

[0014] The present invention is used to fully heat the surface of the TiAl alloy to improve the plasticity by controlling the temperature and the gas pressure.

[0015] The above-mentioned method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating is characterized in that the preheating in step one is carried out using supersonic cold spraying equipment, the preheating time is 10 minutes to 30 minutes, and during the preheating, the distance between the spray gun of the supersonic cold spraying equipment and the surface of the TiAl alloy is 5 mm to 15 mm, and the angle with the surface of the TiAl alloy is 90°.

[0016] The above-mentioned method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating is characterized in that the shot blasting in step 2 uses spherical TC4 pellets, and the diameter of the spherical TC4 pellets is 0.05mm to 0.20mm.

[0017] The present invention adopts TC4 pellets for shot peening, which can avoid the prior art of using cast steel pellets and ceramic pellets with relatively high hardness, which easily cause significant damage to the alloy surface, and using glass pellets with relatively low hardness, which cause insufficient plastic deformation on the TiAl alloy. By controlling the particle size of the TC4 pellets, it is ensured that the TC4 pellets can generate sufficient impact strength on the alloy surface to cause plastic deformation, while avoiding significant damage to the alloy surface.

[0018] The above-mentioned method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating is characterized in that the shot peening in step 2 is carried out using supersonic cold spraying equipment, the shot peening time is 5min to 15min, and the distance between the spray gun of the supersonic cold spraying equipment and the surface of the TiAl alloy during the shot peening is 5mm to 15mm, the angle with the surface of the TiAl alloy is 90°, and the powder feeding rate of the spray gun is 40g / min to 50g / min.

[0019] The present invention achieves a sufficient heating effect on the TiAl alloy surface by controlling the distance between the spray gun and the TiAl alloy surface during preheating. When the distance is too far, the high-temperature airflow is difficult to effectively heat the alloy surface, while when the distance is too close, the surface is heated unevenly. By controlling the angle between the spray gun and the TiAl alloy surface to 90 degrees, the surface can be heated evenly.

[0020] The present invention ensures that the shot particles have sufficient impact strength on the alloy surface during shot peening by controlling the distance between the spray gun and the TiAl alloy surface during shot peening. If the distance is too far, the impact strength of the shot particles on the surface is insufficient, and if the distance is too close, the shot peening on the surface is uneven. By controlling the angle between the spray gun and the TiAl alloy surface to 90 degrees and controlling the powder feeding rate, the uniformity of the surface shot peening is also ensured, thereby generating uniform plastic deformation on the surface.

[0021] The above-mentioned method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating is characterized in that the soaking time in step three is 8 minutes to 15 minutes.

[0022] The above-mentioned method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating is characterized in that the penetrant in step 4 consists of the following components in mass percentage: Si 10-25%, Hf 3-13%, CeO2 1-6%, NaF 5-13%, and the balance is Al2O3.

[0023] The present invention controls the content of Hf and CeO2 in the penetrant to ensure that the Si-Hf-Ce co-penetration coating contains sufficient Hf and Ce, thereby modifying the coating. At the same time, it prevents the Hf and CeO2 content in the penetrant from being too high, which inhibits the penetration of Si and is detrimental to the growth of the silicide coating. A sufficient amount of NaF is used as a catalyst to react with Si, Hf, and CeO2 to generate gaseous fluorides of Si, Hf, and Ce, which decompose on the alloy surface to produce sufficient active atoms of Si, Hf, and Ce to generate a coating. It also prevents the NaF content from being too high, which generates a large amount of gaseous fluorides in a short period of time, causing the pressure in the crucible to rise rapidly, causing the crucible lid to be blown open and resulting in failure in coating preparation. Al2O3 is used as a filler to regulate the deposition rate of Si, Hf, and Ce atoms on the surface of the base alloy and to inhibit high-temperature adhesion of the penetrant.

[0024] The above-mentioned preparation method of a TiAl alloy Si-Hf-Ce co-penetration coating is characterized in that the embedding and penetration process described in step four is: the penetrant is loaded into a crucible, and the substrate is buried in the penetrant and compacted, sealed and placed in a high-temperature resistance furnace, heated to 880°C~1080°C at a rate of 8°C / min~12°C / min and kept warm for 4h~8h, and then ultrasonically cleaned and dried after air cooling; the thickness of the penetrant covering the surface of the substrate after compaction and the distance between the substrate and the inner wall of the crucible are not less than 10mm.

[0025] The present invention controls the heating rate to avoid a too low heating rate resulting in an excessively long coating preparation time, thereby reducing the coating preparation efficiency; and allows sufficient time for air to diffuse into the crucible and react with the penetrant, thereby exacerbating the oxidation consumption of the penetrant. By avoiding an excessively fast heating rate, the penetrant is caused to react in a relatively short period of time, generating an excessive amount of fluoride gas, which increases the pressure in the crucible in a short period of time, causing the crucible cover to break open and the coating preparation to fail. By controlling the temperature of the embedded penetrant, it is avoided that the temperature is too low to achieve the diffusion and infiltration of Si, Hf, and Ce, and that the temperature is too high to cause serious interdiffusion between the coating and the substrate, resulting in a loose coating structure and loss of protective effect.

[0026] The present invention controls the thickness of the penetrant on the surface of the substrate so that the substrate is completely embedded in the penetrant, which can generate sufficient Si, Hf, and Ce atoms to diffuse on the alloy surface to form a coating, ensuring the uniformity of the coating thickness and structure. In addition, covering with a certain thickness of penetrant can fully isolate the substrate from the air, preventing the substrate from being oxidized during the coating preparation process.

[0027] In addition, the present invention also discloses a TiAl alloy Si-Hf-Ce co-penetration coating, characterized in that, obtained by the above-mentioned preparation method, the Si-Hf-Ce co-penetration coating has a multi-layer structure, and the multi-layer structure is, from the outside to the inside,: a Hf and Ce-rich silicide surface layer, a TiSi2+Ti5Si3 outer layer, a TiSi2+Ti5Si3+Ti(Al,Si)2 transition layer, and a TiAl2 inner layer.

[0028] The present invention utilizes an embedded infiltration method, utilizing Si, Hf, and Ce atoms generated by a high-temperature reaction of an infiltrant to diffuse inward from the shot-peened TiAl alloy surface to form a co-infiltration coating. Because Si has a smaller atomic radius and a greater diffusion capacity than Hf and Ce, Si first reacts with the Ti element in the TiAl alloy to form a silicide surface layer, which then diffuses inward to form an outer TiSi2+Ti5Si3 layer. The Al in the TiAl alloy does not react with Si and can only accumulate below the outer TiSi2+Ti5Si3 layer as it grows, forming an inner TiAl2 layer. Simultaneously, diffusion between the outer TiSi2+Ti5Si3 layer and the inner TiAl2 layer forms a transition layer of TiSi2+Ti5Si3+Ti(Al,Si)2. Because Hf and Ce, with their larger atomic radii, have shorter diffusion distances, they accumulate only on the surface, forming an Hf- and Ce-rich silicide surface layer.

[0029] When the multilayer Si-Hf-Ce co-penetration coating prepared by the present invention is applied to a high-temperature oxidizing environment, Hf and Ce are primarily distributed in the surface layer, and the formation free energies of their oxides, HfO2 and CeO2, are lower than those of Ti and Si oxides, TiO2 and SiO2. Therefore, Hf and Ce are first oxidized at high temperatures and then doped into the SiO2 oxide film formed from silicide, thereby optimizing the oxide film structure and inhibiting its growth. Furthermore, the TiAl2 inner layer, which has a high aluminum content, can generate Al2O3, hindering the internal diffusion of oxygen. Furthermore, a transition layer is formed between the TiSi2+Ti5Si3 outer layer and the TiAl2 inner layer, and a metallurgical bond is formed between the Si-Hf-Ce co-penetration coating and the substrate due to element diffusion. Therefore, the coating is not prone to cracking when used under high-temperature conditions.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] 1. The present invention uses high-temperature airflow to preheat and shot peen the TiAl alloy. The plasticity of the TiAl alloy is improved after heating, causing plastic deformation, grain refinement, and the formation of a large number of non-equilibrium defects such as vacancies, dislocations, and twins on the surface of the shot-peened TiAl alloy. This avoids the brittle microcracks generated on the surface of the shot-peened TiAl alloy at room temperature, which lead to crack expansion during subsequent service under stress and cause the workpiece to fail. At the same time, the large number of non-equilibrium defects such as grain boundaries, vacancies, dislocations, and twins on the surface of the TiAl alloy after shot peening can promote the diffusion of Hf and Ce elements with larger radii on the surface of the TiAl alloy.

[0032] 2. The present invention uses TC4 pellets to shot peen the TiAl alloy, which is beneficial for introducing plastic deformation on the alloy surface and avoiding damage to the surface.

[0033] 3. The Si-Hf-Ce co-penetration coating of the present invention has excellent bonding strength with the TiAl alloy, is not easy to fall off, and is beneficial to improving the high-temperature oxidation resistance of the TiAl alloy.

[0034] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a microscopic image of the surface of the Si-Hf-Ce co-penetration coating obtained in Example 1 of the present invention.

[0036] Figure 2 This is the XRD pattern of the Si-Hf-Ce co-penetration coating obtained in Example 1 of the present invention.

[0037] Figure 3 This is a microscopic image of the multilayer structure of the Si-Hf-Ce co-penetration coating obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0038] Example 1

[0039] The Si-Hf-Ce co-penetration coating of this embodiment is composed of a Hf and Ce-rich silicide surface layer, a TiSi2+Ti5Si3 outer layer, a TiSi2+Ti5Si3+Ti(Al,Si)2 transition layer, and a TiAl2 inner layer. The preparation method of the Si-Hf-Ce co-penetration coating includes the following steps:

[0040] Step 1: The TiAl alloy is polished step by step using 80-2000 mesh SiC water sandpaper, then ultrasonically cleaned in anhydrous ethanol for 30 minutes and then dried. The TiAl alloy is preheated for 20 minutes using a supersonic cold spray device with high-temperature argon gas at a temperature of 500°C and a pressure of 0.7 MPa. During preheating, the distance between the front end of the spray gun of the supersonic cold spray device and the surface of the TiAl alloy is 10 mm, and the angle between the front end and the surface of the TiAl alloy is 90°. The atomic nominal composition of the TiAl alloy is Ti-48Al-2Cr-2Nb.

[0041] Step 2: Spherical TC4 pellets with a diameter of 0.10 mm were loaded into the storage bin of the supersonic cold spraying equipment, and the TiAl alloy pretreated in step 1 was shot peened for 10 minutes under high-temperature argon conditions of a temperature of 500°C and a pressure of 0.7 MPa. Then, the powder feeding was stopped and the air flow heating was turned off, and the TiAl alloy was cooled for 8 minutes using room temperature argon. During the shot peening, the distance between the front end of the spray gun of the supersonic cold spraying equipment and the surface of the TiAl alloy was 10 mm, the angle with the surface of the TiAl alloy was 90°, and the powder feeding rate of the spray gun was 45 g / min.

[0042] Step 3: Immerse the TiAl alloy shot-peened in step 2 in an acid wash solution for 10 minutes, then ultrasonically clean it with distilled water for 20 minutes, and dry it to obtain a substrate; the acid wash solution comprises the following components in volume percentage: HF 2%, HNO3 4%, and H2O 94%;

[0043] Step 4: Load the penetrant into the crucible, and bury the substrate obtained in step 3 in the penetrant and compact it. The thickness of the penetrant covering the surface of the substrate and the distance between the substrate and the inner wall of the crucible are not less than 10 mm. Then seal the crucible with high-temperature sealing mud and place it in a high-temperature resistance furnace. Heat it to 1000°C at a rate of 8.3°C / min and keep it warm for 6 hours. After air cooling, take out the sample, ultrasonically clean it with distilled water for 60 minutes and dry it to obtain a Si-Hf-Ce co-penetration coating; the embedded penetrant is an analytical pure powder with a particle size of less than 200 mesh, ball milled for 4 hours and dried at 150°C for 1.5 hours, and the penetrant is composed of the following components in mass percentage: Si 15%, Hf 10%, CeO2 2%, NaF 8%, and the remainder is Al2O3; the high-temperature sealing mud is obtained by mixing 1L of silica sol with 1.5kg of Al2O3.

[0044] The Si-Hf-Ce co-penetration coating obtained in this embodiment was analyzed. Figure 1 and Figure 2 As shown, no microcracks appeared on the surface of the Si-Hf-Ce co-penetration coating, and TiSi2 and Ti5Si3 were generated.

[0045] The Si-Hf-Ce co-penetration coating obtained in this embodiment was cut open and the cross section was microscopically analyzed. Figure 3 As shown in Figure 2, the Si-Hf-Ce co-penetration coating has a multi-layer structure, which is divided into a thin surface layer, a light outer layer and a dark inner layer, and interdiffusion occurs between the outer layer and the inner layer to form a transition layer; the layers of the multi-layer structure are distributed and the points are taken for composition analysis (a total of 5 points are taken, Figure 3 The EDS analysis results are shown in Table 1.

[0046] Table 1 EDS analysis results of Si-Hf-Ce co-penetration coating

[0047]

[0048] As shown in Table 1, the surface layer (X1 and X2) contains a high content of Ti and Si, which is a Ti silicide, and Hf and Ce are mainly distributed in this layer, with the atomic percentage of Hf reaching 8.4% and the atomic percentage of Ce reaching 2.1%, indicating that this layer is mainly a Hf and Ce-rich silicide; the outer layer (X3) mainly contains Ti and Si. According to the atomic ratio of Ti and Si, combined with Figure 2 The XRD pattern shows that the outer layer is a mixture of TiSi2 and Ti5Si3; the inner layer (X5) is an Al-rich layer with an atomic ratio of Ti to Al close to 0.5, which is a TiAl2 phase; the transition layer is between the outer and inner layers. Figure 3It can be seen that the transition layer is composed of strip-shaped TiSi2+Ti5Si3 and dark areas. The atomic ratio of Ti and Al in the dark area (X4) is close to 0.5, but compared with the inner layer (X5), its Si content is higher, so the phase composition of the dark area is Ti(Al,Si)2, that is, the transition layer is composed of TiSi2+Ti5Si3+Ti(Al,Si)2.

[0049] Example 2

[0050] The Si-Hf-Ce co-penetration coating of this embodiment is composed of a Hf and Ce-rich silicide surface layer, a TiSi2+Ti5Si3 outer layer, a TiSi2+Ti5Si3+Ti(Al,Si)2 transition layer, and a TiAl2 inner layer. The preparation method of the Si-Hf-Ce co-penetration coating includes the following steps:

[0051] Step 1: The TiAl alloy is polished step by step using 80-2000 mesh SiC water sandpaper, then ultrasonically cleaned in anhydrous ethanol for 15 minutes and dried, and preheated for 10 minutes using a supersonic cold spray device with high-temperature argon gas at a temperature of 450° C. and a pressure of 0.5 MPa. During preheating, the distance between the front end of the spray gun of the supersonic cold spray device and the surface of the TiAl alloy is 5 mm, and the angle with the surface of the TiAl alloy is 90°; the atomic nominal composition of the TiAl alloy is Ti-48Al-2Cr-2Nb;

[0052] Step 2: Spherical TC4 pellets with a diameter of 0.05 mm were loaded into the storage bin of the supersonic cold spraying equipment, and the TiAl alloy pretreated in step 1 was shot peened for 5 minutes under high-temperature argon conditions of a temperature of 450°C and a pressure of 0.5 MPa. Then, the powder feeding was stopped and the air flow heating was turned off, and the TiAl alloy was cooled for 5 minutes using room temperature argon. During the shot peening, the distance between the front end of the spray gun of the supersonic cold spraying equipment and the surface of the TiAl alloy was 5 mm, the angle with the surface of the TiAl alloy was 90°, and the powder feeding rate of the spray gun was 40 g / min.

[0053] Step 3: Immerse the TiAl alloy shot-peened in step 2 in an acid wash solution for 10 minutes, then ultrasonically clean it with distilled water for 20 minutes, and dry it to obtain a substrate; the acid wash solution comprises the following components in volume percentage: HF 2%, HNO3 4%, and H2O 94%;

[0054] Step 4: Load the penetrant into the crucible, and bury the substrate obtained in step 3 in the penetrant and compact it. The thickness of the penetrant covering the surface of the substrate and the distance between the substrate and the inner wall of the crucible are not less than 10 mm. Then seal the crucible with high-temperature sealing mud and place it in a high-temperature resistance furnace. Heat it to 1000°C at a rate of 8.3°C / min and keep it warm for 6 hours. After air cooling, take out the sample, ultrasonically clean it with distilled water for 60 minutes and dry it to obtain a Si-Hf-Ce co-penetration coating; the embedded penetrant is an analytical pure powder with a particle size of less than 200 mesh, ball milled for 4 hours and dried at 150°C for 1.5 hours, and the penetrant is composed of the following components in mass percentage: Si 15%, Hf 10%, CeO2 2%, NaF 8%, and the remainder is Al2O3; the high-temperature sealing mud is obtained by mixing 1L of silica sol with 1.5kg of Al2O3.

[0055] No microcracks appeared on the surface of the Si-Hf-Ce co-penetration coating obtained in this embodiment.

[0056] Example 3

[0057] The Si-Hf-Ce co-penetration coating of this embodiment is composed of a Hf and Ce-rich silicide surface layer, a TiSi2+Ti5Si3 outer layer, a TiSi2+Ti5Si3+Ti(Al,Si)2 transition layer, and a TiAl2 inner layer. The preparation method of the Si-Hf-Ce co-penetration coating includes the following steps:

[0058] Step 1: The TiAl alloy is polished step by step using 80-2000 mesh SiC water sandpaper, then ultrasonically cleaned in anhydrous ethanol for 45 minutes and dried, and preheated for 30 minutes using a supersonic cold spray device with high-temperature argon gas at a temperature of 650°C and a pressure of 0.8 MPa. During preheating, the distance between the front end of the spray gun of the supersonic cold spray device and the surface of the TiAl alloy is 15 mm, and the angle with the surface of the TiAl alloy is 90°; the atomic nominal composition of the TiAl alloy is Ti-48Al-2Cr-2Nb;

[0059] Step 2: Spherical TC4 pellets with a diameter of 0.20 mm were loaded into the storage bin of the supersonic cold spraying equipment, and the TiAl alloy pretreated in step 1 was shot peened for 15 minutes under high-temperature argon conditions of a temperature of 650°C and a pressure of 0.8 MPa. Then, the powder feeding was stopped and the air flow heating was turned off, and the TiAl alloy was cooled for 10 minutes using room temperature argon. During the shot peening, the distance between the front end of the spray gun of the supersonic cold spraying equipment and the surface of the TiAl alloy was 15 mm, the angle with the surface of the TiAl alloy was 90°, and the powder feeding rate of the spray gun was 50 g / min.

[0060] Step 3: Immerse the TiAl alloy shot-peened in step 2 in an acid wash solution for 10 minutes, then ultrasonically clean it with distilled water for 20 minutes, and dry it to obtain a substrate; the acid wash solution comprises the following components in volume percentage: HF 2%, HNO3 4%, and H2O 94%;

[0061] Step 4: Load the penetrant into the crucible, and bury the substrate obtained in step 3 in the penetrant and compact it. The thickness of the penetrant covering the surface of the substrate and the distance between the substrate and the inner wall of the crucible are not less than 10 mm. Then seal the crucible with high-temperature sealing mud and place it in a high-temperature resistance furnace. Heat it to 1000°C at a rate of 8.3°C / min and keep it warm for 6 hours. After air cooling, take out the sample, ultrasonically clean it with distilled water for 60 minutes and dry it to obtain a Si-Hf-Ce co-penetration coating; the embedded penetrant is an analytical pure powder with a particle size of less than 200 mesh, ball milled for 4 hours and dried at 150°C for 1.5 hours, and the penetrant is composed of the following components in mass percentage: Si 15%, Hf 10%, CeO2 2%, NaF 8%, and the remainder is Al2O3; the high-temperature sealing mud is obtained by mixing 1L of silica sol with 1.5kg of Al2O3.

[0062] No microcracks appeared on the surface of the Si-Hf-Ce co-penetration coating obtained in this embodiment.

[0063] Example 4

[0064] The Si-Hf-Ce co-penetration coating of this embodiment is composed of a Hf and Ce-rich silicide surface layer, a TiSi2+Ti5Si3 outer layer, a TiSi2+Ti5Si3+Ti(Al,Si)2 transition layer, and a TiAl2 inner layer. The preparation method of the Si-Hf-Ce co-penetration coating includes the following steps:

[0065] Step 1: The TiAl alloy is polished step by step using 80-2000 mesh SiC water sandpaper, then ultrasonically cleaned in anhydrous ethanol for 30 minutes and then dried. The TiAl alloy is preheated for 20 minutes using a supersonic cold spray device with high-temperature argon gas at a temperature of 500°C and a pressure of 0.7 MPa. During preheating, the distance between the front end of the spray gun of the supersonic cold spray device and the surface of the TiAl alloy is 10 mm, and the angle between the front end and the surface of the TiAl alloy is 90°. The atomic nominal composition of the TiAl alloy is Ti-48Al-2Cr-2Nb.

[0066] Step 2: Spherical TC4 pellets with a diameter of 0.10 mm were loaded into the storage bin of the supersonic cold spraying equipment, and the TiAl alloy pretreated in step 1 was shot peened for 10 minutes under high-temperature argon conditions of a temperature of 500°C and a pressure of 0.7 MPa. Then, the powder feeding was stopped and the air flow heating was turned off, and the TiAl alloy was cooled for 8 minutes using room temperature argon. During the shot peening, the distance between the front end of the spray gun of the supersonic cold spraying equipment and the surface of the TiAl alloy was 10 mm, the angle with the surface of the TiAl alloy was 90°, and the powder feeding rate of the spray gun was 45 g / min.

[0067] Step 3: Immerse the TiAl alloy shot-peened in step 2 in an acid wash solution for 8 minutes, then ultrasonically clean it with distilled water for 10 minutes, and dry it to obtain a substrate; the acid wash solution comprises the following components in volume percentage: HF 2%, HNO3 4%, and H2O 94%;

[0068] Step 4: Load the penetrant into the crucible, and bury the substrate obtained in step 3 in the penetrant and compact it. The thickness of the penetrant covering the surface of the substrate and the distance between the substrate and the inner wall of the crucible are not less than 10 mm. Then seal the crucible with high-temperature sealing mud and place it in a high-temperature resistance furnace. Heat it to 880°C at a rate of 8°C / min and keep it warm for 8 hours. After air cooling, take out the sample, ultrasonically clean it with distilled water for 45 minutes and dry it to obtain a Si-Hf-Ce co-penetration coating; the embedded penetrant is an analytical pure powder with a particle size of less than 200 mesh, ball milled for 3 hours and dried at 150°C for 1 hour, and the penetrant is composed of the following components in mass percentage: Si 10%, Hf 3%, CeO2 1%, NaF 5%, and the remainder is Al2O3; the high-temperature sealing mud is obtained by mixing 1L of silica sol with 1.5kg of Al2O3.

[0069] No microcracks appeared on the surface of the Si-Hf-Ce co-penetration coating obtained in this embodiment.

[0070] Example 5

[0071] The Si-Hf-Ce co-penetration coating of this embodiment is composed of a Hf and Ce-rich silicide surface layer, a TiSi2+Ti5Si3 outer layer, a TiSi2+Ti5Si3+Ti(Al,Si)2 transition layer, and a TiAl2 inner layer. The preparation method of the Si-Hf-Ce co-penetration coating includes the following steps:

[0072] Step 1: The TiAl alloy is polished step by step using 80-2000 mesh SiC water sandpaper, then ultrasonically cleaned in anhydrous ethanol for 30 minutes and then dried. The TiAl alloy is preheated for 20 minutes using a supersonic cold spray device with high-temperature argon gas at a temperature of 500°C and a pressure of 0.7 MPa. During preheating, the distance between the front end of the spray gun of the supersonic cold spray device and the surface of the TiAl alloy is 10 mm, and the angle between the front end and the surface of the TiAl alloy is 90°. The atomic nominal composition of the TiAl alloy is Ti-48Al-2Cr-2Nb.

[0073] Step 2: Spherical TC4 pellets with a diameter of 0.10 mm were loaded into the storage bin of the supersonic cold spraying equipment, and the TiAl alloy pretreated in step 1 was shot peened for 10 minutes under high-temperature argon conditions of a temperature of 500°C and a pressure of 0.7 MPa. Then, the powder feeding was stopped and the air flow heating was turned off, and the TiAl alloy was cooled for 8 minutes using room temperature argon. During the shot peening, the distance between the front end of the spray gun of the supersonic cold spraying equipment and the surface of the TiAl alloy was 10 mm, and the angle with the surface of the TiAl alloy was 90°. The powder feeding rate of the spray gun was 45 g / min.

[0074] Step 3: Immerse the TiAl alloy shot-peened in step 2 in an acid wash solution for 15 minutes, then ultrasonically clean it with distilled water for 30 minutes, and dry it to obtain a substrate; the acid wash solution comprises the following components in volume percentage: HF 2%, HNO3 4%, and H2O 94%;

[0075] Step 4: Load the penetrant into the crucible, and bury the substrate obtained in step 3 in the penetrant and compact it. The thickness of the penetrant covering the surface of the substrate and the distance between the substrate and the inner wall of the crucible are not less than 10 mm. Then seal the crucible with high-temperature sealing mud and place it in a high-temperature resistance furnace. Heat it to 1080°C at a rate of 12°C / min and keep it warm for 4 hours. After air cooling, take out the sample, ultrasonically clean it with distilled water for 90 minutes and dry it to obtain a Si-Hf-Ce co-penetration coating; the embedded penetrant is an analytical pure powder with a particle size of less than 200 mesh, ball milled for 5 hours and dried at 150°C for 2 hours, and the penetrant is composed of the following components in mass percentage: Si 25%, Hf 13%, CeO2 6%, NaF 13%, and the remainder is Al2O3; the high-temperature sealing mud is obtained by mixing 1L of silica sol with 1.5kg of Al2O3.

[0076] No microcracks appeared on the surface of the Si-Hf-Ce co-penetration coating obtained in this embodiment.

[0077] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural transformation made to the above embodiment based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating, characterized in that: The preparation method comprises the following steps: Step 1: preheating the TiAl alloy using high-temperature airflow after pretreatment; Step 2: Shot peening the TiAl alloy preheated in step 1 under high-temperature airflow conditions; Step 3: Immerse the TiAl alloy shot-blasted in step 2 in a pickling solution, and then ultrasonically clean it with distilled water to obtain a substrate; Step 4: embedding and infiltrating the substrate obtained in step 3 to obtain a Si-Hf-Ce co-infiltrating coating; the embedding and infiltrating agent consists of Si, Hf, CeO2, NaF, and Al2O3.

2. The method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating according to claim 1, characterized in that: The pretreatment process in step 1 is as follows: the TiAl alloy is ground and polished step by step using 80-2000 mesh SiC water sandpaper, and then placed in anhydrous ethanol for ultrasonic cleaning for 15-45 minutes and then dried.

3. The method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating according to claim 1, characterized in that: The high-temperature gas flow in step 1 and step 2 is argon gas, the temperature of the argon gas is 450° C. to 650° C., and the pressure of the argon gas is 0.5 MPa to 0.8 MPa.

4. The method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating according to claim 1, characterized in that: The preheating in step 1 is performed using a supersonic cold spraying device, and the preheating time is 10 min to 30 min. During the preheating, the distance between the spray gun of the supersonic cold spraying device and the surface of the TiAl alloy is 5 mm to 15 mm, and the angle with the surface of the TiAl alloy is 90°.

5. The method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating according to claim 1, characterized in that: The shot blasting in step 2 uses spherical TC4 pellets, and the diameter of the spherical TC4 pellets is 0.05mm to 0.20mm.

6. The method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating according to claim 1, characterized in that: The shot peening in step 2 is carried out using a supersonic cold spraying equipment, and the shot peening time is 5min to 15min. During the shot peening, the distance between the spray gun of the supersonic cold spraying equipment and the surface of the TiAl alloy is 5mm to 15mm, and the angle with the surface of the TiAl alloy is 90°. The powder feeding rate of the spray gun is 40g / min to 50g / min.

7. The method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating according to claim 1, characterized in that: The soaking time in step 3 is 8 minutes to 15 minutes.

8. The method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating according to claim 1, characterized in that: The penetrant in step 4 is composed of the following components in mass percentage: Si 10% to 25%, Hf 3% to 13%, CeO2 1% to 6%, NaF 5% to 13%, and the balance is Al2O3.

9. The method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating according to claim 1, characterized in that: The embedding process described in step four is: loading the penetrant into the crucible, burying the substrate in the penetrant and compacting it, sealing it and placing it in a high-temperature resistance furnace, heating it to 880°C~1080°C at a rate of 8°C / min~12°C / min and keeping it warm for 4h~8h, air cooling it and then ultrasonically cleaning and drying it; the thickness of the penetrant covering the surface of the substrate after compaction and the distance between the substrate and the inner wall of the crucible are not less than 10mm.

10. A TiAl alloy Si-Hf-Ce co-penetration coating, characterized in that: The Si-Hf-Ce co-penetration coating is obtained by the preparation method described in any one of claims 1 to 9, and has a multi-layer structure. The multi-layer structure is, from the outside to the inside,: a Hf and Ce-rich silicide surface layer, a TiSi2+Ti5Si3 outer layer, a TiSi2+Ti5Si3+Ti(Al,Si)2 transition layer, and a TiAl2 inner layer.

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