TiAl alloy Si-Hf-Ce co-permeation coating and preparation method thereof

Abstract

The invention discloses a preparation method of a TiAl alloy Si-Hf-Ce co-permeation coating. The preparation method comprises the following steps that firstly, after TiAl alloy is pretreated, high-temperature airflow is adopted for preheating; secondly, shot blasting is conducted on the TiAl alloy under the high-temperature airflow condition; thirdly, the TiAl alloy is soaked in a pickling solution, and then a matrix is obtained after distilled water is adopted for ultrasonic cleaning; 4, the matrix is subjected to embedding infiltration, and the Si-Hf-Ce co-permeation coating is obtained; the invention further discloses the Si-Hf-Ce co-permeation coating of the TiAl alloy. According to the preparation method, preheating and shot blasting are conducted on the TiAl alloy through high-temperature airflow, the plasticity of the TiAl alloy is improved after the TiAl alloy is heated, so that 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 prevented from being generated on the surface of the TiAl alloy during shot blasting, and the preparation 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 alloy has become one of the most competitive high temperature structural materials for nickel-based high temperature alloys used in aircraft engines. However, Al and Ti easily form TiO at high temperatures. 2 and Al 2 O 3 A mixture of TiO 2 The loose structure cannot effectively prevent oxygen diffusion, resulting in insufficient oxidation resistance of TiAl alloy at high temperatures, greatly limiting the application of TiAl alloy.

[0003] Applying a protective coating on the surface of TiAl alloy is the most effective and economical way to improve its high temperature oxidation resistance. Usually, the powder embedding method is used to infiltrate Si on the surface of TiAl alloy to prepare a silicide coating. This coating has the advantages of low density, high melting point, and good thermal stability. A strong metallurgical bond can be formed between the coating and the base TiAl alloy. The silicide coating generates a protective oxide SiO at high temperature. 2 , which can provide protection for TiAl alloy. In addition, the powder embedding infiltration process is simple, low-cost, and has little restriction on the shape and size of the matrix workpiece, which is suitable for actual production and application.

[0004] However, the brittleness of a single silicide coating is high, which makes it easy to crack inside. At the same time, when oxidized at high temperature, the thermal expansion coefficient of the coating and the surface oxide film does not match, causing the oxide film to peel off and lose its protectiveness. It is usually necessary to add other elements to modify it. Some studies have shown that the active elements Hf and Ce can effectively modify the silicide coating. HfO generated by oxidation of Hf 2 The particles are distributed at the interface between the oxide film and the silicide coating, which inhibits the crack expansion caused by vacancy aggregation, 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 large, and it is difficult to diffuse in TiAl alloy. Therefore, it is difficult to prepare Hf and Ce modified silicide coating on the surface of TiAl alloy by using a simple Si-Hf-Ce ternary diffusion co-peening method. Given that the formation of diffusion-peened coating is based on the diffusion of atoms at high temperature, pre-shot peening of the alloy can produce structural changes such as grain refinement and phase composition transformation on the surface, 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-peened coatings on the surface 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 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 purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art and provide a method for preparing a Si-Hf-Ce co-penetration coating of a TiAl alloy. The preparation method preheats and shot-peens the TiAl alloy using a high-temperature airflow, and the plasticity of the TiAl alloy is improved after heating, so that the surface of the shot-peened TiAl alloy undergoes plastic deformation, refines the grains, and forms a large number of non-equilibrium defects such as vacancies, dislocations, and twins, thereby solving the problem in the prior art that microcracks are easily generated when the TiAl alloy is directly shot-peened.

[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, immersing the TiAl alloy after shot peening in step 2 into a pickling solution, and then ultrasonically cleaning 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-infiltrated coating; the embedding and infiltrating agent is composed of Si, Hf, CeO 2 、NaF、Al 2 O 3 composition.

[0012] The above-mentioned method for preparing a TiAl alloy Si-Hf-Ce co-penetration coating is characterized in that the pretreatment process described in step one is: the TiAl alloy is polished step by step using 80-2000 mesh SiC water sandpaper, and then placed in anhydrous ethanol for 15min-45min ultrasonic cleaning 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 gas flows in step one and step two are both argon gas, the temperature of the argon gas is 450°C to 650°C, and the gas pressure of the argon gas is 0.5MPa to 0.8MPa.

[0014] The 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-diffusion coating is characterized in that the preheating in step one is carried out using a supersonic cold spraying device, the preheating time is 10 minutes to 30 minutes, and 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°.

[0016] 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 uses spherical TC4 pellets, and the diameter of the spherical TC4 pellets is 0.05mm to 0.20mm.

[0017] The present invention adopts TC4 shot for shot peening, which can avoid the use of cast steel shot and ceramic shot with relatively high hardness in the prior art, which is easy to cause serious damage to the alloy surface, and the use of glass shot with relatively low hardness, which causes insufficient plastic deformation on the TiAl alloy; by controlling the particle size of the TC4 shot, it is ensured that the TC4 shot can generate sufficient impact strength on the alloy surface to generate plastic deformation, while avoiding serious 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 a supersonic cold spraying equipment, the shot peening time is 5min to 15min, 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 controls the distance between the spray gun and the TiAl alloy surface during preheating so that the TiAl alloy surface produces a sufficient heating effect. When the distance is too far, the high-temperature airflow is difficult to effectively heat the alloy surface, and 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 be 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 surface shot peening is uneven. By controlling the angle between the spray gun and the TiAl alloy surface to 90° and controlling the powder feeding rate, the uniformity of the surface shot peening is 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 immersion 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 is composed of the following components in mass percentage: Si 10-25%, Hf 3-13%, CeO 2 1~6%, NaF 5~13%, the balance is Al 2 O 3 .

[0023] The present invention is to conduct the Hf and CeO 2 The content of Hf and Ce in the Si-Hf-Ce co-penetration coating is controlled to ensure that the coating contains enough Hf and Ce to achieve the modification of the coating; at the same time, the Hf and CeO in the infiltrant are avoided. 2 Too high a content inhibits the penetration of Si and is not conducive to the growth of the silicide coating. 2 React to generate gaseous fluorides of Si, Hf, and Ce, which decompose on the alloy surface to generate sufficient active atoms of Si, Hf, and Ce to form a coating; avoid excessive NaF content, which will generate a large amount of gaseous fluorides in a short period of time, causing the pressure in the crucible to rise rapidly, causing the crucible cover to be blown open and resulting in coating preparation failure. 2 O 3 It is a filler used to regulate the deposition rate of Si, Hf, and Ce atoms on the surface of the matrix alloy and to inhibit high-temperature bonding of the infiltrant.

[0024] The above-mentioned method for preparing a TiAl alloy Si-Hf-Ce co-diffusion coating is characterized in that the embedding and diffusion process described in step four is: loading the penetrant into a crucible, and 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, and then air cooling it and performing ultrasonic cleaning and drying; 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 the heating rate being too low, which results in a long coating preparation time and reduces the coating preparation efficiency; and allows sufficient time for air to diffuse into the crucible to react with the penetrant, thereby increasing the oxidation consumption of the penetrant. By avoiding too fast a heating rate, the penetrant reacts in a relatively short time, generating an excessive amount of fluoride gas, increasing the pressure in the crucible in a short time, and 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 penetration of Si, Hf, and Ce, and that the temperature is too high to cause serious mutual diffusion between the coating and the substrate, resulting in loose coating tissue 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, diffuse on the alloy surface to form a coating, and ensure the uniformity of the coating thickness and structure; and the penetrant covering a certain thickness can fully isolate the substrate from the air, avoiding oxidation of the substrate 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 the Si-Hf-Ce co-penetration coating is obtained by the above preparation method and has a multi-layer structure, wherein the multi-layer structure is sequentially composed of: a silicide surface layer rich in Hf and Ce, a TiSi 2 +Ti 5 Si 3 Outer layer, TiSi 2 +Ti 5 Si 3 +Ti(Al,Si) 2 Transition layer, TiAl 2 Inner layer.

[0028] The present invention uses the embedding method to utilize Si, Hf, and Ce atoms generated by the reaction of the infiltrant at high temperature to diffuse inward on the surface of the shot-peened TiAl alloy to form a co-infiltrated coating. Since Si has a smaller atomic radius and a stronger diffusion ability than Hf and Ce, Si first reacts with the Ti element in the TiAl alloy to form a silicide surface layer, and then further diffuses inward to form a TiSi 2 +Ti 5 Si3 Outer layer: Al in TiAl alloy does not react with Si, but can only react with TiSi 2 +Ti 5 Si 3 The outer layer grows and is enriched below the outer layer to form TiAl 2 Inner layer; TiSi 2 +Ti 5 Si 3 Outer layer and TiAl 2 TiSi is diffused between the inner layers 2 +Ti 5 Si 3 +Ti(Al,Si) 2 Transition layer: Since Hf and Ce with larger atomic radius have shorter diffusion distances, they are only enriched on the surface, forming a 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 oxidation environment, since Hf and Ce are mainly distributed in the surface layer, and the oxides of Hf and Ce HfO 2 and CeO 2 The free energy of formation is lower than that of Ti and Si oxides TiO 2 and SiO 2 Therefore, Hf and Ce are first oxidized at high temperature and then doped into SiO generated by silicide. 2 The oxide film has the function of optimizing the oxide film structure and inhibiting the growth of the oxide film. 2 The inner layer can generate Al 2 O 3 , hindering the internal diffusion of oxygen. In addition, TiSi 2 +Ti 5 Si 3 Outer layer and TiAl 2 A transition layer is formed between the inner layers, and a metallurgical bond is formed between the Si-Hf-Ce co-diffusion coating and the substrate due to element diffusion, so the coating is not prone to cracking when serving under high temperature conditions.

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

[0031] 1. The present invention adopts high-temperature airflow to preheat and shot peen the TiAl alloy. The plasticity of the TiAl alloy is improved after heating, so that the surface of the shot peened TiAl alloy undergoes plastic deformation, grain refinement, and the formation of a large number of non-equilibrium defects such as vacancies, dislocations, and twins, thereby avoiding brittle microcracks generated on the surface of the shot peened TiAl alloy at room temperature, which may cause crack expansion during subsequent service under a stress environment and cause the workpiece to fail. At the same time, a 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 to introduce plastic deformation on the alloy surface and avoid 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 diagram 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-diffusion 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 silicide surface layer rich in Hf and Ce, a TiSi 2 +Ti 5 Si 3 Outer layer, TiSi 2 +Ti 5 Si 3 +Ti(Al,Si) 2 Transition layer, TiAl 2 The inner layer composition, the preparation method of the Si-Hf-Ce co-penetration coating comprises the following steps:

[0040] Step 1, the TiAl alloy is ground and polished step by step with SiC water sandpaper of 80-2000 mesh, then ultrasonically cleaned in anhydrous ethanol for 30 minutes and then dried, and preheated for 20 minutes with high-temperature argon gas at a temperature of 500°C and a pressure of 0.7MPa using a supersonic cold spraying device. During preheating, the distance between the front end of the spray gun of the supersonic cold spraying device and the surface of the TiAl alloy is 10mm, 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;

[0041] Step 2: Spherical TC4 pellets with a diameter of 0.10 mm are loaded into the storage bin of the supersonic cold spraying equipment, and the TiAl alloy pretreated in step 1 is shot peened for 10 minutes under high-temperature argon conditions at a temperature of 500°C and a gas pressure of 0.7 MPa, and then the powder feeding is stopped and the air flow heating is turned off, and the TiAl alloy is 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 is 10 mm, and the angle with the surface of the TiAl alloy is 90°, and the powder feeding rate of the spray gun is 45 g / min;

[0042] Step 3: The TiAl alloy after shot peening in step 2 is immersed in a pickling solution for 10 minutes, then ultrasonically cleaned with distilled water for 20 minutes, and dried to obtain a substrate; the pickling solution is composed of the following components in volume percentage: HF 2%, HNO 3 4%, H 2 O 94%;

[0043] Step 4: Load the infiltrant into the crucible, and bury the substrate obtained in step 3 in the infiltrant and compact it. The thickness of the infiltrant 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, the crucible is sealed with high-temperature sealing mud and placed in a high-temperature resistance furnace. The temperature is raised to 1000°C at a rate of 8.3°C / min and kept warm for 6 hours. After air cooling, the sample is taken out, ultrasonically cleaned with distilled water for 60 minutes and dried to obtain a Si-Hf-Ce co-infiltration coating; the embedded infiltration agent adopts 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 to obtain, and the infiltrant consists of the following components in mass percentage: Si 15%, Hf 10%, CeO 2 2%, NaF 8%, the balance is Al 2 O 3 The high temperature sealing mud is composed of 1L silica sol and 1.5kg Al 2 O 3 Mix to obtain.

[0044] The Si-Hf-Ce co-penetration coating obtained in this embodiment is analyzed. Figure 1 and Figure 2As shown in the figure, no microcracks appeared on the surface of the Si-Hf-Ce co-penetration coating, and TiSi 2 and Ti 5 Si 3 .

[0045] The Si-Hf-Ce co-penetration coating obtained in this example was cut open and the cross section was microscopically analyzed. Figure 3 As shown in the figure, 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 the outer layer and the inner layer diffuse each other to form a transition layer; the layers of the above multi-layer structure are distributed and points are taken for component 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) has a high content of Ti and Si, which is a Ti silicide, and Hf and Ce are mainly distributed in this layer, with an atomic percentage of Hf of 8.4% and an atomic percentage of Ce of 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 From the XRD spectrum, we can see that the outer layer is TiSi 2 and Ti 5 Si 3 The inner layer (X5) is an Al-rich layer, and the atomic ratio of Ti to Al is close to 0.5, which is TiAl 2 phase; the transition layer between the outer layer and the inner layer is combined Figure 3 It can be seen that the transition layer is composed of strip-shaped TiSi 2 +Ti 5 Si 3 The atomic ratio of Ti and Al in the dark region (X4) is close to 0.5, but its Si content is higher than that in the inner layer (X5), so the phase composition of the dark region is Ti(Al,Si). 2 , that is, the transition layer is composed of TiSi 2 +Ti 5 Si 3 +Ti(Al,Si) 2 composition.

[0049] Example 2

[0050] The Si-Hf-Ce co-penetration coating of this embodiment is composed of a silicide surface layer rich in Hf and Ce, a TiSi 2 +Ti5 Si 3 Outer layer, TiSi 2 +Ti 5 Si 3 +Ti(Al,Si) 2 Transition layer, TiAl 2 The inner layer composition, the preparation method of the Si-Hf-Ce co-penetration coating comprises the following steps:

[0051] Step 1, the TiAl alloy is ground and polished step by step with 80-2000 mesh SiC water sandpaper, then placed in anhydrous ethanol for 15 minutes of ultrasonic cleaning and drying, and preheated for 10 minutes with high-temperature argon gas at a temperature of 450°C and a gas pressure of 0.5MPa using a supersonic cold spraying device. During preheating, the distance between the front end of the spray gun of the supersonic cold spraying device and the surface of the TiAl alloy is 5mm, 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 are loaded into the storage bin of the supersonic cold spraying equipment, and the TiAl alloy pretreated in step 1 is shot peened for 5 minutes under high-temperature argon conditions at a temperature of 450°C and a gas pressure of 0.5 MPa, and then the powder feeding is stopped and the air flow heating is turned off, and the TiAl alloy is 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 is 5 mm, and the angle with the surface of the TiAl alloy is 90°, and the powder feeding rate of the spray gun is 40 g / min;

[0053] Step 3: The TiAl alloy after shot peening in step 2 is immersed in a pickling solution for 10 minutes, then ultrasonically cleaned with distilled water for 20 minutes, and dried to obtain a substrate; the pickling solution is composed of the following components in volume percentage: HF 2%, HNO 3 4%, H 2 O 94%;

[0054] Step 4: Load the infiltrant into the crucible, and bury the substrate obtained in step 3 in the infiltrant and compact it. The thickness of the infiltrant 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, the crucible is sealed with high-temperature sealing mud and placed in a high-temperature resistance furnace. The temperature is raised to 1000°C at a rate of 8.3°C / min and kept warm for 6 hours. After air cooling, the sample is taken out, ultrasonically cleaned with distilled water for 60 minutes and dried to obtain a Si-Hf-Ce co-infiltration coating; the embedded infiltration agent adopts 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 to obtain, and the infiltrant consists of the following components in mass percentage: Si 15%, Hf 10%, CeO 22%, NaF 8%, the balance is Al 2 O 3 The high temperature sealing mud is composed of 1L silica sol and 1.5kg Al 2 O 3 Mix to obtain.

[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 silicide surface layer rich in Hf and Ce, a TiSi 2 +Ti 5 Si 3 Outer layer, TiSi 2 +Ti 5 Si 3 +Ti(Al,Si) 2 Transition layer, TiAl 2 The inner layer composition, the preparation method of the Si-Hf-Ce co-penetration coating comprises the following steps:

[0058] Step 1, the TiAl alloy is ground and polished step by step with 80-2000 mesh SiC water sandpaper, then placed in anhydrous ethanol for 45 minutes of ultrasonic cleaning and drying, and preheated for 30 minutes with high-temperature argon gas at a temperature of 650°C and a gas pressure of 0.8MPa using a supersonic cold spraying device. During preheating, the distance between the front end of the spray gun of the supersonic cold spraying device and the surface of the TiAl alloy is 15mm, 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 are loaded into the storage bin of the supersonic cold spraying equipment, and the TiAl alloy pretreated in step 1 is shot peened for 15 minutes under high-temperature argon conditions at a temperature of 650°C and a gas pressure of 0.8 MPa, and then the powder feeding is stopped and the air flow heating is turned off, and the TiAl alloy is 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 is 15 mm, and the angle with the surface of the TiAl alloy is 90°, and the powder feeding rate of the spray gun is 50 g / min;

[0060] Step 3: The TiAl alloy after shot peening in step 2 is immersed in a pickling solution for 10 minutes, then ultrasonically cleaned with distilled water for 20 minutes, and dried to obtain a substrate; the pickling solution is composed of the following components in volume percentage: HF 2%, HNO 3 4%, H 2 O 94%;

[0061] Step 4: Load the infiltrant into the crucible, and bury the substrate obtained in step 3 in the infiltrant and compact it. The thickness of the infiltrant 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, the crucible is sealed with high-temperature sealing mud and placed in a high-temperature resistance furnace. The temperature is raised to 1000°C at a rate of 8.3°C / min and kept warm for 6 hours. After air cooling, the sample is taken out, ultrasonically cleaned with distilled water for 60 minutes and dried to obtain a Si-Hf-Ce co-infiltration coating; the embedded infiltration agent adopts 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 to obtain, and the infiltrant consists of the following components in mass percentage: Si 15%, Hf 10%, CeO 2 2%, NaF 8%, the balance is Al 2 O 3 The high temperature sealing mud is composed of 1L silica sol and 1.5kg Al 2 O 3 Mix to obtain.

[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 silicide surface layer rich in Hf and Ce, a TiSi 2 +Ti 5 Si 3 Outer layer, TiSi 2 +Ti 5 Si 3 +Ti(Al,Si) 2 Transition layer, TiAl 2 The inner layer composition, the preparation method of the Si-Hf-Ce co-penetration coating comprises the following steps:

[0065] Step 1, the TiAl alloy is ground and polished step by step with SiC water sandpaper of 80-2000 mesh, then ultrasonically cleaned in anhydrous ethanol for 30 minutes and then dried, and preheated for 20 minutes with high-temperature argon gas at a temperature of 500°C and a pressure of 0.7MPa using a supersonic cold spraying device. During preheating, the distance between the front end of the spray gun of the supersonic cold spraying device and the surface of the TiAl alloy is 10mm, 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;

[0066] Step 2: Spherical TC4 pellets with a diameter of 0.10 mm are loaded into the storage bin of the supersonic cold spraying equipment, and the TiAl alloy pretreated in step 1 is shot peened for 10 minutes under high-temperature argon conditions at a temperature of 500°C and a gas pressure of 0.7 MPa, and then the powder feeding is stopped and the air flow heating is turned off, and the TiAl alloy is 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 is 10 mm, and the angle with the surface of the TiAl alloy is 90°, and the powder feeding rate of the spray gun is 45 g / min;

[0067] Step 3: The TiAl alloy after shot peening in step 2 is immersed in a pickling solution for 8 minutes, then ultrasonically cleaned with distilled water for 10 minutes, and dried to obtain a substrate; the pickling solution is composed of the following components in volume percentage: HF 2%, HNO 3 4%, H 2 O 94%;

[0068] Step 4: Load the infiltrant into the crucible, and bury the substrate obtained in step 3 into the infiltrant and compact it. The thickness of the infiltrant 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, the crucible is sealed with high-temperature sealing mud and placed in a high-temperature resistance furnace. The temperature is raised to 880°C at a rate of 8°C / min and kept warm for 8 hours. After air cooling, the sample is taken out, ultrasonically cleaned with distilled water for 45 minutes and dried to obtain a Si-Hf-Ce co-infiltration coating; the embedded infiltration agent adopts 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 to obtain the infiltrant, and the infiltrant consists of the following components in mass percentage: Si 10%, Hf 3%, CeO 2 1%, NaF 5%, the balance is Al 2 O 3 The high temperature sealing mud is composed of 1L silica sol and 1.5kg Al 2 O 3 Mix to obtain.

[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 silicide surface layer rich in Hf and Ce, a TiSi 2 +Ti 5 Si 3 Outer layer, TiSi 2 +Ti 5 Si 3 +Ti(Al,Si) 2 Transition layer, TiAl 2The inner layer composition, the preparation method of the Si-Hf-Ce co-penetration coating comprises the following steps:

[0072] Step 1, the TiAl alloy is ground and polished step by step with SiC water sandpaper of 80-2000 mesh, then ultrasonically cleaned in anhydrous ethanol for 30 minutes and then dried, and preheated for 20 minutes with high-temperature argon gas at a temperature of 500°C and a pressure of 0.7MPa using a supersonic cold spraying device. During preheating, the distance between the front end of the spray gun of the supersonic cold spraying device and the surface of the TiAl alloy is 10mm, 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;

[0073] Step 2: Spherical TC4 pellets with a diameter of 0.10 mm are loaded into the storage bin of the supersonic cold spraying equipment, and the TiAl alloy pretreated in step 1 is shot peened for 10 minutes under high-temperature argon conditions at a temperature of 500°C and a gas pressure of 0.7 MPa, and then the powder feeding is stopped and the air flow heating is turned off, and the TiAl alloy is 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 is 10 mm, and the angle with the surface of the TiAl alloy is 90°; the powder feeding rate of the spray gun is 45 g / min;

[0074] Step 3: The TiAl alloy after shot peening in step 2 is immersed in a pickling solution for 15 minutes, then ultrasonically cleaned with distilled water for 30 minutes, and dried to obtain a substrate; the pickling solution is composed of the following components in volume percentage: HF 2%, HNO 3 4%, H 2 O 94%;

[0075] Step 4: Load the infiltrant into the crucible, and bury the substrate obtained in step 3 into the infiltrant and compact it. The thickness of the infiltrant 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, the crucible is sealed with high-temperature sealing mud and placed in a high-temperature resistance furnace. The temperature is raised to 1080°C at a rate of 12°C / min and kept warm for 4 hours. After air cooling, the sample is taken out, ultrasonically cleaned with distilled water for 90 minutes and dried to obtain a Si-Hf-Ce co-infiltration coating; the embedded infiltration agent adopts 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 to obtain the infiltrant, and the infiltrant consists of the following components in mass percentage: Si 25%, Hf 13%, CeO 2 6%, NaF 13%, the balance is Al 2 O 3 The high temperature sealing mud is composed of 1L silica sol and 1.5kg Al 2 O 3 Mix to obtain.

[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 still falls within the protection scope 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, immersing the TiAl alloy after shot peening in step 2 into a pickling solution, and then ultrasonically cleaning 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-infiltrated 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: the TiAl alloy is ground and polished step by step using 80-2000 mesh SiC water sandpaper, and then placed in anhydrous ethanol for 15min-45min ultrasonic cleaning 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 gas 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 peening 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 supersonic cold spraying equipment, the shot peening time is 5min to 15min, 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.

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 infiltrant in step 4 is composed of the following components in percentage by mass: 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 and penetrating process described in step four is: loading the penetrant into a crucible, and 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-diffusion coating is obtained by the preparation method described in any one of claims 1 to 9, and 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.

Images