High-temperature-resistant and heat-insulating coating suitable for titanium-aluminum alloy, and preparation method for high-temperature-resistant and heat-insulating coating

Abstract

Provided in the present invention are a high-temperature-resistant and heat-insulating coating suitable for a titanium-aluminum alloy, and a preparation method for the high-temperature-resistant and heat-insulating coating. The high-temperature-resistant and heat-insulating coating is composed of eight layers of thin film layer structures. A titanium-aluminum alloy base body (10) is provided with a first Ni-Al intermediate layer (20), a second Ni-Al intermediate layer (30), a TiAlCr thin film layer (40), a first Al2O3 thin film layer (50), a first WC thin film layer (60), a second Al2O3 thin film layer (70), a second WC thin film layer (80) and an MoSiCrC thin film layer (90) in sequence from the surface outwards. The heat-insulating coating has excellent heat insulation performance and a high homogenization degree, is compact and non-porous, and has very good mechanical properties, and the bonding strength between the coating and the base body and the bonding strength between the layers are high.

Description

A high-temperature resistant heat-insulating coating suitable for titanium-aluminum alloy and a preparation method thereof Technical Field

[0001] The invention relates to a high-temperature resistant heat-insulating coating suitable for titanium-aluminum alloy and a preparation method thereof. Background Art

[0002] At high temperatures, titanium-aluminum alloys are prone to forming a non-protective mixed oxide film of TiO2 and Al2O3 on their surfaces, significantly reducing their high-temperature oxidation resistance and restricting their practical applications. The service temperature limit of titanium-aluminum alloys is 800-900°C, which is insufficient for use in extreme environments such as aerospace. To increase the service temperature of titanium-aluminum alloys and enhance their oxidation resistance in high-temperature environments, the main approach is to apply oxidation-resistant thermal insulation coatings or composite coatings to their surfaces. However, traditional thermal insulation materials are typically lightweight, porous, and have low thermal conductivity. While they offer excellent thermal insulation properties, they often suffer from low strength and poor corrosion resistance, making them unsuitable for use in extremely harsh service environments. Materials with excellent mechanical properties typically have denser structures, hindering their ability to achieve excellent thermal insulation. Due to differences in material expansion coefficients, temperature fluctuations, and interfacial constraints under high-temperature service conditions, thermal stresses can occur between the substrate and coating, and between the layers of the composite coating. This can lead to thermal cracking, delamination, and shedding of the coating, exposing the substrate to the external environment and compromising the long-term performance of the composite coating. Summary of the Invention

[0003] The present invention aims to provide a high-temperature resistant heat-insulating coating suitable for titanium-aluminum alloys.

[0004] Another object of the present invention is to provide a method for preparing the above-mentioned high-temperature resistant thermal insulation coating.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A high-temperature resistant thermal insulation coating suitable for titanium-aluminum alloys consists of an eight-layer thin film structure. From the surface of the titanium-aluminum alloy substrate outward, there are, in order, a first Ni-Al intermediate layer, a second Ni-Al intermediate layer, a TiAlCr thin film layer, a first Al2O3 thin film layer, a first WC thin film layer, a second Al2O3 thin film layer, a second WC thin film layer and a MoSiCrC thin film layer.

[0007] Furthermore, the thickness of the first Ni-Al intermediate layer and the second Ni-Al intermediate layer is the same, which is 110-130 nm; the thickness of the TiAlCr thin film layer is 295-305 nm; the thickness of the first Al2O3 thin film layer and the second Al2O3 thin film layer is the same, which is 290-310 nm; the thickness of the first WC thin film layer and the second WC thin film layer is the same, which is 290-310 nm; and the thickness of the MoSiCrC thin film layer is 480-520 nm.

[0008] Furthermore, the atomic percentage of aluminum in the first Ni-Al intermediate layer and the second Ni-Al intermediate layer shows a decreasing trend, the atomic percentage of tungsten in the first WC film layer and the second WC film layer shows an increasing trend, the atomic percentage of aluminum in the first Al2O3 film layer and the second Al2O3 film layer is the same, and the atomic percentage of aluminum in the Al2O3 film layer is 30-40at.%.

[0009] Furthermore, the atomic percentage of aluminum in the first Ni-Al intermediate layer is 45 to 55 at.%, and the atomic percentage of aluminum in the second Ni-Al intermediate layer is 15 to 30 at.%.

[0010] Furthermore, the atomic percentage of titanium in the TiAlCr thin film layer is 25 to 40 at.%, the atomic percentage of aluminum is 40 to 55 at.%, and the atomic percentage of chromium is 15 to 25 at.%.

[0011] Furthermore, the atomic percentage of tungsten in the first WC thin film layer is 12 to 30 at.%, and the atomic percentage of tungsten in the second WC thin film layer is 35 to 45 at.%.

[0012] Furthermore, the atomic percentage of molybdenum in the MoSiCrC thin film layer is 40-50 at.%, the atomic percentage of silicon is 20-30 at.%, the atomic percentage of chromium is 10-20 at.%, and the atomic percentage of carbon is 20-30 at.%.

[0013] A method for preparing a high-temperature resistant heat-insulating coating suitable for titanium-aluminum alloys, comprising:

[0014] Step S1, substrate treatment: machining, grinding, polishing, cleaning, and drying the titanium-aluminum alloy substrate in sequence;

[0015] Step S2, pre-sputtering: placing the treated substrate in a vacuum chamber, closing the vacuum chamber and evacuating the chamber, introducing argon gas to a vacuum chamber pressure of 2-3 Pa, turning on the bias power supply, applying a bias voltage to the substrate, glow discharge to form an argon plasma, and pre-sputtering the substrate; nickel, aluminum, titanium aluminum, aluminum oxide, tungsten, chromium, and silicon targets are respectively set in the vacuum chamber, and pre-sputtering is performed on each target material;

[0016] Step S3, depositing a first Ni-Al intermediate layer: turning on the bias power supply, using a nickel target and an aluminum target as cathode targets, turning on the target power supply, sputtering the aluminum target with DC and the nickel target with medium frequency, to obtain the first Ni-Al intermediate layer;

[0017] Step S4, depositing a second Ni-Al intermediate layer: The method is the same as the method for depositing the first Ni-Al intermediate layer, except that the aluminum content is controlled (i.e., the aluminum content is controlled by adjusting the current of the intermediate frequency power supply and the DC power supply and regulating the sputtering power);

[0018] Step S5, depositing a TiAlCr thin film layer: changing the bias power supply, using a titanium aluminum target or a chromium target as a cathode target, turning on the target power supply, and using DC sputtering to obtain a TiAlCr thin film layer;

[0019] Step S6, depositing the first Al2O3 thin film layer: when the predetermined sputtering power is reached, the Al2O3 thin film layer is sputtered using a medium frequency, and after the deposition is completed, the alumina target is turned off;

[0020] Step S7, depositing the first WC thin film layer: evacuate the gas in the vacuum chamber, introduce acetylene (C2H2), and start the substrate to rotate at a certain speed. When a predetermined sputtering power is reached, the WC thin film layer is sputtered using a medium frequency. After the deposition is completed, the tungsten target is turned off and the introduction of acetylene is stopped.

[0021] Step S8, depositing a second Al2O3 thin film layer: evacuate the gas in the vacuum chamber and reintroduce argon gas, and repeat step S6;

[0022] Step S9, depositing a second WC thin film layer: evacuate the vacuum chamber and reintroduce acetylene, repeating step S7. The acetylene flow rate during deposition of the second WC thin film layer is lower than the acetylene flow rate during deposition of the first WC thin film layer (i.e., the tungsten content is controlled by controlling the acetylene flow rate).

[0023] Step S10, depositing a MoSiCrC thin film layer: continuously introducing acetylene, changing the bias power supply, and simultaneously turning on the chromium target, silicon target, and molybdenum target, using DC sputtering to deposit the MoSiCrC thin film layer.

[0024] Furthermore, the grinding in step S1 is specifically as follows: using 200#, 400#, 600#, 800# and 1000# sandpaper to coarsely grind and finely grind in the same direction until the surface of the substrate is smooth and has no obvious scratches; polishing is specifically as follows: adding a small amount of H2O2 to the SiO2 polishing liquid for reverse polishing for 18 to 22 minutes, wherein the H2O2 accounts for 0.5% to 5% of the volume of the polishing liquid; cleaning is specifically as follows: first using acetone solution to clean for 2 to 6 minutes, and then alternately cleaning with anhydrous ethanol and deionized water, and the number of alternating cleaning times is not less than 3 times; drying is specifically as follows: using a dust-free cloth to wipe dry.

[0025] Furthermore, in step S2, the vacuum is pumped to 2.8×10 -3 ~3.2×10 -3Pa; the argon gas flow rate is 55-65 sccm; during the substrate pre-sputtering process, the bias voltage is 800±100DC, and the pre-sputtering time is 8-12 minutes; during the target pre-sputtering process, the DC current is 0.45-0.55A, and the pre-sputtering time is 13-17 minutes.

[0026] Furthermore, in step S3, the bias value is 48-52 DC, the DC power supply is 0.25-0.35 A, the medium frequency power supply is 0.45-0.55 A, and the deposition time is 18-22 min.

[0027] Furthermore, in step S5, the bias voltage is 78-82 DC, the DC power supply is 0.45-0.55 A, and the deposition time is 48-52 min.

[0028] Furthermore, in step S6, the predetermined sputtering power is 65-75 W, and the deposition time is 43-47 min.

[0029] Furthermore, in step S7, the acetylene flow rate is 20-26 sccm, the substrate rotation rate is 15-25 r / min, the predetermined sputtering power is 55-65 W, and the deposition time is 48-52 min.

[0030] Furthermore, in step S10, the acetylene flow rate is 18-20 sccm, the bias voltage is 48-52 DC, the DC power supply is 0.45-0.55 A, and the deposition time is 48-52 min.

[0031] The following are the effects of the technical solution of the present invention:

[0032] The present invention effectively alleviates the interlayer internal stress between the film and the substrate, and between the films, and improves the bonding strength between the film and the substrate, and between the films, through the composite coating structure design of the first Ni-Al intermediate layer, the second Ni-Al intermediate layer, the TiAlCr thin film layer, the first Al2O3 thin film layer, the first WC thin film layer, the second Al2O3 thin film layer, the second WC thin film layer and the MoSiCrC thin film layer, avoids the occurrence of thermal cracks, crack propagation, coating peeling, shedding and other problems in repeated high-temperature environments, and ensures the integrity and stability of the composite coating structure; and the composite coating structure has good thermal insulation performance and antioxidant ability, and is highly homogenized and densified, meeting the use requirements in harsh high-temperature environments such as the aerospace and automotive industries.

[0033] The present invention adopts a composite coating structure with an aluminum content gradient design of a Ni-Al intermediate layer, and through the mutual cooperation between the thin films, not only does it avoid element interdiffusion between the composite coating structure and the substrate during high-temperature oxidation, maintains the stability of the interface elements, and ensures the stability of the overall structure of the coating, but it also further enhances the bonding force between the substrate and the film and reduces thermal stress. By utilizing the alternating stacking of Al2O3 thin film layers and WC thin film layers with a tungsten content gradient design of the WC thin film layer, the antioxidant capacity and antioxidant effect are further enhanced, the increase of internal stress between the ceramic Al2O3 thin film layers and the WC thin film layers is avoided, and the expansion of thermal cracks is avoided. At the same time, the alternatingly stacked structural layers and the TiAlCr thin film layers and the MoSiCrC thin film layers form a gradient structure (hardness gradient and thermal expansion coefficient gradient), ensuring the integrity and synergy of the composite coating. Finally, the MoSiCrC thin film layer with high melting point, high hardness, corrosion resistance, wear resistance and other excellent properties ensures that the overall composite coating structure has excellent anti-ablation performance (within the range of 1800-2000°C). The overall coating structure is dense, pore-free and crack-free, and has excellent anti-wear, anti-erosion, anti-oxidation, and thermal insulation properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG1 is a schematic structural diagram of a high-temperature resistant heat-insulating coating according to an embodiment of the present invention.

[0035] FIG2 is a surface scanning electron microscope image of the high temperature resistant heat insulation coating in an embodiment of the present invention.

[0036] FIG3 is an indentation test diagram of the high temperature resistant heat insulation coating in an embodiment of the present invention.

[0037] FIG4 is a diagram showing the high-temperature friction test results of the high-temperature resistant heat-insulating coating in an embodiment of the present invention.

[0038] Among them, 10, titanium aluminum alloy substrate; 20, first Ni-Al intermediate layer; 30, second Ni-Al intermediate layer; 40, TiAlCr thin film layer; 50, first Al2O3 thin film layer; 60, first WC thin film layer; 70, second Al2O3 thin film layer; 80, second WC thin film layer; 90, MoSiCrC thin film layer. Modes for Carrying Out the Invention

[0039] The technical solutions in the embodiments of the present invention will be clearly described. The described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0040] Example 1:

[0041] A high-temperature resistant thermal insulation coating suitable for titanium-aluminum alloys, comprising an eight-layer thin film structure. From the surface of a titanium-aluminum alloy substrate 10, there are arranged, in order from the outside, a first Ni-Al intermediate layer 20, a second Ni-Al intermediate layer 30, a TiAlCr thin film layer 40, a first Al2O3 thin film layer 50, a first WC thin film layer 60, a second Al2O3 thin film layer 70, a second WC thin film layer 80, and a MoSiCrC thin film layer 90. The first Ni-Al intermediate layer 20 and the second Ni-Al intermediate layer 30 have the same thickness of 110 nm. The atomic percentage of aluminum in the first Ni-Al intermediate layer 20 and the second Ni-Al intermediate layer 30 decreases. The atomic percentage of aluminum in the first Ni-Al intermediate layer 20 is 45 at.%, and the atomic percentage of aluminum in the second Ni-Al intermediate layer 30 is 15 at.%. The thickness of the TiAlCr thin film layer 40 is 295 nm. The atomic percentage of titanium in the TiAlCr film layer 40 is 30 at.%, the atomic percentage of aluminum is 45 at.%, and the atomic percentage of chromium is 25 at.%; the thickness of the first Al2O3 film layer 50 and the second Al2O3 film layer 70 are the same, which is 290 nm; the atomic percentage of aluminum in the first Al2O3 film layer 50 and the second Al2O3 film layer 70 are the same, which is 30 at.%; the thickness of the first WC film layer 60 and the second WC film layer 80 are the same, which is 290 nm. m, the atomic percentages of tungsten elements in the first WC film layer 60 and the second WC film layer 80 show an increasing trend. The atomic percentage of tungsten elements in the first WC film layer 60 is 12 at.%, and the atomic percentage of tungsten elements in the second WC film layer 80 is 35 at.%; the thickness of the MoSiCrC film layer 90 is 480 nm, and the atomic percentages of molybdenum elements in the MoSiCrC film layer 90 are 40 at.%, the atomic percentages of silicon elements are 20 at.%, the atomic percentages of chromium elements are 10 at.%, and the atomic percentages of carbon elements are 30 at.%.

[0042] Example 2:

[0043] A high-temperature resistant thermal insulation coating suitable for titanium-aluminum alloys is composed of an eight-layer thin film structure. From the surface of a titanium-aluminum alloy substrate 10, there are, in order from the outside, a first Ni-Al intermediate layer 20, a second Ni-Al intermediate layer 30, a TiAlCr thin film layer 40, a first Al2O3 thin film layer 50, a first WC thin film layer 60, a second Al2O3 thin film layer 70, a second WC thin film layer 80, and a MoSiCrC thin film layer 90. The first Ni-Al intermediate layer 20 and the second Ni-Al intermediate layer 30 have the same thickness of 120 nm. The atomic percentage of aluminum in the first Ni-Al intermediate layer 20 and the second Ni-Al intermediate layer 30 shows a decreasing trend. The atomic percentage of aluminum in the first Ni-Al intermediate layer 20 is 50 at.%, and the atomic percentage of aluminum in the second Ni-Al intermediate layer 30 is 22 at.%; the thickness of the TiAlCr thin film layer 40 is 300 nm. The atomic percentage of titanium in the TiAlCr film layer 40 is 35 at.%, the atomic percentage of aluminum is 45 at.%, and the atomic percentage of chromium is 20 at.%; the thickness of the first Al2O3 film layer 50 and the second Al2O3 film layer 70 are the same, which is 300 nm; the atomic percentage of aluminum in the first Al2O3 film layer 50 and the second Al2O3 film layer 70 are the same, which is 35 at.%; the thickness of the first WC film layer 60 and the second WC film layer 80 are the same, which is 300 nm. m, the atomic percentages of tungsten elements in the first WC film layer 60 and the second WC film layer 80 show an increasing trend. The atomic percentage of tungsten elements in the first WC film layer 60 is 21 at.%, and the atomic percentage of tungsten elements in the second WC film layer 80 is 40 at.%; the thickness of the MoSiCrC film layer 90 is 500 nm, and the atomic percentages of molybdenum elements in the MoSiCrC film layer 90 are 42 at.%, the atomic percentages of silicon elements are 22 at.%, the atomic percentages of chromium elements are 11 at.%, and the atomic percentages of carbon elements are 25 at.%.

[0044] The surface of the composite coating obtained in Example 2 was scanned using an electron microscope, and the scanning electron microscope image is shown in Figure 2 (the scanning electron microscope images of the composite coatings obtained in Example 1 and Example 3 are roughly the same as Figure 2, and the present invention does not display them in detail). It can be clearly seen that the surface of the layer obtained in this example is smooth, flat, uniform and dense, without defects such as holes or microcracks. The surface structure of the film layer is dense and smooth, which can effectively block the oxygen in the high-temperature furnace environment from contacting the substrate, and has a good antioxidant and wear-resistant effect.

[0045] The Vickers indentation method was used with a diamond cone indenter with a vertex angle of 136°. The indentation experiment was carried out with a load of 5N to test the sample obtained in Example 2. The results are shown in FIG3 (the test results of the composite coatings obtained in Example 1 and Example 3 are roughly the same as FIG3 , and the present invention will not show them in detail). As can be seen from FIG3 , the titanium aluminum alloy after the test was almost crack-free as a whole, with only very slight cracks at the indentation edge. No film peeling occurred, and the film remained extremely intact, indicating that the residual stress in the film was small, and problems such as crack extension and peeling caused by thermal stress would not occur. The film had good fracture toughness and excellent film-base bonding strength.

[0046] High-temperature friction and wear tests were conducted to investigate the coating's wear resistance at high temperatures: The tests were conducted at a constant temperature of 800°C, with a load of 3N on the friction pair and 30,000 friction cycles. The test results are shown in Figure 4 (the test results for the composite coatings obtained in Examples 1 and 3 are substantially the same as those in Figure 3 and are not detailed in the present invention). As shown in Figure 4, the multilayer composite structure prepared using the present invention exhibited only slight wear, with shallow wear scars and small widths. The coating remained intact, and no peeling or failure occurred during the entire friction and wear process. This demonstrates that the high-temperature, oxidation-resistant composite coating prepared on the titanium-aluminum alloy surface exhibited good wear and abrasion resistance in the experiment.

[0047] Example 3:

[0048] A high-temperature resistant thermal insulation coating suitable for titanium-aluminum alloys is composed of an eight-layer thin film structure. From the surface of a titanium-aluminum alloy substrate 10, there are, in order from the outside, a first Ni-Al intermediate layer 20, a second Ni-Al intermediate layer 30, a TiAlCr thin film layer 40, a first Al2O3 thin film layer 50, a first WC thin film layer 60, a second Al2O3 thin film layer 70, a second WC thin film layer 80, and a MoSiCrC thin film layer 90. The first Ni-Al intermediate layer 20 and the second Ni-Al intermediate layer 30 have the same thickness of 130 nm. The atomic percentage of aluminum in the first Ni-Al intermediate layer 20 and the second Ni-Al intermediate layer 30 shows a decreasing trend. The atomic percentage of aluminum in the first Ni-Al intermediate layer 20 is 55 at.%, and the atomic percentage of aluminum in the second Ni-Al intermediate layer 30 is 30 at.%; the thickness of the TiAlCr thin film layer 40 is 305 nm. The atomic percentage of titanium in the TiAlCr film layer 40 is 40 at.%, the atomic percentage of aluminum is 45 at.%, and the atomic percentage of chromium is 15 at.%; the thickness of the first Al2O3 film layer 50 and the second Al2O3 film layer 70 are the same, which is 310 nm; the atomic percentage of aluminum in the first Al2O3 film layer 50 and the second Al2O3 film layer 70 are the same, which is 40 at.%; the thickness of the first WC film layer 60 and the second WC film layer 80 are the same, which is 310 nm. m, the atomic percentages of tungsten elements in the first WC film layer 60 and the second WC film layer 80 show an increasing trend. The atomic percentage of tungsten elements in the first WC film layer 60 is 30 at.%, and the atomic percentage of tungsten elements in the second WC film layer 80 is 45 at.%; the thickness of the MoSiCrC film layer 90 is 520 nm, and the atomic percentages of molybdenum elements in the MoSiCrC film layer 90 are 44 at.%, the atomic percentages of silicon elements are 24 at.%, the atomic percentages of chromium elements are 12 at.%, and the atomic percentages of carbon elements are 20 at.%.

[0049] Comparative Example 1:

[0050] A titanium-aluminum alloy thermal insulation coating consists of a seven-layer thin film structure, wherein the surface of the titanium-aluminum alloy substrate is arranged outward in order: a Ni-Al intermediate layer, a TiAlCr thin film layer, a first Al2O3 thin film layer, a first WC thin film layer, a second Al2O3 thin film layer, a second WC thin film layer and a MoSiCrC thin film layer; except for the Ni-Al intermediate layer, the remaining layers are consistent with the corresponding thin film layers in Example 2, the Ni-Al intermediate layer has a thickness of 240 nm and the atomic percentage of aluminum in the Ni-Al intermediate layer is 50 at.%.

[0051] Comparative Example 2:

[0052] A titanium-aluminum alloy thermal insulation coating consists of an eight-layer thin film structure, wherein the titanium-aluminum alloy substrate surface is arranged outward in order: a first Ni-Al intermediate layer, a second Ni-Al intermediate layer, a TiAlCr thin film layer, a first Al2O3 thin film layer, a first WC thin film layer, a second Al2O3 thin film layer, a second WC thin film layer and a MoSiCrC thin film layer; the first Ni-Al intermediate layer and the second Ni-Al intermediate layer have the same thickness of 120 nm, and the atomic percentage of aluminum in the first Ni-Al intermediate layer and the second Ni-Al intermediate layer increases, the atomic percentage of aluminum in the first Ni-Al intermediate layer is 22 at.%, and the atomic percentage of aluminum in the second Ni-Al intermediate layer is 50 at.%; the remaining layers are consistent with the corresponding thin film layers in Example 2.

[0053] Comparative Example 3:

[0054] A titanium-aluminum alloy thermal insulation coating consists of an eight-layer thin film structure, wherein from the surface of the titanium-aluminum alloy substrate outward are a first Ni-Al intermediate layer, a second Ni-Al intermediate layer, a TiAlCr thin film layer, a first Al2O3 thin film layer, a first WC thin film layer, a second Al2O3 thin film layer, a second WC thin film layer and a MoSiCrC thin film layer; the thickness of the first WC thin film layer and the second WC thin film layer is the same, which is 300 nm, and the atomic percentage of tungsten element in the first WC thin film layer and the second WC thin film layer is the same, which is 30 at.%; the remaining layers are consistent with the corresponding thin film layers in Example 2.

[0055] Comparative Example 4:

[0056] A titanium-aluminum alloy thermal insulation coating consists of an eight-layer thin film structure, wherein from the surface of the titanium-aluminum alloy substrate outward are a first Ni-Al intermediate layer, a second Ni-Al intermediate layer, a TiAlCr thin film layer, a first Al2O3 thin film layer, a first WC thin film layer, a second Al2O3 thin film layer, a second WC thin film layer and a MoSiCrC thin film layer; the thickness of the first WC thin film layer and the second WC thin film layer is the same, which is 300 nm, and the atomic percentage of tungsten in the first WC thin film layer and the second WC thin film layer shows a decreasing trend, the atomic percentage of tungsten in the first WC thin film layer is 40 at.%, and the atomic percentage of tungsten in the second WC thin film layer is 21 at.%; the remaining layers are consistent with the corresponding thin film layers in Example 2.

[0057] A DUH-211S Shimadzu dynamic ultramicrohardness tester was used, with a diamond micro-Vickers indenter, a test load of 10 mN, and a maximum load holding time of 6 seconds. Hardness tests were performed on the titanium-aluminum alloy substrate samples with thermal insulation composite coatings in Examples 1 to 3 and Comparative Examples 1 to 4 at room temperature and a high temperature of 800°C. The test results are shown in Table 1 below:

[0058] Table 1

[0059] Project Group Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Room temperature (25°C) 44.8 GPa 45.2 GPa 45.7 GPa 44.7 GPa 44.9 GPa 44.8 GPa 45.1 GPa 800°C High temperature 38.8 GPa 39.1 GPa 39.5 GPa 23.5 GPa 23.2 GPa 20.4 GPa 18.9 GPa

[0060] It can be clearly seen from Table 1 that the multilayer composite coating prepared by this method has a tight interface and low internal stress, and the interfacial dislocation movement between each film layer can be effectively hindered in a high temperature environment. Therefore, the hardness drop in a high temperature environment is not obvious and has a higher hardness value.

[0061] A high-temperature oxidation test was carried out in a muffle furnace. The titanium-aluminum alloy substrate samples with thermal insulation composite coatings in Examples 1 to 3 and Comparative Examples 1 to 4 were placed in a muffle furnace, respectively. Under air atmosphere, the heating rate was 30°C / min, and the temperature was raised from room temperature (25°C) to a high temperature of 850°C. The temperature was maintained at high temperature, and the surface changes of the samples were observed. The test structure is shown in Table 2 below (wherein the blank group is titanium-aluminum alloy without surface treatment):

[0062] Table 2

[0063] Project group maintain for 20h maintain for 60h maintain for 100h maintain for 150h maintain for 200h Example 1 No obvious change in the surface No obvious change in the surface No obvious change in the surface No obvious change in the surface No obvious change in the surface Example 2 No obvious change in the surface No obvious change in the surface No obvious change in the surface No obvious change in the surface No obvious change in the surface Example 3 No obvious change in the surface No obvious change in the surface No obvious change in the surface No obvious change in the surface No obvious change in the surface Comparative Example 1 No obvious change in the surface No obvious change in the surface Cracks, peeling, and falling off of the coating ------ Comparative Example 2 No obvious change in the surface No obvious change in the surface Cracks appear on the surface No obvious change in the surface Cracks appear on the surface Obvious cracking and falling off problems --- Comparative Example 4 No obvious change in the surface Fine cracks appear on the surface Cracks and falling off of the surface film ----- The surface color of the blank group changes, and the surface film (oxide film) cracks and falls off ---------

[0064] Note: “---” means no more observations will be made.

[0065] It is obvious from the above table that the multi-layer composite film structure prepared on the surface of titanium-aluminum alloy according to the present invention can still maintain the integrity of the coating structure after a 200-h thermal cycle oxidation test at 850°C, thereby significantly improving the oxidation resistance of titanium-aluminum alloy. At the same time, the bonding strength between each film layer is high, and problems such as cracking and coating peeling will not occur due to thermal stress in a continuous high-temperature thermal environment.

Claims

1. A high temperature resistant heat insulation coating suitable for titanium aluminum alloy, characterized in that: The structure is composed of eight thin film layers. From the surface of the titanium-aluminum alloy substrate outward, there are the first Ni-Al intermediate layer, the second Ni-Al intermediate layer, the TiAlCr thin film layer, the first Al2O3 thin film layer, the first WC thin film layer, the second Al2O3 thin film layer, the second WC thin film layer and the MoSiCrC thin film layer.

2. The thermal insulation coating according to claim 1, characterized in that: The thickness of the first Ni-Al intermediate layer is the same as that of the second Ni-Al intermediate layer, which is 110-130nm; the thickness of the TiAlCr thin film layer is 295-305nm; the thickness of the first Al2O3 thin film layer is the same as that of the second Al2O3 thin film layer, which is 290-310nm; the thickness of the first WC thin film layer is the same as that of the second WC thin film layer, which is 290-310nm; and the thickness of the MoSiCrC thin film layer is 480-520nm.

3. The thermal insulation coating according to claim 1 or 2, characterized in that: The atomic percentage of aluminum in the first Ni-Al intermediate layer and the second Ni-Al intermediate layer is decreasing, the atomic percentage of tungsten in the first WC film layer and the second WC film layer is increasing, the atomic percentage of aluminum in the first Al2O3 film layer and the second Al2O3 film layer is the same, and the atomic percentage of aluminum in the Al2O3 film layer is 30-40at.%.

4. The thermal insulation coating according to claim 3, characterized in that: The atomic percentage of aluminum in the first Ni-Al intermediate layer is 45-55 at.%, and the atomic percentage of aluminum in the second Ni-Al intermediate layer is 15-30 at.%.

5. The thermal insulation coating according to claim 3, characterized in that: The atomic percentage of tungsten in the first WC thin film layer is 12 to 30 at.%, and the atomic percentage of tungsten in the second WC thin film layer is 35 to 45 at.%.

6. The thermal insulation coating according to claim 3, characterized in that: The atomic percentage of molybdenum in the MoSiCrC thin film layer is 40-50 at.%, the atomic percentage of silicon is 20-30 at.%, the atomic percentage of chromium is 10-20 at.%, and the atomic percentage of carbon is 20-30 at.%.

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