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

Abstract

The invention provides a high-temperature-resistant heat-insulating coating suitable for a titanium-aluminum alloy, and relates to the field of heat-insulating coatings, the high-temperature-resistant heat-insulating coating is composed of eight film layer structures, a first Ni-Al intermediate layer (20), a second Ni-Al intermediate layer (30), a TiAlCr film layer (40), a first Al2O3 film layer (50), a first WC film layer (60), a second Al2O3 film layer (70), a second WC film layer (80) and a MoSiCrC film layer (90) are sequentially arranged on the surface of a titanium-aluminum alloy matrix (10) outwards. The heat insulation coating has the advantages of excellent heat insulation performance, high homogenization degree, compactness, no hole and good mechanical property, and the bonding strength between the coating and a substrate semiconductor wafer and between layers is high.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal insulation coatings, and particularly relates to a high-temperature resistant thermal insulation coating suitable for titanium aluminide alloys and a preparation method thereof. Background Art

[0002] With the continuous improvement of the scientific and technological level of China's aerospace industry, the development of new structural materials with high comprehensive performance, low resource consumption, low environmental load, and strong competitive advantages and their surface protection coatings has become an issue of great concern in the field of new material development in recent years; at the same time, the development and application of energy-saving and consumption-reducing technologies have also become the mainstream direction of technological development in various countries. Titanium aluminide alloys have the advantages of high specific strength, low density, good corrosion resistance, and good creep resistance, and are widely used in high-temperature components in the fields of aerospace, petrochemical, navigation, automotive industry, etc., such as aerospace engine components, marine internal combustion engine parts, etc.

[0003] However, a non-protective mixed oxide film of TiO 2 and Al 2 O 3 is easily formed on the surface of titanium aluminide alloys at high temperatures, resulting in a great reduction in their high-temperature oxidation resistance, thus restricting the practical application of titanium aluminide alloys; at the same time, the service temperature limit of titanium aluminide alloys is about 800 - 900 °C, which cannot meet the extremely harsh service environments such as aerospace and navigation. In order to increase the use temperature of titanium aluminide alloys and improve their antioxidant ability in high-temperature environments, the main method is to prepare antioxidant thermal insulation coatings or composite coatings on the surface of titanium aluminide alloys; however, traditional thermal insulation materials usually have the characteristics of light weight, loose, porous, and low thermal conductivity. Although their thermal insulation performance is excellent, they often have low strength and weak erosion resistance, resulting in their inability to be applicable to extremely harsh service environments; materials with excellent mechanical properties usually have a denser structure and cannot achieve excellent thermal insulation performance. In addition, due to the differences in the thermal expansion coefficients of materials, temperature changes, and the influence of interface constraint effects under high-temperature service conditions, thermal stress effects are generated between the substrate and the coating, and between the layers of the composite coating, resulting in problems such as thermal cracks, peeling, and shedding of the coating, thereby causing the substrate to be directly or indirectly exposed to the external environment and affecting the long-term usability of the composite coating. Summary of the Invention

[0004] Aiming at the above problems existing in the prior art, the purpose of the present invention is to provide a high-temperature resistant thermal insulation coating suitable for titanium aluminide alloys. This thermal insulation coating has excellent thermal insulation performance, high degree of homogenization, is dense and pore-free at the same time, has good mechanical properties, has a high bonding strength between the coating and the substrate, and between the layers, and will not have defects such as thermal cracks, peeling, and shedding, meeting the usage requirements of titanium aluminide alloys in harsh environments.

[0005] Another object of the present invention is to provide a method for preparing a high-temperature heat-insulating coating suitable for titanium aluminide alloy for preparing the above coating.

[0006] The object of the present invention is achieved by the following technical solutions: A high-temperature heat-insulating coating suitable for titanium aluminide alloy is composed of an eight-layer thin film layer structure. From the surface of the titanium aluminide alloy substrate outwards, there are a first Ni-Al intermediate layer, a second Ni-Al intermediate layer, a TiAlCr thin film layer, a first Al 2 O 3 thin film layer, a first WC thin film layer, a second Al 2 O 3 thin film layer, a second WC thin film layer and a MoSiCrC thin film layer.

[0007] Based on further optimization of the above solution, the first Ni-Al intermediate layer and the second Ni-Al intermediate layer have the same thickness, which is 110 - 130 nm; the thickness of the TiAlCr thin film layer is 295 - 305 nm; the first Al 2 O 3 thin film layer and the second Al 2 O 3 thin film layer have the same thickness, which is 290 - 310 nm; the first WC thin film layer and the second WC thin film layer have the same thickness, which is 290 - 310 nm; the thickness of the MoSiCrC thin film layer is 480 - 520 nm.

[0008] Based on further optimization of the above solution, the atomic percentage of aluminum element in the first Ni-Al intermediate layer and the second Ni-Al intermediate layer shows a decreasing trend, the atomic percentage of tungsten element in the first WC thin film layer and the second WC thin film layer shows an increasing trend, the atomic percentage of aluminum element in the first Al 2 O 3 thin film layer and the second Al 2 O 3 thin film layer is the same, and the atomic percentage of aluminum element in the Al 2 O 3 thin film layer is 30 - 40 at.%.

[0009] Based on further optimization of the above solution, the atomic percentage of aluminum element in the first Ni-Al intermediate layer is 45 - 55 at.%, and the atomic percentage of aluminum element in the second Ni-Al intermediate layer is 15 - 30 at.%.

[0010] Based on further optimization of the above solution, the atomic percentage of titanium element in the TiAlCr thin film layer is 25 - 40 at.%, the atomic percentage of aluminum element is 40 - 55 at.%, and the atomic percentage of chromium element is 15 - 25 at.%.

[0011] Based on further optimization of the above solution, the atomic percentage of tungsten element in the first WC thin film layer is 12-30 at.%, and the atomic percentage of tungsten element in the second WC thin film layer is 35-45 at.%.

[0012] Based on further optimization of the above solution, the atomic percentage of molybdenum element in the MoSiCrC thin film layer is 40-50 at.%, the atomic percentage of silicon element is 20-30 at.%, the atomic percentage of chromium element is 10-20 at.%, and the atomic percentage of carbon element is 20-30 at.%.

[0013] In the present invention, by first depositing two Ni-Al interlayers with a decreasing trend of aluminum element on the surface of the titanium-aluminum alloy substrate and then depositing a TiAlCr thin film layer, a "double buffer" effect of dynamic stress distribution is formed in the repeatedly acting high-temperature environment, effectively absorbing the strain energy generated during the thermal cycle. At the same time, a hardness gradient is formed, the interfacial stress concentration is reduced, and problems such as the generation of interfacial microcracks and the peeling or falling off of the coating are avoided. Through the gradient design of the two Ni-Al interlayers, the diffusion between the Ni-Al interlayer with high aluminum content and the titanium-aluminum alloy forms a ternary intermetallic compound, significantly improving the bonding strength between the interlayer and the substrate. At the same time, by using the interfacial reaction between the Ni-Al interlayer with low aluminum content and the TiAlCr thin film layer, the interfacial chemical bonding is enhanced, the generation of brittle phases is inhibited, and the bonding strength between the substrate and the thin film layer is effectively improved, further avoiding the peeling problem of the thin film layer. In addition, by using the design of the double Ni-Al interlayer, a double diffusion barrier is formed (both inhibiting the outward diffusion of titanium and aluminum from the coating and blocking the inward diffusion of elements such as chromium into the substrate), maintaining the stability of the interfacial elements, and thus ensuring the overall stability of the coating performance. And in the high-temperature environment, the Ni-Al interlayer with high aluminum content effectively fills the substrate dislocations, and the Ni-Al interlayer with low aluminum content promotes the refinement of the columnar crystals of the TiAlCr thin film layer, thereby improving the overall density and hardness of the composite coating.

[0014] Through the structural design of the Ni-Al interlayer, TiAlCr thin film layer, and Al 2 O 3 thin film layer, a gradually decreasing thermal expansion coefficient gradient is formed, thereby avoiding interfacial cracking caused by sudden changes in the thermal expansion coefficient and improving the interfacial bonding strength. Through Al 2 O 3Structural design of the thin film layer and the WC thin film layer, and the tungsten element content of the two WC thin film layers gradually increases. First, the "hard-brittle" alternating dispersion is used to thermally stress, and the ductility is used to restrain the cracking tendency of brittleness, avoiding crack propagation in the thin film layer and improving the overall thermal shock and fatigue resistance of the coating. Second, the phonon scattering and thermal reflection at the interface are used to extend the heat conduction path, not only effectively reducing the heat transfer rate to the substrate but also avoiding heat accumulation and improving the overall heat insulation effect. Third, a dual antioxidant mechanism is formed to improve the antioxidant effect of the coating and avoid defects generated after coating oxidation. Fourth, the interfacial bonding force is synergistically improved through chemical diffusion and the transition of the thermal expansion coefficient, avoiding spalling problems due to interface failure at high temperatures. Finally, by preparing the MoSiCrC thin film layer on the surface layer, first, it cooperates with the gradient-designed WC thin film layer to form a solid solution, enhance the interfacial bonding force, and avoid brittle fracture. Second, a hardness gradient is formed with each thin film layer to reduce the embedded damage of hard particles. Third, through the high-temperature oxidation characteristics of the MoSiCrC thin film layer, the pores, microcracks, etc. during the deposition process of the WC thin film layer are effectively filled, preventing crack propagation. Fourth, through the MoSiCrC thin film layer with high melting point, high hardness, corrosion resistance, oxidation resistance, and wear resistance, the overall coating and the substrate are protected. 2 O 3 A preparation method of a high-temperature heat-insulating coating suitable for titanium aluminide alloys, comprising:

[0015] Step S1, substrate treatment: successively machining, grinding, polishing, cleaning, and drying the titanium aluminide alloy substrate; Step S2, pre-sputtering: placing the treated substrate in a vacuum chamber, closing the vacuum chamber and evacuating, introducing argon to make the air pressure in the vacuum chamber reach 2-3 Pa, turning on the bias power supply, applying a bias voltage on the substrate, and forming argon plasma by glow discharge to pre-sputter the substrate; nickel, aluminum, titanium aluminum, alumina, tungsten, chromium, and silicon targets are respectively arranged in the vacuum chamber, and each target is pre-sputtered; Step S3, depositing the first Ni-Al intermediate layer: turning on the bias power supply, using the nickel target and the aluminum target as cathode targets, turning on the target power supply, sputtering the aluminum target with direct current and sputtering the nickel target with medium frequency to obtain the first Ni-Al intermediate layer; Step S4, depositing the second Ni-Al intermediate layer: the method is the same as that for depositing the first Ni-Al intermediate layer, except for the control of the aluminum element content (i.e., controlling the aluminum content by adjusting the current of the medium frequency power supply and the direct current power supply and regulating the sputtering power); Step S5, depositing the TiAlCr thin film layer: changing the bias power supply, using the titanium aluminum target and the chromium target as cathode targets, turning on the target power supply, and sputtering with direct current to obtain the TiAlCr thin film layer; Step S6, depositing the first Al O 2 O3 Thin film layer: When the predetermined sputtering power is reached, sputter Al with medium frequency 2 O 3 thin film layer. After the deposition is completed, turn off the alumina target; Step S7, deposit the first WC thin film layer: evacuate the gas in the vacuum chamber, introduce acetylene (C 2 H 2 ), and start the substrate to rotate at a certain rate. When the predetermined sputtering power is reached, sputter the WC thin film layer with medium frequency. After the deposition is completed, turn off the tungsten target and stop introducing acetylene; Step S8, deposit the second Al 2 O 3 thin film layer: evacuate the gas in the vacuum chamber and reintroduce argon, repeat step S6; Step S9, deposit the second WC thin film layer: evacuate the gas in the vacuum chamber and reintroduce acetylene, repeat step S7. The acetylene flow rate introduced when depositing the second WC thin film layer is lower than the acetylene flow rate introduced when depositing the first WC thin film layer (i.e., control the tungsten element content by controlling the acetylene flow rate); Step S10, deposit the MoSiCrC thin film layer: continuously introduce acetylene, change the bias power supply, and at the same time turn on the chromium target, silicon target and molybdenum target, and use DC sputtering to deposit the MoSiCrC thin film layer.

[0016] Based on the further optimization of the above scheme, the grinding in step S1 is specifically: coarsely grind and finely grind the substrate surface with 200#, 400#, 600#, 800# and 1000# sandpapers in the same direction until the surface of the substrate is smooth and there are no obvious scratches; the polishing is specifically: add a small amount of H 2 in the SiO 2 polishing liquid 2 and perform reverse polishing for 18 - 22 min. Among them, H 2 O 2 accounts for 0.5% - 5% of the volume of the polishing liquid; the cleaning is specifically: first clean with acetone solution for 2 - 6 min, and then alternately clean with anhydrous ethanol and deionized water, and the number of alternate cleaning times is not less than 3 times; the drying is specifically: dry with a dust-free cloth.

[0017] Based on the further optimization of the above scheme, in step S2, evacuate the vacuum to 2.8×10 -3 ~3.2×10 -3 Pa; the argon gas flow rate is 55 - 65 sccm; during the pre-sputtering process of the substrate, the bias voltage is 800 ± 100 DC, and the pre-sputtering time is 8 - 12 min; during the pre-sputtering process of the target, the DC current is 0.45 - 0.55 A, and the pre-sputtering time is 13 - 17 min.

[0018] Based on further optimization of the above solution, in step S3, the bias voltage value is 48 - 52 DC, the DC power supply is 0.25 - 0.35 A, the intermediate frequency power supply is 0.45 - 0.55 A, and the deposition time is 18 - 22 min.

[0019] Based on further optimization of the above solution, in step S5, the bias voltage value is 78 - 82 DC, the DC power supply is 0.45 - 0.55 A, and the deposition time is 48 - 52 min.

[0020] Based on further optimization of the above solution, in step S6, the predetermined sputtering power is 65 - 75 W, and the deposition time is 43 - 47 min.

[0021] Based on further optimization of the above solution, 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.

[0022] Based on further optimization of the above solution, 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.

[0023] The following are the effects of the technical solution of the present invention: 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 Al 2 O 3 thin film layer, the first WC thin film layer, the second Al 2 O 3 thin film layer, the second WC thin film layer and the MoSiCrC thin film layer, the present invention effectively alleviates the interlayer internal stress between the thin film and the substrate, and between the thin films, improves the bonding force between the thin film and the substrate, and between the thin films, and avoids problems such as thermal cracks, crack propagation, coating peeling and falling off in an environment of repeated high temperatures, ensuring the integrity and stability of the composite coating structure; and this composite coating structure has good heat insulation performance and antioxidant ability, with high degree of homogenization and densification, meeting the use requirements in harsh high - temperature environments such as aerospace and automotive industries.

[0024] Through the design of the aluminum content gradient of the composite coating structure in cooperation with the Ni - Al intermediate layer, and through the mutual cooperation between the thin films, the present invention not only avoids the element inter - diffusion between the composite coating structure and the substrate during the high - temperature oxidation process, maintains the stability of the interface elements, ensures the stability of the overall coating structure, but also further improves the bonding force between the substrate and the thin film, and reduces the thermal stress; by using Al 2 O 3The alternating lamination of the thin film layer and the WC thin film layer, combined with the tungsten content gradient design of the WC thin film layer, further enhances the antioxidant capacity and antioxidant effect, and avoids ceramic Al 2 O 3 The internal stress between the thin film layer and the WC thin film layer increases, and the propagation of thermal cracks is avoided. At the same time, the alternately laminated structural layer forms a gradient structure (hardness gradient and thermal expansion coefficient gradient) with the TiAlCr thin film layer and the MoSiCrC thin film layer, ensuring the integrity and synergy of the composite coating. Finally, through the MoSiCrC thin film layer with excellent properties such as high melting point, high hardness, corrosion resistance, and wear resistance, it is ensured that the overall composite coating structure has excellent ablation resistance (in the range of 1800 - 2000 °C). The coating structure is overall dense, pore-free, and crack-free, and has excellent properties such as anti-wear, anti-erosion, antioxidant, and heat insulation. Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of the high-temperature resistant and heat-insulating coating in the embodiment of the present invention.

[0026] Figure 2 It is a surface scanning electron microscope image of the high-temperature resistant and heat-insulating coating in the embodiment of the present invention.

[0027] Figure 3 It is an indentation experiment diagram of the high-temperature resistant and heat-insulating coating in the embodiment of the present invention.

[0028] Figure 4 It is a high-temperature friction test result diagram of the high-temperature resistant and heat-insulating coating in the embodiment of the present invention.

[0029] Among them, 10 is a titanium-aluminum alloy substrate; 20 is a first Ni-Al intermediate layer; 30 is a second Ni-Al intermediate layer; 40 is a TiAlCr thin film layer; 50 is a first Al 2 O 3 thin film layer; 60 is a first WC thin film layer; 70 is a second Al 2 O 3 thin film layer; 80 is a second WC thin film layer; 90 is a MoSiCrC thin film layer. Detailed Embodiments

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0031] Embodiment 1: A high-temperature resistant and heat-insulating coating suitable for titanium-aluminum alloy, which is composed of an eight-layer thin film layer structure. From the surface of the titanium-aluminum alloy substrate 10 outwards are the first Ni-Al intermediate layer 20, the second Ni-Al intermediate layer 30, the TiAlCr thin film layer 40, and the first Al2 O 3 thin film layer 50, first WC thin film layer 60, second Al 2 O 3 thin film layer 70, second WC thin film layer 80 and 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, and the atomic percentage of aluminum element 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 element in the first Ni-Al intermediate layer 20 is 45 at.%, and the atomic percentage of aluminum element 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 element in the TiAlCr thin film layer 40 is 30 at.%, the atomic percentage of aluminum element is 45 at.%, and the atomic percentage of chromium element is 25 at.%; the first Al 2 O 3 thin film layer 50 and the second Al 2 O 3 thin film layer 70 have the same thickness of 290 nm, the first Al 2 O 3 thin film layer 50 and the second Al 2 O 3 thin film layer have the same atomic percentage of aluminum element, and the atomic percentage of aluminum element in the Al 2 O 3 thin film layer is 30 at.%; the first WC thin film layer 60 and the second WC thin film layer 80 have the same thickness of 290 nm, and the atomic percentage of tungsten element in the first WC thin film layer 60 and the second WC thin film layer 80 shows an increasing trend. The atomic percentage of tungsten element in the first WC thin film layer 60 is 12 at.%, and the atomic percentage of tungsten element in the second WC thin film layer 80 is 35 at.%; the thickness of the MoSiCrC thin film layer 90 is 480 nm, the atomic percentage of molybdenum element in the MoSiCrC thin film layer 90 is 40 at.%, the atomic percentage of silicon element is 20 at.%, the atomic percentage of chromium element is 10 at.%, and the atomic percentage of carbon element is 30 at.%.

[0032] Example 2: A high-temperature resistant and heat-insulating coating suitable for titanium-aluminum alloy, which consists of an eight-layer thin film layer structure. From the surface of the titanium-aluminum alloy substrate 10 outwards, there are a first Ni-Al intermediate layer 20, a second Ni-Al intermediate layer 30, a TiAlCr thin film layer 40, a first Al 2 O 3 thin film layer 50, a first WC thin film layer 60, a second Al 2 O 3A 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. In the TiAlCr thin film layer 40, the atomic percentage of titanium is 35 at.%, the atomic percentage of aluminum is 45 at.%, and the atomic percentage of chromium is 20 at.%; the first Al 2 O 3 thin film layer 50 and the second Al 2 O 3 thin film layer 70 have the same thickness of 300 nm. The atomic percentage of aluminum in the first Al 2 O 3 thin film layer 50 and the second Al 2 O 3 thin film layer 70 is the same. The atomic percentage of aluminum in the Al 2 O 3 thin film layer is 35 at.%. The first WC thin film layer 60 and the second WC thin film layer 80 have the same thickness of 300 nm. The atomic percentage of tungsten in the first WC thin film layer 60 and the second WC thin film layer 80 shows an increasing trend. The atomic percentage of tungsten in the first WC thin film layer 60 is 21 at.%, and the atomic percentage of tungsten in the second WC thin film layer 80 is 40 at.%. The thickness of the MoSiCrC thin film layer 90 is 500 nm. In the MoSiCrC thin film layer 90, the atomic percentage of molybdenum is 42 at.%, the atomic percentage of silicon is 22 at.%, the atomic percentage of chromium is 11 at.%, and the atomic percentage of carbon is 25 at.%.

[0033] The surface of the composite coating obtained in Example 2 was scanned by an electron microscope. The scanning electron microscope image is as shown in Figure 2 (The scanning electron microscope images of the composite coatings obtained in Example 1 and Example 3 are substantially the same, and the present invention will not show them in detail). It can be clearly seen that the surface of the coating layer obtained in this example is smooth, flat, uniform, and dense, without defects such as holes or microcracks. The surface structure of the thin film layer is dense and has a high smoothness, which can effectively block the contact between oxygen in the high-temperature furnace environment and the substrate, playing a good role in anti-oxidation and wear resistance. Figure 2

[0034] A diamond conical indenter with a vertex angle of 136° was used in the Vickers indentation method. The indentation experiment was carried out on the specimen obtained in Example 2 with a load of 5 N. The results are as shown in Figure 3As shown (the test results of the composite coatings obtained in Example 1 and Example 3 are roughly the same, and the present invention will not show them in detail); Figure 3 it can be seen that: Figure 3 After testing, there are almost no cracks in the overall observation of the titanium-aluminum alloy, and only very slight cracks appear at the edge of the indentation. No film peeling phenomenon occurs, and the film remains extremely intact, indicating that the residual stress in the film is small, and problems such as crack propagation and peeling caused by thermal stress will not occur, and it has good fracture toughness and excellent film-substrate bonding strength.

[0035] The high-temperature wear resistance of the coating was studied by high-temperature friction and wear tests: A high-temperature friction test was carried out at a constant high temperature of 800 °C, with a load of 3 N on the friction pair and 30,000 revolutions of friction cycles. The test results are as Figure 4 shown (the test results of the composite coatings obtained in Example 1 and Example 3 are roughly the same, and the present invention will not show them in detail). Figure 3 it can be seen that for the multi-layer composite structure prepared by the present invention, only slight wear occurs, the wear scar depth is relatively shallow and the width is small, the coating remains intact, and no peeling failure occurs during the entire friction and wear process; it shows that the high-temperature oxidation-resistant composite coating prepared on the surface of the titanium-aluminum alloy exhibits good anti-wear and wear-resistant properties in the experiment. Figure 4

[0036] Example 3: A high-temperature heat-insulating coating suitable for titanium-aluminum alloy, which is composed of an eight-layer thin film layer structure. From the surface of the titanium-aluminum alloy substrate 10 outwards, there are a first Ni-Al intermediate layer 20, a second Ni-Al intermediate layer 30, a TiAlCr thin film layer 40, a first Al 2 O 3 thin film layer 50, a first WC thin film layer 60, a second Al 2 O 3 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 element 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 element in the first Ni-Al intermediate layer 20 is 55 at.%, and the atomic percentage of aluminum element 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 element in the TiAlCr thin film layer 40 is 40 at.%, the atomic percentage of aluminum element is 45 at.%, and the atomic percentage of chromium element is 15 at.%; the first Al 2 O 3 thin film layer 50 and the second Al 2 O 3 ​The thickness of the thin film layer 70 is the same, which is 310 nm, and the first Al 2 O 3 thin film layer 50 has the same atomic percentage of aluminum element as the second Al 2 O 3 thin film layer 70. The atomic percentage of aluminum element in the Al 2 O 3 thin film layer is 40 at.%. The thicknesses of the first WC thin film layer 60 and the second WC thin film layer 80 are the same, which is 310 nm. The atomic percentage of tungsten element in the first WC thin film layer 60 and the second WC thin film layer 80 shows an increasing trend. The atomic percentage of tungsten element in the first WC thin film layer 60 is 30 at.%, and the atomic percentage of tungsten element in the second WC thin film layer 80 is 45 at.%. The thickness of the MoSiCrC thin film layer 90 is 520 nm. The atomic percentage of molybdenum element in the MoSiCrC thin film layer 90 is 44 at.%, the atomic percentage of silicon element is 24 at.%, the atomic percentage of chromium element is 12 at.%, and the atomic percentage of carbon element is 20 at.%.

[0037] Example 4: A preparation method of a high-temperature resistant and heat-insulating coating applicable to titanium-aluminum alloy for preparing the high-temperature resistant and heat-insulating coatings described in Examples 1 to 3 (it should be noted that the preparation methods of the high-temperature resistant and heat-insulating coatings in Examples 1 to 3 are the same. The difference is that the deposition time is controlled corresponding to the thickness of the prepared thin film layer, and at the same time, the target power is controlled according to the element content of the thin film layer), including: Step S1, substrate treatment: successively carry out machining, grinding, polishing, cleaning, and drying on the titanium-aluminum alloy substrate 10; Grinding: successively carry out rough grinding and fine grinding in the same direction with 200#, 400#, 600#, 800#, and 1000# sandpapers until the substrate surface is smooth and there are no obvious scratches; Polishing: add a small amount of H 2 in the SiO 2 O 2 polishing solution and carry out reverse polishing for 18 - 22 min (preferably 20 min). Among them, the H 2 O 2 accounts for 0.5% - 5% (preferably 3%) of the volume of the polishing solution; Cleaning: first clean with acetone solution for 2 - 6 min (preferably 4 min), and then alternately clean with absolute ethanol and deionized water. The number of alternate cleaning times is not less than 3 times (for example: absolute ethanol cleaning - deionized water cleaning - absolute ethanol cleaning); Drying: dry with a dust-free cloth.

[0038] Step S2, Pre-sputtering: Place the treated substrate in the vacuum chamber, close the vacuum chamber and evacuate it. Evacuate to 2.8×10 -3 ~3.2×10 -3 Pa, introduce argon gas with a gas flow rate of 55 - 65 sccm (preferably 60 sccm) to make the air pressure in the vacuum chamber reach 2 - 3 Pa (preferably 2.5 Pa). Turn on the bias power supply and apply a bias voltage on the substrate. The bias voltage is 800 ± 100 DC. Glow discharge forms argon plasma to pre-sputter the substrate, and the pre-sputtering time is 8 - 12 min (preferably 10 min); Nickel, aluminum, titanium aluminum, aluminum oxide, tungsten, chromium, and silicon targets are respectively set in the vacuum chamber, and each target is pre-sputtered. The DC current is 0.45 - 0.55 A (preferably 0.5 A), and the pre-sputtering time is 13 - 17 min (preferably 15 min).

[0039] Step S3, Deposit the first Ni - Al intermediate layer 20: Turn on the bias power supply, with a bias voltage value of 48 - 52 DC (preferably 50 DC). Use a nickel target (high purity, purity 99.99%) and an aluminum target (high purity, purity 99.99%) as cathode targets. Turn on the target power supply, sputter the aluminum target with DC and the nickel target with medium frequency. The DC power supply is 0.25 - 0.35 A (specifically set according to the specific aluminum content), and the medium frequency power supply is 0.45 - 0.55 A (specifically set according to the specific nickel content) to obtain the first Ni - Al intermediate layer 20, and the deposition time is 18 - 22 min (specifically set according to the thickness of the deposited thin film layer).

[0040] Step S4, Deposit the second Ni - Al intermediate layer 30: The method is the same as depositing the first Ni - Al intermediate layer 20, except for the control of the aluminum element content (that is, by adjusting the currents of the medium frequency power supply and the DC power supply to control the sputtering power and achieve the control of the aluminum content. In this embodiment, the current of the medium frequency power supply, that is, the power, should be higher than the current value in Step S3, and the current of the DC power supply, that is, the power, should be lower than the current value in Step S3).

[0041] Step S5, Deposit the TiAlCr thin film layer 40: Change the bias power supply, with a bias voltage value of 78 - 82 DC (preferably 80 DC). Use a titanium aluminum target and a chromium target (high purity, purity 99.99%) as cathode targets (wherein, the atomic ratio of the titanium aluminum target and the chromium target is specifically adjusted according to the target composition). Turn on the target power supply and sputter with DC. The DC power supply is 0.45 - 0.55 A (preferably 0.5 A) to obtain the TiAlCr thin film layer 40, and the deposition time is 48 - 52 min (specifically set according to the thickness of the deposited thin film layer).

[0042] Step S6, Deposit the first Al 2 O 3Thin film layer 50: When the predetermined sputtering power is reached, the predetermined sputtering power is 65 - 75 W, and Al is sputtered by medium frequency. 2 O 3 thin film layer, the deposition time is 43 - 47 min (specifically set according to the thickness of the thin film layer). After the deposition is completed, the alumina target (high purity, purity 99.99%) is turned off.

[0043] It should be noted that: During the thin film deposition in steps S3 - S6, argon gas is continuously introduced.

[0044] Step S7, depositing the first WC thin film layer 60: Evacuate the gas in the vacuum chamber, introduce acetylene (C 2 H 2 ), the acetylene flow rate is 20 - 26 sccm (select the acetylene flow rate according to the specific tungsten content), and start the substrate to rotate at a certain rate, the substrate rotation rate is 15 - 25 r / min (preferably 20 r / min to improve the coating uniformity). When the predetermined sputtering power is reached, the predetermined sputtering power is 55 - 65 W, and the WC thin film layer is sputtered by medium frequency. The deposition time is 48 - 52 min (specifically set according to the thickness of the thin film layer). After the deposition is completed, turn off the tungsten target (high purity, purity 99.99%) and stop introducing acetylene.

[0045] Step S8, depositing the second Al 2 O 3 thin film layer 70: Evacuate the gas in the vacuum chamber and re - introduce argon gas (the gas flow rate is the same as the argon gas flow rate in step S2), and repeat step S6; Step S9, depositing the second WC thin film layer 80: Evacuate the gas in the vacuum chamber and re - introduce acetylene, repeat step S7. The acetylene flow rate introduced when depositing the second WC thin film layer 80 is lower than the acetylene flow rate introduced when depositing the first WC thin film layer 60 (that is, the tungsten element content is controlled by controlling the acetylene flow rate); Step S10, depositing the MoSiCrC thin film layer 90: Continuously introduce acetylene, the acetylene flow rate is 18 - 20 sccm, change the bias power supply, the bias power supply is 48 - 52 DC, at the same time, turn on the chromium target, silicon target and molybdenum target, and use DC sputtering. The DC power supply is 0.45 - 0.55 A (specifically set the acetylene flow rate and the powers of the chromium target, silicon target and molybdenum target according to the contents of molybdenum, silicon, chromium and carbon in the MoSiCrC thin film layer 90), deposit the MoSiCrC thin film layer 90, and the deposition time is 48 - 52 min (specifically set according to the thickness of the thin film layer).

[0046] Example 5: A preparation method of a high-temperature resistant and heat-insulating coating suitable for titanium aluminide alloy. On the basis of step S10 in Example 4, after the MoSiCrC thin film layer 90 is completely deposited, post-treatment is also carried out, that is, the substrate with the composite coating structure is heated in a vacuum or inert atmosphere, heated to 600 - 800 °C and kept warm for 1 - 2 h, so as to promote interface diffusion and ensure the stability of each phase.

[0047] Comparative Example 1: A titanium aluminide alloy heat-insulating coating is composed of a seven-layer thin film layer structure. From the surface of the titanium aluminide alloy substrate outwards, there are Ni-Al intermediate layer, TiAlCr thin film layer, first Al 2 O 3 thin film layer, first WC thin film layer, second Al 2 O 3 thin film layer, second WC thin film layer and MoSiCrC thin film layer; except for the Ni-Al intermediate layer, the other layers are the same as the corresponding thin film layers in Example 2. The thickness of the Ni-Al intermediate layer is 240 nm and the atomic percentage of aluminum element in the Ni-Al intermediate layer is 50 at.%.

[0048] Comparative Example 2: A titanium aluminide alloy heat-insulating coating is composed of an eight-layer thin film layer structure. From the surface of the titanium aluminide alloy substrate outwards, there are first Ni-Al intermediate layer, second Ni-Al intermediate layer, TiAlCr thin film layer, first Al 2 O 3 thin film layer, first WC thin film layer, second Al 2 O 3 thin film layer, second WC thin film layer and 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 element in the first Ni-Al intermediate layer and the second Ni-Al intermediate layer shows an increasing trend. The atomic percentage of aluminum element in the first Ni-Al intermediate layer is 22 at.%, and the atomic percentage of aluminum element in the second Ni-Al intermediate layer is 50 at.%; the other layers are the same as the corresponding thin film layers in Example 2.

[0049] Comparative Example 3: A titanium aluminide alloy heat-insulating coating is composed of an eight-layer thin film layer structure. From the surface of the titanium aluminide alloy substrate outwards, there are first Ni-Al intermediate layer, second Ni-Al intermediate layer, TiAlCr thin film layer, first Al 2 O 3 thin film layer, first WC thin film layer, second Al 2 O 3A thin film layer, a second WC thin film layer, and a MoSiCrC thin film layer; the first WC thin film layer and the second WC thin film layer have the same thickness of 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 other layers are the same as the corresponding thin film layers in Example 2.

[0050] Comparative Example 4: A titanium-aluminum alloy thermal insulation coating is composed of an eight-layer thin film layer structure. From the surface of the titanium-aluminum alloy substrate outwards, there are a first Ni-Al intermediate layer, a second Ni-Al intermediate layer, a TiAlCr thin film layer, a first Al 2 O 3 thin film layer, a first WC thin film layer, a second Al 2 O 3 thin film layer, a second WC thin film layer, and a MoSiCrC thin film layer; the first WC thin film layer and the second WC thin film layer have the same thickness of 300 nm, and the atomic percentage of tungsten element in the first WC thin film layer and the second WC thin film layer shows a decreasing trend. The atomic percentage of tungsten element in the first WC thin film layer is 40 at.%, and the atomic percentage of tungsten element in the second WC thin film layer is 21 at.%; the other layers are the same as the corresponding thin film layers in Example 2.

[0051] Using a DUH-211S Shimadzu dynamic ultra-microhardness tester, with a diamond micro-Vickers indenter, an experimental load of 10 mN, and a maximum load holding time of 6 s, the hardness of the titanium-aluminum alloy substrate specimens with the thermal insulation composite coating in Examples 1 to 3 and Comparative Examples 1 to 4 was tested at room temperature and 800 °C. The test results are shown in Table 1 below: Table 1,

[0052] It can be clearly seen from Table 1 that the multi-layer composite coating prepared by the present method has a tight interface bonding and small internal stress. Each thin film layer can effectively hinder the movement of interface dislocations in a high-temperature environment. Therefore, the hardness decrease is not obvious in a high-temperature environment and has a high hardness value.

[0053] High-temperature oxidation tests were carried out in a muffle furnace. The titanium-aluminum alloy substrate specimens with the thermal insulation composite coating in Examples 1 to 3 and Comparative Examples 1 to 4 were respectively placed in the muffle furnace. Under an air atmosphere and a heating rate of 30 °C / min, the temperature was raised from room temperature (25 °C) to 850 °C, and the temperature was maintained at a high temperature. The surface changes of the specimens were observed. The test results are shown in Table 2 below (where the blank group is the titanium-aluminum alloy without surface treatment): Table 2,

[0054] Note: "---" indicates that the observation will no longer be carried out.

[0055] It can be clearly seen from the above table that the multi-layer composite film structure prepared on the surface of the titanium-aluminum alloy in the present invention can still maintain the integrity of the coating structure after 200 h of thermal cycle oxidation test at 850 °C, significantly improving the oxidation resistance of the titanium-aluminum alloy; at the same time, the bonding strength between the thin film layers is high, and problems such as cracking and coating spalling 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 high temperature resistant heat insulation coating suitable for titanium aluminum alloy 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. A high temperature resistant heat insulating coating suitable for titanium aluminum alloy 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 high temperature resistant heat insulation coating suitable for titanium aluminum alloy 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 high temperature resistant heat insulation coating suitable for titanium aluminum alloy 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 high temperature resistant heat insulation coating suitable for titanium aluminum alloy 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.%.

7. A method for preparing a high temperature resistant heat insulating coating suitable for titanium aluminum alloy according to any one of claims 3 to 6, characterized in that: include: Step S1, substrate treatment: machining, grinding, polishing, cleaning and drying the titanium aluminum alloy substrate in sequence; Step S2, pre-sputtering: placing the treated substrate in a vacuum chamber, closing the vacuum chamber and evacuating the chamber, introducing argon gas to make the vacuum chamber pressure reach 2-3 Pa, turning on the bias power supply, applying bias on the substrate, glow discharge to form argon plasma, and pre-sputtering the substrate; nickel, aluminum, titanium aluminum, aluminum oxide, tungsten, chromium, and silicon targets are respectively arranged in the vacuum chamber, and pre-sputtering is performed on each target material; 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 target materials, turning on the target power supply, sputtering the aluminum target with direct current and sputtering the nickel target with medium frequency, to obtain the first Ni-Al intermediate layer; Step S4, depositing a second Ni-Al intermediate layer: the method is the same as the method of depositing the first Ni-Al intermediate layer, except for the control of the aluminum content; 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 direct current sputtering to obtain a TiAlCr thin film layer; Step S6, depositing the first Al2O3 thin film layer: when the predetermined sputtering power is reached, the Al2O3 thin film layer is sputtered with a medium frequency, and after the deposition is completed, the alumina target is turned off; Step S7, depositing the first WC film layer: evacuate the gas in the vacuum chamber, introduce acetylene, and start the substrate to rotate at a certain speed. When the predetermined sputtering power is reached, the WC film layer is sputtered with a medium frequency. After the deposition is completed, the tungsten target is turned off and the introduction of acetylene is stopped; Step S8, depositing a second Al2O3 thin film layer: evacuate the gas in the vacuum chamber and re-introduce argon gas, repeat step S6, and the acetylene flow rate introduced when depositing the second WC thin film layer is lower than the acetylene flow rate introduced when depositing the first WC thin film layer; Step S9, depositing a second WC film layer: evacuate the gas in the vacuum chamber, re-introduce acetylene, and repeat step S7; Step S10, depositing a MoSiCrC thin film layer: continuously introducing acetylene, changing the bias power supply, turning on the chromium target, silicon target and molybdenum target at the same time, and using direct current sputtering to deposit a MoSiCrC thin film layer.

8. The method for preparing a high temperature resistant heat insulating coating suitable for titanium aluminum alloy according to claim 7, characterized in that: The grinding in step S1 is specifically as follows: using 200#, 400#, 600#, 800# and 1000# sandpaper to perform coarse grinding and fine grinding in the same direction in sequence 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 cleaning with acetone solution for 2 to 6 minutes, and then cleaning alternately with anhydrous ethanol and deionized water, with the alternating cleaning times being no less than 3 times; drying is specifically as follows: drying with a dust-free cloth.

9. The method for preparing a high temperature resistant heat insulating coating suitable for titanium aluminum alloy according to claim 7, characterized in that: In step S2, the vacuum is evacuated to 2.8×10 -3 ~3.2×10 -3 Pa; the argon gas flow rate is 55-65sccm; during the substrate pre-sputtering process, the bias voltage is 800±100DC, and the pre-sputtering time is 8-12min; during the target pre-sputtering process, the DC current is 0.45-0.55A, and the pre-sputtering time is 13-17min.

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