Heat-conducting coating with high heat diffusion coefficient and preparation method of heat-conducting coating

Abstract

The invention relates to a heat-conducting coating with a high heat diffusion coefficient and a preparation method thereof, belongs to the technical field of surface engineering, and solves the problems of high cost and low heat conductivity of an existing method for solving the problem of non-uniform thermal stress distribution of an aircraft structure. Comprising the steps that Cu powder, Ag powder and NiCoCrAlY powder are weighed according to the mass ratio, and first raw material powder is obtained; niCoCrAlY powder is weighed to serve as second raw material powder; the surface of the base body is pretreated; an argon cooling device is started, and argon blowing is conducted on the to-be-sprayed position of the base body; putting first raw material powder into a plasma spraying device, and spraying on the surface of the pretreated matrix to obtain a first pre-coating layer; the argon cooling device is closed, spraying is conducted on the surface of the base body, and a second pre-coating layer is obtained; an argon cooling device is started, second raw material powder is sprayed to the surface of the second pre-coating layer through the plasma spraying device, and a third pre-coating layer is obtained; and carrying out vacuum heat treatment on the third pre-coating to obtain the coating. The coating prepared by the method is low in cost and high in thermal conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of surface engineering, and in particular to a high thermal diffusivity thermal conductive coating and a preparation method thereof. Background Art

[0002] With the development of aerospace technology, the flight speed of products is getting faster and faster. During high-speed flight, they will face a thermomechanical coupling environment caused by aerodynamic heating. Due to the local rapid temperature rise, the regional thermal stress concentration in special parts causes deformation, which affects the overall appearance and structure of the product and seriously limits the design scope of the structural specialty. In order to solve the problem of local stagnation point thermal stress concentration in the product, methods such as thermal shaping, hot rolling technology and neutron diffraction, as well as the preparation of thermal conductive coatings on the structure can be used to solve the problem of thermal stress concentration and uneven distribution. However, methods such as thermal shaping, hot rolling technology and neutron diffraction require specific large-scale equipment and will bring the risk of cracking of large parts. The existing method of solving the uneven thermal stress distribution of aerospace vehicle structures through coatings has the problems of high cost and low thermal conductivity. Summary of the Invention

[0003] In view of the above analysis, the embodiments of the present invention aim to provide a method for preparing a thermally conductive coating with a high thermal diffusivity coefficient, so as to solve the problems of high cost and low thermal conductivity of the existing method of solving the uneven thermal stress distribution of aerospace vehicle structures through coating.

[0004] The purpose of the present invention is mainly achieved through the following technical solutions:

[0005] The present invention provides a method for preparing a thermally conductive coating with a high thermal diffusivity, comprising the following steps:

[0006] S1: Weigh Cu powder, Ag powder and NiCoCrAlY powder according to the mass ratio and mix them to obtain a first raw material powder;

[0007] S2: According to the mass ratio, NiCoCrAlY powder is weighed separately as the second raw material powder;

[0008] S3: pre-treating the substrate surface;

[0009] S4: Turn on the argon cooling device to blow argon gas to the position to be sprayed on the substrate;

[0010] S5: placing the first raw material powder in a plasma spraying device and spraying it on the pretreated substrate surface to obtain a first pre-coating layer;

[0011] S6: Turn off the argon cooling device and continue spraying on the substrate surface to obtain a second pre-coating layer;

[0012] S7: turning on the argon cooling device and spraying the second raw material powder onto the surface of the second pre-coating layer through the plasma spraying device to obtain a third pre-coating layer comprising the second raw material powder coating layer;

[0013] S8: performing vacuum heat treatment on the third pre-coating layer to obtain a composite thermal conductive coating layer.

[0014] Furthermore, in step S1, the purity of the Cu powder, Ag powder and NiCoCrAlY powder raw materials is greater than 99.9%; the mass fraction of the Cu powder is 36.2-100%, the mass fraction of the Ag powder is 0-22.5%, and the mass fraction of the NiCoCrAlY powder is 0-53.6%.

[0015] Furthermore, in step S1, the particle size of the Cu powder is 15-100 μm, the particle size of the Ag powder is 30-45 μm, and the particle size of the NiCoCrAlY powder is 10-65 μm.

[0016] Furthermore, in step S2, the mass fraction of the NiCoCrAlY powder is 10-35% of the mass of the first raw material powder.

[0017] Furthermore, in step S3, the substrate is one of titanium alloy, aluminum alloy, high-temperature alloy, carbon fiber composite, and alumina fiber composite; and the pretreatment method is one or more of grinding, laser cleaning, sand blasting, and plasma activation.

[0018] Furthermore, in step S4, the flow rate of argon in the argon cooling device is 30 to 50 L / min.

[0019] Furthermore, in step S5, the thickness of the first pre-coating layer is 10 to 100 μm;

[0020] The process parameters of the plasma spraying are: operating voltage of 50-80V, operating current of 400-800A, argon flow rate of 20-50L / min, hydrogen flow rate of 10-35L / min, powder feeding speed of 1-6L / min, and spraying distance of 80-120mm.

[0021] Furthermore, in step S7, the thickness of the second raw material powder coating layer is 80 to 150 μm;

[0022] The process parameters of the plasma spraying are: working voltage of 50-80V, working current of 400-600A, argon flow rate of 10-300L / min, hydrogen flow rate of 10-25L / min, powder feeding speed of 1-3L / min, and spraying distance of 90-110mm.

[0023] Furthermore, in step S8, the vacuum heat treatment is: annealing the third pre-coating layer in a vacuum annealing furnace, the heat treatment temperature is 800-1000° C., the heat treatment time is 1-6 hours, heating with the furnace, and vacuum cooling with the furnace.

[0024] The present invention also provides a high thermal diffusivity thermal conductive coating, which is prepared by the above-mentioned preparation method and includes a thermal conductive layer and an anti-oxidation layer in sequence along the direction away from the substrate surface. The thermal conductive layer is a coating composed of one or more of Cu powder, Ag powder and NiCoCrAlY powder, and the anti-oxidation layer is a dense metal layer composed of NiCoCrAlY powder.

[0025] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0026] 1. The present invention achieves high thermal diffusion performance by using one or more of Cu powder, Ag powder, and NiCoCrAlY powder to form an inner thermal conductive layer. Meanwhile, NiCoCrAlY powder is coated on the outer surface of the inner thermal conductive layer as an anti-oxidation layer. Under an argon atmosphere, the inner thermal conductive layer is rationally proportioned to improve the bonding strength between the composite thermal conductive coating and the substrate without affecting the thermal diffusion performance. The outer anti-oxidation layer can ensure the stable performance of the inner thermal conductive layer at high temperatures. Finally, the composite thermal conductive coating is stabilized at high temperatures through post-treatment with vacuum heat treatment, greatly improving the thermal diffusion performance of the composite thermal conductive coating. Compared with other inner thermal diffusion coatings, such as fiber membranes (thermal conductivity of 110 W / m·K, requiring additional bonding), this coating has the advantages of low cost, excellent thermal conductivity, simple in-situ plasma spraying preparation, and strong functional expansion. The coating prepared by the present invention has a bonding strength of ≥25 MPa, a thermal conductivity of ≥177 W / m·K, and a thermal diffusion rate of ≥74 mm² / s.

[0027] 2. Compared with the existing methods of solving the problem of thermal stress concentration in the aerospace field through hot shaping, hot rolling technology and neutron diffraction, which require large equipment, resulting in high costs and the risk of cracking of large parts, the present invention adopts atmospheric plasma spraying to prepare directly in the atmosphere, heats the powder material to a molten or semi-molten state, and sprays it onto the surface of the substrate at high speed. This high-temperature and high-speed flame flow helps the powder particles to spread rapidly when hitting the substrate to form a coating, and will not have an impact on the substrate. The coating preparation can also be completed on thin-walled structures, and the coating thickness is controllable. In the present invention, the outer layer NiCoCrAlY powder has antioxidant stability and can still remain stable under high-temperature aerobic conditions without performance degradation. According to needs, high-emissivity coatings or infrared stealth coatings and other functional coatings can be further added to the surface of the NiCoCrAlY powder (the outer anti-oxidation layer), so that its application has scalable characteristics.

[0028] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of the present invention will be described in the following description, and some advantages will become apparent from the description or be learned through practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0030] Figure 1 is a cross-sectional metallographic image of the coating in Example 2 of the present invention;

[0031] Figure 2 The scanning electron microscope cross-sectional micromorphology and the corresponding regional surface scanning EDS spectrum in Example 3 of the present invention;

[0032] Figure 3 The scanning electron microscope cross-sectional micromorphology and the corresponding regional surface scanning EDS spectrum in Example 5 of the present invention;

[0033] Figure 4 This is a comparison chart of the thermal diffusion performance of Example 1 of the present invention and Comparative Example 3. DETAILED DESCRIPTION

[0034] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0035] The present invention provides a high thermal diffusivity thermal conductive coating, which comprises a thermal conductive layer and an anti-oxidation layer in sequence along a direction away from the surface of a substrate. The thermal conductive layer is a coating composed of one or more of Cu powder, Ag powder and NiCoCrAlY powder, and the anti-oxidation layer is a dense metal layer composed of NiCoCrAlY powder.

[0036] The present invention also provides a method for preparing a thermally conductive coating with a high thermal diffusivity, which is used to prepare the above-mentioned thermally conductive coating, comprising the following steps:

[0037] S1: Weigh Cu powder, Ag powder and NiCoCrAlY powder according to the mass ratio and mix them to obtain a first raw material powder;

[0038] S2: According to the mass ratio, NiCoCrAlY powder is weighed separately as the second raw material powder;

[0039] S3: pre-treating the substrate surface;

[0040] S4: Turn on the argon cooling device to blow argon gas to the position to be sprayed on the substrate;

[0041] S5: placing the first raw material powder in a plasma spraying device and spraying it on the pretreated substrate surface to obtain a first pre-coating layer;

[0042] S6: Turn off the argon cooling device and continue spraying on the substrate surface to obtain a second pre-coating layer;

[0043] S7: turning on the argon cooling device and spraying the second raw material powder onto the surface of the second pre-coating layer through the plasma spraying device to obtain a third pre-coating layer comprising the second raw material powder coating layer;

[0044] S8: performing vacuum heat treatment on the third pre-coating layer to obtain a composite thermal conductive coating layer.

[0045] Specifically, in step S1, the purity of the Cu powder, Ag powder and NiCoCrAlY powder raw materials is greater than 99.9%; the mass fraction of the Cu powder is 36.2-100%, the mass fraction of the Ag powder is 0-22.5%, and the mass fraction of the NiCoCrAlY powder is 0-53.6%; the particle size of the Cu powder is 15-100 μm, the particle size of the Ag powder is 30-45 μm, and the particle size of the NiCoCrAlY powder is 10-65 μm.

[0046] Preferably, the mass fraction of the Cu powder is 65.7-100%, the mass fraction of the Ag powder is 0-16.94%, and the mass fraction of the NiCoCrAlY powder is 0-22.52%; the particle size of the Cu powder is 15-100 μm, the particle size of the Ag powder is 30-45 μm, and the particle size of the NiCoCrAlY powder is 10-65 μm.

[0047] Specifically, in step S2, the mass fraction of the NiCoCrAlY powder is 10-35% of the mass of the first raw material powder. Exemplarily, the mass fraction of the NiCoCrAlY powder is 15%, 16.46%, 20%, 23.58%, 30%, and 33.22% of the mass of the first raw material powder.

[0048] Specifically, in step S3, the substrate is one of titanium alloy, aluminum alloy, high-temperature alloy, carbon fiber composite, and alumina fiber composite; and the pretreatment method is one or more of grinding, laser cleaning, sand blasting, and plasma activation.

[0049] Specifically, in step S4, in the argon cooling device, the flow rate of argon is 30 to 50 L / min. Exemplarily, the flow rate of argon is 35 L / min, 40 L / min, and 45 L / min.

[0050] Specifically, in step S5, the thickness of the first pre-coating layer is 10 to 100 μm; the process parameters of the plasma spraying are:

[0051] The operating voltage is 50-80V, illustratively, the operating voltage is 55V, 60V, 65V, 70V, 75V;

[0052] The operating current is 400-800A. For example, the operating current is 410A, 420A, 430A, 440A, 450A, 460A, 470A, 480A, 490A, 500A, 510A, 520A, 530A, 540A, 550A, 560A, 570A, 580A, 590A, 600A, 610A, 620A, 630A, 640A, 650A, 660A, 670A, 680A, 690A, 700A, 710A, 720A, 730A, 740A, 750A, 760A, 770A, 780A, and 790A.

[0053] The argon flow rate is 20 to 50 L / min. For example, the argon flow rate is 22 L / min, 24 L / min, 25 L / min, 26 L / min, 28 L / min, 30 L / min, 32 L / min, 34 L / min, 35 L / min, 36 L / min, 38 L / min, 40 L / min, 42 L / min, 44 L / min, 46 L / min, and 48 L / min.

[0054] The hydrogen flow rate is 10 to 35 L / min. For example, the hydrogen flow rate is 11 L / min, 13 L / min, 14 L / min, 15 L / min, 16 L / min, 17 L / min, 19 L / min, 21 L / min, 22 L / min, 23 L / min, 25 L / min, 27 L / min, 29 L / min, 31 L / min, and 33 L / min.

[0055] The powder feeding speed is 1 to 6 L / min. For example, the powder feeding speed is 1.5 L / min, 2 L / min, 2.2 L / min, 2.5 L / min, 3 L / min, 3.5 L / min, 4 L / min, 4.5 L / min, 5 L / min, and 5.5 L / min.

[0056] The spraying distance is 80 to 120 mm, and illustratively, the spraying distance is 90 mm, 100 mm, and 110 mm; argon gas is used as both the shielding gas and the powder feeding gas.

[0057] Specifically, after obtaining the first pre-coating layer, the argon cooling device is turned off in step S6 to continue spraying on the substrate surface in order to increase the temperature of the substrate during spraying, thereby reducing the thermal stress of the coating spraying and improving the stability of the coating;

[0058] Specifically, the spraying process parameters in step S6 are consistent with the spraying process parameters in step S5, and the thickness of the second pre-coating layer is 500 to 1500 μm;

[0059] Specifically, in step S7, the thickness of the second raw material powder coating layer is 80 to 150 μm; the process parameters of the plasma spraying are:

[0060] The operating voltage is 50-80V, illustratively, the operating voltage is 55V, 60V, 65V, 70V, 71V, 75V;

[0061] The operating current is 400-600A. For example, the operating current is 410A, 420A, 430A, 440A, 450A, 460A, 470A, 480A, 490A, 500A, 510A, 520A, 530A, 540A, 550A, 560A, 570A, 580A, 590A, and 600A.

[0062] The argon flow rate is 10 to 300 L / min. For example, the argon flow rate is 20 L / min, 40 L / min, 60 L / min, 80 L / min, 100 L / min, 120 L / min, 140 L / min, 160 L / min, 180 L / min, 200 L / min, 220 L / min, 240 L / min, 260 L / min, and 280 L / min.

[0063] The hydrogen flow rate is 10 to 25 L / min. For example, the hydrogen flow rate is 11 L / min, 13 L / min, 14 L / min, 15 L / min, 17 L / min, 18 L / min, 19 L / min, 21 L / min, 22 L / min, 23 L / min, and 25 L / min.

[0064] The powder feeding speed is 1 to 3 L / min. For example, the powder feeding speed is 1.5 L / min, 1.9 L / min, 2 L / min, 2.2 L / min, 2.5 L / min, and 3 L / min.

[0065] The spraying distance is 90 to 110 mm. For example, the spraying distance is 90 mm, 94 mm, 100 mm, and 110 m. Argon is used as both a shielding gas and a powder feeding gas. The high temperature of the flame generated by the plasma can promote the full fusion of the powder to form a coating with high thermal diffusion performance.

[0066] Specifically, in step S8, the vacuum heat treatment is as follows: annealing the third pre-coating layer in a vacuum annealing furnace at a heat treatment temperature of 800 to 1000°C for 1 to 6 hours, heating with the furnace, and vacuum cooling with the furnace. This is because the coating of the present invention is prepared in the form of atmospheric plasma spraying, and the coating has a certain porosity. When the temperature is higher than 800°C and lower than 1000°C, the coating will not melt due to internal softening, thereby reducing the internal pores, thereby improving the thermal diffusion coefficient and thermal conductivity. When the temperature is lower than 800°C, the coating does not soften and the thermal conductivity cannot be improved. When the temperature is higher than 1000°C, the coating will deform due to near melting, and the thickness uniformity cannot be guaranteed, thus losing the actual application effect. Vacuum heat treatment makes up for the problems of uneven plasma spray coating and insufficient density, helps to release stress inside the coating, makes the structure more uniform, thereby improving the thermal diffusion performance of the coating, and at the same time, vacuum heat treatment helps the mutual fusion of the various components in the coating and further enhances the stability of the coating.

[0067] It should be noted that the composite thermally conductive coating finally prepared by the present invention includes a thermally conductive layer and an anti-oxidation layer in sequence along the direction away from the surface of the substrate. The thermally conductive layer is a coating composed of one or more of Cu powder, Ag powder and NiCoCrAlY powder, and the anti-oxidation layer is a dense metal layer composed of NiCoCrAlY powder. It should be noted that the present invention achieves the effect of high thermal diffusion performance by using one or more of Cu powder, Ag powder and NiCoCrAlY powder to form an inner thermally conductive layer; at the same time, NiCoCrAlY powder is coated on the outer surface of the inner thermally conductive layer as an anti-oxidation layer; under an argon atmosphere, the inner thermally conductive layer improves the bonding strength between the composite thermally conductive coating and the substrate through reasonable proportioning without affecting the thermal diffusion performance, and the outer anti-oxidation layer can ensure that the performance of the inner thermally conductive layer remains stable at high temperatures; finally, the composite thermally conductive coating is stabilized at high temperature by post-treatment of vacuum heat treatment, which greatly improves the thermal diffusion performance of the composite thermally conductive coating. Compared with other inner thermal diffusion coatings such as fiber membranes (thermal conductivity 110W / m·K, requiring additional bonding), this method does not require additional bonding steps, reducing costs.

[0068] In addition, compared with the existing methods of solving the problem of thermal stress concentration in the aerospace field through hot shaping, hot rolling technology and neutron diffraction, which require large equipment, resulting in high cost and easy to bring about the risk of cracking of large parts, the present invention adopts the form of atmospheric plasma spraying to prepare directly in the atmosphere, heat the powder material to a molten or semi-molten state, and spray it onto the surface of the substrate at high speed. This high-temperature and high-speed flame flow helps the powder particles to spread rapidly when hitting the substrate to form a coating, and will not have an impact on the substrate. The coating preparation can also be completed in a thin-walled structure, and the coating thickness is controllable. In the present invention, the outer layer NiCoCrAlY powder has antioxidant stability and can still remain stable under high-temperature aerobic conditions without performance degradation. According to needs, high-emissivity coatings or infrared stealth coatings and other functional coatings can be further added to the surface of the NiCoCrAlY powder (the outer anti-oxidation layer), so that its application has scalable characteristics.

[0069] The coating prepared by the present invention has a bonding force of ≥25Mpa (e.g., 25.73-32.10Mpa), a thermal conductivity of ≥177W / m·K (e.g., 177.155-204.785W / m·K), and a thermal diffusion rate of ≥74mm^2 / s (e.g., 74.57-88.24mm^2 / s).

[0070] Example 1

[0071] The high thermal diffusivity thermal conductive coating of this embodiment includes a thermal conductive layer and an anti-oxidation layer in the direction away from the substrate surface. The thermal conductive layer is a coating composed of Cu powder, Ag powder and NiCoCrAlY powder, and the anti-oxidation layer is a dense metal layer composed of NiCoCrAlY powder.

[0072] The thermal conductive coating is prepared by the following steps:

[0073] S1: Weigh Cu powder, Ag powder and NiCoCrAlY powder according to the mass ratio and mix them to obtain a first raw material powder;

[0074] Among them, there are 65.7g Cu powder (mass fraction 65.7%), 15.2g Ag powder (mass fraction 15.2%) and 19.1g NiCoCrAlY powder (mass fraction 19.1%); among them, the particle size of Cu powder is 15-100μm, the particle size of Ag powder is 15-45μm, and the particle size of NiCoCrAlY powder is 10-65μm.

[0075] S2: According to the mass ratio, NiCoCrAlY powder is weighed separately as the second raw material powder;

[0076] Among them, NiCoCrAlY powder 20g (accounting for 20% of the mass of the first raw material powder);

[0077] S3: pre-treating the substrate surface;

[0078] The pretreatment method is sand blowing, with a sand blowing pressure of 0.4Mpa and a sand blowing distance of 400mm;

[0079] S4: Turn on the argon cooling device to blow argon gas to the position to be sprayed on the substrate;

[0080] Among them, the flow rate of argon is 30L / min;

[0081] S5: placing the first raw material powder in a plasma spraying device and spraying it on the surface of the substrate after sandblasting to obtain a first pre-coating layer with a thickness of 96 μm;

[0082] The process parameters of plasma spraying are as follows: operating voltage of 75V, operating current of 650A, argon flow rate of 28L / min, hydrogen flow rate of 16L / min, powder feeding speed of 2.2L / min, and spraying distance of 100mm, in which argon is used as both shielding gas and powder feeding gas.

[0083] S6: Turn off the argon cooling device and continue spraying on the substrate surface to obtain a second pre-coating layer with a thickness of 986 μm;

[0084] S7: spraying the second raw material powder (NiCoCrAlY powder) onto the surface of the second pre-coating layer by a plasma spraying device to obtain a third pre-coating layer comprising the second raw material powder coating layer (90 μm thick);

[0085] The process parameters of plasma spraying are as follows: operating voltage of 75V, operating current of 580A, argon flow rate of 120L / min, hydrogen flow rate of 14L / min, powder feeding speed of 2.5L / min, and spraying distance of 100mm, in which argon is used as both shielding gas and powder feeding gas.

[0086] S8: performing vacuum heat treatment on the third pre-coating layer to obtain a composite thermal conductive coating layer.

[0087] The third pre-coating layer is annealed in a vacuum annealing furnace at a heat treatment temperature of 860° C. for 6 hours, with heating and vacuum cooling in the furnace.

[0088] The interfaces of the coatings prepared above were observed using a scanning electron microscope (Regulus 8230) and a metallographic scanning device (PTI-2000). The coatings had relatively few gaps between the layers, indicating a good bonding effect.

[0089] The bonding strength between the coating and the high-temperature alloy substrate was tested using a universal mechanical testing machine (UTM-300B), which showed that the bonding strength of the coating was 29.89 MPa.

[0090] The thermal conductivity and thermal diffusion rate of the thermal conductive coating were tested using the flash method, showing that the thermal conductivity of the coating was 177.155 W / m·K and the thermal diffusion rate was 74.57 mm^2 / s.

[0091] Example 2

[0092] The high thermal diffusivity thermal conductive coating of this embodiment includes a thermal conductive layer and an anti-oxidation layer in the direction away from the substrate surface. The thermal conductive layer is a coating composed of Cu powder, and the anti-oxidation layer is a dense metal layer composed of NiCoCrAlY powder.

[0093] The thermal conductive coating is prepared by the following steps:

[0094] S1: 121.51 g (mass fraction 100%) of Cu powder was weighed as the first raw material powder according to the mass ratio; wherein the particle size of the Cu powder was 15-100 μm.

[0095] S2: According to the mass ratio, NiCoCrAlY powder is weighed separately as the second raw material powder;

[0096] Among them, NiCoCrAlY powder 20g (accounting for 16.46% of the mass of the first raw material powder)

[0097] S3: pre-treating the substrate surface;

[0098] The pretreatment method is sand blowing, with a sand blowing pressure of 0.4Mpa and a sand blowing distance of 400mm;

[0099] S4: Turn on the argon cooling device to blow argon gas to the position to be sprayed on the substrate;

[0100] Among them, the flow rate of argon gas is 40L / min;

[0101] S5: placing the first raw material powder in a plasma spraying device and spraying it on the surface of the substrate after sandblasting to obtain a first pre-coating layer with a thickness of 50 μm;

[0102] The process parameters of plasma spraying are as follows: operating voltage of 80V, operating current of 760A, argon flow rate of 34L / min, hydrogen flow rate of 22L / min, powder feeding speed of 3L / min, and spraying distance of 100mm, in which argon is used as both shielding gas and powder feeding gas.

[0103] S6: Turn off the argon cooling device and continue spraying on the substrate surface to obtain a second pre-coating layer with a thickness of 975 μm;

[0104] S7: spraying the second raw material powder (NiCoCrAlY powder) onto the surface of the second pre-coating layer by a plasma spraying device to obtain a third pre-coating layer comprising the second raw material powder coating layer (thickness 100 μm);

[0105] Among them, the process parameters of plasma spraying are: working voltage of 71V, working current of 440A, argon flow rate of 180L / min, hydrogen flow rate of 18L / min, powder feeding speed of 1.9L / min, and spraying distance of 94mm, among which argon is used as both shielding gas and powder feeding gas.

[0106] S8: performing vacuum heat treatment on the third pre-coating layer to obtain a composite thermal conductive coating layer.

[0107] The third pre-coating layer is annealed in a vacuum annealing furnace at a heat treatment temperature of 950° C. for 4 hours, with heating and vacuum cooling in the furnace.

[0108] Scanning electron microscope (Regulus 8230) and metallographic scanning equipment (PTI-2000) were used to observe the interface of the coating prepared above. The metallographic cross-section pictures are shown in Fig. Figure 1 As shown, there are fewer gaps between the coating layers, showing a good bonding effect.

[0109] The bonding strength between the coating and the high-temperature alloy substrate was tested using a universal mechanical testing machine (UTM-300B), which showed that the bonding strength of the coating was 28.97 MPa.

[0110] The thermal conductivity and thermal diffusion rate of the thermal conductive coating were tested using the flash method, showing that the thermal conductivity of the coating was 189.551 W / m·K and the thermal diffusion rate was 75.79 mm^2 / s.

[0111] Example 3

[0112] The high thermal diffusivity thermal conductive coating of this embodiment includes a thermal conductive layer and an anti-oxidation layer in the direction away from the substrate surface. The thermal conductive layer is a coating composed of Cu powder and Ag powder, and the anti-oxidation layer is a dense metal layer composed of NiCoCrAlY powder.

[0113] The thermal conductive coating is prepared by the following steps:

[0114] S1: Weigh Cu powder and Ag powder according to the mass ratio and mix them to obtain a first raw material powder;

[0115] Among them, Cu powder is 50g (mass fraction 83.06%), and Ag powder is 10.2g (mass fraction 16.94%); wherein, the particle size of Cu powder is 15-100μm, and the particle size of Ag powder is 15-45μm.

[0116] S2: According to the mass ratio, NiCoCrAlY powder is weighed separately as the second raw material powder;

[0117] Among them, NiCoCrAlY powder 20g (accounting for 33.22% of the mass of the first raw material powder)

[0118] S3: pre-treating the substrate surface;

[0119] The pretreatment method is sand blowing, with a sand blowing pressure of 0.4Mpa and a sand blowing distance of 400mm;

[0120] S4: Turn on the argon cooling device to blow argon gas to the position to be sprayed on the substrate;

[0121] Among them, the flow rate of argon gas is 50L / min;

[0122] S5: placing the first raw material powder in a plasma spraying device and spraying it on the surface of the substrate after sandblasting to obtain a first pre-coating layer with a thickness of 25 μm;

[0123] The process parameters of plasma spraying are as follows: operating voltage of 80V, operating current of 750A, argon flow rate of 35L / min, hydrogen flow rate of 25L / min, powder feeding speed of 4L / min, and spraying distance of 110mm, in which argon is used as both shielding gas and powder feeding gas.

[0124] S6: Turn off the argon cooling device and continue spraying on the substrate surface to obtain a second pre-coating layer with a thickness of 978 μm;

[0125] S7: spraying the second raw material powder (NiCoCrAlY powder) onto the surface of the second pre-coating layer by a plasma spraying device to obtain a third pre-coating layer comprising the second raw material powder coating layer (thickness 100 μm);

[0126] The process parameters of plasma spraying are as follows: operating voltage of 55V, operating current of 480A, argon flow rate of 220L / min, hydrogen flow rate of 21L / min, powder feeding speed of 2.2L / min, and spraying distance of 110mm, in which argon is used as both shielding gas and powder feeding gas.

[0127] S8: performing vacuum heat treatment on the third pre-coating layer to obtain a composite thermal conductive coating layer.

[0128] The third pre-coating layer is annealed in a vacuum annealing furnace at a heat treatment temperature of 950° C. for 6 hours, with heating and vacuum cooling in the furnace.

[0129] Scanning electron microscope (Regulus 8230) and metallographic scanning equipment (PTI-2000) were used to observe the interface of the above-prepared coating. The SEM morphology and EDS spectrum data of the corresponding area are shown in Figure 2. Figure 2 As shown in the figure, the coating surface has fewer pores and a higher copper content.

[0130] The bonding strength between the coating and the high-temperature alloy substrate was tested using a universal mechanical testing machine (UTM-300B), which showed that the bonding strength of the coating was 32.10 MPa.

[0131] The thermal conductivity and thermal diffusion rate of the thermal conductive coating were tested using the flash method, showing that the thermal conductivity of the coating was 204.785 W / m·K and the thermal diffusion rate was 88.24 mm^2 / s.

[0132] Example 4

[0133] The high thermal diffusivity thermal conductive coating of this embodiment includes a thermal conductive layer and an anti-oxidation layer in the direction away from the substrate surface. The thermal conductive layer is a coating composed of Cu powder, Ag powder and NiCoCrAlY powder, and the anti-oxidation layer is a dense metal layer composed of NiCoCrAlY powder.

[0134] The thermal conductive coating is prepared by the following steps:

[0135] S1: Weigh Cu powder and NiCoCrAlY powder according to the mass ratio and mix them to obtain a first raw material powder;

[0136] Among them, there are 65.7g Cu powder (mass fraction 77.48%) and 19.1g NiCoCrAlY powder (mass fraction 22.52%); wherein the particle size of the Cu powder is 15-100μm, and the particle size of the NiCoCrAlY powder is 10-65μm.

[0137] S2: According to the mass ratio, NiCoCrAlY powder is weighed separately as the second raw material powder;

[0138] Among them, NiCoCrAlY powder 20g (accounting for 23.58% of the mass of the first raw material powder)

[0139] S3: pre-treating the substrate surface;

[0140] The pretreatment method is sand blowing, with a sand blowing pressure of 0.4Mpa and a sand blowing distance of 400mm;

[0141] S4: Turn on the argon cooling device to blow argon gas to the position to be sprayed on the substrate;

[0142] Among them, the flow rate of argon gas is 45L / min;

[0143] S5: placing the first raw material powder in a plasma spraying device and spraying it on the surface of the substrate after sandblasting to obtain a first pre-coating layer with a thickness of 76 μm;

[0144] The process parameters of plasma spraying are as follows: operating voltage of 50 V, operating current of 400 A, argon flow rate of 25 L / min, hydrogen flow rate of 11 L / min, powder feeding speed of 2 L / min, and spraying distance of 120 mm, in which argon is used as both shielding gas and powder feeding gas.

[0145] S6: Turn off the argon cooling device and continue spraying on the substrate surface to obtain a second pre-coating layer with a thickness of 1000 μm;

[0146] S7: spraying the second raw material powder (NiCoCrAlY powder) onto the surface of the second pre-coating layer by a plasma spraying device to obtain a third pre-coating layer comprising the second raw material powder coating layer (thickness 100 μm);

[0147] The process parameters of plasma spraying are as follows: operating voltage of 75V, operating current of 580A, argon flow rate of 120L / min, hydrogen flow rate of 14L / min, powder feeding speed of 2.5L / min, and spraying distance of 100mm, in which argon is used as both shielding gas and powder feeding gas.

[0148] S8: performing vacuum heat treatment on the third pre-coating layer to obtain a composite thermal conductive coating layer.

[0149] The third pre-coating layer is annealed in a vacuum annealing furnace at a heat treatment temperature of 820° C. for 2 hours, with heating and vacuum cooling in the furnace.

[0150] Scanning electron microscope (Regulus 8230) and metallographic scanning equipment (PTI-2000) were used to observe the interface of the above-prepared coating. The SEM morphology and EDS spectrum data of the corresponding area are shown in Figure 2. Figure 3 As shown; the coating surface has fewer pores.

[0151] The bonding strength between the coating and the high-temperature alloy substrate was tested using a universal mechanical testing machine (UTM-300B), which showed that the bonding strength of the coating was 25.73 MPa.

[0152] The thermal conductivity and thermal diffusion rate of the thermal conductive coating were tested using the flash method, showing that the thermal conductivity of the coating was 189.751 W / m·K and the thermal diffusion rate was 77.12 mm^2 / s.

[0153] Comparative Example 1

[0154] This comparative example provides a high thermal diffusivity thermal conductive coating and a preparation method thereof. The steps are similar to those in Example 3, except that when S5 sprays the first raw material powder, the spraying parameters used are: operating voltage of 40 V, operating current of 350 A, argon flow rate of 15 L / min, hydrogen flow rate of 8 L / min, powder feeding speed of 2.2 L / min, and spraying distance of 110 mm.

[0155] The bonding strength between the coating and the high-temperature alloy substrate was tested using a universal mechanical testing machine (UTM-300B), which showed that the bonding strength of the coating was 16.87 MPa.

[0156] The thermal conductivity and thermal diffusion rate of the thermal conductive coating were tested using the flash method, showing that the thermal conductivity of the coating was 153.266W / m·K and the thermal diffusion rate was 65.87mm^2 / s.

[0157] Comparative Example 2

[0158] This comparative example provides a high thermal diffusivity thermal conductive coating and a preparation method thereof. The steps are similar to those of Example 1, except that vacuum heat treatment is not performed in S8.

[0159] The bonding strength between the coating and the high-temperature alloy substrate was tested using a universal mechanical testing machine (UTM-300B), which showed that the bonding strength of the coating was 21.36 MPa.

[0160] The thermal conductivity and thermal diffusion rate of the thermal conductive coating were tested using the flash method, showing that the thermal conductivity of the coating was 101.245 W / m·K and the thermal diffusion rate was 48.15 mm^2 / s.

[0161] It can be seen from the embodiments and comparative examples that the coating prepared by the method of the present invention has a bonding force ≥25Mpa (such as 25.73-32.10Mpa), a thermal conductivity ≥177W / m·K (such as 177.155-204.785W / m·K), and a thermal diffusion rate ≥74mm^2 / s (such as 74.57-88.24mm^2 / s).

[0162] It can be seen from Example 3 and Comparative Example 1 that some of the plasma spraying parameters of Comparative Example 1 do not meet the requirements of the present invention, especially when the spraying voltage and current are reduced, the corresponding thermal conductivity of the coating is seriously reduced. Under the conditions that the parameters of other steps are the same, the thermal conductivity and bonding strength are reduced to a certain extent.

[0163] It can be seen from Example 1 and Comparative Example 2 that vacuum heat treatment will significantly affect the thermal conductivity of the coating. Under the same other conditions, the thermal conductivity of Example 1 after vacuum heat treatment (177.155 W / m·K) is increased by 74.98% compared with Comparative Example 3 (101.245 W / m·K) which has not undergone vacuum heat treatment.

[0164] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a high thermal diffusivity thermal conductive coating, characterized in that: The following steps are involved: S1: Weigh Cu powder, Ag powder and NiCoCrAlY powder according to the mass ratio and mix them to obtain a first raw material powder; S2: According to the mass ratio, NiCoCrAlY powder is weighed separately as the second raw material powder; S3: pre-treating the substrate surface; S4: Turn on the argon cooling device to blow argon gas to the position to be sprayed on the substrate; S5: placing the first raw material powder in a plasma spraying device and spraying it on the pretreated substrate surface to obtain a first pre-coating layer; S6: Turn off the argon cooling device and continue spraying on the substrate surface to obtain a second pre-coating layer; S7: turning on the argon cooling device and spraying the second raw material powder onto the surface of the second pre-coating layer through the plasma spraying device to obtain a third pre-coating layer comprising the second raw material powder coating layer; S8: performing vacuum heat treatment on the third pre-coating layer to obtain a composite thermal conductive coating layer.

2. The preparation method according to claim 1, characterized in that In step S1, the purity of the Cu powder, Ag powder and NiCoCrAlY powder raw materials is greater than 99.9%; the mass fraction of the Cu powder is 36.2-100%, the mass fraction of the Ag powder is 0-22.5%, and the mass fraction of the NiCoCrAlY powder is 0-53.6%.

3. The preparation method according to claim 2, characterized in that In step S1, the particle size of the Cu powder is 15-100 μm, the particle size of the Ag powder is 30-45 μm, and the particle size of the NiCoCrAlY powder is 10-65 μm.

4. The preparation method according to claim 1, characterized in that In step S2, the mass fraction of the NiCoCrAlY powder is 10-35% of the mass of the first raw material powder.

5. The preparation method according to claim 1, characterized in that In step S3, the substrate is one of titanium alloy, aluminum alloy, high-temperature alloy, carbon fiber composite, and alumina fiber composite; and the pretreatment method is one or more of grinding, laser cleaning, sand blasting, and plasma activation.

6. The preparation method according to claim 1, characterized in that In step S4, in the argon cooling device, the flow rate of argon is 30 to 50 L / min.

7. The preparation method according to claim 1, characterized in that In step S5, the thickness of the first pre-coating layer is 10 to 100 μm; The process parameters of the plasma spraying are: operating voltage of 50-80V, operating current of 400-800A, argon flow rate of 20-50L / min, hydrogen flow rate of 10-35L / min, powder feeding speed of 1-6L / min, and spraying distance of 80-120mm.

8. The preparation method according to claim 1, characterized in that In step S7, the thickness of the second raw material powder coating layer is 80 to 150 μm; The process parameters of the plasma spraying are: working voltage of 50-80V, working current of 400-600A, argon flow rate of 10-300L / min, hydrogen flow rate of 10-25L / min, powder feeding speed of 1-3L / min, and spraying distance of 90-110mm.

9. The preparation method according to claim 1, characterized in that In step S8, the vacuum heat treatment is: annealing the third pre-coating layer in a vacuum annealing furnace at a heat treatment temperature of 800-1000° C. for 1-6 hours, heating with the furnace and vacuum cooling with the furnace.

10. A high thermal diffusivity thermal conductive coating, prepared by the preparation method according to any one of claims 1 to 9, characterized in that: Along the direction away from the substrate surface, it includes a heat conducting layer and an anti-oxidation layer in sequence. The heat conducting layer is a coating composed of one or more of Cu powder, Ag powder and NiCoCrAlY powder, and the anti-oxidation layer is a dense metal layer composed of NiCoCrAlY powder.

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