Ceramic composite powder, coating for niobium alloy surface and preparation method

Abstract

The invention provides ceramic composite powder, a coating for a niobium alloy surface and a preparation method, the ceramic composite powder comprises sphere-like particles, and the materials of the sphere-like particles comprise MoSi2, SiC whiskers and Y2O3; the MoSi2 and the Y2O3 are coated on the surface of the SiC crystal whisker. According to the preparation method, the structural composition and the preparation process of the ceramic composite powder are designed, and the ceramic composite powder is subjected to multi-scale toughening, so that the mechanical property and the oxidation resistance of the prepared coating are effectively improved; the coating for the niobium alloy surface, which integrates toughness, is high in bonding strength and has both oxidation resistance and thermal shock resistance, is prepared.

Description

Technical Field

[0001] The present invention relates to the field of mechanical manufacturing technology, specifically to the field of high-temperature coatings, and in particular to a ceramic composite powder, a coating for a niobium alloy surface, and a preparation method thereof. Background Art

[0002] Niobium alloys (such as Nb-521 and C-103) are excellent materials for extreme environments such as rocket engine nozzles and spacecraft thermal protection systems due to their excellent high-temperature strength (>1500°C), low density, and good thermal conductivity. However, niobium alloys are prone to severe oxidation in high-temperature, oxygen-rich environments (>800°C), forming loose Nb2O5 oxides, which lead to rapid material failure.

[0003] The traditional solution is to prepare an anti-oxidation coating on the surface of niobium alloy to isolate oxygen. MoSi2 has excellent high-temperature oxidation resistance because of its high melting point of 2030°C. It can maintain high mechanical strength at high temperatures and can form a dense SiO2 protective film in a high-temperature oxidizing atmosphere to prevent further oxidation. In addition, its thermal expansion coefficient is similar to that of niobium alloy, and its performance matches, making it a commonly used anti-oxidation coating material.

[0004] CN110387523A discloses a multi-layer gradient composite high-temperature anti-oxidation coating on the surface of a niobium alloy, comprising a base coating and a top coating formed sequentially on the surface of the niobium alloy. The main components of the base coating are Nb5Si3 and NbSi2 and contain Ti, Cr, Al, Hf and B elements; the main components of the top coating are Mo s Si3 and MoSi2, along with Hf and B elements, are used in this invention. The resulting multi-layer gradient composite high-temperature anti-oxidation coating on the niobium alloy is subjected to a high-temperature heat treatment (e.g., 1700°C to 1800°C or above). During oxidation, the undercoat layer on the niobium alloy surface inhibits the diffusion of Si elements from the topcoat into the coating. Simultaneously, sufficient Si in the undercoat layer continuously acts on the surface of the topcoat to form a continuous, dense SiO2 film, ultimately increasing the service temperature and lifespan of the multi-layer gradient composite high-temperature anti-oxidation coating on the niobium alloy surface.

[0005] CN107190261A discloses a high-temperature, oxidation-resistant composite silicide coating on the surface of a niobium alloy and its preparation method. The Nb521 alloy is pickled, sandblasted, ultrasonically cleaned, and dried before use. A NbSi2 inner coating containing Al2O3 adsorbed particles is prepared using a halide vapor infiltration method. An MoSi2 outer coating is prepared using an atmospheric supersonic plasma spraying method. This composite coating system, fabricated by roughening and siliconizing followed by thermal spraying, significantly improves the oxidation resistance of the niobium-based alloy at 1500°C, achieving a service life of 128 hours or more. The Al2O3 intermediate layer designed in this invention forms an element barrier at high temperatures, effectively preventing erosion caused by interdiffusion of coating elements.

[0006] CN104630699A discloses a method for preparing an oxidation-resistant coating on the surface of a niobium alloy. Using a vacuum-activated infiltration process, a (Mo, W)Si2 composite gradient coating is prepared. This coating possesses the properties of both molybdenum silicide and tungsten silicide. During the silicide process, a molybdenum-tungsten silicide composite coating formed by silicon diffusion forms an oxidation-resistant layer, niobium silicide forms an intermediate layer, and niobium trisilicide forms a transition layer. The coating exhibits an oxidation resistance life of 80 hours at 1800°C and a thermal shock resistance of 1500 cycles from 1800°C to room temperature. High-speed, high-temperature airflow scour tests have demonstrated an anti-scour life of 10 hours at 1600°C with an airflow velocity of approximately 1.2 km / s, and 7 hours at 1700°C.

[0007] Although MoSi2-containing coatings have excellent oxidation resistance at high temperatures, they are susceptible to simultaneous oxidation of silicon and molybdenum at low temperatures of 400°C to 600°C, leading to brittle fracture and powdering of the coating (the "Pesting effect"). Therefore, overcoming the low-temperature oxidation characteristics of MoSi2 is a key challenge in its application. However, existing technologies focus primarily on its high-temperature oxidation resistance, with limited improvements in low-temperature toughness.

[0008] Therefore, it is of great significance to develop a MoSi2-based ceramic composite powder that is strong and tough, has high bonding strength, and has both antioxidant and thermal shock resistance, and to apply it to the inner wall of a large-area niobium alloy nozzle with high efficiency and high quality. Summary of the Invention

[0009] To address the shortcomings of the existing technology, the present invention aims to provide a ceramic composite powder, a coating for niobium alloy surfaces, and a preparation method. By designing the structural composition and preparation process of the ceramic composite powder and performing multi-scale toughening on the ceramic composite powder, the present invention effectively improves the mechanical properties and oxidation resistance of the resulting coating. The result is a coating that exhibits both strength and toughness, high bond strength, and balanced oxidation resistance and thermal shock resistance.

[0010] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a ceramic composite powder, wherein the ceramic composite powder comprises spherical particles, wherein the spherical particles are made of MoSi2, SiC whiskers and Y2O3;

[0012] The MoSi2 and the Y2O3 are wrapped on the surface of the SiC whisker.

[0013] The quasi-spherical particles of the present invention have high sphericity and are spherical or nearly spherical in shape.

[0014] When the coating prepared from the ceramic composite powder of the present invention is used under high temperature conditions (greater than 1000°C), the Y2O3 therein can form high melting point yttrium silicate, such as Y2SiO5, Y2Si2O7 or Y4Si3O 12 , filling into the SiO2 glass layer, it can stabilize the distribution of silicon-oxygen bonds (Si-O), delay the penetration of oxygen, and thus inhibit the powdering and oxidation tendency of MoSi2 at low temperatures of 400℃ to 600℃.

[0015] The present invention also introduces SiC whiskers into the ceramic composite powder. When cracks are generated due to external force, the high aspect ratio and high strength of the SiC whiskers can change the crack path, consume more energy, and hinder the expansion of cracks in the MoSi2 matrix through crack deflection and bridging effects, thereby improving the fracture toughness of the coating based on the ceramic composite powder.

[0016] In the present invention, MoSi2, SiC whiskers and Y2O3 are compounded to form spherical particles, and MoSi2 and Y2O3 powders are coated on the surface of SiC whiskers with a high aspect ratio, so that the SiC whiskers can maintain their original morphology during the spraying process and play a pinning role in the coating, which is beneficial to enhancing the toughening effect of the silicon carbide whiskers in the coating. At the same time, the spherical structure has good fluidity and structural stability, and can form a three-dimensional interlocking toughening network inside the coating, which is more conducive to obtaining a uniform, dense and consistent coating.

[0017] Preferably, in the spherical particles, the mass percentage of the MoSi2 is 82wt% to 92wt%, the mass percentage of the SiC whiskers is 5wt% to 10wt%, and the mass percentage of the Y2O3 is 3wt% to 8wt%.

[0018] Preferably, in the spherical particles, the average particle size of the MoSi2 is 1 μm to 5 μm.

[0019] Preferably, in the spherical particles, the SiC whiskers have an average diameter of 0.1 μm to 2 μm and an average length of 10 μm to 50 μm.

[0020] Preferably, in the spherical particles, the average particle size of the Y2O3 is 1 μm to 10 μm.

[0021] Preferably, the average particle size of the spherical particles is 15 μm to 45 μm.

[0022] In a second aspect, the present invention provides a method for preparing the ceramic composite powder according to the first aspect, the preparation method comprising:

[0023] A mixture comprising the MoSi2, the SiC whiskers and the Y2O3 is prepared; the mixture is mixed with a solvent to prepare a slurry; the slurry is spray-granulated; and sintered to obtain the ceramic composite powder.

[0024] The present invention prepares a ceramic composite powder with high sphericity through spray granulation. During the subsequent spraying process, the ceramic composite powder with a spherical structure can maintain structural stability, thereby forming a three-dimensional interlocking toughening network inside the coating. In addition, the ceramic composite powder with a spherical structure has good fluidity, which is more conducive to obtaining a uniform, dense and consistent coating.

[0025] Preferably, the mixture is prepared by sequentially ultrasonically dispersing and ball milling the MoSi2, the SiC whiskers and the Y2O3 in a liquid medium.

[0026] Preferably, the solvent comprises water and / or ethanol.

[0027] Preferably, the solid content of the slurry is 45% to 55%.

[0028] Preferably, the sintering temperature is 1350°C to 1650°C.

[0029] Preferably, the sintering time is 1 hour to 3 hours.

[0030] Preferably, the sintering is performed in an inert environment.

[0031] In a third aspect, the present invention provides a coating for a niobium alloy surface, wherein the coating is prepared from the ceramic composite powder according to the first aspect.

[0032] In a fourth aspect, the present invention provides a method for preparing a coating on a niobium alloy surface as described in the third aspect, the method comprising:

[0033] Spraying the ceramic composite powder described in the first aspect onto the surface of the workpiece by supersonic plasma spraying;

[0034] Covering the workpiece surface once by the spray gun path is considered 1 time, the workpiece is preheated n times by the plasma flame flow, and then sprayed m times to obtain the coating;

[0035] The preheating times n is ≥ 2 times; the spraying times m is ≥ 5 times.

[0036] The present invention prepares a coating on a workpiece by supersonic plasma spraying, first preheating for more than 2 times, and then spraying for more than 5 times, to reduce the temperature difference between the workpiece and the coating, and ensure that the workpiece and the coating are sufficiently cooled to prevent excessive thermal stress from causing the coating to fall off. In the preparation method of the coating provided by the present invention, the coating is integrally formed, uniform and dense, with good consistency, and does not require high-temperature sintering, overcoming the problems of long high-temperature treatment time and complex procedures in traditional coating preparation technology, as well as limited high-temperature treatment of large-scale equipment and high-temperature deformation of thin-walled parts. In combination with the ceramic composite powder provided by the present invention, efficient preparation of coatings with good uniformity, strong and tough integration, high bonding strength, and both antioxidant and thermal shock resistance is achieved.

[0037] In the present invention, the material of the workpiece includes niobium alloy. In addition to niobium alloy, it can also include other materials that can be used under high-temperature working conditions. For example, it can include nickel alloy and / or ceramic-based composite materials. The present invention is no longer specifically limited. Any workpiece including niobium alloy and used under high-temperature working conditions is applicable to the technical solution of the present invention.

[0038] Preferably, the interval between two adjacent preheating times is 0.5s to 3s.

[0039] Preferably, the interval between two adjacent sprayings is 5s to 15s.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The present invention combines MoSi2, SiC whiskers and Y2O3 to form spherical particles, wherein Y2O3 can form high-melting-point yttrium silicate under high-temperature conditions, stabilize the distribution of silicon-oxygen bonds (Si-O), delay the penetration of oxygen, and thus inhibit the pulverization and oxidation tendency of MoSi2 at low temperatures of 400°C to 600°C; SiC whiskers can hinder the expansion of cracks in the MoSi2 matrix through crack deflection and bridging effects; MoSi2, SiC whiskers and Y2O3 form a three-dimensional interlocking toughening network inside the coating, and the spherical structure has good fluidity and structural stability, which is conducive to obtaining a coating that is uniform and dense, has good consistency, is strong and tough, has high bonding strength, and takes both antioxidant and thermal shock resistance into consideration.

[0042] (2) The present invention prepares ceramic composite powders with high sphericity by spray granulation. During the subsequent spraying process, the ceramic composite powders with quasi-spherical structure can maintain structural stability and have good fluidity, which is more conducive to obtaining a uniform, dense and consistent coating and forming a three-dimensional interlocking toughening network inside the coating.

[0043] (3) In the method for preparing the coating for the surface of niobium alloy provided by the present invention, the coating is integrally formed, uniform and dense, with good consistency, and does not require high-temperature sintering, thereby overcoming the problems of traditional coating preparation technology such as long high-temperature treatment time, complex procedures, limited high-temperature treatment of large-scale equipment, and high-temperature deformation of thin-walled parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is an optical microscope image of the cross section of the coating provided in Example 1.

[0045] Figure 2 is a SEM image of the ceramic composite powder provided in Example 1.

[0046] Figure 3 This is a SEM image of MoSi2 used to prepare the ceramic composite powder in Example 1.

[0047] Figure 4 : is a SEM image of the SiC whiskers used to prepare the ceramic composite powder in Example 2.

[0048] Figure 5 This is an SEM image of Y2O3 used in preparing ceramic composite powder in Example 2. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusions.

[0051] In the description of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0052] In a first embodiment, the present invention provides a ceramic composite powder comprising spherical particles, wherein the spherical particles are made of MoSi2, SiC whiskers and Y2O3;

[0053] The MoSi2 and the Y2O3 are wrapped on the surface of the SiC whisker.

[0054] When the coating prepared from the ceramic composite powder of the present invention is used under high temperature conditions, the added Y2O3 can form high melting point yttrium silicate, such as Y2SiO5, Y2Si2O7 or Y4Si3O 12 , filling into the SiO2 glass layer, it can stabilize the distribution of silicon-oxygen bonds (Si-O), delay the penetration of oxygen, and thus inhibit the powdering and oxidation tendency of MoSi2 at low temperatures of 400℃ to 600℃.

[0055] The present invention also introduces SiC whiskers into the ceramic composite powder. When cracks are generated due to external force, the high aspect ratio and high strength of the SiC whiskers can change the crack path, consume more energy, and hinder the expansion of cracks in the MoSi2 matrix through crack deflection and bridging effects, thereby improving the fracture toughness of the coating based on the ceramic composite powder.

[0056] In the present invention, MoSi2, SiC whiskers and Y2O3 are compounded to form spherical particles, and MoSi2 and Y2O3 powders are coated on the surface of SiC whiskers with a high aspect ratio, so that the SiC whiskers can maintain their original morphology during the spraying process and play a pinning role in the coating, which is beneficial to enhancing the toughening effect of the silicon carbide whiskers in the coating. At the same time, the spherical structure has good fluidity and structural stability, and can form a three-dimensional interlocking toughening network inside the coating, which is more conducive to obtaining a uniform, dense and consistent coating.

[0057] In some embodiments, in the spherical particles, the mass percentage of the MoSi2 is 82wt% to 92wt%, for example, it can be 82wt%, 83wt%, 84wt%, 85wt%, 86wt%, 87wt%, 88wt%, 89wt%, 90wt%, 91wt% or 92wt%; the mass percentage of the SiC whiskers is 5wt% to 10wt%, for example, it can be 5wt%, 6wt%, 7wt%, 8wt%, 9wt% or 10wt%; the mass percentage of the Y2O3 is 3wt% to 8wt%, for example, it can be 3wt%, 4wt%, 5wt%, 6wt%, 7wt% or 8wt%. In the spherical particles, the mass percentages of MoSi2, SiC whiskers and Y2O3 include but are not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0058] In the present invention, MoSi2 and Y2O3 with smaller average particle sizes are selected to be compounded with SiC whiskers, which is more conducive to the encapsulation of SiC whiskers and more likely to form spherical particles with high sphericity.

[0059] In some embodiments, in the spherical particles, the average particle size of the MoSi2 is 1 μm to 5 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm or 5 μm, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0060] In some embodiments, in the spherical particles, the average diameter of the SiC whiskers is 0.1 μm to 2 μm, for example, 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 0.9 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm, and the average length is 10 μm to 50 μm, for example, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0061] In some embodiments, in the spherical particles, the average particle size of the Y2O3 is 1 μm to 10 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0062] In some embodiments, the average particle size of the spherical particles is 15 μm to 45 μm, for example, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm or 45 μm, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0063] In a second specific embodiment, the present invention provides a method for preparing the ceramic composite powder as described in the first embodiment, the preparation method comprising:

[0064] A mixture comprising the MoSi2, the SiC whiskers and the Y2O3 is prepared; the mixture is mixed with a solvent to prepare a slurry; the slurry is spray-granulated; and sintered to obtain the ceramic composite powder.

[0065] The present invention prepares ceramic composite powder with high sphericity through spray granulation. During the subsequent spraying process, the ceramic composite powder with a spherical structure can maintain structural stability, thereby forming a three-dimensional interlocking toughening network inside the coating. In addition, the ceramic composite powder with a spherical structure has good fluidity, which is more conducive to obtaining a uniform, dense and consistent coating.

[0066] In some embodiments, the mixture is prepared by sequentially ultrasonically dispersing and ball-milling the MoSi2, the SiC whiskers, and the Y2O3 in a liquid medium, wherein the liquid medium comprises water and / or ethanol.

[0067] In some embodiments, the ultrasonic dispersion time is 10 min to 60 min, for example, 10 min, 20 min, 30 min, 40 min, 50 min or 60 min, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0068] In some embodiments, the ball milling time is 1 h to 5 h, for example, 1 h, 2 h, 3 h, 4 h or 5 h, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0069] In some embodiments, the solvent comprises water and / or ethanol.

[0070] In some embodiments, the solid content of the slurry is 45% to 55%, for example, it can be 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54% or 55%, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0071] In the present invention, the slurry also includes a binder and a dispersant. Those skilled in the art can reasonably select and set the types and contents of the binder and the dispersant. For example, the binder can be, for example, polyvinyl alcohol, and the dispersant can be, for example, polyethylene glycol. Taking the total mass of the slurry as 100%, the mass percentage of the binder in the solid matter can be 8% to 12%, for example, 8%, 9%, 10%, 11% or 12%, and the mass percentage of the dispersant in the solid matter can be 0.5% to 2%, for example, 0.5%, 1%, 1.2%, 1.4%, 1.6%, 1.8% or 2%, including but not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0072] In the present invention, the purpose of sintering after spray granulation is to remove impurities such as binders and dispersants introduced during granulation, while also bonding the low-melting-point particles within the powder to form a ceramic composite powder with high internal cohesive strength. In the present invention, if the sintering temperature is too high, the powder will become clumpy or ablated. If the sintering temperature is too low, the internal components of the ceramic composite powder will form loose connections, resulting in low internal cohesive strength.

[0073] In some embodiments, the sintering temperature is 1350°C to 1650°C, for example, it can be 1350°C, 1400°C, 1450°C, 1500°C, 1550°C, 1600°C or 1650°C, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0074] In some embodiments, the sintering time is 1 h to 3 h, for example, 1 h, 1.5 h, 2 h, 2.5 h or 3 h, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0075] In some embodiments, the sintering is performed in an inert environment, which includes a nitrogen environment and / or an inert gas environment, and the inert gas environment includes an argon environment.

[0076] In some embodiments, the inlet temperature of the spray drying is 230°C to 270°C, for example, 230°C, 240°C, 250°C, 260°C or 270°C, including but not limited to the values ​​listed, and other values ​​not listed within the numerical range are also applicable.

[0077] In some embodiments, the outlet temperature of the spray drying is 100°C to 130°C, for example, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C, including but not limited to the values ​​listed, and other values ​​not listed within the numerical range are also applicable.

[0078] In a third embodiment, the present invention provides a coating for a niobium alloy surface, wherein the coating is prepared from the ceramic composite powder provided in the first embodiment.

[0079] In a fourth embodiment, the present invention provides a method for preparing a coating on a niobium alloy surface as described in the third embodiment, the method comprising:

[0080] Spraying the ceramic composite powder provided in the first embodiment onto the surface of the workpiece by supersonic plasma spraying;

[0081] Covering the workpiece surface once by the spray gun path is considered 1 time, the workpiece is preheated n times by the plasma flame flow, and then sprayed m times to obtain the coating;

[0082] The preheating times n is ≥ 2 times; the spraying times m is ≥ 5 times.

[0083] This invention uses supersonic plasma spraying to create a uniform, dense, and consistent coating on a workpiece surface. The coating is integrated and formed without the need for high-temperature sintering. This overcomes the long and complex high-temperature processing times and process limitations of traditional coating preparation techniques, as well as the limitations of high-temperature processing in large-scale equipment and the high-temperature deformation of thin-walled parts. Combined with the ceramic composite powder provided by this invention, this allows for the efficient production of coatings that exhibit excellent uniformity, a strong and tough structure, high bonding strength, and balanced oxidation and thermal shock resistance.

[0084] In the present invention, the number of preheating times n is ≥ 2 times, for example, 2 times, 3 times, 4 times, or 5 times, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable; the number of spraying times m is ≥ 5 times, for example, 5 times, 10 times, 15 times, or 20 times, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable. In the present invention, the number of spraying times affects the thickness of the coating and can be adjusted according to the required coating thickness.

[0085] In some embodiments, the interval between two adjacent preheating times is 0.5s to 3s, for example, 0.5s, 1s, 1.5s, 2s, 2.5s or 3s, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0086] In some embodiments, the interval time between two adjacent sprayings is 5s to 15s, for example, it can be 5s, 6s, 7s, 8s, 9s, 10s, 11s, 12s, 13s, 14s or 15s, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0087] In some embodiments, the main gas of the supersonic plasma spraying is Ar, and the flow rate of the Ar is 70 L / min to 100 L / min, for example, it can be 70 L / min, 75 L / min, 80 L / min, 85 L / min, 90 L / min, 95 L / min or 100 L / min, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0088] In some embodiments, the secondary gas for supersonic plasma spraying is H2, and the flow rate of H2 is 10L / min to 20L / min, for example, it can be 10L / min, 12L / min, 14L / min, 16L / min, 18L / min or 20L / min, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0089] In some embodiments, the spraying power of the supersonic plasma spraying is 48kW to 52kW, for example, 48kW, 49kW, 50kW, 51kW or 52kW, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0090] In some embodiments, the powder feeding rate of the supersonic plasma spraying is 5 g / min to 10 g / min, for example, it can be 5 g / min, 6 g / min, 7 g / min, 8 g / min, 9 g / min or 10 g / min, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0091] In some embodiments, the powder feeding gas pressure of the supersonic plasma spraying is 0.3 MPa to 0.7 MPa, for example, it can be 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa, 0.5 MPa, 0.55 MPa, 0.6 MPa, 0.65 MPa or 0.7 MPa, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0092] In some embodiments, during the supersonic plasma spraying process, cooling gas is added behind the workpiece, and the pressure of the cooling gas is 0.6 MPa to 0.7 MPa, for example, it can be 0.6 MPa, 0.62 MPa, 0.64 MPa, 0.66 MPa, 0.68 MPa or 0.7 MPa, including but not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 0.65 MPa.

[0093] In some embodiments, during the supersonic plasma spraying process, a purge gas is added to the surface of the workpiece, and the pressure of the purge gas is 0.3 MPa to 0.5 MPa, for example, it can be 0.32 MPa, 0.34 MPa, 0.36 MPa, 0.38 MPa, 0.4 MPa, 0.42 MPa, 0.44 MPa, 0.46 MPa, 0.48 MPa or 0.5 MPa, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 0.4 MPa.

[0094] In the present invention, before spraying the coating on the workpiece surface, the step of sandblasting the workpiece surface is also included. The sandblasting process includes: using clean compressed air filtered by oil and water to sandblast the workpiece surface to remove oil and rust layers on the workpiece surface to expose a fresh surface. After the sandblasting, the roughness of the workpiece surface reaches Sa2.5 level or above, and in order to avoid work hardening, the sandblasting time should not be too long.

[0095] After the sandblasting is completed, the workpiece after the sandblasting is placed in anhydrous ethanol for ultrasonic cleaning, and the ultrasonic cleaning time is 1 minute to 5 minutes, for example, it can be 1 minute, 2 minutes, 3 minutes, 4 minutes or 5 minutes. After the ultrasonic cleaning is completed, it is naturally air-dried.

[0096] In some embodiments, during the sandblasting process, the pressure of the compressed air is not less than 0.7 MPa, for example, it can be 0.7 MPa, 0.72 MPa, 0.74 MPa, 0.76 MPa, 0.78 MPa, 0.8 MPa, 0.9 MPa or 1 MPa, and the sandblasting angle is 65° to 72°, for example, it can be 65°, 66°, 67°, 68°, 69°, 70°, 71° or 72°, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable. The sandblasting angle is preferably 70°.

[0097] In some embodiments, the average particle size of the sandblasting used in the sandblasting treatment is 16 mesh to 22 mesh, for example, it can be 16 mesh, 17 mesh, 18 mesh, 19 mesh, 20 mesh, 21 mesh or 22 mesh, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0098] In some embodiments, the sandblasting used in the sandblasting treatment includes any one or a combination of at least two of brown corundum sand, copper ore sand or steel sand, and limited but non-limiting combinations include a combination of brown corundum sand and copper ore sand, a combination of steel sand and brown corundum sand, or a combination of copper ore sand and steel sand.

[0099] Example 1

[0100] This embodiment provides a ceramic composite powder, which is composed of 87wt% MoSi2, 8wt% SiC whiskers and 5wt% Y2O3. Figure 2 As shown in the SEM image in the middle, the morphology of the ceramic composite powder is nearly spherical.

[0101] The preparation method of the ceramic composite powder comprises:

[0102] (1) Preparation of slurry: MoSi2 with an average particle size of 3 μm, SiC whiskers with a diameter of 1.2 μm and a length of 25 μm, and Y2O3 with an average particle size of 6 μm were weighed in a mass ratio of 87:8:5, placed in water, and ultrasonically dispersed for 10 min; then ball milled for 2.5 h using water as a medium to obtain a mixture; the obtained mixture was mixed with polyvinyl alcohol and polyethylene glycol in water to obtain a slurry, in which, based on the total mass of solid matter as 100%, the mass percentage of polyvinyl alcohol was 9%, and the mass percentage of polyethylene glycol was 1.2%; the SEM of the MoSi2 was as follows: Figure 3 shown.

[0103] (2) Spray granulation: The inlet temperature was set at 260°C and the outlet temperature was set at 130°C. The slurry prepared in step (1) was spray granulated, and then sintered at 1550°C for 3 hours under argon protection. The powder was sieved to obtain a ceramic composite powder with an average particle size of 45 μm.

[0104] This embodiment also provides a coating for the surface of a niobium alloy, wherein the coating is prepared from the ceramic composite powder provided in this embodiment, such as Figure 1 The optical microscope image of the cross section of the coating shown has a thickness of 150 μm. The preparation method of the coating includes:

[0105] (I) Pretreatment of the workpiece surface: using brown corundum sand with a particle size of 20 mesh, setting the pressure of clean compressed air to 0.75 MPa and the blasting angle to 70°, the workpiece surface was sandblasted to a roughness of Sa2.5 or above. The sandblasted workpiece was then placed in anhydrous ethanol, ultrasonically cleaned for 2 minutes, removed, and naturally air-dried.

[0106] (II) Supersonic plasma spray coating: Ar was used as the primary gas and H₂ as the secondary gas. The primary gas flow rate was set at 85 L / min, the secondary gas flow rate was set at 15 L / min, the spray power was set at 50 kW, the powder feed rate was set at 7 g / min, and the powder feed gas pressure was set at 0.5 MPa. A cooling gas pressure of 0.65 MPa was added behind the workpiece, and a purge gas pressure of 0.4 MPa was added to the substrate surface. The workpiece was preheated using the plasma flame three times, with a 1-second interval between each spraying. The coating was then sprayed 15 times, with a 10-second interval between each spraying, to obtain the coating.

[0107] Example 2

[0108] This embodiment provides a ceramic composite powder having a spherical structure and composed of 82 wt % MoSi 2 , 10 wt % SiC whiskers and 8 wt % Y 2 O 3 .

[0109] The preparation method of the ceramic composite powder comprises:

[0110] (1) Preparation of slurry: MoSi2 with an average particle size of 1 μm, SiC whiskers with a diameter of 0.1 μm and a length of 10 μm, and Y2O3 with an average particle size of 1 μm were weighed in a mass ratio of 82:10:8, placed in water, and ultrasonically dispersed for 15 min; then ball milled for 3 h using water as a medium to obtain a mixture; the obtained mixture was mixed with polyvinyl alcohol and polyethylene glycol in water to obtain a slurry, in which, based on the total mass of solid matter as 100%, the mass percentage of polyvinyl alcohol was 10%, and the mass percentage of polyethylene glycol was 1%; the SEM of the SiC whiskers was as follows: Figure 3 As shown, the SEM of the Y2O3 is as shown Figure 4 As shown;

[0111] (2) Spray granulation: The inlet temperature was set at 250°C and the outlet temperature was set at 120°C. The slurry prepared in step (1) was spray granulated, and then sintered at 1350°C for 1 hour under argon protection. The powder was sieved to obtain a ceramic composite powder with an average particle size of 35 μm.

[0112] This embodiment further provides a coating for a niobium alloy surface. The coating is prepared from the ceramic composite powder provided in this embodiment. The thickness of the coating is 200 μm. The preparation method of the coating includes:

[0113] (I) Pre-treating the workpiece surface: same as in Example 1;

[0114] (II) Supersonic plasma spray coating: The process is the same as in Example 1 except that the workpiece is preheated twice with a plasma flame flow, each time with an interval of 0.8 seconds, and then sprayed 20 times with an interval of 8 seconds between each spraying.

[0115] Example 3

[0116] This embodiment provides a ceramic composite powder having a spherical structure and composed of 92 wt % MoSi 2 , 5 wt % SiC whiskers and 3 wt % Y 2 O 3 .

[0117] The preparation method of the ceramic composite powder comprises:

[0118] (1) Preparation of slurry: except that MoSi2 with an average particle size of 5 μm, SiC whiskers with a diameter of 2 μm and a length of 50 μm, and Y2O3 with an average particle size of 10 μm were weighed in a mass ratio of 92:5:3, the rest was the same as in Example 1;

[0119] (2) Spray granulation: The inlet temperature was set at 250°C and the outlet temperature was set at 120°C. The slurry prepared in step (1) was spray granulated, and then sintered at 1650°C for 5 hours under argon protection. The powder was sieved to obtain a ceramic composite powder with an average particle size of 45 μm.

[0120] This embodiment further provides a coating for a niobium alloy surface. The coating is prepared from the ceramic composite powder provided in this embodiment. The thickness of the coating is 50 μm. The preparation method of the coating includes:

[0121] (I) Pre-treating the workpiece surface: same as in Example 1;

[0122] (II) Supersonic plasma spray coating: The process is the same as in Example 1 except that the workpiece is preheated 4 times with a 1.5 second interval between each application and then sprayed 5 times with a 12 second interval between each application.

[0123] Example 4

[0124] This embodiment provides a ceramic composite powder having a spherical structure and composed of 87 wt % MoSi 2 , 8 wt % SiC whiskers and 5 wt % Y 2 O 3 .

[0125] The preparation method of the ceramic composite powder is the same as that of Example 1, except that the average particle size of MoSi2 is 8 μm and the average particle size of Y2O3 is 10 μm.

[0126] This embodiment also provides a coating for the surface of a niobium alloy and a preparation method thereof. Except that the coating is prepared from the ceramic composite powder provided in this embodiment, the rest is the same as that of Example 1.

[0127] Example 5

[0128] This embodiment provides a ceramic composite powder having a spherical structure and composed of 92 wt % MoSi 2 , 3 wt % SiC whiskers and 5 wt % Y 2 O 3 .

[0129] The preparation method of the ceramic composite powder is the same as that of Example 1, except that MoSi2, SiC whiskers and Y2O3 are weighed in a mass ratio of 92:3:5;

[0130] This embodiment also provides a coating for the surface of a niobium alloy and a preparation method thereof. Except that the coating is prepared from the ceramic composite powder provided in this embodiment, the rest is the same as that of Example 1.

[0131] Example 6

[0132] This embodiment provides a ceramic composite powder having a spherical structure and composed of 83 wt % MoSi 2 , 12 wt % SiC whiskers and 5 wt % Y 2 O 3 .

[0133] The preparation method of the ceramic composite powder is the same as that of Example 1, except that MoSi2, SiC whiskers and Y2O3 are weighed in a mass ratio of 83:12:5;

[0134] This embodiment also provides a coating for the surface of a niobium alloy and a preparation method thereof. Except that the coating is prepared from the ceramic composite powder provided in this embodiment, the rest is the same as that of Example 1.

[0135] Example 7

[0136] This embodiment provides a ceramic composite powder having a spherical structure and composed of 90 wt % MoSi 2 , 8 wt % SiC whiskers and 2 wt % Y 2 O 3 .

[0137] The preparation method of the ceramic composite powder is the same as that of Example 1, except that MoSi2, SiC whiskers and Y2O3 are weighed in a mass ratio of 90:8:2;

[0138] This embodiment also provides a coating for the surface of a niobium alloy and a preparation method thereof. Except that the coating is prepared from the ceramic composite powder provided in this embodiment, the rest is the same as that of Example 1.

[0139] Example 8

[0140] This embodiment provides a ceramic composite powder having a spherical structure and composed of 82 wt % MoSi 2 , 8 wt % SiC whiskers and 10 wt % Y 2 O 3 .

[0141] The preparation method of the ceramic composite powder is the same as that of Example 1, except that MoSi2, SiC whiskers and Y2O3 are weighed in a mass ratio of 82:8:10;

[0142] This embodiment also provides a coating for the surface of a niobium alloy and a preparation method thereof. Except that the coating is prepared from the ceramic composite powder provided in this embodiment, the rest is the same as that of Example 1.

[0143] Example 9

[0144] This embodiment provides a ceramic composite powder and a preparation method thereof, which is the same as that of Example 1 except that the average particle size of the ceramic composite powder is 25 μm;

[0145] This embodiment also provides a coating for the surface of a niobium alloy and a preparation method thereof. Except that the coating is prepared from the ceramic composite powder provided in this embodiment, the rest is the same as that of Example 1.

[0146] Example 10

[0147] This embodiment provides a ceramic composite powder and a preparation method thereof, which is the same as that of Example 1 except that the average particle size of the ceramic composite powder is 65 μm;

[0148] This embodiment also provides a coating for the surface of a niobium alloy and a preparation method thereof. Except that the coating is prepared from the ceramic composite powder provided in this embodiment, the rest is the same as that of Example 1.

[0149] Example 11

[0150] This embodiment provides a coating for a niobium alloy surface and a preparation method thereof. Except that the workpiece surface is preheated only once and the coating is prepared by spraying only once, the rest is the same as in Example 1.

[0151] Example 12

[0152] This embodiment provides a coating for a niobium alloy surface and a preparation method thereof. The coating is prepared by directly spraying three times with an interval of 10 seconds between each spraying, except that the workpiece surface is not preheated. Otherwise, the coating is prepared as in Example 1.

[0153] Comparative Example 1

[0154] This comparative example provides a ceramic composite powder, which is the same as Example 1 except that the ceramic composite powder does not include SiC whiskers and is composed only of 95wt% MoSi2 and 5wt% Y2O3;

[0155] This comparative example also provides a coating for the surface of a niobium alloy and a preparation method thereof. Except that the coating is prepared from the ceramic composite powder provided in this comparative example, the rest is the same as that of Example 1.

[0156] Comparative Example 2

[0157] This comparative example provides a ceramic composite powder, which is the same as Example 1 except that the ceramic composite powder does not include Y2O3 and is composed only of 92wt% MoSi2 and 8wt% SiC whiskers;

[0158] This comparative example also provides a coating for the surface of a niobium alloy and a preparation method thereof. Except that the coating is prepared from the ceramic composite powder provided in this comparative example, the rest is the same as that of Example 1.

[0159] Performance testing:

[0160] Optical microscope: The cross section of the coating prepared in Example 1 was tested by optical microscope. The test results are shown in Figure 1 ;

[0161] SEM test: SEM test was performed on the ceramic composite powder provided in Example 1, the MoSi2 used to prepare the ceramic composite powder, and the SiC whiskers and Y2O3 used to prepare the ceramic composite powder in Example 2. The test results are shown in Table 1. Figures 2 to 5 .

[0162] Elastic modulus test: The elastic modulus of the coatings provided in all the above embodiments and comparative examples was tested using a micro / nanoindenter (STeP500-NHT3-MCT3, Anton Paar, Austria) equipped with a standard Vickers diamond indenter (α = 136° ± 0.2°). The test conditions were: maximum load of 500 mN, loading and unloading rates of 1000 mN / min, and a holding time of 10 s. Five points were randomly selected for each coating sample for testing, and the average value was taken as the final data. The test results are shown in Table 1.

[0163] Bonding strength test: The bonding strength of the coatings provided in all the above embodiments and comparative examples was measured using the national standard GB8642-2002. Five coating samples were measured each time and the average value was taken. The test results are shown in Table 1.

[0164] Thermal Shock Resistance Testing: The thermal shock resistance of the coatings provided in all the aforementioned examples and comparative examples was tested. The test method was as follows: a niobium alloy specimen sprayed with the coating was placed in a 1300°C electric furnace, held at this temperature for 5 minutes, then removed and quickly cooled in 30°C water. This was counted as one thermal shock. When the coating peeled off to a 30% area, it was considered a complete failure, and the number of thermal shocks at which complete failure occurred was recorded. The test results are shown in Table 1.

[0165] Gas flushing life test: The gas flushing life of the coatings provided in all the above embodiments and comparative examples was tested. The test method is: use an oxyacetylene flame torch to heat the coating surface to 1400°C within 150 seconds, maintain it at the peak temperature for 180 seconds, and then quickly cool it to 300°C using high-pressure airflow to complete one cycle. The number of cycles when defects appear on the coating surface is recorded. The test results are shown in Table 1.

[0166] Table 1

[0167]

[0168] According to the test data from Example 1 shown in Table 1, the coating produced using the ceramic composite powder provided by the present invention via supersonic plasma spraying exhibits an average bond strength of 37 MPa, demonstrating excellent resistance to the high-speed detonation waves of detonation engines. After 300 gas-flushing cycles, the coating's surface morphology remained excellent, with no noticeable defects, fully meeting the requirements for rocket engine operation. The coating also withstood 253 thermal shock cycles, far exceeding the requirement of 50 cycles without spalling.

[0169] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A ceramic composite powder, characterized in that: The ceramic composite powder includes spherical particles, and the materials of the spherical particles include MoSi2, SiC whiskers and Y2O3; The MoSi2 and the Y2O3 are wrapped on the surface of the SiC whisker.

2. The ceramic composite powder according to claim 1, wherein In the spherical particles, the mass percentage of the MoSi2 is 82wt% to 92wt%, the mass percentage of the SiC whiskers is 5wt% to 10wt%, and the mass percentage of the Y2O3 is 3wt% to 8wt%.

3. The ceramic composite powder according to claim 1 or 2, characterized in that In the spherical particles, the average particle size of the MoSi2 is 1 μm to 5 μm; And / or, in the spherical particles, the SiC whiskers have an average diameter of 0.1 μm to 2 μm and an average length of 10 μm to 50 μm; And / or, in the spherical particles, the average particle size of the Y2O3 is 1 μm to 10 μm.

4. The ceramic composite powder according to any one of claims 1 to 3, characterized in that The average particle size of the spherical particles is 15 μm to 45 μm.

5. A method for preparing the ceramic composite powder according to any one of claims 1 to 4, characterized in that: The preparation method comprises: A mixture comprising the MoSi2, the SiC whiskers and the Y2O3 is prepared; the mixture is mixed with a solvent to prepare a slurry; the slurry is spray-granulated; and sintered to obtain the ceramic composite powder.

6. The preparation method according to claim 5, wherein The mixture is prepared by sequentially ultrasonically dispersing and ball milling the MoSi2, the SiC whiskers and the Y2O3 in a liquid medium; And / or, the solid content of the slurry is 45% to 55%.

7. The preparation method according to claim 5 or 6, characterized in that The sintering temperature is 1350°C to 1650°C; And / or, the sintering time is 1 hour to 3 hours; And / or, the sintering is performed in an inert environment.

8. A coating for a niobium alloy surface, characterized in that: The coating is prepared from the ceramic composite powder according to any one of claims 1 to 4.

9. A method for preparing a coating on a niobium alloy surface as claimed in claim 8, characterized in that: The preparation method comprises: Spraying the ceramic composite powder according to any one of claims 1 to 4 onto the surface of a workpiece by supersonic plasma spraying; Covering the workpiece surface once by the spray gun path is considered 1 time, the workpiece is preheated n times by the plasma flame flow, and then sprayed m times to obtain the coating; The preheating times n is ≥ 2 times; the spraying times m is ≥ 5 times.

10. The preparation method according to claim 9, characterized in that The interval between two adjacent preheatings is 0.5s to 3s; And / or, the interval between two adjacent spraying times is 5s to 15s.

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