Si / SiC / ZrSi2 gradient coating of laser cladding C / C composite material and preparation method of Si / SiC / ZrSi2 gradient coating

Abstract

The invention discloses a laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating and a preparation method thereof, and belongs to the technical field of anti-oxidation coatings. The material comprises a C / C composite material matrix and a Si / SiC / ZrSi2 gradient coating prepared on the surface of the C / C composite material matrix through three times of laser cladding; wherein the Si / SiC / ZrSi2 gradient coating is prepared from a Si / C composite inner coating and a ZrSi2 outer coating through laser remelting; the distribution of the Zr element in the Si / SiC / ZrSi2 gradient coating is gradually increased from the surface of the C / C composite material matrix to the outside, and the distribution of the Si element in the Si / SiC / ZrSi2 gradient coating is gradually thinned from the surface of the C / C composite material matrix to the outside; the Si / C composite inner coating is prepared from Si / C composite powder through laser cladding; and the ZrSi2 outer coating is prepared by carrying out laser cladding on ZrSi2 powder. The method is used for solving the technical problems that an existing preparation method is complex in process, the intrinsic performance of the C / C composite material is damaged, and the coating performance is poor.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of antioxidant coating and specifically relates to a laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating and a preparation method thereof. BACKGROUND

[0002] With the development of aviation science and technology, the service environment of C / C composite material thermal structural components is more severe, and the high-temperature oxidation characteristics will make the ablation performance and various physical and chemical properties of the C / C composite material rapidly decrease. Developing high-temperature long-time oxidation-resistant ablation coating C / C composite material is a key link in the research and development technology of new-generation aerospace vehicles and cutting-edge weapons and equipment. Among numerous coating materials, silicon-based ceramics can generate a self-healing and low-oxygen-permeation-coefficient SiO2 protective film at high temperatures, which can not only effectively prevent the infiltration of external oxygen into the coating, but also heal the micro-cracks and pores in the coating to promote the densification of the coating and relieve the thermal mismatch between the coating and the coating and between the coating and the substrate, and is considered to be one of the effective materials for improving the coating density, reducing the coating thermal stress and improving the application of C / C matrix in long-time and severe complex environments.

[0003] In silicon-based ceramic materials, zirconium disilicide (ZrSi2) ceramic has many advantages as a high-temperature oxidation-resistant ablative coating material. Literature 1 "Oxidation of carbon / carbon composite coated with SiC-(SiZrSi2)-ZrSi2, Wen-Cheng J. Wei, Tsung-Ming Wu, Carbon, 1994, 32(4): 605-613." uses a thermal reaction sintering method to prepare a SiC-(SiZrSi2)-ZrSi2 multilayer composite coating on the surface of a C / C composite material. Through plasma flame ablation testing, it is found that the ablation performance of the coating is significantly better than that of C / C composite material and SiC-coated C / C composite material, with a length direction size reduction of only 2%. However, the coating prepared by this method will cause certain erosion to the substrate, and the thermal stress between the multilayer coating is not released, resulting in cracking at the coating interface during the test, which reduces its oxidation resistance. Literature 2 "ZrSi2-SiC / SiC gradient coating of micro-structure and anti-oxidation property on C / C composites prepared by SAPS, Fei Liu, Hejun Li, Qiangang Fu, Xinhai He, Wei Zhang, Coatings, 2022, 12(10): 1377." uses an embedding method and atmospheric plasma spraying to prepare a ZrSi2-SiC / SiC gradient coating, which effectively reduces the thermal stress of the C / C composite material oxidation-resistant coating and realizes a weight loss of only 0.1% after 198 h of oxidation at 1500 ℃. It can be seen that the gradient coating can effectively reduce the CTE mismatch between the SiC coating and the outer coating, improve the interfacial bonding strength, and improve the thermal shock resistance of the coating to avoid cracking. However, due to the limitations of the preparation process, the preparation period of the above-mentioned methods is relatively long, and the embedding process also causes certain erosion to the substrate, and the sprayed outer coating is relatively loose, which is not conducive to the oxidation protection of the coating.

[0004] Therefore, there is an urgent need for a preparation technology that is simple in process, does not damage the intrinsic properties of C / C composite materials, and at the same time ensures the quality of the coating. SUMMARY

[0005] In order to overcome the above-mentioned defects of the prior art, the purpose of the present application is to provide a laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating and a preparation method thereof, which uses a laser cladding technology based on synchronous powder feeding, obtains the required coating through laser cladding of an inner Si / SiC coating, laser cladding of an outer ZrSi2 coating and laser remelting in three steps in an argon environment, so as to solve the technical problems of complex process, damage to the intrinsic properties of the C / C composite material and poor coating performance of the existing preparation method.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions: The present application provides a laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating, which comprises a C / C composite material substrate and a Si / SiC / ZrSi2 gradient coating formed on the surface of the C / C composite material substrate through three times of laser cladding; wherein the Si / SiC / ZrSi2 gradient coating is formed by laser remelting of an inner Si / C composite coating and an outer ZrSi2 coating; the Zr element in the Si / SiC / ZrSi2 gradient coating gradually increases in density from the surface of the C / C composite material substrate to the outer distribution, and the Si element gradually becomes sparse from the surface of the C / C composite material substrate to the outer distribution; the inner Si / C composite coating is formed on the surface of the C / C composite material substrate by laser cladding of Si / C composite powder; and the outer ZrSi2 coating is formed on the inner Si / C composite coating by laser cladding of ZrSi2 powder.

[0007] In an embodiment, the Si / C composite powder comprises Si powder, C powder and Al2O3 powder, and the mass ratio of the Si powder, the C powder and the Al2O3 powder is (14-8):2:1.

[0008] In an embodiment, the Si / C composite powder comprises Si powder, C powder and Al2O3 powder, and the mass ratio of the Si powder, the C powder and the Al2O3 powder is 11:2:1.

[0009] The present application also provides a preparation method of the laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating, which comprises the following steps: The Si powder, the C powder and the Al2O3 powder are uniformly mixed with a PVA aqueous solution by ball milling, and Si / C composite powder is prepared by spray granulation; the ZrSi2 powder is uniformly mixed with a PVA aqueous solution by ball milling, and ZrSi2 powder is prepared by spray granulation; and the C / C composite material substrate is pretreated for standby use; The C / C composite material substrate is preheated, and the Si / C composite powder on the surface of the C / C composite material substrate is laser cladded by synchronous powder feeding to obtain a Si / SiC coating C / C composite material; The Si / SiC coated C / C composite material is preheated, and ZrSi2 powder is synchronously sent on the surface of the Si / SiC coated C / C composite material by laser cladding to obtain a Si / SiC / ZrSi2 coated C / C composite material; The Si / SiC / ZrSi2 coated C / C composite material is preheated and then laser remelted to obtain a laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating.

[0010] In an embodiment, the Si / C composite powder is spherical, and the particle size of the Si / C composite powder is 30-75 μm; the particle size of the Si powder is 50-75 μm, the particle size of the C powder is 30-50 μm, and the particle size of the ZrSi2 powder is 10-20 μm; the ZrSi2 powder is spherical, and the particle size of the ZrSi2 powder is 30-75 μm; and the mass concentration of the PVA aqueous solution is 2-5%.

[0011] In an embodiment, the preheating temperature is 400-500 ℃.

[0012] In an embodiment, the laser cladding parameters of the Si / C composite powder are as follows: the power is 400 W, the scanning speed is 200 mm / min, the spot diameter is not less than 3 mm, the powder carrying gas flow is not less than 5 L / min, and the rotation speed of the powder feeding disc is not less than 5 r / min.

[0013] In an embodiment, the laser cladding parameters of the ZrSi2 powder are as follows: the power is 300 W-500 W, the scanning speed is 100-300 mm / min, the spot diameter is not less than 2.5 mm, the powder carrying gas flow is not less than 5 L / min, and the rotation speed of the powder feeding disc is not less than 5 r / min.

[0014] In an embodiment, the laser parameters of the laser remelting are as follows: the power is 300 W-500 W, the scanning speed is 100-300 mm / min, and the spot diameter is not less than 3 mm.

[0015] In an embodiment, the laser cladding and the laser remelting use a fiber laser, are carried out in an argon atmosphere, and the oxygen content is below 100 ppm.

[0016] In an embodiment, the pre-treatment process is as follows: The C / C composite material substrate is polished flat using 320-800 mesh sandpaper, is ultrasonically cleaned in industrial alcohol, and is dried for standby use.

[0017] Compared with the prior art, the present application has the following beneficial effects: The application provides a laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating, a Si / SiC / ZrSi2 gradient coating is laser cladded on the surface of a C / C composite material in an argon environment by a three-step method with laser as an energy source, the obtained coating is dense and uniform, is well combined with the substrate, and the gradient distribution of the ZrSi2 component effectively relieves the problem of mismatch of the thermal expansion coefficient of the coating and the C / C composite material. The metallurgical bonding interface formed by laser remelting enables the coating and the substrate to have extremely high bonding strength, and ensures the long-term stability of the protection effect.

[0018] The application also provides a preparation method of the laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating, Si and C mixed powder and ZrSi2 powder are respectively treated into spherical powder with good fluidity by a spray granulation method, and the Si / SiC / ZrSi2 gradient coating is prepared by a three-step method with laser as an energy source: the Si / SiC coating is obtained by laser cladding of Si / C composite powder, the Si / SiC / ZrSi2 coating is obtained by laser cladding of ZrSi2 powder, and the Si / SiC / ZrSi2 gradient coating is obtained by laser remelting. Compared with a traditional complex process which needs to pre-configure multiple gradient component powders and perform multiple depositions, the three-step process of "inner layer cladding-outer layer cladding-laser remelting" is innovatively adopted, the Zr and Si elements in the outer layer ZrSi2 are driven to occur interdiffusion and in-situ reaction with the inner layer SiC by accurately controlling laser remelting parameters, and thus the gradient structure with continuously changing composition is constructed in-situ. This method not only omits the cumbersome gradient powder preparation step and simplifies the process flow, but also can accurately control the thickness, shape and gradient distribution of the coating by adjusting the laser power, scanning speed and other parameters. The prepared coating is dense and uniform, effectively avoids the brittleness problem caused by excessive silicon infiltration in the traditional silicon infiltration process, and the heat affected zone of the laser process is small, and the substrate performance is not damaged.

[0019] The application provides an effective surface strengthening scheme for solving the application bottleneck of the C / C composite material in a high-temperature oxidation environment, and is particularly suitable for hot end components in the field of aviation and aerospace, high-temperature clamps in the field of new energy and the like. The method has the advantages of simple process, controllable cost and good repeatability, provides reliable technical support for long-life and high-reliability application of high-performance C / C composite material components in extreme environments, and has good industrialization prospect and market competition advantage. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a cross-section SEM image of the Si / SiC / ZrSi2 gradient coating C / C composite material prepared in Example 1 of the application; Figure 2 It is a cross-section SEM image and an EDS image of the Si / SiC / ZrSi2 gradient coating C / C composite material prepared in Example 1 of the application; Figure 3 SEM cross-section image of Si / SiC / ZrSi2 gradient coated C / C composite material prepared for Example 2 of the present application; Figure 4 SEM cross-section image of Si / SiC / ZrSi2 gradient coated C / C composite material prepared for Example 3 of the present application; Figure 5 SEM cross-section image of Si / SiC / ZrSi2 gradient coated C / C composite material prepared for Example 4 of the present application; Figure 6 SEM cross-section image of Si / SiC / ZrSi2 gradient coated C / C composite material prepared for Example 5 of the present application; Figure 7 SEM cross-section image of Si / SiC / ZrSi2 gradient coated C / C composite material prepared for Comparative Example 1 of the present application; Figure 8 SEM cross-section image of Si / SiC / ZrSi2 gradient coated C / C composite material prepared for Comparative Example 2 of the present application; Figure 9 SEM cross-section image of ZrSi2 coated C / C composite material prepared for Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0021] To enable persons skilled in the art to understand the features and effects of the present application, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific words used in the text are of the usual meaning understood by those skilled in the art of the present application, and in the event of a conflict, the definition in the specification shall prevail.

[0022] Theories or mechanisms described and disclosed herein, whether correct or not, should not be considered limiting of the scope of the present application, which is limited only by the claims. The present application can be implemented in ways other than those specifically described herein.

[0023] In this text, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents and concentrations, are for the sake of brevity and convenience. Therefore, the description of numerical ranges or percentage ranges should be considered to have encompassed and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0024] In this text, unless otherwise specified, "comprise", "include", "contain", "have" or similar terms encompass the meaning of "consist of" and "consist essentially of", for example, "A comprises a" encompasses the meaning of "A comprises a and other" and "A comprises only a".

[0025] Herein, all possible combinations of the technical features in each embodiment or example are not described in order to make the description simple. Therefore, as long as the combinations of the technical features do not contradict, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope of the present disclosure.

[0026] The present application provides a laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating in one aspect, which comprises a C / C composite material substrate and a Si / SiC / ZrSi2 gradient coating formed on the surface of the C / C composite material substrate by three times of laser cladding; wherein the Si / SiC / ZrSi2 gradient coating is formed by laser remelting of a Si / C composite inner coating and a ZrSi2 outer coating; the Zr element in the Si / SiC / ZrSi2 gradient coating gradually increases in density from the surface of the C / C composite material substrate to the outer distribution, and the Si element gradually becomes sparse from the surface of the C / C composite material substrate to the outer distribution; the Si / C composite inner coating is formed on the surface of the C / C composite material substrate by laser cladding of Si / C composite powder; and the ZrSi2 outer coating is formed on the Si / C composite inner coating by laser cladding of ZrSi2 powder.

[0027] Specifically, the Si / SiC / ZrSi2 gradient coating is formed by laser cladding of two layers of powder, the first layer of cladding powder is Si / C composite powder, the second layer of cladding powder is ZrSi2 powder, and the substrate is C / C composite material, and the coating composition is gradientized by laser remelting.

[0028] The Si / C composite powder comprises Si powder, C powder and Al2O3 powder, and the mass ratio of the Si powder, the C powder and the Al2O3 powder is (14-8):2:1.

[0029] In the embodiment of the present application, the components of the Si / C composite powder are Si powder, C powder and Al2O3 powder with a mass ratio of 11:2:1.

[0030] The present application also provides a preparation method of a laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating in another aspect, which comprises the following steps: Step 1, preparation of coating raw material: uniformly mix Si powder, C powder and Al2O3 powder with a mass ratio of 11:2:1 and PVA aqueous solution by ball milling, and prepare spherical Si / C composite powder with a particle size of 30-75 μm by spray granulation; uniformly mix ZrSi2 powder and PVA aqueous solution by ball milling, and prepare spherical ZrSi2 powder with a particle size of 30-75 μm by spray granulation; wherein the particle size of the Si powder used in the coating raw material is 50-75 μm, the particle size of the C powder is 30-50 μm, and the particle size of the ZrSi2 powder is 10-20 μm; the mass concentration of the PVA aqueous solution used is 2-5%. Step 2, preparing the substrate: polishing the C / C composite substrate flat with 320-800 mesh sandpaper, ultrasonic cleaning the C / C composite in industrial alcohol, and drying for standby; Step 3, cladding the inner coating: using a fiber laser to prepare the inner coating in an argon atmosphere, preheating the C / C composite substrate to 400-500 DEG C, and cladding spherical Si / C composite powder on the surface of the C / C composite by laser cladding with synchronous powder feeding to obtain a Si / SiC coated C / C composite. The laser cladding parameters of the coating are as follows: power 400 W, scanning speed 200 mm / min, spot diameter not less than 3 mm, powder carrying gas flow not less than 5 L / min, and powder feeding disc rotation speed not less than 5 r / min.

[0031] Step 4, cladding the outer coating: using a fiber laser to prepare the outer coating in an argon atmosphere, preheating the Si / SiC coated C / C composite to 400-500 DEG C, and cladding spherical ZrSi2 powder on the surface of the Si / SiC coated C / C composite by laser cladding with synchronous powder feeding to obtain a Si / SiC / ZrSi2 coated C / C composite. The laser cladding parameters of the coating are as follows: power 300 W-500 W, scanning speed 100-300 mm / min, spot diameter not less than 2.5 mm, powder carrying gas flow not less than 5 L / min, and powder feeding disc rotation speed not less than 5 r / min.

[0032] Step 5, laser remelting: using a fiber laser to remelt in an argon atmosphere, preheating the Si / SiC / ZrSi2 coated C / C composite to 400-500 DEG C, and starting laser remelting. The laser parameters of the coating are as follows: power 300 W-500 W, scanning speed 100-300 mm / min, and spot diameter not less than 3 mm.

[0033] The composite is heated in argon by a built-in heating table of a laser cladding equipment to ensure that the oxygen content in the forming cabin is below 100 ppm.

[0034] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not to limit the scope of the application. Furthermore, it should be understood that those skilled in the art can make various modifications or changes to the application after reading the content taught by the application, and these equivalent forms also fall within the scope defined by the appended claims of the application.

[0035] The following examples use apparatus and equipment that are conventional in the art. The experimental methods in the following examples, unless otherwise specified, are generally in accordance with conventional conditions, or as suggested by the manufacturer. The following examples use various raw materials, unless otherwise specified, which are conventional commercially available products, and which are of conventional specifications in the art. In the specification of the present application and in the following examples, unless otherwise specified, "%" means percent by weight, "parts" means parts by weight, and ratios are by weight.

[0036] Example 1 The present example provides a method for preparing a laser cladding C / C composite Si / SiC / ZrSi2 gradient coating, comprising the following steps: 1) Preparation of coating raw materials: Si powder, C powder, and AI2O3 powder with a mass ratio of 11:2:1 are ball-milled with a 3% PVA aqueous solution for 6 h, and the uniformly mixed slurry is prepared into spherical Si / C composite powder with a particle size of 30-75 μm by spray granulation; ZrSi2 powder is ball-milled with a 3% PVA aqueous solution for 6 h, and the uniformly mixed slurry is prepared into spherical ZrSi2 powder with a particle size of 30-75 μm by spray granulation; both kinds of spherical powder are placed in a 70 ℃ oven for drying.

[0037] 2) Preparation of substrate: polish the C / C composite material flat with 800 mesh sandpaper, ultrasonically clean the C / C composite material in industrial alcohol, and dry for standby use.

[0038] 3) Cladding of inner coating: wash the laser cladding forming chamber with argon gas, control the oxygen content in the forming chamber to be below 100 ppm, preheat the C / C composite material to 450 ℃ for 10 min with an internal heating table in the forming chamber, then place the spherical Si / C composite powder into the powder feeding tank, and use a synchronous powder feeding fiber laser to cladding the spherical Si / C composite powder on the surface of the C / C composite material to obtain a Si / SiC coated C / C composite material. The laser cladding parameters for the coating are a power of 400 W, a scanning speed of 200 mm / min, a spot diameter of 3 mm, a powder carrying gas flow rate of 5 L / min, a powder feeding disc rotation speed of 5 r / min, and the heating table is turned on at 450 ℃ throughout the process.

[0039] 4) Cladding of outer coating: place the spherical ZrSi2 powder into the powder feeding tank, and use a synchronous powder feeding fiber laser to cladding the spherical ZrSi2 powder on the surface of the Si / SiC coated C / C composite material in an atmosphere with an oxygen content of 100 ppm or less to obtain a Si / SiC / ZrSi2 coated C / C composite material. The laser cladding parameters for the coating are a power of 450 W, a scanning speed of 200 mm / min, a spot diameter of 2.5 mm, a powder carrying gas flow rate of 5 L / min, a powder feeding disc rotation speed of 5 r / min, and the heating table is turned on at 450 ℃ throughout the process.

[0040] 5) Laser remelting: laser remelting Si / SiC / ZrSi2 coating C / C composite material by fiber laser in an atmosphere with oxygen content of 100 ppm or less to obtain Si / SiC / ZrSi2 gradient coating C / C composite material. The laser parameters of the coating are 450 W of power, 200 mm / min of scanning speed, 3 mm of spot diameter, and 450 ℃ of full-process opening of the heating table.

[0041] The energy of the embodiment is perfectly coordinated, as shown in the figure, the ZrSi2 grains of the outer coating uniformly penetrate into the inner coating Si / SiC, the ZrSi2 grains are distributed and densified from the inside to the outside of the coating, forming a ZrSi2 gradient distribution, the interface between the inner and outer coatings is smooth, the coating interface is well combined, and the coating is relatively dense. Figure 1 As can be seen, the Zr element is gradually densified from the inside to the outside of the coating, and the Si element is gradually diluted from the inside to the outside of the coating, realizing the gradient preparation of the Si / SiC / ZrSi2 coating. Figure 2

[0042] Example 2 The preparation method of the laser cladding Si / SiC / ZrSi2 gradient coating of the C / C composite material provided in this embodiment and example 1 is the same as steps 1) to 3), and the difference lies in steps 4) and 5), which are as follows: 4) Cladding outer coating: placing spherical ZrSi2 powder into a powder feeding tank, cladding the spherical ZrSi2 powder on the surface of the Si / SiC coating C / C composite material by a synchronous powder feeding fiber laser in an atmosphere with oxygen content of 100 ppm or less to obtain a Si / SiC / ZrSi2 coating C / C composite material. The laser cladding parameters of the coating are 500 W of power, 200 mm / min of scanning speed, 2.5 mm of spot diameter, 5 L / min of powder carrying gas flow, 5 r / min of powder feeding disc rotation speed, and 450 ℃ of full-process opening of the heating table.

[0043] 5) Laser remelting: laser remelting Si / SiC / ZrSi2 coating C / C composite material by fiber laser in an atmosphere with oxygen content of 100 ppm or less to obtain Si / SiC / ZrSi2 gradient coating C / C composite material. The laser parameters of the coating are 300 W of power, 200 mm / min of scanning speed, 3 mm of spot diameter, and 450 ℃ of full-process opening of the heating table.

[0044] The energy of the outer coating preparation of this embodiment is sufficient, and the outer coating is well melted, but the remelting energy is weak, as shown in the figure, the ZrSi2 grains of the outer coating are not uniformly distributed in the inner coating Si / SiC, and the interface between the inner and outer coatings is not smooth. Figure 3 ​It can be seen that the composition gradient is weakened, the interface exists, the ZrSi2 grains in the outer coating are larger, and the Si in the inner coating penetrates less outward.

[0045] Example 3 The preparation method of the laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating provided in this example and example 1 is the same as steps 1) to 3), and the difference lies in steps 4) and 5), which are as follows: 4) Cladding outer coating: put spherical ZrSi2 powder into the powder feeding tank, and cladding the spherical ZrSi2 powder on the surface of the Si / SiC coating C / C composite material by the synchronous powder feeding fiber laser in an atmosphere with an oxygen content of 100 ppm or less, to obtain a Si / SiC / ZrSi2 coating C / C composite material. Among them, the laser cladding parameters of the coating are power 300 W, scanning speed 200 mm / min, spot diameter 2.5 mm, powder feeding gas flow rate 5 L / min, powder feeding disc rotation speed 5 r / min, and heating table full process opening 450℃.

[0046] 5) Laser remelting: laser remelting the Si / SiC / ZrSi2 coating C / C composite material by the fiber laser in an atmosphere with an oxygen content of 100 ppm or less to obtain a Si / SiC / ZrSi2 gradient coating C / C composite material. Among them, the laser parameters of the coating are power 500 W, scanning speed 200 mm / min, spot diameter 3 mm, and heating table full process opening 450℃.

[0047] The preparation energy of the outer coating of this example is slightly smaller, and there is obvious unmelted powder when not remelted, but after remelting, sufficient remelting energy can melt the unmelted powder while forming a composition gradient of the coating. Figure 4 It can be seen that the composition gradient is slightly weaker than that of example 1, and the interface exists obviously.

[0048] Example 4 The preparation method of the laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating provided in this example and example 1 is the same as steps 1) to 3), and the difference lies in steps 4) and 5), which are as follows: 4) cladding outer coating: put the spherical ZrSi2 powder into the powder feeding tank, and melt the spherical ZrSi2 powder on the surface of the Si / SiC coating C / C composite material by the fiber laser with synchronous powder feeding in an atmosphere with an oxygen content of 100 ppm or less, to obtain a Si / SiC / ZrSi2 coating C / C composite material. Among them, the laser cladding parameters of the coating are power 400 W, scanning speed 200 mm / min, spot diameter 2.5 mm, powder carrying gas flow 5 L / min, powder feeding disc rotation speed 5 r / min, and heating table full process opening 450℃.

[0049] 5) laser remelting: laser remelting of the Si / SiC / ZrSi2 coating C / C composite material by a fiber laser in an atmosphere with an oxygen content of 100 ppm or less to obtain a Si / SiC / ZrSi2 gradient coating C / C composite material. Among them, the laser parameters of the coating are power 300 W, scanning speed 200 mm / min, spot diameter 3 mm, and heating table full process opening 450℃.

[0050] The remelting power of this embodiment is slightly smaller, the remelting energy is weaker, and the composition gradient is weakened, which is Figure 5 It can be seen that the interface can be observed, which is similar to example 2. The lower remelting energy makes the ZrSi2 grains of the outer coating larger, and the Si in the inner coating penetrates less outward.

[0051] Example 5 The preparation method of the laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating provided by this embodiment and example 1 is the same as steps 1) to 3), and the difference lies in steps 4) and 5), which are as follows: 4) cladding outer coating: put the spherical ZrSi2 powder into the powder feeding tank, and melt the spherical ZrSi2 powder on the surface of the Si / SiC coating C / C composite material by the fiber laser with synchronous powder feeding in an atmosphere with an oxygen content of 100 ppm or less, to obtain a Si / SiC / ZrSi2 coating C / C composite material. Among them, the laser cladding parameters of the coating are power 400 W, scanning speed 200 mm / min, spot diameter 2.5 mm, powder carrying gas flow 5 L / min, powder feeding disc rotation speed 5 r / min, and heating table full process opening 450℃.

[0052] 5) laser remelting: laser remelting of the Si / SiC / ZrSi2 coating C / C composite material by a fiber laser in an atmosphere with an oxygen content of 100 ppm or less to obtain a Si / SiC / ZrSi2 gradient coating C / C composite material. Among them, the laser parameters of the coating are power 300 W, scanning speed 200 mm / min, spot diameter 3 mm, and heating table full process opening 450℃.

[0053] The remelting power of this embodiment is slightly larger, and the remelting energy is relatively strong, so that Figure 6 As can be seen, in the gradient coating formed, the higher remelting energy makes the ZrSi2 grains of the outer coating sufficiently refined, but the interface exists.

[0054] Comparative Example 1 The preparation method of the laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating provided by this comparative example and Example 1 is the same as that of steps 1) to 3), and the difference lies in steps 4) and 5), which are specifically as follows: 4) Cladding the outer coating: Put the spherical ZrSi2 powder into the powder feeding tank, and use the fiber laser to cladding the spherical ZrSi2 powder on the surface of the Si / SiC coating C / C composite material in an atmosphere with an oxygen content of 100 ppm or less, to obtain a Si / SiC / ZrSi2 coating C / C composite material. Among them, the laser cladding parameters of the coating are power 250 W, scanning speed 200 mm / min, spot diameter 2.5 mm, powder carrying gas flow rate 5 L / min, powder feeding disc rotation speed 5 r / min, and heating table full process opening 450℃.

[0055] 5) Laser remelting: Use the fiber laser to perform laser remelting on the Si / SiC / ZrSi2 coating C / C composite material in an atmosphere with an oxygen content of 100 ppm or less to obtain a Si / SiC / ZrSi2 gradient coating C / C composite material. Among them, the laser parameters of the coating are power 250 W, scanning speed 200 mm / min, spot diameter 3 mm, and heating table full process opening 450℃.

[0056] The preparation power of the outer coating of this comparative example is relatively low, the remelting power is relatively low, the laser energy is insufficient, the ZrSi2 powder cannot be completely melted, the molten pool is uneven, and the cracking at the coating interface is obvious. From Figure 7 As can be seen, in the coating formed, there are cracks at the interface, and there are also some penetrating cracks, which shows that sufficient laser energy can adjust the molten pool effect, reduce the influence of thermal stress during the preparation of the inner coating, and reduce the initiation of cracks.

[0057] Comparative Example 2 The preparation method of the laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating provided by this comparative example and Example 1 is the same as that of steps 1) to 3), and the difference lies in steps 4) and 5), which are specifically as follows: 4) Overcladding: Put the spherical ZrSi2 powder into the powder feeder tank, and melt the spherical ZrSi2 powder on the surface of the Si / SiC coating C / C composite material by a fiber laser with synchronous powder feeding in an atmosphere with an oxygen content of 100 ppm or less to obtain a Si / SiC / ZrSi2 coating C / C composite material. Among them, the laser cladding parameters of the coating are power 550 W, scanning speed 200 mm / min, spot diameter 2.5 mm, powder carrying gas flow rate 5 L / min, powder feeder rotation speed 5 r / min, and heating platform full-process opening 450°C.

[0058] 5) Laser remelting: Laser remelting of the Si / SiC / ZrSi2 coating C / C composite material by a fiber laser in an atmosphere with an oxygen content of 100 ppm or less to obtain a Si / SiC / ZrSi2 gradient coating C / C composite material. Among them, the laser parameters of the coating are power 550 W, scanning speed 200 mm / min, spot diameter 3 mm, and heating platform full-process opening 450°C.

[0059] The overcoat of the present comparative example is prepared at a relatively high power, and the remelting power is also relatively high. The excessive laser energy makes the inner and outer coating components fully penetrate each other, and it is difficult to achieve the effect of gradient distribution of coating components, as shown in Figure 8 ZrSi2 in the coating is almost uniformly distributed.

[0060] Comparative Example 3 The preparation method of the laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating provided by the present comparative example and Example 1 is the same as steps 1) to 2), except that there is no overcladding inner coating and remelting step, but ZrSi2 powder is directly cladded on the C / C composite material to prepare a ZrSi2 coating, as follows: 3) Overcladding of ZrSi2 coating: Put the spherical ZrSi2 powder into the powder feeder tank, and melt the spherical ZrSi2 powder on the surface of the Si / SiC coating C / C composite material by a fiber laser with synchronous powder feeding in an atmosphere with an oxygen content of 100 ppm or less to obtain a Si / SiC / ZrSi2 coating C / C composite material. Among them, the laser cladding parameters of the coating are power 550 W, scanning speed 200 mm / min, spot diameter 2.5 mm, powder carrying gas flow rate 5 L / min, powder feeder rotation speed 5 r / min, and heating platform full-process opening 450°C.

[0061] The present comparative example directly prepares a ZrSi2 coating on the C / C composite material. Due to the large difference in thermal expansion coefficient between ZrSi2 and the C / C composite material, the lack of an inner coating to alleviate the difference in thermal expansion makes the coating prone to cracking, as Figure 9 It can be seen that the ZrSi2 coating has obvious penetrating cracks.

[0062] Comparative Example 4 A preparation method of a C / C composite gradient oxidation-resistant coating provided in the prior art with publication number CN106588125A. First, the C / C composite test piece is subjected to surface roughening treatment with 400# sandpaper. Then, the required SiC ceramic powder and the mixed powder with a mass ratio of SiC:ZrB2=1:1 are weighed with an electronic balance respectively; the SiC ceramic powder and the SiC+ZrB2 mixed powder are successively layered and coated on the surface of the C / C composite test piece, with a layer thickness of 1 mm each, and are dried for standby. The dried C / C composite test piece is subjected to surface cladding by laser cladding technology, with a laser power of 2.4 kW, a spot diameter of 4 mm, a scanning speed of 300 mm / min, and an overlap rate of 30%.

[0063] In the above-mentioned Comparative Example 4, the method of pre-setting powder on the C / C composite is used to provide coating raw materials, and the gradient is realized by layering and coating different coating raw materials on the C / C composite. The operation is relatively complicated, and the prepared coating has obvious partition of SiC and ZrB2. The gradient degree of the comparative example is not obvious, and the composition gradient cannot be completely realized. Compared with the comparative example, the operation of the embodiment of the present application is simple, and the gradient coating can be prepared at one time by the laser cladding equipment with multiple powder tanks. The method of laser remelting can effectively control the element gradient distribution effect of the inner and outer coatings. In addition, the component settings of the inner and outer coatings in the embodiment of the present application are also based on the structural compatibility of Si and ZrSi2 and the relative matching of the thermophysical parameters. Si has a low melting point, which plays a role of liquid phase mediation in the laser cladding process. Liquid Si acts as a "carrier" and a "reaction medium", transports the Zr element in the outer layer to the inner layer and participates in the reaction, and finally "freezes" to form an ideal gradient structure with gradually decreasing Si content and gradually increasing Zr content from the inside to the outside under rapid solidification.

[0064] In summary, the present application provides a laser cladding C / C composite Si / SiC / ZrSi2 gradient coating and a preparation method thereof. Si and C mixed powder and ZrSi2 powder are respectively treated into spherical powder with good fluidity by a spray granulation method. The Si / SiC / ZrSi2 gradient coating is prepared by a three-step method using laser as the energy source: laser cladding of Si / C composite powder to obtain Si / SiC coating, laser cladding of ZrSi2 powder to obtain Si / SiC / ZrSi2 coating, and laser remelting to obtain Si / SiC / ZrSi2 gradient coating. By adjusting the parameters in the laser cladding process, the effects of laser power, scanning speed and other process parameters on the microstructure of the coating, the interface bonding effect and the gradient distribution effect are explored, and the preparation of high-quality gradient coating is realized.

[0065] The above merely illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the present application.

Claims

1. A laser-clad C / C composite material Si / SiC / ZrSi2 gradient coating, characterized in that, The invention comprises a C / C composite matrix and a Si / SiC / ZrSi2 gradient coating formed by three laser cladding processes on the surface of the C / C composite matrix. The Si / SiC / ZrSi2 gradient coating is formed by laser remelting of a Si / C composite inner coating and a ZrSi2 outer coating. In the Si / SiC / ZrSi2 gradient coating, the Zr element gradually increases in density from the surface of the C / C composite matrix outwards, while the Si element gradually decreases in density from the surface of the C / C composite matrix outwards. The Si / C composite inner coating is formed by laser cladding of Si / C composite powder on the surface of the C / C composite matrix. The ZrSi2 outer coating covers the Si / C composite inner coating and is formed by laser cladding of ZrSi2 powder.

2. The laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating according to claim 1, characterized in that, The Si / C composite powder includes Si powder, C powder and Al2O3 powder, and the mass ratio of Si powder, C powder and Al2O3 powder is (14~8):2:

1.

3. The laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating according to claim 2, characterized in that, The Si / C composite powder comprises Si powder, C powder and Al2O3 powder, with a mass ratio of Si powder, C powder and Al2O3 powder of 11:2:

1.

4. A method for preparing a laser cladding Si / SiC / ZrSi2 gradient coating of C / C composite material as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Si powder, C powder, Al2O3 powder and PVA aqueous solution were ball-milled and mixed evenly, and Si / C composite powder was prepared by spray granulation; ZrSi2 powder and PVA aqueous solution were ball-milled and mixed evenly, and ZrSi2 powder was prepared by spray granulation; C / C composite matrix was pretreated for later use. The C / C composite matrix is ​​preheated, and Si / C composite powder is clad onto the surface of the C / C composite matrix by laser cladding with synchronously fed powder to obtain Si / SiC coated C / C composite material; The Si / SiC coated C / C composite material is preheated, and ZrSi2 powder is clad onto the surface of the Si / SiC coated C / C composite material by synchronous powder feeding laser to obtain the Si / SiC / ZrSi2 coated C / C composite material. The Si / SiC / ZrSi2 coated C / C composite material was preheated and then laser remelted to obtain a laser clad C / C composite material Si / SiC / ZrSi2 gradient coating.

5. The method for preparing a laser-cladized Si / SiC / ZrSi2 gradient coating of C / C composite material according to claim 4, characterized in that, The Si / C composite powder is spherical with a particle size of 30-75 μm; the Si powder has a particle size of 50-75 μm, the C powder has a particle size of 30-50 μm, and the ZrSi2 powder has a particle size of 10-20 μm; the ZrSi2 powder is spherical with a particle size of 30-75 μm; and the PVA aqueous solution has a mass concentration of 2-5%.

6. The method for preparing a laser-clad C / C composite material Si / SiC / ZrSi2 gradient coating according to claim 4, characterized in that, The preheating temperature is 400-500 ℃.

7. The method for preparing a laser-cladized Si / SiC / ZrSi2 gradient coating of C / C composite material according to claim 4, characterized in that, The laser cladding parameters for the Si / C composite powder are as follows: power of 400 W, scanning speed of 200 mm / min, spot diameter of not less than 3 mm, powder carrier gas flow rate of not less than 5 L / min, and powder feeding tray rotation speed of not less than 5 r / min.

8. The method for preparing a laser-clad C / C composite material Si / SiC / ZrSi2 gradient coating according to claim 4, characterized in that, The laser cladding parameters for the ZrSi2 powder are as follows: power of 300 W-500 W, scanning speed of 100-300 mm / min, spot diameter of not less than 2.5 mm, powder carrier gas flow rate of not less than 5 L / min, and powder feeding tray rotation speed of not less than 5 r / min.

9. The method for preparing a laser-cladized Si / SiC / ZrSi2 gradient coating of C / C composite material according to claim 4, characterized in that, The laser parameters for laser remelting are: power 300 W-500 W, scanning speed 100-300 mm / min, and spot diameter not less than 3 mm.

10. The method for preparing the laser cladding C / C composite material Si / SiC / ZrSi2 gradient coating according to claim 4, characterized in that, The laser cladding and laser remelting are performed using a fiber laser in an argon atmosphere with an oxygen content of less than 100 ppm. The preprocessing process is as follows: Use 320-800 grit sandpaper to smooth the C / C composite matrix, then place the C / C composite matrix in industrial alcohol for ultrasonic cleaning and dry it for later use.

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