Magnetic abrasive for in-situ generation of SiC hard phase and preparation method thereof

Abstract

The invention provides a magnetic abrasive for in-situ generation of a SiC hard phase and a preparation method of the magnetic abrasive, and belongs to the technical field of magnetic abrasives. The method comprises the following steps: by taking polycarbosilane as a raw material, generating a SiC hard phase on the surface of a ferromagnetic phase in situ by adopting a sol-gel method, so as to obtain the magnetic abrasive with a core-shell structure. The prepared magnetic abrasive material is spherical, in the grinding process, contact stress of the abrasive material and a machined workpiece is uniform, deep scratches are avoided, the magnetic abrasive material is good in self-sharpening performance and high in grinding force, and the problems that a traditional magnetic abrasive material is short in service life and complex in machining technology can be solved; and the requirement for precise grinding and polishing of the hard ceramic coating is met. And meanwhile, the silicon carbide superhard grinding phases are radially and uniformly distributed on the surface of the ferromagnetic phase, so that the original high magnetic conductivity of the ferromagnetic phase matrix can be ensured, the grinding pressure is increased, the processing efficiency of the magnetic grinding material is improved, and the service life of the magnetic grinding material is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic abrasives, and particularly to a magnetic abrasive for in-situ generating SiC hard phase and a preparation method thereof. Background Art

[0002] As the core power device in the aerospace field, aeroengines are developing towards high thrust-to-weight ratio and high performance, and their performance directly affects the performance and reliability of aircraft. Among them, turbine blades are key components in the engine that bear high temperature and high pressure. They are composed of a metal matrix and a surface protection coating system, accounting for 30% - 35% of the total cost of the entire engine. Turbine blades are exposed to complex conditions such as high temperature, oxidation, and hot corrosion for a long time. The thermal barrier coating system can ensure the performance stability of turbine blades in high-temperature environments and extend their service life, which is an effective thermal protection means. The ceramic layer in the thermal barrier coating, as the basic unit for realizing the heat insulation function, can increase the working temperature limit of the blade. However, due to the intrinsic refractory characteristics of the ceramic layer material of the thermal barrier coating and the preparation process problems, there are certain roughness, microcracks and other defects on the surface after the ceramic layer is prepared. These defects are extremely likely to expand under high-temperature and high-pressure service conditions, resulting in the spalling failure of the ceramic layer and inducing major safety problems. Reducing the surface roughness of the ceramic layer of the thermal barrier coating is the key means to polish the surface of complex-shaped blades to improve the service life of the blades and the stability of the engine. The ceramic layer of the thermal barrier coating itself has high hardness, high brittleness, and complex shape. Traditional processing methods are easy to damage the matrix, and it is difficult to improve the surface quality of the ceramic layer of the thermal barrier coating by traditional sand belts and grinding wheels. Moreover, the method of improving the surface quality by adjusting the preparation method and parameters has a higher cost and a more complex process. Therefore, exploring a precise processing method for the surface of complex ceramic layers and solving the improvement of the surface quality of hard and brittle materials is a hot issue in current research.

[0003] As an emerging high-efficiency precision machining technology, magnetic abrasive finishing technology has advantages such as good profiling, self-adaptability, and high machining accuracy, and is particularly suitable for the complex curved surface characteristics of engine blades. It can improve the surface quality of the coating, improve the surface flatness, roughness, etc., improve the performance and service life of the coating itself, and enable it to better play the role of thermal barrier coatings. However, current magnetic abrasive finishing technology also has shortcomings such as low grinding efficiency, high abrasive cost, and short service life. Therefore, in the process of preparing magnetic abrasives, it is necessary to ensure simple processes, economical raw material costs, and at the same time meet the characteristic requirements such as high magnetic permeability, high surface hardness, and long service life, so as to promote the further development and application of magnetic abrasive finishing technology. Currently, the reported preparation methods of magnetic abrasives mainly include sintering method, bonding method, chemical composite plating, atomization rapid solidification method, sol-gel method and other technological means. In the later stage of preparation by the sintering method and the bonding method, the sintered block needs to be crushed, and the crushing force is not easy to control, resulting in the inability to accurately control the morphology and particle size of the abrasive, the disordered distribution of abrasive phases, and a large number of cracks inside the abrasive. These problems will ultimately have a negative impact on the processing quality of the abrasive. The main problems of the chemical composite plating method are, first, the poor bonding performance of the two components in the abrasive, second, the low efficiency of preparing the abrasive, and it will also cause environmental pollution and is not suitable for large-scale batch production. The atomization rapid solidification method converts the ferromagnetic matrix into a liquid state by means of high temperature, and then combines the metal matrix with ceramic particles through rapid atomization and condensation by means of high-pressure and high-speed jets to obtain magnetic abrasives with a relatively high sphericity. However, this method has defects such as high equipment cost, complex process, high energy consumption, and poor compatibility between the metal matrix and ceramic particles. These key factors severely limit its popularization and application on a larger scale. The sol-gel method first disperses the raw materials into a solvent to form a low-viscosity solution, which can achieve molecular-level uniformity in a short time, so that when the reactants form a gel, they are likely to be uniformly mixed at the molecular level, which can ensure the consistency of the performance of each part of the magnetic abrasive and improve the product quality and stability.

[0004] Although there are also methods for preparing SiC magnetic abrasives on the market currently, these existing technologies all have defects to varying degrees. For example, a relatively high reaction temperature is required in the process of synthesizing SiC, which is likely to cause iron powder agglomeration; the conversion rate of SiC is relatively low, and it is only suitable for grinding metal materials with relatively low hardness, but the processing efficiency for metal materials with relatively high surface hardness of the abrasive is low; and in the initial stage of preparing magnetic abrasives, the problem of uneven coating on the surface of the hard phase is likely to occur, affecting the grinding efficiency. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing a magnetic abrasive with in-situ generated SiC hard phase, including the following steps: using polycarbosilane as a raw material, and in-situ generating SiC hard phase on the surface of the ferromagnetic phase by the sol-gel method to obtain a magnetic abrasive with a core-shell structure.

[0006] Preferably, the ferromagnetic phase includes a ferro-nickel alloy.

[0007] Preferably, the method for preparing the magnetic abrasive with in-situ generated SiC hard phase includes the following steps:

[0008] (1) Add spherical ferromagnetic phase powder into a polycarbosilane precursor solution, disperse evenly, and evaporate the solvent to obtain a coated product;

[0009] (2) Dry and heat-treat the coated product in sequence to obtain a magnetic abrasive with a core-shell structure.

[0010] Preferably, the particle size of the spherical ferromagnetic phase powder in step (1) is 100 μm - 200 μm.

[0011] Preferably, the particle size of the polycarbosilane in step (1) is 50 μm - 100 μm.

[0012] Preferably, the concentration of the polycarbosilane precursor solution in step (1) is 15 - 25 wt%.

[0013] Preferably, the temperature for evaporating the solvent in step (1) is 50 - 80 °C.

[0014] Preferably, the drying temperature in step (2) is 80 - 120 °C, and the time is 10 - 24 h.

[0015] Preferably, during the heat treatment in step (2), the heating rate is 2 °C / min - 5 °C / min, the heat treatment temperature is 1250 - 1350 °C, the heat treatment time is 1 h - 3 h, and the cooling rate is 3 - 30 °C / min.

[0016] The present invention also provides a magnetic abrasive prepared according to the above preparation method.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention uses the polycarbosilane sol-gel method to prepare a silicon carbide superhard abrasive phase. The prepared superhard abrasive phase has a strong binding ability with the ferromagnetic phase, and their heights are basically the same. During the grinding process, excellent processing effects can be ensured, and the sphericity and uniformity of the morphology characteristics of the magnetic abrasive can be guaranteed to the greatest extent, which has certain advantages for meeting the preparation requirements of high-performance magnetic abrasives.

[0019] The magnetic abrasive prepared by the present invention is spherical. During the grinding process, each part of the workpiece can be evenly stressed, and no deep scratches will appear.

[0020] The magnetic abrasive prepared by the present invention has good self-sharpening property and strong grinding force, can solve the problems of low service life and complex processing technology of traditional magnetic abrasives, and can perform precision grinding and polishing on workpieces.

[0021] The silicon carbide superhard abrasive phase is evenly distributed radially on the surface of the ferromagnetic phase, which can ensure the original high magnetic permeability of the ferromagnetic phase matrix and increase the grinding pressure. Description of the Drawings

[0022] Figure 1 It is a process flow chart for preparing FeNi@SiC magnetic abrasive in Example 1.

[0023] Figure 2 It is the morphology, cross-section and EDS distribution diagrams of the FeNi@SiC magnetic abrasive prepared in Example 1.

[0024] Figure 3 It is the XRD diagram of the FeNi@SiC magnetic abrasive prepared in Example 1.

[0025] Figure 4 It is the SEM diagram of the FeNi@SiC magnetic abrasive prepared in Comparative Example 1.

[0026] Figure 5 It is the SEM diagram of the FeNi@SiC magnetic abrasive prepared in Example 1.

[0027] Figure 6 It is the SEM diagram of the FeNi@SiC magnetic abrasive prepared in Comparative Example 2.

[0028] Figure 7 It is the SEM diagram of the FeNi@SiC magnetic abrasive prepared in Comparative Example 3.

[0029] Figure 8 It is the SEM diagram of the FeNi@SiC magnetic abrasive prepared in Example 2.

[0030] Figure 9 It is the SEM diagram of the FeNi@SiC magnetic abrasive prepared in Comparative Example 4.

[0031] Figure 10 It is the three-dimensional morphology diagrams before and after polishing the gadolinium zirconate thermal barrier coating with the FeNi@SiC magnetic abrasive prepared in Example 1.

[0032] Figure 11 It is the three-dimensional morphology diagrams before and after polishing the gadolinium zirconate thermal barrier coating with the FeNi@SiC magnetic abrasive prepared in Example 2.

[0033] Figure 12 It is the three-dimensional morphology diagrams before and after polishing the gadolinium zirconate thermal barrier coating with the FeNi@SiC magnetic abrasive prepared in Comparative Example 1.

[0034] Figure 13 The three-dimensional topography maps before and after polishing the gadolinium zirconate thermal barrier coating with the FeNi@SiC magnetic abrasive prepared using Comparative Example 2.

[0035] Figure 14 The three-dimensional topography maps before and after polishing the gadolinium zirconate thermal barrier coating with the FeNi@SiC magnetic abrasive prepared using Comparative Example 3.

[0036] Figure 15 The three-dimensional topography maps before and after polishing the gadolinium zirconate thermal barrier coating with the FeNi@SiC magnetic abrasive prepared using Comparative Example 4.

[0037] Figure 16 The hysteresis loops of the powders under different conditions. Specific Embodiments

[0038] The present invention provides a method for preparing a magnetic abrasive with an in-situ generated SiC hard phase, comprising the following steps: using polycarbosilane as a raw material, and in-situ generating the SiC hard phase on the surface of a ferromagnetic phase by a sol-gel method to obtain a magnetic abrasive with a core-shell structure.

[0039] Aiming at the problem in the existing technology for preparing Fe-based SiC magnetic abrasives that the conversion rate of silicon carbide is low (28.5%), and the magnetic abrasive with a low content of silicon carbide cannot meet the processing requirements for ceramic coatings with higher hardness, the present invention proposes to use polycarbosilane with a high conversion rate of silicon carbide as a carbon source. While ensuring a high SiC conversion rate (up to 50.6% at most), it can also reduce the synthesis temperature of the abrasive. The technical solution provided by the present invention reduces the synthesis temperature by about 50 °C compared to the process of only synthesizing silicon carbide using carbon powder and silicon powder.

[0040] Aiming at the problem in the existing technology for preparing Fe-based SiC magnetic abrasives that the surface of the hard phase is unevenly coated in the initial stage of preparing the magnetic abrasive, the present invention can achieve uniform wrapping of the hard slurry on the substrate by in-situ generating the SiC hard phase on the surface of the ferromagnetic phase by a sol-gel method, and uniform coating of the hard phase can be achieved by combining with subsequent sintering.

[0041] In the present invention, the ferromagnetic phase includes an iron-nickel alloy. Preferably, the iron-nickel alloy includes, but is not limited to, invar alloy, permalloy, FeNi 50 、FeNi 30 Any one of them.

[0042] The present invention selects FeNi 50 powder as the matrix phase under the condition of meeting the magnetic requirements. The melting point of FeNi is 1450 - 1480 °C, which can meet the temperature requirements during the SiC synthesis process.

[0043] In the present invention, the preparation method of the magnetic abrasive for in-situ generating SiC hard phase comprises the following steps:

[0044] (1) Adding ferromagnetic spherical powder into a polycarbosilane precursor solution, dispersing evenly, and evaporating the solvent to obtain a coated product;

[0045] (2) Sequentially drying and heat-treating the coated product to obtain a magnetic abrasive with a core-shell structure.

[0046] In the present invention, the ferromagnetic spherical powder in step (1) is preferably used after being cleaned.

[0047] The present invention does not strictly limit the cleaning method, and conventional cleaning methods in the art are applicable to the present invention. However, from the perspective of improving the cleaning effect, ultrasonic cleaning is preferably adopted. The ultrasonic cleaning time is 8 - 15 min, and preferably, the ultrasonic cleaning time is 10 min.

[0048] In the present invention, the particle size of the ferromagnetic spherical powder in step (1) is 100 μm - 200 μm.

[0049] In the present invention, the particle size of the polycarbosilane in step (1) is 50 μm - 100 μm to ensure its uniform dissolution in the solvent.

[0050] The present invention does not strictly limit the type of solvent for dissolving polycarbosilane, and solvents that can conventionally dissolve polycarbosilane in the art are applicable to the present invention, such as toluene, xylene, etc. The solvent is preferably xylene.

[0051] In the present invention, the concentration of the polycarbosilane precursor solution in step (1) is 15 - 25 wt%, and preferably, the concentration of the polycarbosilane precursor solution is 20 wt%.

[0052] In the present invention, the temperature for evaporating the solvent in step (1) is 50 - 80 °C, and preferably, the temperature for evaporating the solvent is 80 °C.

[0053] In the present invention, the drying temperature in step (2) is 80 - 120 °C, the time is 10 - 24 h, and preferably, the drying temperature is 80 °C and the time is 10 h.

[0054] In the present invention, during the heat treatment in step (2), the heating rate is 2 °C / min - 5 °C / min, the heat treatment temperature is 1250 - 1350 °C, the heat treatment time is 1 h - 3 h, and the cooling rate is 3 - 30 °C / min. Preferably, the heating rate during the heat treatment is 5 °C / min, the heat treatment time is 3 h, and the cooling rate is 3 °C / min.

[0055] In the present invention, the drying or heat treatment is carried out under an inert atmosphere condition, and the inert atmosphere is nitrogen.

[0056] The present invention also provides a magnetic abrasive prepared according to the preparation method.

[0057] Polycarbosilane (PCS) is an organosilicon polymer widely used in the preparation of silicon carbide (SiC) ceramic materials. Polycarbosilane is dissolved in a suitable solvent (such as toluene, xylene, etc.) to form a homogeneous solution. Under the action of heating or a catalyst, the molecular chains of polycarbosilane undergo partial cross-linking or cleavage to generate low-molecular-weight organosilicon compounds, and these compounds are further hydrolyzed to form a sol. The reactive silicon species (such as Si-OH or Si-OR) in the sol are the key intermediates for subsequent gelation and ceramization reactions.

[0058] The present invention utilizes polycarbosilane to form a gel through a hydrolysis and condensation reaction, and then decomposes at high temperature to generate SiC. The porous structure and nano-scale pores of the gel provide space for the growth of SiC grains. By controlling the gelation conditions, the size and distribution of SiC grains can be regulated. The ceramization reaction at high temperature is the driving force for the formation of the SiC phase, and the chemical reaction of carbon and silicon elements directly determines the quality and performance of SiC. By adjusting the composition and process parameters of polycarbosilane, the size and distribution of SiC grains can be precisely controlled, thereby optimizing the performance of the abrasive phase.

[0059] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope protected by the present invention.

[0060] In the following embodiments, the test methods or testing methods, unless otherwise specified, are all conventional methods; the raw materials and auxiliaries, unless otherwise specified, are all obtained from conventional commercial channels or prepared by conventional methods.

[0061] Example 1

[0062] A preparation method of a magnetic abrasive with an in-situ generated SiC hard phase is as follows:

[0063] (1) Add polycarbosilane (50 μm - 100 μm) to xylene solvent (10 ml), and stir until the polycarbosilane is completely dissolved to obtain a polycarbosilane precursor solution with a concentration of 20%, and set aside;

[0064] (2) Weigh FeNi after ultrasonic cleaning (10 min) 50Spherical powder (Permalloy, 10 g, 100 μm - 200 μm) was added to the polycarbosilane precursor solution and mixed evenly, followed by ultrasonic treatment for 10 min until FeNi 50 The spherical powder was uniformly dispersed in the polycarbosilane precursor solution. The solvent was slowly evaporated under stirring, causing the polycarbosilane to gradually coat FeNi 50 on the spherical surface. Then, the temperature was controlled at 80 °C to further evaporate the solvent and accelerate the coating process, obtaining the coated product;

[0065] (3) The coated product was placed in a nitrogen atmosphere (nitrogen flow rate: 50 mL / min) for drying to remove the residual solvent. The drying temperature was 120 °C and the drying time was 10 h to form a solid state of the product, obtaining the dried product;

[0066] (4) The dried product was placed in a tubular furnace and, under the protection of a nitrogen atmosphere (nitrogen flow rate: 50 mL / min), the heating rate was controlled at 5 °C / min and heated to 1300 °C, with a holding time of 3 h. During the pyrolysis process, the sol on the surface of the FeNi 50 spherical powder would in-situ generate SiC on its surface, and the reaction formed a core-shell structure of FeNi@SiC. The cooling rate was controlled at 3 °C / min and cooled to room temperature. The product was washed and sieved to obtain FeNi@SiC magnetic abrasive.

[0067] Testing and Analysis

[0068] Figure 1 It is the process flow chart for preparing FeNi@SiC magnetic abrasive in Example 1.

[0069] Figure 2 They are the morphology, cross-section, and EDS distribution diagrams of the FeNi@SiC magnetic abrasive prepared in Example 1. It can be seen that Figure 2 the abrasive has relatively obvious small granular protrusions, which can provide cutting and grinding pressure to ensure the material removal efficiency. Moreover, the cross-section of the abrasive shows a relatively obvious shell-like structure. It can be clearly seen from the EDS distribution diagram the distribution law of elements, showing an obvious enrichment of Si element.

[0070] Figure 3 It is the XRD diagram of the FeNi@SiC magnetic abrasive prepared in Example 1. It can be seen that Figure 3 the FeNi@SiC magnetic abrasive prepared in Example 1 of the present invention has obvious SiC peaks, and the PDF card number is 00 - 029 - 1129.

[0071] Comparative Example 1

[0072] A preparation method of a magnetic abrasive for in-situ generating SiC hard phase is as follows:

[0073] (1) Add polycarbosilane (50 μm - 100 μm) to xylene solvent (10 ml), stir until the polycarbosilane is completely dissolved to obtain a polycarbosilane precursor solution with a concentration of 10%, and set it aside;

[0074] (2) Weigh the FeNi 50 spherical powder (permalloy, 10 g, 100 μm - 200 μm) after ultrasonic cleaning (10 min), add it to the polycarbosilane precursor solution, mix evenly, and perform ultrasonic treatment for 10 min until the FeNi 50 spherical powder is evenly dispersed in the polycarbosilane precursor solution. Slowly evaporate the solvent under stirring to gradually coat the polycarbosilane on the FeNi 50 spherical surface. Then control the temperature at 80 °C and further evaporate the solvent to accelerate the coating process to obtain the coated product;

[0075] (3) Place the coated product in a nitrogen atmosphere (nitrogen flow rate 50 mL / min), dry it to remove the residual solvent. The drying temperature is 120 °C and the drying time is 10 h to form a solid state of the product to obtain the dried product;

[0076] (4) Under the protection of a nitrogen atmosphere (nitrogen flow rate 50 mL / min), control the heating rate at 5 °C / min for the dried product, heat it to 1300 °C, and keep it for 3 h. During the pyrolysis process, the sol on the surface of the FeNi 50 spherical powder will in-situ generate SiC on its surface, and the reaction forms a core-shell structure of FeNi@SiC. Control the cooling rate at 3 °C / min and cool it to room temperature to obtain the FeNi@SiC magnetic abrasive.

[0077] Comparative Example 2

[0078] A preparation method of a magnetic abrasive for in-situ generating SiC hard phase, the specific steps are as follows:

[0079] (1) Add polycarbosilane (50 μm - 100 μm) to xylene solvent (10 ml), stir until the polycarbosilane is completely dissolved to obtain a polycarbosilane precursor solution with a concentration of 30%, and set it aside;

[0080] (2) Weigh the FeNi 50 spherical powder (permalloy, 10 g, 100 μm - 200 μm) after ultrasonic cleaning (10 min), add it to the polycarbosilane precursor solution, mix evenly, and perform ultrasonic treatment for 10 min until the FeNi 50 spherical powder is evenly dispersed in the polycarbosilane precursor solution. Slowly evaporate the solvent under stirring to gradually coat the polycarbosilane on the FeNi 50The spherical surface is then controlled at a temperature of 80 °C to further evaporate the solvent, accelerating the coating process to obtain the coated product;

[0081] (3) Place the coated product in a nitrogen atmosphere (nitrogen flow rate: 50 mL / min) for drying to remove the residual solvent. The drying temperature is 120 °C and the drying time is 10 h to form a solid state of the product, obtaining the dried product;

[0082] (4) Under the protection of a nitrogen atmosphere (nitrogen flow rate: 50 mL / min), control the heating rate at 5 °C / min and heat up to 1300 °C, with a holding time of 3 h. During the pyrolysis process, the sol on the surface of the FeNi 50 spherical powder will in-situ generate SiC on its surface, and the reaction forms a core-shell structure of FeNi@SiC. Control the cooling rate at 3 °C / min and cool down to room temperature to obtain the FeNi@SiC magnetic abrasive.

[0083] Test the morphology of the FeNi@SiC magnetic abrasives prepared in Example 1 and Comparative Examples 1-2. The results are as Figures 4 - 6 shown. It can be seen from Figures 4 - 6 that the morphology of the FeNi@SiC magnetic abrasive prepared in Example 1 is better than that of Comparative Examples 1-2.

[0084] Example 2

[0085] A preparation method of a magnetic abrasive for in-situ generating SiC hard phase, the specific steps are as follows:

[0086] (1) Add polycarbosilane (50 μm - 100 μm) to xylene solvent (10 ml), stir until the polycarbosilane is completely dissolved to obtain a polycarbosilane precursor solution with a concentration of 20%, and set aside;

[0087] (2) Weigh the FeNi 50 spherical powder (Permalloy, 10 g, 100 μm - 200 μm) after ultrasonic cleaning (10 min), add it to the polycarbosilane precursor solution and mix evenly. Ultrasonically treat for 30 min until the FeNi 50 spherical powder is uniformly dispersed in the polycarbosilane precursor solution. Slowly evaporate the solvent under stirring to gradually coat the polycarbosilane on the FeNi 50 spherical surface. Then control the temperature at 80 °C to further evaporate the solvent, accelerating the coating process to obtain the coated product;

[0088] (3) Place the coated product in a nitrogen atmosphere (nitrogen flow rate: 50 mL / min) for drying to remove the residual solvent. The drying temperature is 120 °C and the drying time is 10 h to form a solid state of the product, obtaining the dried product;

[0089] (4) Under the protection of a nitrogen atmosphere (nitrogen flow rate: 50 mL / min), control the heating rate to 5 °C / min, heat up to 1300 °C, and keep the temperature for 3 h. During the pyrolysis process, the sol on the surface of the FeNi 50 spherical powder will in-situ generate SiC on its surface, and the reaction forms a core-shell structure of FeNi@SiC. Control the cooling rate to 3 °C / min and cool down to room temperature to obtain the FeNi@SiC magnetic abrasive.

[0090] Comparative Example 3

[0091] A preparation method of a magnetic abrasive with an in-situ generated SiC hard phase, the specific steps are as follows:

[0092] (1) Add polycarbosilane (50 μm - 100 μm) to xylene solvent (10 ml), stir until the polycarbosilane is completely dissolved, and obtain a polycarbosilane precursor solution with a concentration of 20%, and set aside;

[0093] (2) Weigh the FeNi 50 spherical powder (Permalloy, 10 g, 100 μm - 200 μm) after ultrasonic cleaning (10 min), add it to the polycarbosilane precursor solution and mix evenly, and perform ultrasonic treatment for 30 min until the FeNi 50 spherical powder is uniformly dispersed in the polycarbosilane precursor solution. Slowly evaporate the solvent under stirring to gradually coat the polycarbosilane on the FeNi 50 spherical surface. Then control the temperature at 80 °C, further evaporate the solvent, and accelerate the coating process to obtain the coated product;

[0094] (3) Place the coated product in a nitrogen atmosphere (nitrogen flow rate: 50 mL / min), dry it to remove the residual solvent. The drying temperature is 120 °C and the drying time is 10 h to form a solid product and obtain the dried product;

[0095] (4) Under the protection of a nitrogen atmosphere (nitrogen flow rate: 50 mL / min), control the heating rate to 5 °C / min, heat up to 1200 °C, and keep the temperature for 3 h. During the pyrolysis process, the sol on the surface of the FeNi 50 spherical powder will in-situ generate SiC on its surface, and the reaction forms a core-shell structure of FeNi@SiC. Control the cooling rate to 3 °C / min and cool down to room temperature to obtain the FeNi@SiC magnetic abrasive.

[0096] Comparative Example 4

[0097] A preparation method of a magnetic abrasive with an in-situ generated SiC hard phase, the specific steps are as follows:

[0098] (1) Add polycarbosilane (50 μm - 100 μm) into xylene solvent (10 ml), stir until the polycarbosilane is completely dissolved to obtain a polycarbosilane precursor solution with a concentration of 20%, and set it aside;

[0099] (2) Weigh the FeNi 50 spherical powder (permalloy, 10 g, 100 μm - 200 μm) after ultrasonic cleaning (10 min), add it into the polycarbosilane precursor solution and mix evenly, and perform ultrasonic treatment for 30 min until the FeNi 50 spherical powder is uniformly dispersed in the polycarbosilane precursor solution. Slowly evaporate the solvent under stirring to gradually coat the polycarbosilane on the surface of the FeNi 50 spherical surface. Then control the temperature at 80 °C to further evaporate the solvent and accelerate the coating process to obtain the coated product;

[0100] (3) Place the coated product in a nitrogen atmosphere (nitrogen flow rate 50 mL / min) for drying to remove the residual solvent. The drying temperature is 120 °C and the drying time is 10 h to form a solid state of the product to obtain the dried product;

[0101] (4) Under the protection of a nitrogen atmosphere (nitrogen flow rate 50 mL / min) for the dried product, control the heating rate at 5 °C / min and heat up to 1400 °C, and keep the temperature for 3 h. During the pyrolysis process, the sol on the surface of the FeNi 50 spherical powder will in-situ generate SiC on its surface, and the reaction forms a core-shell structure of FeNi@SiC. Control the cooling rate at 3 - 30 °C / min and cool down to room temperature to obtain FeNi@SiC magnetic abrasive.

[0102] Test the morphology of the FeNi@SiC magnetic abrasives prepared in Example 2 and Comparative Examples 3 - 4. The results are as Figures 7 - 9 shown. It can be seen from Figures 7 - 9 that the morphology of the FeNi@SiC magnetic abrasive prepared in Example 2 is better than that of Comparative Examples 3 - 4. Especially when the pyrolysis temperature is 1400 °C, the abrasive will show caking and irregular morphology.

[0103] Application Example

[0104] Use the FeNi@SiC magnetic abrasive prepared in Example 1 on a refitting machine tool to polish the gadolinium zirconate substrate. The results are as Figure 10 shown. It can be seen from Figure 10 that most of the protrusions on the surface of the gadolinium zirconate after polishing are removed, the surface of the gadolinium zirconate substrate becomes flat, and the surface micro-undulation significantly becomes smaller, improving the surface integrity and surface quality of the gadolinium zirconate.

[0105] The FeNi@SiC magnetic abrasive prepared in Example 2 was used on a refitted machine tool to polish gadolinium zirconate substrates. The results are as Figure 11 shown. It can be seen from Figure 11 that after polishing, some protrusions on the surface of gadolinium zirconate were removed, the surface of the gadolinium zirconate substrate became flatter, and the surface micro-undulations became smaller.

[0106] The FeNi@SiC magnetic abrasive prepared in Comparative Example 1 was used on a refitted machine tool to polish gadolinium zirconate substrates. The results are as Figure 12 shown. It can be seen from Figure 12 that after polishing, a small number of protrusions on the surface of gadolinium zirconate were ground off, and the surface of the substrate looked flatter than before. The surface micro-height difference also decreased.

[0107] The FeNi@SiC magnetic abrasive prepared in Comparative Example 2 was used on a refitted machine tool to polish gadolinium zirconate substrates. The results are as Figure 13 shown. It can be seen from Figure 13 that after polishing, a small amount of protrusions on the surface of gadolinium zirconate were removed, but there were still obvious uneven areas on the substrate surface, and it was difficult to achieve an ideal flatness effect.

[0108] The FeNi@SiC magnetic abrasive prepared in Comparative Example 3 was used on a refitted machine tool to polish gadolinium zirconate substrates. The results are as Figure 14 shown. It can be seen from Figure 14 that after polishing, some protrusions remained on the surface of gadolinium zirconate, the removal rate was insufficient, and there were still obvious uneven areas on the substrate surface.

[0109] The FeNi@SiC magnetic abrasive prepared in Comparative Example 4 was used on a refitted machine tool to polish gadolinium zirconate substrates. The results are as Figure 15 shown. It can be seen from Figure 15 that after polishing, a large number of protrusions still remained on the surface of gadolinium zirconate, only a small part was cut down, and the substrate surface was still uneven, with obvious undulation marks visible to the naked eye.

[0110] Taking the magnetic abrasive prepared by replacing the nickel-iron alloy in the example with pure iron as the control group, the magnetic permeability of the magnetic abrasives prepared in the example, comparative examples, and control group was tested under the same experimental conditions. The results are as Figure 16 shown. It can be seen from Figure 16 that the magnetic abrasives prepared under different conditions maintained the original high magnetic permeability of the iron-nickel spherical powder and could exhibit excellent magnetic conductivity during magnetic abrasive polishing.

[0111] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a magnetic abrasive for in-situ generating SiC hard phase, characterized in that, It includes the following steps: Using polycarbosilane as a raw material, a SiC hard phase is in-situ generated on the surface of the ferromagnetic phase by the sol-gel method to obtain a magnetic abrasive with a core-shell structure.

2. The preparation method of the magnetic abrasive for in-situ generating SiC hard phase according to claim 1, characterized in that, The ferromagnetic phase includes a ferro-nickel alloy.

3. The preparation method of the magnetic abrasive for in-situ generating SiC hard phase according to claim 1, characterized in that, It includes the following steps: (1) Add spherical ferromagnetic phase powder into the polycarbosilane precursor solution, disperse evenly, and evaporate the solvent to obtain the coated product; (2) Subject the coated product to drying and heat treatment in sequence to obtain a magnetic abrasive with a core-shell structure.

4. The preparation method of the magnetic abrasive for in-situ generating SiC hard phase according to claim 3, characterized in that, In step (1), the particle size of the spherical ferromagnetic phase powder is 100 μm - 200 μm.

5. The preparation method of the magnetic abrasive for in-situ generating SiC hard phase according to claim 3, characterized in that, In step (1), the particle size of the polycarbosilane is 50 μm - 100 μm.

6. The preparation method of the magnetic abrasive for in-situ generating SiC hard phase according to claim 3, characterized in that, In step (1), the concentration of the polycarbosilane precursor solution is 15 - 25 wt%.

7. The preparation method of the magnetic abrasive for in-situ generating SiC hard phase according to claim 3, characterized in that, In step (1), the temperature for evaporating the solvent is 50 - 80 °C.

8. The preparation method of the magnetic abrasive for in-situ generating SiC hard phase according to claim 3, characterized in that, In step (2), the drying temperature is 80 - 120 °C and the time is 10 - 24 h.

9. The preparation method of the magnetic abrasive for in-situ generating SiC hard phase according to claim 3, characterized in that, In step (2), during heat treatment, the heating rate is 2 °C / min - 5 °C / min, the heat treatment temperature is 1250 - 1350 °C, the heat treatment time is 1 h - 3 h, and the cooling rate is 3 - 30 °C / min.

10. A magnetic abrasive prepared by the preparation method according to any one of claims 1 - 9.

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