TiC-Fe-Cr coating powder material for automobile brake disc and preparation method and application thereof

Abstract

The application belongs to the technical field of laser cladding, and particularly relates to a TiC-Fe-Cr coating powder material for automobile brake discs and a preparation method and application thereof. The coating powder material is obtained through mixing, wet grinding, spray drying, compression molding, sintering and crushing, and spherical densification treatment of 60-80% TiC powder, 15-30% Fe powder, 4-11% Cr powder and 0.8-2.2% polyethylene glycol, and the coating powder material is attached to the surface of the brake disc in a laser cladding mode. By means of the settings, the application provides a coating powder material which solves the problem of the lack of laser cladding materials special for aluminum alloy brake discs, and overcomes the technical bottlenecks of the heavy weight, fast wear, dust production, easy rust of traditional gray cast iron brake discs, and the low hardness and poor wear resistance of aluminum alloy brake discs.

Description

Technical Field

[0001] This invention belongs to the field of laser cladding technology, and particularly relates to a TiC-Fe-Cr coating powder material for automotive brake discs, its preparation method and application. Background Technology

[0002] Laser cladding technology consists of three main components: cladding materials, cladding processes, and cladding equipment. These three components together determine the final effect of laser cladding. As the core component of this technology, cladding materials are the key foundation for achieving coating performance and substrate compatibility.

[0003] Currently, there are two core technical challenges in the brake disc field: First, the performance bottleneck of traditional gray cast iron brake discs. With increasing environmental awareness, higher aesthetic requirements for automobiles, and the growing demand for lightweight design in electric vehicles, the wear dust generated during braking, rust susceptibility, and high fuel and electricity consumption due to their heavy weight have become significant factors restricting their development. Second, the performance limitations of aluminum alloy brake discs. Although aluminum alloys offer advantages such as lightweight design, compared to gray cast iron, they have lower hardness and poorer wear resistance, failing to meet the requirements of brake discs to withstand long-term intense friction, severely limiting the application of aluminum alloys in the brake disc field.

[0004] To address the aforementioned issues, the industry has developed a clear solution: replacing gray cast iron with aluminum alloy as the brake disc substrate to resolve lightweight and environmental concerns; simultaneously, employing laser cladding technology to protect the surface of the aluminum alloy brake disc, creating a high-performance coating to compensate for the low hardness and poor wear resistance of aluminum alloy. This approach leverages the lightweight advantages of aluminum alloy while using laser cladding technology to impart excellent wear resistance and high-temperature resistance to the brake disc surface, making it the mainstream direction for current brake disc technology upgrades.

[0005] Although laser cladding technology provides an effective way to improve the performance of aluminum alloy brake discs, existing solutions still have a key bottleneck—the lack of special cladding materials that meet the laser cladding requirements of aluminum alloy automotive brake discs.

[0006] As mentioned earlier, cladding materials are a core component of laser cladding technology. Their design directly affects the performance of aluminum alloy brake disc coatings and is a crucial factor in the success of laser cladding coating preparation. While general-purpose laser cladding materials exist in the industry, they are not customized for the characteristics of aluminum alloy substrates and the working conditions of brake discs. They either fail to achieve a balance between lightweight and high wear resistance, or exhibit poor adhesion to the aluminum alloy substrate, making it difficult to form a stable metallurgical interface. Therefore, developing specialized materials and coatings suitable for laser cladding of aluminum alloy automotive brake discs has become a key obstacle to overcoming existing technological bottlenecks and promoting the industrial application of aluminum alloy brake discs. Summary of the Invention

[0007] The purpose of this invention is to provide a TiC-Fe-Cr coated powder material for automotive brake discs, its preparation method, and its application, in order to solve the above-mentioned problems.

[0008] To achieve the above objectives, the present invention provides the following solution:

[0009] A TiC-Fe-Cr coating powder material for automotive brake discs is obtained by mixing 60-80% TiC powder, 15-30% Fe powder, 4-11% Cr powder and 0.8-2.2% polyethylene glycol, followed by wet milling, spray drying, pressing, sintering and crushing, and spherical densification treatment.

[0010] A method for preparing the TiC-Fe-Cr coated powder material for automotive brake discs, comprising:

[0011] S1. Mixing: Take 60-80% TiC powder, 15-30% Fe powder, 4-11% Cr powder and 0.8-2.2% polyethylene glycol and mix them evenly to prepare a mixture;

[0012] S2. Wet milling: The mixture is placed in a ball mill and ethanol or deionized water is added as the ball milling medium for wet milling.

[0013] S3. Spray drying: The wet-milled mixture is introduced into a spray drying tower for spray granulation.

[0014] S4. Pressing and molding: The dried mixture is pressed into a blank using a powder press;

[0015] S5. Sintering and crushing: The preform is placed in a vacuum degreasing and sintering integrated furnace to remove the molding agent polyethylene glycol and then sintered. After sintering, an impact crusher is used to crush the material to obtain the crushed material.

[0016] S6. Spherical densification treatment: The crushed material is melted using a high-temperature vertical tube furnace with plasma, and spherical droplets are formed by surface tension. After cooling, the material is classified by particle size to obtain the coating powder material.

[0017] Preferably, in step S2, the ball mill uses TiC-12Fe cemented carbide balls as the grinding balls, the ball-to-material mass ratio is 2-5:1, and the grinding time is 24-60 hours.

[0018] Preferably, the outlet temperature of the spray drying tower in step S3 is 100-160°C.

[0019] Preferably, the temperature of the polyethylene glycol removal process in step S5 is 300-480℃, the temperature of the sintering process is 1350-1450℃, and the temperature is maintained for 60-240 minutes after sintering.

[0020] Preferably, in step S6, the feeding rate inside the plasma high-temperature vertical tube furnace is 40-240 g / min.

[0021] Preferably, the particle size classification in step S6 is performed by air classifier to obtain a coating powder material with a particle size of 10-75 μm.

[0022] The application of the TiC-Fe-Cr coating powder material for automotive brake discs involves attaching the coating powder material to the surface of the brake disc via laser cladding.

[0023] Preferably, the laser power of the laser cladding is 1200-4500W, the scanning speed is 300-600mm / min, the spot diameter is 2-5mm, the powder feeding amount is 15-60g / min, and the overlap rate is 30-50%.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] (1) The automotive brake disc of the present invention uses aluminum alloy as the base material. With the significant characteristic that the density of aluminum alloy is only about 37.5% of that of gray cast iron, the overall weight of the brake disc can be greatly reduced. This lightweight advantage meets the current automotive industry's (especially electric vehicles) performance requirements for weight reduction and energy saving, and provides key support for improving vehicle range, optimizing energy consumption and enhancing handling performance.

[0026] (2) The present invention selects ceramic TiC and metal Fe and Cr as friction components of wear-resistant coating on the surface of automobile brake disc. Through the synergistic effect of multiple materials, while ensuring that the coating has excellent wear resistance, it effectively takes into account the lightweight requirements of brake disc, and achieves a dual technological breakthrough of high wear resistance and lightweight.

[0027] (3) This invention utilizes a plasma high-temperature vertical tube furnace to induce the broken powder to fall freely through the high-temperature furnace tube in a high-temperature environment, causing it to melt rapidly and form spherical droplets using surface tension. After rapid cooling and solidification, the irregular powder is successfully transformed into highly dense spherical TiC-Fe-Cr powder. This process not only achieves the spherization of the powder but also significantly improves the loose packing density and flow rate of the powder, laying the foundation for the preparation of high-performance laser cladding coatings.

[0028] (4) In the process of laser cladding coating preparation, this invention innovatively sets up a nitrogen protection pipeline. By forming a stable and dense gas curtain in the molten pool area with nitrogen, the molten pool can be effectively isolated from oxygen in the air. This design can avoid cladding defects caused by aluminum oxide formation on the aluminum alloy surface due to reaction with oxygen, and build a reliable inert protective environment for the formation of a high-quality cladding layer, fundamentally ensuring the metallurgical bonding quality and overall performance stability of the coating and the substrate.

[0029] (5) In the high-temperature environment of laser cladding, the TiC-Fe-Cr coating prepared by this invention will form FeCr alloy with metallic Fe. The coating thus obtained has the characteristics of high strength, excellent thermal conductivity and outstanding wear resistance of TiC ceramics, and also integrates the characteristics of low cost, high temperature resistance and oxidation resistance of FeCr alloy, thus achieving complementary advantages in performance.

[0030] Therefore, through customized TiC-Fe-Cr cladding materials and optimized preparation and cladding processes, this invention not only solves the core technical problem of "lack of dedicated laser cladding materials for aluminum alloy brake discs," but also comprehensively overcomes the technical bottlenecks of traditional gray cast iron brake discs ("heavy weight, rapid wear, dust generation, and easy rusting") and aluminum alloy brake discs ("low hardness and poor wear resistance"), providing a reliable solution for the lightweight, high-performance, and environmentally friendly upgrade of automotive brake discs. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 SEM images of TiC-15Fe-5Cr spherical powder and coating prepared by the method of the present invention;

[0033] Figure 2 SEM images of TiC-22.5Fe-7.5Cr spherical powder and coating prepared by the method of the present invention;

[0034] Figure 3 SEM images of TiC-19Fe-6Cr spherical powder and coating prepared by the method of this invention;

[0035] Figure 4 SEM images of TiC-29Fe-11Cr spherical powder and coating prepared using the method of this invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Example 1

[0039] This embodiment discloses a method for preparing an aluminum alloy automotive brake disc coating, the specific steps of which include:

[0040] (1) Ingredients: Ingredients are prepared according to mass percentage, wherein the mass fraction of TiC powder is 80%, the mass fraction of Fe powder is 15%, the mass fraction of Cr powder is 5%, and the amount of polyethylene glycol (PEG) added is 2.2% of the total mass.

[0041] (2) Wet grinding: The prepared material is placed in an inclined ball mill, with ethanol as the grinding medium and TiC-12Fe hard alloy balls as the grinding balls. The ball-to-material mass ratio is 5:1, and the grinding time is 24h.

[0042] (3) Spray drying: The wet-milled slurry is sprayed and granulated using a spray drying tower. The temperature of the air outlet of the equipment is set to 160℃.

[0043] (4) Molding: The spray-dried powder is pressed into a cylindrical blank with a pressure of φ10mm×2mm by a powder press at a pressure of 160MPa.

[0044] (5) Sintering: The cylindrical blank after forming is deformed at 300°C in a vacuum degreasing and sintering furnace, and then heated to 1450°C for 60 minutes.

[0045] (6) Crushing: The sintered cylindrical alloy block is crushed using a self-designed impact crusher. To avoid the introduction of other impurities, the impact part of the crusher is made of TiC-12Fe hard alloy material.

[0046] (7) Spherical densification: The crushed powder is subjected to spherical densification treatment at 3400℃ at a feeding speed of 240g / min using a plasma high-temperature vertical furnace tube. The powder is rapidly heated to a molten state as it falls from top to bottom through the high-temperature vertical furnace tube and forms spherical droplets under the action of surface tension. The spherical droplets fall from the bottom of the furnace tube and cool down rapidly. After solidification, highly dense spherical TiC-15Fe-5Cr powder is obtained.

[0047] (8) The densified powder was classified by particle size using an air classifier to obtain TiC-15Fe-5Cr spherical powder with a particle size of 10μm-53μm.

[0048] (9) After the aluminum alloy 7075 automotive brake disc is sequentially subjected to corundum powder sandblasting, high-pressure deionized water rinsing, and compressed air drying, a TiC-15Fe-5Cr powder coating is prepared using laser cladding technology. During the cladding process, in order to avoid oxidation reaction between the aluminum alloy surface and oxygen in the air, a flexible nitrogen protection pipe with a flow rate of 12L / min is installed at the powder outlet of the laser cladding equipment to isolate the molten pool from oxygen in the air.

[0049] The process parameters for laser cladding are shown in Table 2:

[0050] Table 1. Process parameters for preparing TiC-15Fe-5Cr coatings using laser cladding technology

[0051]

[0052] (10) The prepared coating is coarsely ground and polished using a mechanical grinding machine to make the surface roughness Ra=1.6μm.

[0053] Example 2:

[0054] (1) Ingredients: Ingredients are prepared according to mass percentage, wherein the mass fraction of TiC powder is 70%, the mass fraction of Fe powder is 22.5%, the mass fraction of Cr powder is 7.5%, and the amount of polyethylene glycol (PEG) added is 1.2% of the total mass.

[0055] (2) Wet grinding: Place the prepared material in an inclined ball mill, use deionized water as the grinding medium, use TiC-12Fe hard alloy balls as grinding balls, the ball-to-material mass ratio is 3:1, and the grinding time is 36h.

[0056] (3) Spray drying: The wet-milled slurry is sprayed and granulated using a spray drying tower. The temperature of the air outlet of the equipment is set to 120℃.

[0057] (4) Molding: The spray-dried powder is pressed into a cylindrical blank with a pressure of φ10mm×2mm by a powder press at a pressure of 120MPa.

[0058] (5) Sintering: The cylindrical blank after forming is deformed at 360°C in a vacuum degreasing and sintering furnace, and then heated to 1420°C for sintering, with a holding time of 120 min.

[0059] (6) Crushing: The sintered cylindrical alloy block is crushed using a self-designed impact crusher. To avoid the introduction of other impurities, the impact part of the crusher is made of TiC-12Fe hard alloy material.

[0060] (7) Spherical densification: The crushed powder is subjected to spherical densification treatment at 3200℃ at a feeding speed of 120g / min using a plasma high-temperature vertical furnace tube. The powder is rapidly heated to a molten state as it falls from top to bottom through the high-temperature vertical furnace tube and forms spherical droplets under the action of surface tension. The spherical droplets fall from the bottom of the furnace tube and cool down rapidly. After solidification, highly dense spherical TiC-22.5Fe-7.5Cr powder is obtained.

[0061] (8) The powder after densification in step g is classified by particle size using an air classifier to obtain TiC-22.5Fe-7.5Cr powder with a particle size of 15μm-45μm.

[0062] (9) After sequentially subjecting the 6061 aluminum alloy automotive brake disc to corundum powder sandblasting, high-pressure deionized water rinsing, and compressed air drying, a coating of TiC-22.5Fe-7.5Cr powder was prepared using laser cladding technology. During the cladding process, to prevent oxidation of the aluminum alloy surface by contact with oxygen in the air, a flexible nitrogen-protected pipeline with a flow rate of 9.5 L / min was installed at the powder outlet of the laser cladding equipment to isolate the molten pool from oxygen in the air. The process parameters for laser cladding are shown in Table 3.

[0063] Table 2. Process parameters for preparing TiC-22.5Fe-7.5Cr coatings using laser cladding technology

[0064]

[0065] (10) The prepared coating is coarsely ground and polished using a mechanical grinding machine to make the surface roughness Ra=0.4μm.

[0066] Example 3:

[0067] (1) Ingredients: Ingredients are prepared according to mass percentage, wherein the mass fraction of TiC powder is 75%, the mass fraction of Fe powder is 19%, the mass fraction of Cr powder is 6%, and the amount of polyethylene glycol (PEG) added is 1.5% of the total mass.

[0068] (2) Wet grinding: The prepared material is placed in an inclined ball mill, with ethanol as the grinding medium and TiC-12Fe hard alloy balls as the grinding balls. The ball-to-material mass ratio is 4:1, and the grinding time is 48h.

[0069] (3) Spray drying: The wet-milled slurry is sprayed and granulated using a spray drying tower. The temperature of the air outlet of the equipment is set to 140℃.

[0070] (4) Molding: The spray-dried powder is pressed into a cylindrical blank with a pressure of φ10mm×2mm by a powder press at a pressure of 90MPa.

[0071] (5) Sintering: The cylindrical blank after forming is deformed at 420°C in a vacuum degreasing and sintering furnace, and then heated to 1400°C for 180 min.

[0072] (6) Crushing: The sintered cylindrical alloy block is crushed using a self-designed impact crusher. To avoid the introduction of other impurities, the impact part of the crusher is made of TiC-12Fe hard alloy material.

[0073] (7) Spherical densification: The crushed powder is subjected to spherical densification at 3300℃ at a feeding speed of 180g / min using a plasma high-temperature vertical furnace tube. The powder is rapidly heated to a molten state as it falls from top to bottom through the high-temperature vertical furnace tube and forms spherical droplets under the action of surface tension. The spherical droplets fall from the bottom of the furnace tube and cool down rapidly. After solidification, highly dense spherical TiC-19Fe-6Cr powder is obtained.

[0074] (8) The powder after densification in step g is classified by particle size using an air classifier to obtain TiC-19Fe-6Cr powder with a particle size of 20μm-53μm.

[0075] (9) After sequentially subjecting the 7075 aluminum alloy automotive brake disc to corundum powder sandblasting, high-pressure deionized water rinsing, and compressed air drying, a TiC-19Fe-6Cr powder coating was prepared using laser cladding technology. During the cladding process, to prevent oxidation of the aluminum alloy surface by contact with oxygen in the air, a flexible nitrogen-protected pipeline with a flow rate of 10.5 L / min was installed at the powder outlet of the laser cladding equipment to isolate the molten pool from oxygen in the air. The process parameters for laser cladding are shown in Table 4.

[0076] Table 3. Process parameters for preparing TiC-19Fe-6Cr coatings using laser cladding technology

[0077]

[0078] (10) The prepared coating is coarsely ground and polished using a mechanical grinding machine to make the surface roughness Ra=0.8μm.

[0079] Example 4:

[0080] (1) Ingredients: Ingredients are prepared according to mass percentage, wherein the mass fraction of TiC powder is 60%, the mass fraction of Fe powder is 29%, the mass fraction of Cr powder is 11%, and the amount of polyethylene glycol (PEG) added is 0.8% of the total mass.

[0081] (2) Wet grinding: Place the prepared material in an inclined ball mill, use deionized water as the grinding medium, use TiC-12Fe hard alloy balls as grinding balls, the ball-to-material mass ratio is 2:1, and the grinding time is 60h.

[0082] (3) Spray drying: The wet-milled slurry is sprayed and granulated using a spray drying tower. The temperature of the air outlet of the equipment is set to 100℃.

[0083] (4) Molding: The spray-dried powder is pressed into a cylindrical blank with a pressure of φ10mm×2mm by a powder press at a pressure of 20MPa.

[0084] (5) Sintering: The cylindrical blank after forming is deformed at 480°C in a vacuum degreasing and sintering furnace, and then heated to 1350°C for 240 min.

[0085] (6) Crushing: The sintered cylindrical alloy block is crushed using a self-designed impact crusher. To avoid the introduction of other impurities, the impact part of the crusher is made of TiC-12Fe hard alloy material.

[0086] (7) Spherical densification: The crushed powder is subjected to spherical densification treatment at 3100℃ at a feeding speed of 40g / min using a plasma high-temperature vertical furnace tube. The powder is rapidly heated to a molten state as it falls from top to bottom through the high-temperature vertical furnace tube and forms spherical droplets under the action of surface tension. The spherical droplets fall from the bottom of the furnace tube and cool down rapidly. After solidification, highly dense spherical TiC-29Fe-11Cr powder is obtained.

[0087] (8) The powder after densification in step g is classified by particle size using an air classifier to obtain TiC-29Fe-11Cr powder with a particle size of 20μm-75μm.

[0088] (9) After sequentially subjecting the 6061 aluminum alloy automotive brake disc to corundum powder sandblasting, high-pressure deionized water rinsing, and compressed air drying, a coating of TiC-29Fe-11Cr powder was prepared using laser cladding technology. During the cladding process, to prevent oxidation of the aluminum alloy surface by contact with oxygen in the air, a flexible nitrogen-protected pipeline with a flow rate of 8 L / min was installed at the powder outlet of the laser cladding equipment to isolate the molten pool from oxygen in the air. The process parameters for laser cladding are shown in Table 5.

[0089] Table 4. Process parameters for preparing TiC-29Fe-11Cr coatings using laser cladding technology

[0090]

[0091] (10) Use a mechanical grinding machine to rough grind and polish the prepared coating to make the surface roughness Ra=0.2μm.

[0092] Experimental Example 1

[0093] This test example involves detecting the porosity of the coating, specifically including:

[0094] (1) Sample taking:

[0095] From the laser-clad aluminum alloy brake disc, cut a 10mm×10mm×5mm sample along the vertical direction of the coating (ensuring the "coating-substrate interface" is included). Take 3 parallel samples for each embodiment, avoiding the edge area (to prevent cutting damage to the coating).

[0096] (2) Metallographic preparation:

[0097] The sample was cold-mounted with resin (the mounting material was epoxy resin + curing agent in a ratio of 10:1). After curing, it was wet-polished with 400#, 800#, 1200# and 2000# silicon carbide sandpaper in sequence, and then polished on a polishing cloth with 1μm diamond polishing paste until the coating surface was free of scratches and had a mirror-like reflective surface.

[0098] (3) Microscopic observation:

[0099] The polished sample was placed in a scanning electron microscope (VEGA3TESCAN) in backscattered electron mode (BSE) at an accelerating voltage of 20.0 kV and a working distance of 15 mm. Five fields of view (each field of view area ≥ 50 μm × 50 μm) were selected in the middle of the coating and near the coating-substrate interface to capture microscopic images. The captured microscopic images of the TiC-29Fe-11Cr spherical powder product of this invention are shown below. Figure 1-4 As shown.

[0100] (4) Porosity calculation:

[0101] The SEM images were processed using image analysis software (Image-ProPlus). The "pores" were set as black areas. The percentage of the pore area in each field of view was automatically calculated. The average value of the five fields of view was taken as the porosity of the sample. Finally, the average value of three parallel samples was taken as the porosity of the coating in the example.

[0102] The experimental results are shown in Table 5 below.

[0103] Experimental results show that the coating porosity of Examples 1-4 of the present invention is only 0.08%-0.13%, which is much lower than the 1.24% of the existing gray cast iron brake disc.

[0104] The low porosity stems from two aspects: First, this invention uses a process of "wet grinding (24-60h) + spray drying (100-160℃) + vacuum sintering (1350-1450℃) + plasma spherical densification (3100-3400℃)" to prepare highly dense spherical TiC-Fe-Cr powder, ensuring coating density from the raw material end; Second, the use of "nitrogen protection (8-12L / min) + precise parameters (laser power 1200-4500W, powder feed rate 15-60g / min)" during laser cladding avoids oxidation of the molten pool and the formation of pores.

[0105] This advantage directly solves two major problems: ① the problem of "oil / water seeping in during braking and accelerating internal corrosion" caused by the high porosity of traditional gray cast iron; ② the problem of "intensified internal wear and shortened service life" caused by the high porosity (usually >0.5%) of conventional laser cladding coatings, laying the foundation for long-term service of the coating.

[0106] Experimental Example 2

[0107] This test example focuses on the coating hardness (HV). 0.3 The detection of ) specifically includes:

[0108] (1) Sample pretreatment:

[0109] The same metallographic preparation process as that used for "coating porosity detection" was adopted to ensure that the surface roughness Ra of the coating is ≤0.2μm (to avoid surface scratches affecting indentation measurement). Three parallel samples were taken for each example.

[0110] (2) Hardness tester calibration:

[0111] Use a Vickers hardness tester (HVS-1000 model) and a standard hardness block (hardness value of about 1200HV, close to the hardness of the coating) to calibrate the equipment to ensure that the test force and indentation measurement accuracy meet the standards.

[0112] (3) Hardness test:

[0113] Fix the sample on the hardness tester stage with the coating facing upwards. Set the test parameters as follows: test force 0.3 kgf (2.942 N), holding time 15 s (to avoid indentation cracking due to coating brittleness). Select 5 test points evenly on the coating surface (point spacing ≥ 2 times the diagonal length of the indentation, avoiding coating edges and pores). After loading at each point, measure the length of the two diagonals of the indentation (accurate to 0.1 μm).

[0114] (4) Hardness calculation:

[0115] According to the formula:

[0116]

[0117] (Where F is the test force in N; d is the average value of the indentation diagonal in mm) Calculate the Vickers hardness at each point, remove outliers (deviations exceeding ±5%), and take the average value. Finally, the average value of three parallel samples is taken as the coating hardness (HV) of the example. 0.3 ).

[0118] The experimental results are shown in Table 5 below.

[0119] Experimental results also show that the coating hardness (HV) of Examples 1-4 of the present invention is [missing information]. 0.3 The hardness (HV) of gray cast iron brake discs reaches 1192.51-1311.29, which is higher than that of existing gray cast iron brake discs. 0.3 =284.33) is 4.2-4.6 times that of 484.33.

[0120] The core reason for the hardness advantage is the customized "TiC-Fe-Cr composite system" of this invention: TiC (60%-80%), as a high-hardness hard phase, forms a continuous wear-resistant skeleton; Fe-Cr alloy (Fe15%-30%+Cr4%-11%), as a metallic phase, not only enhances its own hardness through solid solution strengthening, but also tightly wraps TiC particles to prevent them from falling off. The two work together to achieve a balance of "high hardness + low brittleness".

[0121] This performance directly overcomes the core weakness of aluminum alloy brake discs—the low hardness of the aluminum alloy matrix (approximately 60-100 HV). 0.3 The problem of aluminum alloy brake discs being unable to withstand the intense friction of braking has been addressed by making their surface hardness reach or even exceed that of gray cast iron. Furthermore, the coating protects the base material from direct wear, thus clearing a key obstacle for the application of aluminum alloys in the field of brake discs.

[0122] Experimental Example 3

[0123] This test example is for coating adhesion strength testing, specifically including:

[0124] (1) Sample preparation:

[0125] An integrated "coating-aluminum alloy substrate" sample with dimensions of Φ10mm×20mm (coating thickness 500-800μm, substrate thickness ≥15mm) was cut from the coated brake disc. Three parallel samples were taken for each embodiment. The two end faces of the sample were sanded to ensure that the two end faces were parallel and perpendicular to the sample axis.

[0126] (2) Bonding and curing:

[0127] A high-strength epoxy adhesive (such as E-7 adhesive, shear strength ≥30MPa) was used to bond the "coated end face" of the sample to a Φ10mm×10mm 45# steel transition block (the surface of the transition block was polished to Ra≤0.8μm), ensuring complete adhesion between the coating and the transition block (no air bubbles). The sample was cured in an 80℃ oven for 2 hours, and after cooling to room temperature, excess adhesive was removed.

[0128] (3) Tensile test:

[0129] Mount the specimen on the fixture of the universal testing machine (CMT5105 model), ensuring that the tensile axis is perpendicular to the coating-substrate interface. Set the tensile rate to 1 mm / min and apply a uniform load until the coating peels off from the substrate (or the substrate breaks). Record the maximum load F (in N) at failure.

[0130] (4) Calculation of bond strength:

[0131] According to the formula

[0132]

[0133] (Where S is the bonding area between the coating and the substrate, in mm) 2 S=πr 2 The bonding strength is calculated using the sample with r=5mm. If the failure occurs inside the coating (r=5mm), the data is invalid and the test needs to be repeated. The final bonding strength of the coating in the example is the average of the three valid samples.

[0134] The experimental results are shown in Table 5 below.

[0135] Experimental results show that the coating bonding strength of Examples 1-4 of the present invention reaches 107-129MPa, while the existing gray cast iron brake disc does not have the requirement of "coating-substrate bonding" (integral casting), and the bonding strength of conventional laser cladding coatings is mostly below 80MPa, which is easy to fall off under braking impact.

[0136] The achievement of high bonding strength relies on two major design aspects: ① At the material level, Fe acts as a metallic binder phase to form a continuous metal network, which forms a metallurgical bond with the aluminum alloy substrate (avoiding the problem of poor bonding between conventional ceramic coatings and metal substrates); ② At the process level, the aluminum alloy substrate is pretreated by "corundum powder sandblasting + high-pressure deionized water rinsing" to remove the surface oxide layer, and nitrogen protection is used during laser cladding to prevent the formation of new alumina, ensuring that there are no inclusions at the interface between the coating and the substrate.

[0137] This advantage solves a key safety hazard of brake discs—when the bonding strength of traditional coatings is insufficient, the coating may peel off during braking, leading to the risk of "instantaneous instability of the brake disc and extended braking distance." The high bonding strength of this invention ensures that the coating remains tightly bonded to the substrate under high-frequency friction and high-temperature impact, meeting the safety requirements of the braking system.

[0138] Test Example 4

[0139] This test example is for the wear rate detection of a 1500m coating, specifically including:

[0140] (1) Sample preparation:

[0141] In the embodiments, the coated aluminum alloy brake discs are processed into "coated friction discs" with a diameter of Φ50mm×10mm (the coating surface is polished to Ra≤0.8μm). The paired friction blocks are made of mainstream brake pad materials on the market (such as semi-metallic brake pads with a size of 15mm×10mm×5mm). Two parallel friction discs are used in each embodiment.

[0142] (2) Equipment debugging:

[0143] The MMW-1 disc friction and wear testing machine was used, and the test parameters were set as follows: friction pressure 0.5MPa (simulating automobile braking load), friction disc rotation speed 1000r / min (sliding linear velocity of about 2.62m / s, close to the braking speed in urban road conditions), and total sliding distance 1500m (calculated by rotation speed × time, about 9.5min). The friction force was recorded in real time during the test.

[0144] (3) Wear measurement:

[0145] Before the test, weigh the friction disk (m1) using an electronic balance with an accuracy of 0.1 mg (such as FA2004). After the test, clean the surface of the friction disk with anhydrous ethanol (to remove wear dust), dry it, and weigh it again to determine the mass loss (m2).

[0146]

[0147] (4) Wear rate calculation:

[0148] According to the formula:

[0149]

[0150] Where ρ is the density of the TiC-Fe-Cr coating, approximately 5.6 g / cm³. 3 F represents the normal load corresponding to the frictional pressure, approximately 19.6 N; L represents the total sliding distance, 1500 m.

[0151] Calculate the wear rate, with units converted to 10. -8 mm 3 / (N m), and finally the average value of two parallel samples was taken as the coating wear rate of the example.

[0152] The experimental results are shown in Table 5 below.

[0153] Experimental results show that the wear rate of the 1500µm coating in Examples 1-4 of this invention is only 6.14-8.08×10⁻⁶. -8 mm 3 / (N·m), is the wear rate of existing gray cast iron brake discs (27.12×10). -8 mm 3 / (N 1 / 3 to 1 / 4 of m)

[0154] Excellent wear resistance stems from the synergistic effect of "high hardness + low porosity + FeCr alloy anti-oxidation": ① The high-hardness TiC skeleton resists friction and wear, reducing coating material loss; ② Low porosity prevents wear particles from entering the coating and aggravating abrasive wear; ③ The FeCr alloy formed by Cr elements improves the coating's high-temperature oxidation resistance (the highest temperature during braking is above 600℃), avoiding "oxidative wear" caused by oxide layer peeling.

[0155] This performance directly solves two major environmental and lifespan problems of gray cast iron brake discs: ① High wear rate leads to short brake disc lifespan and increases user costs; ② High wear generates a large amount of cast iron dust, polluting the environment and harming human health. The coating of this invention has a low wear rate, which not only extends the brake disc replacement cycle but also reduces dust emissions.

[0156] Experimental Example 5

[0157] This test example involves a 120-hour salt spray corrosion test in air, specifically including:

[0158] (1) Sample pretreatment:

[0159] A 50mm×50mm×5mm sample was cut from the coated brake disc. The coating surface was wiped with anhydrous ethanol (to remove oil stains). The edges of the sample were sealed with silicone rubber (to prevent the aluminum alloy substrate from being exposed and corroded, which would interfere with the coating corrosion results). Three parallel samples were taken for each example.

[0160] (2) Salt spray chamber parameter settings:

[0161] Using a salt spray test chamber, prepare a 5% (mass fraction) sodium chloride solution (adjust the pH to 6.5-7.2 with hydrochloric acid), set the test temperature to 35℃, and the salt spray deposition rate to 1.5 mL / (h). 80cm 2 The spraying method is continuous spraying.

[0162] (3) Experimental procedure:

[0163] Place the samples in the salt spray chamber at a 30° angle to the vertical (to ensure uniform salt spray coverage of the coating surface) and avoid mutual obstruction between samples. Spray continuously for 120 hours without interruption.

[0164] (4) Result evaluation:

[0165] After the test, remove the sample and rinse it with running deionized water (25-35℃) for 10 seconds to remove surface salt deposits. Then, dry it with compressed air (0.1MPa). Observe the coating surface according to GB / T1766-2008 "Rating Method for Aging of Paint and Varnish Coatings" to determine whether there are obvious corrosion phenomena such as rust (red iron oxide spots), blistering, and peeling. Record the results.

[0166] The experimental results are shown in Table 5 below.

[0167] The results of the 120-hour salt spray test showed that the coatings of Examples 1-4 of the present invention did not show obvious rust, while the existing gray cast iron brake discs showed obvious rust.

[0168] The corrosion resistance advantage stems from the role of Cr: Cr forms a dense chromium oxide (Cr2O3) protective film on the coating surface, preventing oxygen and moisture in the air from contacting the interior of the coating and the aluminum alloy substrate, and the low porosity prevents corrosive media from penetrating into the coating-substrate interface and causing interfacial corrosion.

[0169] This performance solves a long-standing problem with gray cast iron brake discs—gray cast iron is prone to rusting in humid, salt spray environments, which not only affects the appearance of the car, but also causes "uneven brake disc surface and abnormal braking noise" due to corrosion. The anti-corrosion performance of the coating of this invention ensures that the brake disc maintains its good appearance and stable braking even after long-term use.

[0170] Table 5. Performance test data of the coatings prepared in the various embodiments of the present invention and gray cast iron brake discs currently used in the market:

[0171]

[0172] This invention, through five core performance tests—coating porosity, coating hardness (HV0.3), coating bonding strength, 1500m coating wear rate, and 120 hours of salt spray corrosion in air—compared the TiC-Fe-Cr coatings (aluminum alloy substrate) prepared in Examples 1-4 with the mainstream gray cast iron brake discs of existing technologies. The results fully demonstrate that the embodiments of this invention are comprehensively superior to existing technologies in terms of performance and precisely solve the core technical problems in the field of brake discs. Through customized TiC-Fe-Cr cladding materials and optimized preparation and cladding processes, it not only solves the core technical problem of "lack of dedicated laser cladding materials for aluminum alloy brake discs," but also comprehensively overcomes the technical bottlenecks of traditional gray cast iron brake discs ("heavy weight, rapid wear, dust generation, and easy rusting") and aluminum alloy brake discs ("low hardness and poor wear resistance"), providing a reliable solution for the lightweight, high-performance, and environmentally friendly upgrade of automotive brake discs.

[0173] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing TiC-Fe-Cr coated powder material for automotive brake discs, characterized in that, The coating powder material is obtained by mixing 70-80% TiC powder, 15-30% Fe powder, 4-11% Cr powder, and 0.8-2.2% polyethylene glycol, followed by wet milling, spray drying, pressing, sintering, crushing, and spheroidization densification. The specific steps include: S1. Mixing: Take 70-80% TiC powder, 15-30% Fe powder, 4-11% Cr powder and 0.8-2.2% polyethylene glycol and mix them evenly to prepare a mixture; S2. Wet milling: The mixture is placed in a ball mill and ethanol or deionized water is added as the ball milling medium for wet milling. S3. Spray drying: The wet-milled mixture is introduced into a spray drying tower for spray granulation. S4. Pressing and molding: The dried mixture is pressed into a blank using a powder press; S5. Sintering and crushing: The preform is placed in a vacuum degreasing and sintering furnace to remove the molding agent polyethylene glycol and then sintered. After sintering, an impact crusher is used to crush the material to obtain the crushed material. S6. Spherical densification treatment: The crushed material is melted using a high-temperature vertical tube furnace with plasma, and spherical droplets are formed by surface tension. After cooling, the material is classified by particle size to obtain the coating powder material. The coating powder material is attached to the surface of the brake disc by laser cladding.

2. The method for preparing TiC-Fe-Cr coated powder material for automotive brake discs according to claim 1, characterized in that: In step S2, the ball mill uses TiC-12Fe cemented carbide balls as the grinding balls, with a ball-to-material mass ratio of 2-5:1 and a grinding time of 24-60 hours.

3. The method for preparing TiC-Fe-Cr coated powder material for automotive brake discs according to claim 1, characterized in that: The outlet temperature of the spray drying tower in step S3 is 100-160℃.

4. The method for preparing TiC-Fe-Cr coated powder material for automotive brake discs according to claim 1, characterized in that: The temperature for removing the molding agent polyethylene glycol in step S5 is 300-480℃, the temperature for sintering is 1350-1450℃, and the temperature is maintained at 60-240 min after sintering.

5. The method for preparing TiC-Fe-Cr coated powder material for automotive brake discs according to claim 1, characterized in that: In step S6, the feeding rate inside the plasma high-temperature vertical tube furnace is 40-240 g / min.

6. The method for preparing TiC-Fe-Cr coated powder material for automotive brake discs according to claim 1, characterized in that: The particle size classification in step S6 is performed by using an air classifier to obtain a coating powder material with a size of 10-75 μm.

7. The application of the TiC-Fe-Cr coating powder material for automotive brake discs prepared according to claim 1 on automotive brake discs, characterized in that, The laser power of the laser cladding is 1200-4500W, the scanning speed is 300-600mm / min, the spot diameter is 2-5mm, the powder feeding rate is 15-60g / min, and the overlap rate is 30-50%.

Images