Laser cladding alloy powder for cast steel brake disc and method for synthesizing nickel-based vanadium carbide composite coating

Abstract

The application discloses a laser cladding alloy powder for cast steel brake disc and a method for synthesizing a nickel-based vanadium carbide composite coating, the laser cladding alloy powder comprising A components (Ni powder, coated Ni@C powder and V powder) and B components (TiC powder) in a mass ratio of 100:0.5-2, wherein the carbon content of the coated Ni@C powder in the A components is 0.75-3.75 wt%, the V powder content is 5-15 wt%, and the balance is Ni and inevitable trace impurities. The alloy powder is used to form a cladding coating on the surface of a cast steel brake disc substrate by a laser cladding method. The coating formed by the laser cladding powder is well metallurgically compatible with the cast steel brake disc substrate, the in-situ synthesized small vanadium carbide particles can be uniformly and dispersedly distributed in the formed cladding coating, the wear resistance of the coating is effectively improved, the cladding coating has better toughness and lower crack sensitivity, the service life of the brake disc is improved, and good economic benefits are achieved.

Description

Method for laser cladding alloy powder and synthesizing nickel-based vanadium carbide composite coating for cast steel brake discs Technical Field

[0001] This invention relates to the field of metal matrix composite technology, and more specifically, to a method for laser cladding alloy powder for cast steel brake discs and synthesizing a nickel-based vanadium carbide composite coating on the surface of cast steel brake discs. Background Technology

[0002] In recent years, the construction of rail transit, represented by high-speed rail and urban subways, has made breakthrough progress, fully supporting my country's national strategy of building a strong transportation nation. As of December 31, 2021, the total operating mileage of China's rail transit exceeded 150,000 kilometers, including more than 40,000 kilometers of high-speed rail and more than 8,700 kilometers of urban rail transit, ranking among the world's leading positions. Rail transit not only needs to run fast, but also needs to brake effectively; the braking system is the fundamental guarantee for its safe operation. With the development of railways and urban rail transit towards high speeds, the heat load on brake discs has surged. When the speed of a high-speed train reaches 350 km / h, the surface temperature of the brake disc reaches over 700℃ during emergency braking. The harsh service conditions require brake discs to have high strength, high heat resistance, large specific heat capacity, and excellent comprehensive properties such as thermal conductivity, corrosion resistance, and wear resistance.

[0003] Brake disc materials include cast iron, cast steel, composite materials, and surface-modified new types of brake discs, suitable for rail transit at different speeds. The brake discs used in urban rail transit and ordinary railway trains are mainly made of vermicular graphite cast iron and gray cast iron, with operating speeds generally below 200 km / h. High-speed train brake discs are primarily made of cast steel, possessing high strength and toughness, as well as high resistance to thermal cracking, good wear resistance, and thermal fatigue resistance, with operating speeds generally ranging from 200 to 350 km / h. During high-speed braking, the brake disc surface is subjected to frictional wear and high-temperature thermal fatigue, leading to failure. Therefore, there is an urgent need to effectively repair failed cast steel brake discs or improve their surface properties to extend their service life.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for laser cladding alloy powder for cast steel brake discs and for synthesizing a nickel-based vanadium carbide composite coating on the surface of cast steel brake discs, so as to improve the above-mentioned technical problems.

[0006] This invention is implemented as follows:

[0007] In a first aspect, the present invention provides a laser cladding alloy powder for brake discs, comprising component A and component B in a mass ratio of 100:0.5 to 2. Component A includes Ni powder, coated Ni@C powder, and V powder, wherein the carbon content in the coated Ni@C powder is 0.75% to 3.75% of the mass of component A, and the mass of vanadium powder is 5% to 15% of the mass of component A. The balance of component A is Ni and unavoidable trace impurities. Component B is TiC powder.

[0008] Secondly, the present invention also provides a method for synthesizing a vanadium carbide composite coating, which includes: forming a cladding coating on the surface of a cast steel brake disc substrate by laser cladding alloy powder of the above-mentioned brake disc using a laser cladding method.

[0009] Thirdly, the present invention also provides a cast steel brake disc, which is obtained by forming a cladding coating on the cast steel brake disc substrate using the above-described method for synthesizing vanadium carbide composite coating.

[0010] The present invention has the following beneficial effects: the coating formed by laser cladding of the laser cladding powder composed of components A and B has good metallurgical compatibility with the cast steel brake disc substrate. The vanadium carbide small particles synthesized in situ can be uniformly dispersed in the formed cladding coating, which can effectively improve the wear resistance of the coating. Moreover, the cladding coating has good toughness and low crack sensitivity, so that the cladding coating can effectively repair the surface friction layer of the brake disc and enhance the surface hardness and wear resistance of the cast steel brake disc, thereby improving the service life of the brake disc and having good economic benefits. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 is a schematic diagram of a high-speed train and brake disc components in an embodiment of the present invention: (a) is a high-speed train; (b) is an axle-mounted brake disc; (c) is a wheel-mounted brake disc; (d) is a brake caliper; and (e) is a schematic diagram of the braking process.

[0013] Figure 2 is a schematic diagram of a laser cladding brake disc in an embodiment of the present invention: (a) is a laser cladding system; (b) is a laser cladding pattern on the surface of the brake disc; (c) is a schematic diagram of a laser cladding head.

[0014] Figure 3 shows a comparison of the XRD patterns of the coating surfaces after laser cladding in Example 1 and Comparative Example 1 of the present invention. After calibration, it can be seen that C and V in Example 1 and Comparative Example 1 both react in situ to generate VC. 0.88In addition, Ni is used as a binder phase. When TiC particles are further added in Example 1, TiVC2 is generated in the coating.

[0015] Figure 4 shows the microstructure of the coating after laser cladding in Example 1 of the present invention. In Figure 4, (a), (b), and (c) are SEM morphology images of the dispersed small particle phase at different magnifications, and (d), (e), and (f) are SEM morphology images of the core-shell structure-encapsulated microstructure at different magnifications.

[0016] Figure 5 shows the microstructure of the coating after laser cladding in Comparative Example 1 of the present invention. In Figure 5, (a), (b), and (c) are SEM images of dendritic precipitates at different magnifications, and (d), (e), and (f) are SEM images of dispersed small particle phases at different magnifications.

[0017] Figure 6 is a schematic diagram of the elemental distribution of the coating in Example 1 of the present invention by energy spectrum surface scanning, showing that after the addition of TiC particles, TiVC2 is formed in the coating along the growth of TiC particles, thereby suppressing the formation of dendrites.

[0018] Figure 7 is a schematic diagram of the energy spectrum surface scan elemental distribution of the coating in Comparative Example 1 of the present invention. In the coating without TiC particles, the generated VC 0.88 It exhibits a dendritic morphology;

[0019] Figure 8 shows the elemental distribution around TiC particles obtained by transmission electron microscopy (HADDF) mode of the coating of Example 1 of the present invention, confirming the presence and distribution characteristics of Ni, Fe, V, Ti and C elements.

[0020] Figure 9 shows the crystal structure and diffraction pattern of the coating of Example 1 of the present invention obtained by transmission electron microscopy in HADDF mode, which confirms the formation of Ni binder phase and TiVC2 phase, and that there is no obvious orientation relationship at the interface. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0022] The following is a detailed description of the method for synthesizing nickel-based vanadium carbide composite coatings for cast steel brake discs using nickel-based laser cladding alloy powder and in-situ synthesis of nickel-based vanadium carbide composite coatings provided by the present invention.

[0023] Through research, the inventors discovered that since friction, high temperature, and thermal fatigue are mainly concentrated on and near the surface of brake discs, surface treatment can be used to repair or enhance the performance of cast steel brake discs. Laser cladding has advantages such as concentrated energy density, low coating dilution rate, high coating-substrate bonding strength, and small heat-affected zone, making it suitable for surface strengthening and remanufacturing of cast steel brake discs. Laser cladding materials mainly include nickel-based, iron-based, and cobalt-based alloy powders. Different material compositions have different properties, and selecting laser cladding alloy powders that match the base material of the cast steel brake disc is key to achieving brake disc repair or performance enhancement. Based on this, the inventors proposed the following technical solution after extensive research and practice.

[0024] Some embodiments of the present invention provide a laser cladding alloy powder for brake discs, comprising component A and component B in a mass ratio of 100:0.5 to 2. Component A includes Ni powder, coated Ni@C powder, and V powder, wherein the content of coated Ni@C powder is 5% to 15% of the mass of component A, and the mass of V powder is 5% to 15% of the mass of component A. The balance of component A is Ni and unavoidable trace impurities. Component B is TiC powder.

[0025] Since friction, high temperature, and thermal fatigue are mainly concentrated on and near the surface of the brake disc, laser cladding technology can extend the service life of the brake disc surface and enable repair and reuse. Laser cladding has the advantages of concentrated energy density, low coating dilution rate, high coating-substrate bonding strength, and small heat-affected zone. For rail transit with speeds of 350 km / h and below, processing the surface of failed brake discs to eliminate defects, and then laser cladding with materials compatible with the steel substrate, allows for the repair and remanufacturing of brake discs, extending their service life and reducing operating costs. Nickel has good wettability with the steel substrate and good self-fluxing properties; therefore, nickel-based powder is the most widely used laser cladding material. Nickel-coated graphite powder (i.e., coated Ni@C powder) has a typical core-shell structure, with the graphite surface coated with approximately 1 μm of Ni powder. This effectively avoids powder agglomeration and unevenness caused by the large density difference between graphite and other metal powders, and promotes the uniform distribution of the in-situ synthesized vanadium carbide ceramic phase in the coating.

[0026] The significant differences in thermophysical properties between the added carbide ceramic phase (such as WC, TiC, Cr3C2, etc.) and the matrix metal can easily lead to low interfacial bonding strength, decreased toughness, and easy cracking of the coating. Laser cladding in-situ synthesis involves a chemical reaction between different elements or compounds under laser irradiation, forming ceramic particles or intermetallic compounds on the surface of the metal matrix, thereby strengthening the matrix. In the above scheme, coated Ni@C powder and V powder can generate VC in-situ under laser conditions. The selection of coated Ni@C powder avoids the problem of uneven distribution of C powder during laser cladding, which can affect coating quality due to its relatively light weight. Simultaneously, because TiC and VC have similar lattice parameters, a small amount of TiC powder can act as a heterogeneous nucleation substrate phase, promoting the formation and dispersion of VC, inhibiting the formation of brittle dendrites, and improving the plasticity and toughness of the coating. The alloy formed by laser cladding of this laser cladding powder has good metallurgical compatibility with the cast steel brake disc substrate. The vanadium carbide particles synthesized in situ can be uniformly dispersed in the formed cladding coating, which effectively improves the wear resistance of the coating. In addition, the cladding coating has good toughness and low crack sensitivity, which enables the cladding coating to effectively repair the surface friction layer of the brake disc and enhance the surface hardness and wear resistance of the cast steel brake disc.

[0027] Specifically, in some embodiments, in order to achieve better in-situ reaction results, the mass ratio of Ni to C in the coated Ni@C powder is 75:25, and the coated Ni@C powder is commercially available coated Ni@C powder with a purity of 99%.

[0028] For reference, both vanadium powder and TiC powder are commercially available, and both have a purity of 99.9%.

[0029] Furthermore, in some embodiments, in order to ensure uniform mixing among the components, the particle size of the coated Ni@C powder, vanadium powder, and TiC powder is 50 μm to 150 μm.

[0030] In some embodiments, in order to improve the overall performance of the alloy coating formed by laser cladding of alloy powder, the A component is optimized, that is, the carbon content in the coated Ni@C powder is 2.5% to 3.75% of the mass of the A component, such as 2.5%, 2.75%, 3%, 3.25%, 3.5% or 3.75%, and the mass of the V powder is 10% to 15% of the mass of the A component, such as 10%, 11%, 12%, 13%, 14% or 15%.

[0031] Furthermore, some embodiments of the present invention also provide a method for synthesizing a nickel-based vanadium carbide composite coating, which includes: forming a cladding coating on the surface of a cast steel brake disc substrate by laser cladding alloy powder of the above-mentioned brake disc using a laser cladding method.

[0032] It should be noted that the above methods can be used to repair and remanufacture used cast steel brake discs for reuse. Alternatively, a coating can be directly applied to the surface of a new cast steel brake disc to enhance its surface properties. Both methods can extend the service life of the cast steel brake disc. The cast steel brake disc targeted in this embodiment of the invention is shown in Figure 1, which is a brake disc for high-speed trains. The axle-mounted brake disc, wheel-mounted brake disc, brake caliper, and braking process are all shown in Figure 1.

[0033] Specifically, in some embodiments, the process parameters for laser cladding are as follows: the cast steel brake disc substrate is preheated to 180℃~220℃, for example, 200℃, before laser cladding; the laser power is 2.5~4kW, for example, 3kW; during the cladding process, the brake disc rotates with the rotary table; the actual cladding speed is 8mm / s~25mm / s; the overlap rate is 38~42%, for example, 40%; and the laser spot diameter is: For example, The powder is fed in a coaxial manner with a feeding rate of 13g / min to 50g / min, for example, 25g / min, and an argon flow rate of 20L / min to 30L / min, for example, 25L / min.

[0034] For reference, the final thickness of the cladding coating is controlled to be 2.5–3 mm during the laser cladding process.

[0035] In some embodiments, the material of the cast steel brake disc substrate is 24CrNiMo cast steel. For example, the chemical composition of this cast steel brake disc substrate is: C: 0.24%, Cr: 1.12%, Mn: 0.65%, Ni: 1.0%, Si: 0.12%, Mo: 0.49%, Fe: balance. The alloy formed by laser cladding of the above-mentioned laser cladding alloy powder has good compatibility with the cast steel brake disc substrate of this material, and its bonding performance is excellent.

[0036] In some embodiments, referring to Figure 2, laser cladding is performed using the laser cladding system and laser cladding operation shown in Figure 2. When surface repair of waste cast steel brake discs to synthesize a vanadium carbide composite coating, the specific operation steps are as follows:

[0037] (1) The surface morphology and cracks of the waste 24CrNiMo brake disc were inspected, and the repairability of the waste brake disc was determined by liquid dye penetrant testing.

[0038] (2) The repairable brake disc is surface machined to remove surface defects and wear marks. The surface roughness after machining is Ra1.6 and the surface flatness is ±0.2mm.

[0039] (3) Remove oil and impurities from the surface of the machined brake disc with alcohol, and prepare a nickel-based vanadium carbide composite coating with a thickness of 2.5-3 mm by laser cladding.

[0040] (4) After the nickel-based composite coating brake disc is obtained after cladding, it is kept at 180℃~220℃ (e.g. 200℃) for 3~5h (e.g. 4h) and then cooled to room temperature with the furnace.

[0041] (5) After the cladding is completed, the coated brake disc is surface machined to ensure that the surface roughness after turning is Ra0.8.

[0042] (6) The coated brake disc obtained after cladding is subjected to flaw detection, including penetrant staining, magnetic particle and ultrasonic testing according to the relevant standards.

[0043] Some embodiments of the present invention also provide a cast steel brake disc, which is obtained by forming a cladding coating on the cast steel brake disc substrate using the above-described method for synthesizing a vanadium carbide composite coating.

[0044] In some embodiments, after the cast steel brake disc substrate is coated with the above alloy coating, the average hardness of the cast steel brake disc surface is greater than 370 HV, and the wear volume is less than 2900 mm². 3 Impact toughness greater than 28 J / cm 2 .

[0045] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0046] In the following examples and comparative examples, commercial Ni powder, coated Ni@C powder, commercial V powder, and commercial TiC powder were purchased from Changsha Tianjiu Metal Materials Co., Ltd. The cast steel brake disc substrate is made of 24CrNiMo, with the following chemical composition: C: 0.24%, Cr: 1.12%, Mn: 0.65%, Ni: 1.0%, Si: 0.12%, Mo: 0.49%, Fe: balance. It is a wheel-mounted or axle-mounted brake disc for high-speed trains.

[0047] Example 1

[0048] This embodiment provides a laser cladding alloy powder for brake discs, and a method for synthesizing a nickel-based vanadium carbide composite coating on the surface of a cast steel brake disc substrate using the laser cladding alloy powder for brake discs.

[0049] Specifically, the laser-clad alloy powder for the brake disc comprises component A and component B. Component A includes commercial Ni powder, commercial coated Ni@C powder (99% purity) in a mass ratio of 75:25, and commercial V powder (99.9% purity). The amount of coated Ni@C powder added is 15% by mass, the amount of commercial V powder added is 15% by mass, and the balance is Ni and unavoidable trace impurities. The powder particle size is 50–150 micrometers. Component B is commercial TiC powder with a purity of 99.9% and a particle size of 50–150 micrometers. Component B is added to the powder of component A at a mass percentage of 1.0%, and the mixture is obtained by mixing for 4 hours using a dual-motion mixer.

[0050] The steps for synthesizing a vanadium carbide composite coating on the surface of a cast steel brake disc substrate are as follows:

[0051] (1) The surface morphology and cracks of the waste 24CrNiMo brake disc were inspected, and the repairability of the waste brake disc was determined by liquid dye penetrant testing.

[0052] (2) The repairable brake disc is surface machined to remove surface defects and wear marks. The surface roughness after machining is Ra1.6 and the surface flatness is ±0.2mm.

[0053] (3) After machining, the surface of the brake disc is cleaned of oil and impurities with alcohol. A 2.8mm thick coating is then applied to its surface using laser cladding. The cladding process is as follows: the brake disc substrate is preheated to 200℃ before laser cladding, the laser power is 3.5kW, the brake disc rotates with the rotary table during the cladding process, the actual cladding speed is 15mm / s, the overlap rate is 40%, and the laser spot diameter is: The powder is fed in a coaxial manner with a powder feeding rate of 40 g / min and an argon flow rate of 25 L / min.

[0054] (4) After the nickel-based composite coating brake disc is obtained after cladding, it is kept in a furnace at 200°C for 4 hours and then cooled to room temperature with the furnace.

[0055] (5) After the cladding is completed, the coated brake disc is surface machined to ensure that the surface roughness after turning is Ra0.8.

[0056] (6) The coated brake disc obtained after cladding is subjected to flaw detection, including penetrant staining, magnetic particle and ultrasonic testing according to the relevant standards.

[0057] Example 2

[0058] This embodiment provides a laser cladding alloy powder for brake discs, and a method for synthesizing a nickel-based vanadium carbide composite coating on the surface of a cast steel brake disc substrate using the laser cladding alloy powder for brake discs.

[0059] Specifically, the laser-clad alloy powder for the brake disc comprises component A and component B. Component A includes commercial Ni powder, commercial coated Ni@C powder (99% purity) in a mass ratio of 75:25, and commercial V powder (99.9% purity). The coated Ni@C powder is added at a mass percentage of 10%, the commercial V powder at a mass percentage of 15%, and the balance is Ni and unavoidable trace impurities. The powder particle size is 50–150 micrometers. Component B is commercial TiC powder with a purity of 99.9% and a particle size of 50–150 micrometers. Component B is added to the powder of component A at a mass percentage of 0.5%, and the mixture is blended for 4 hours using a dual-motion mixer to obtain a mixed powder.

[0060] The steps for synthesizing a vanadium carbide composite coating on the surface of a cast steel brake disc substrate are as follows:

[0061] (1) The surface morphology and cracks of the waste 24CrNiMo brake disc were inspected, and the repairability of the waste brake disc was determined by liquid dye penetrant testing.

[0062] (2) The repairable brake disc is surface machined to remove surface defects and wear marks. The surface roughness after machining is Ra1.6 and the surface flatness is ±0.2mm.

[0063] (3) After machining, the surface of the brake disc is cleaned of oil and impurities with alcohol. A cladding coating with a thickness of 2.8 mm is then prepared on its surface by laser cladding. The cladding process is as follows: the brake disc substrate is preheated to 200℃ before laser cladding, the laser power is 3.5kW, the brake disc rotates with the rotary table during the cladding process, the actual cladding speed is 15mm / s, the overlap rate is 40%, and the laser spot diameter is: The powder is fed in a coaxial manner with a powder feeding rate of 40 g / min and an argon flow rate of 25 L / min.

[0064] (4) After the nickel-based composite coating brake disc is obtained after cladding, it is kept in a furnace at 200°C for 4 hours and then cooled to room temperature with the furnace.

[0065] (5) After the cladding is completed, the coated brake disc is surface machined to ensure that the surface roughness after turning is Ra0.8.

[0066] (6) The coated brake disc obtained after cladding is subjected to flaw detection, including penetrant staining, magnetic particle and ultrasonic testing according to the relevant standards.

[0067] Example 3

[0068] This embodiment provides a laser cladding alloy powder for brake discs, and a method for synthesizing a nickel-based vanadium carbide composite coating on the surface of a cast steel brake disc substrate using the laser cladding alloy powder for brake discs.

[0069] Specifically, the laser-clad alloy powder for the brake disc comprises component A and component B. Component A includes commercial Ni powder, commercial coated Ni@C powder (99% purity) in a mass ratio of 75:25, and commercial V powder (99.9% purity). The coated Ni@C powder is added at a mass percentage of 15%, the commercial vanadium powder is added at a mass percentage of 10%, and the balance is Ni and unavoidable trace impurities. The powder particle size is 50–150 micrometers. Component B is commercial TiC powder with a purity of 99.9% and a particle size of 50–150 micrometers. Component B is added to the powder of component A at a mass percentage of 2%, and the mixture is obtained by mixing for 4 hours using a dual-motion mixer.

[0070] The steps for synthesizing a vanadium carbide composite coating on the surface of a cast steel brake disc substrate are as follows:

[0071] (1) The surface morphology and cracks of the waste 24CrNiMo brake disc were inspected, and the repairability of the waste brake disc was determined by liquid dye penetrant testing.

[0072] (2) The repairable brake disc is surface machined to remove surface defects and wear marks. The surface roughness after machining is Ra1.6 and the surface flatness is ±0.2mm.

[0073] (3) After machining, the surface of the brake disc is cleaned of oil and impurities with alcohol. A cladding coating with a thickness of 2.8 mm is then prepared on its surface by laser cladding. The cladding process is as follows: the brake disc substrate is preheated to 200℃ before laser cladding, the laser power is 3.5kW, the brake disc rotates with the rotary table during the cladding process, the actual cladding speed is 15mm / s, the overlap rate is 40%, and the laser spot diameter is: The powder is fed in a coaxial manner with a powder feeding rate of 40 g / min and an argon flow rate of 25 L / min.

[0074] (4) After the nickel-based composite coating brake disc is obtained after cladding, it is kept in a furnace at 200°C for 4 hours and then cooled to room temperature with the furnace.

[0075] (5) After the cladding is completed, the coated brake disc is surface machined to ensure that the surface roughness after turning is Ra0.8.

[0076] (6) The coated brake disc obtained after cladding is subjected to flaw detection, including penetrant staining, magnetic particle and ultrasonic testing according to the relevant standards.

[0077] Example 4

[0078] This embodiment provides a laser cladding alloy powder for brake discs, and a method for synthesizing a nickel-based vanadium carbide composite coating on the surface of a cast steel brake disc substrate using the laser cladding alloy powder for brake discs.

[0079] Specifically, the laser-clad alloy powder for the brake disc comprises component A and component B. Component A includes commercial Ni powder, commercial coated Ni@C powder (99% purity) in a mass ratio of 75:25, and commercial V powder (99.9% purity). The coated Ni@C powder is added at 5% by mass, the commercial vanadium powder is added at 5% by mass, and the balance is Ni and unavoidable trace impurities. The powder particle size is 50–150 micrometers. Component B is commercial TiC powder with a purity of 99.9% and a particle size of 50–150 micrometers. Component B is added to the powder of component A at a mass percentage of 1%, and the mixture is blended for 4 hours using a dual-motion mixer to obtain a mixed powder.

[0080] The steps for synthesizing a vanadium carbide composite coating on the surface of a cast steel brake disc substrate are as follows:

[0081] (1) The surface morphology and cracks of the waste 24CrNiMo brake disc were inspected, and the repairability of the waste brake disc was determined by liquid dye penetrant testing.

[0082] (2) The repairable brake disc is surface machined to remove surface defects and wear marks. The surface roughness after machining is Ra1.6 and the surface flatness is ±0.2mm.

[0083] (3) After machining, the surface of the brake disc is cleaned of oil and impurities with alcohol. A cladding coating with a thickness of 2.8 mm is then prepared on its surface by laser cladding. The cladding process is as follows: the brake disc substrate is preheated to 200℃ before laser cladding, the laser power is 3.5kW, the brake disc rotates with the rotary table during the cladding process, the actual cladding speed is 15mm / s, the overlap rate is 40%, and the laser spot diameter is: The powder is fed in a coaxial manner with a powder feeding rate of 40 g / min and an argon flow rate of 25 L / min.

[0084] (4) After the nickel-based composite coating brake disc is obtained after cladding, it is kept in a furnace at 200°C for 4 hours and then cooled to room temperature with the furnace.

[0085] (5) After the cladding is completed, the coated brake disc is surface machined to ensure that the surface roughness after turning is Ra0.8.

[0086] (6) The coated brake disc obtained after cladding is subjected to flaw detection, including penetrant staining, magnetic particle and ultrasonic testing according to the relevant standards.

[0087] Comparative Example 1

[0088] This comparative example provides a cast steel brake disc made of 24CrNiMo, with the following chemical composition: C: 0.24%, Cr: 1.12%, Mn: 0.65%, Ni: 1.0%, Si: 0.12%, Mo: 0.49%, Fe: balance.

[0089] Comparative Example 2

[0090] This embodiment provides a laser cladding alloy powder for brake discs, and a method for synthesizing a nickel-based vanadium carbide composite coating on the surface of a cast steel brake disc substrate using the laser cladding alloy powder for brake discs.

[0091] The laser cladding alloy powder for the brake disc contains commercial Ni powder, commercial coated Ni@C powder (99% purity) in a mass ratio of 75:25, and commercial V powder (99.9% purity). The Ni@C powder is added at a mass percentage of 15%, the commercial V powder is added at a mass percentage of 15%, and the balance is Ni and unavoidable trace impurities. The powder particle size is 50-150 micrometers. The two components are mixed in a dual-motion mixer for 4 hours to obtain a mixed powder.

[0092] The steps for synthesizing a vanadium carbide composite coating on the surface of a cast steel brake disc substrate are as follows:

[0093] (1) The surface morphology and cracks of the waste 24CrNiMo brake disc were inspected, and the repairability of the waste brake disc was determined by liquid dye penetrant testing.

[0094] (2) The repairable brake disc is surface machined to remove surface defects and wear marks. The surface roughness after machining is Ra1.6 and the surface flatness is ±0.2mm.

[0095] (3) After machining, the surface of the brake disc is cleaned of oil and impurities with alcohol. A 2.5mm thick cladding coating is then prepared on its surface by laser cladding. The cladding process is as follows: the brake disc substrate is preheated to 200℃ before laser cladding, the laser power is 3.5kW, the brake disc rotates with the rotary table during the cladding process, the actual cladding speed is 15mm / s, the overlap rate is 40%, and the laser spot diameter is: The powder is fed in a coaxial manner with a powder feeding rate of 40 g / min and an argon flow rate of 25 L / min.

[0096] (4) After the nickel-based composite coating brake disc is obtained after cladding, it is kept in a furnace at 200°C for 4 hours and then cooled to room temperature with the furnace.

[0097] (5) After the cladding is completed, the coated brake disc is surface machined to ensure that the surface roughness after turning is Ra0.8.

[0098] (6) The coated brake disc obtained after cladding is subjected to flaw detection, including penetrant staining, magnetic particle and ultrasonic testing according to the relevant standards.

[0099] Comparative Example 3

[0100] This embodiment provides a laser cladding alloy powder for brake discs, and a method for synthesizing a nickel-based vanadium carbide composite coating on the surface of a cast steel brake disc substrate using the laser cladding alloy powder for brake discs.

[0101] The laser cladding alloy powder for the brake disc contains commercial Ni powder, commercial coated Ni@C powder (99% purity) in a mass ratio of 75:25, and commercial V powder (99.9% purity). The Ni@C powder is added at a mass percentage of 3%, the commercial V powder is added at a mass percentage of 5%, and the balance is Ni and unavoidable trace impurities. The powder particle size is 50-150 micrometers. The two components are mixed in a dual-motion mixer for 4 hours to obtain a mixed powder.

[0102] The steps for synthesizing a vanadium carbide composite coating on the surface of a cast steel brake disc substrate are as follows:

[0103] (1) The surface morphology and cracks of the waste 24CrNiMo brake disc were inspected, and the repairability of the waste brake disc was determined by liquid dye penetrant testing.

[0104] (2) The repairable brake disc is surface machined to remove surface defects and wear marks. The surface roughness after machining is Ra1.6 and the surface flatness is ±0.2mm.

[0105] (3) After machining, the surface of the brake disc is cleaned of oil and impurities with alcohol. A 3mm thick cladding coating is then prepared on its surface by laser cladding. The cladding process is as follows: the brake disc substrate is preheated to 200℃ before laser cladding, the laser power is 2.5kW, the brake disc rotates with the rotary table during the cladding process, the actual cladding speed is 25mm / s, the overlap rate is 40%, and the laser spot diameter is: The powder is fed in a coaxial manner with a powder feeding rate of 20 g / min and an argon flow rate of 25 L / min.

[0106] (4) After the nickel-based composite coating brake disc is obtained after cladding, it is kept in a furnace at 200°C for 4 hours and then cooled to room temperature with the furnace.

[0107] (5) After the cladding is completed, the coated brake disc is surface machined to ensure that the surface roughness after turning is Ra0.8.

[0108] (6) The coated brake disc obtained after cladding is subjected to flaw detection, including penetrant staining, magnetic particle and ultrasonic testing according to the relevant standards.

[0109] Comparative Example 4

[0110] This embodiment provides a laser cladding alloy powder for brake discs, and a method for synthesizing a nickel-based vanadium carbide composite coating on the surface of a cast steel brake disc substrate using the laser cladding alloy powder for brake discs.

[0111] The laser cladding alloy powder for the brake disc contains commercial Ni powder, commercial coated Ni@C powder (99% purity) in a mass ratio of 75:25, and commercial vanadium powder (99.9% purity). The Ni@C powder is added at 7% by mass, the commercial vanadium powder is added at 10% by mass, and the balance is Ni and unavoidable trace impurities. The powder particle size is 50-150 micrometers. The two components are mixed in a dual-motion mixer for 4 hours to obtain a mixed powder.

[0112] The steps for synthesizing a vanadium carbide composite coating on the surface of a cast steel brake disc substrate are as follows:

[0113] (1) The surface morphology and cracks of the waste 24CrNiMo brake disc were inspected, and the repairability of the waste brake disc was determined by liquid dye penetrant testing.

[0114] (2) The repairable brake disc is surface machined to remove surface defects and wear marks. The surface roughness after machining is Ra1.6 and the surface flatness is ±0.2mm.

[0115] (3) After machining, the surface of the brake disc is cleaned of oil and impurities with alcohol. A cladding coating with a thickness of 3 mm is then prepared on its surface by laser cladding. The cladding process is as follows: the brake disc substrate is preheated to 200℃ before laser cladding, the laser power is 4kW, the brake disc rotates with the rotary table during the cladding process, the actual cladding speed is 10mm / s, the overlap rate is 40%, and the laser spot diameter is: The powder is fed in a coaxial manner with a powder feeding rate of 50 g / min and an argon flow rate of 25 L / min.

[0116] (4) After the nickel-based composite coating brake disc is obtained after cladding, it is kept in a furnace at 200°C for 4 hours and then cooled to room temperature with the furnace.

[0117] (5) After the cladding is completed, the coated brake disc is surface machined to ensure that the roughness after turning is Ra0.8.

[0118] (6) The coated brake disc obtained after cladding is subjected to flaw detection, including penetrant staining, magnetic particle and ultrasonic testing according to the relevant standards.

[0119] Test case

[0120] XRD analysis was performed on the coatings formed after laser cladding in Example 1 and Comparative Example 1, and the results are shown in Figure 3. After calibration, it can be seen that C and V in Example 1 and Comparative Example 1 reacted in situ to form VC. 0.88 In addition, Ni serves as a binder phase. When TiC particles were further added in Example 1, TiVC2 was generated in the coating. Microstructure analysis was performed on the coatings of Example 1 and Comparative Example 1, and their microstructure images are shown in Figures 4 and 5. In Figure 4, (a), (b), and (c) are SEM images of the dispersed small particle phase at different magnifications, and (d), (e), and (f) are SEM images of the core-shell structure-encapsulated microstructure at different magnifications. In Figure 5, (a), (b), and (c) are SEM images of the dendritic precipitate phase at different magnifications, and (d), (e), and (f) are SEM images of the dispersed small particle phase at different magnifications. The comparison revealed that the addition of TiC promoted the in-situ generation of TiVC2 in the coating along the growth morphology of the TiC particles, thereby inhibiting the formation of dendrites and enhancing the plasticity and toughness of the coating.

[0121] Energy dispersive spectroscopy (EDS) elemental analysis was performed on the coatings of Example 1 and Comparative Example 1. The schematic diagrams of their EDS elemental distribution are shown in Figures 6 and 7, respectively. Figure 6 shows that the main elements included are Ni, Ti, V, and C. Figure 7 shows that the main elements included are Ni, V, Fe, and C. This indicates that the addition of TiC particles altered the microstructure morphology of TiVC2, thereby suppressing dendrite formation and resulting in a dispersed distribution of the reinforcing phase in the coating.

[0122] Transmission electron microscopy (TEM) observation of Example 1 shows the elemental distribution around the TiC particles obtained in HADDF mode in Example 1 of this invention. It can be seen that the distributions of Ni and Fe elements overlap, as do the distributions of V, Ti, and C elements, confirming the presence and distribution characteristics of Ni, Fe, V, Ti, and C elements. Figure 9 shows the crystal structure and diffraction pattern obtained in HRTEM mode in Example 1 of this invention. After calibration, it is shown that (a), (b), and (c) in Figure 9 are TiVC2, and (d), (e), and (f) are Ni. This confirms the formation of the Ni binder phase and the TiVC2 phase, and there is no obvious orientation relationship at the interface.

[0123] For Examples 1-4 and Comparative Examples 1-4, the average hardness was tested according to GB / T 4340.1-2009 "Metallic materials - Vickers hardness test - Part 1: Test method", the impact toughness was tested according to GB / T229-2020 "Metallic materials - Charpy pendulum impact test method", and the friction coefficient and wear resistance were tested according to T / CSTM 00646.1-2021 "Metallic materials - Pin-disc friction and wear test - Part 1: Room temperature friction and wear test method". Penetrant testing, ultrasonic testing, and magnetic particle testing were performed according to JB / T 9218-2015 "Non-destructive testing - Penetrant testing method", GB / T 72331-2009 "Ultrasonic testing of cast steel parts - Part 1: General purpose cast steel parts", and GB / T15822.1-2005 "Non-destructive testing - Magnetic particle testing - Part 1: General rules". The test results and flaw detection results are shown in Table 1.

[0124] Table 1

[0125]

[0126] In summary, the nickel-based alloy formed by laser cladding of the brake disc using laser cladding alloy powder in this embodiment of the invention exhibits good metallurgical compatibility with the 24CrNiMo steel substrate, as well as better toughness and low crack sensitivity. The in-situ synthesized VC particles are dispersed in the coating, effectively improving the wear resistance of the coating. The in-situ preparation of a nickel-based vanadium carbide composite coating on the surface of the brake disc through laser cladding can effectively repair the surface friction layer of the brake disc and extend its service life.

[0127] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A laser-clad alloy powder for cast steel brake discs, characterized in that, It comprises component A and component B in a mass ratio of 100:0.5~2. Component A includes Ni powder, coated Ni@C powder, and V powder. The carbon content in the coated Ni@C powder is 0.75%~3.75% of the mass of component A, and the mass of the V powder is 5%~15% of the mass of component A. The balance of component A is Ni and unavoidable trace impurities. Component B is TiC powder. The mass ratio of Ni to C in the coated Ni@C powder is 55~80:45~20. The particle size of the coated Ni@C powder, the V powder, and the TiC powder are all 50μm~150μm.

2. The laser-clad alloy powder for brake discs according to claim 1, characterized in that, The carbon content in the coated Ni@C powder is 2.5% to 3.75% of the mass of component A, and the mass of the V powder is 10% to 15% of the mass of component A.

3. A method for synthesizing a nickel-based vanadium carbide composite coating, characterized in that, It includes: The laser cladding alloy powder for cast steel brake discs as described in claim 1 or 2 is used to form a cladding coating on the surface of the cast steel brake disc substrate by laser cladding.

4. The method for synthesizing a nickel-based vanadium carbide composite coating according to claim 3, characterized in that, The laser cladding process parameters are as follows: the cast steel brake disc substrate is preheated to 180℃~220℃ before laser cladding, the laser power is 2.5~4kW, the brake disc rotates with the rotary table during the cladding process, the actual cladding speed is 8mm / s~25mm / s, the overlap rate is 38~42%, the laser spot diameter is φ9~11mm, the coaxial powder feeding method is adopted, the powder feeding rate is 13g / min~50g / min, and the argon flow rate is 20 L / min~30L / min.

5. The method for synthesizing a nickel-based vanadium carbide composite coating according to claim 3, characterized in that, The thickness of the cladding coating is controlled to be 2.5~3mm.

6. The method for synthesizing a nickel-based vanadium carbide composite coating according to any one of claims 3 to 5, characterized in that, The cast steel brake disc with cladding coating obtained after laser cladding is heat-treated at 180℃~220℃ for 3~5h and then cooled to room temperature in the furnace; and / or, the base of the cast steel brake disc is a scrap cast steel brake disc, and before laser cladding, surface defects and wear marks are removed, and the surface is machined to a surface roughness of Ra1.5~Ra1.7 and a surface flatness of ±0.2mm; and / or, the cast steel brake disc with cladding coating after laser cladding is subjected to surface machining and machined to a surface roughness of Ra0.7~Ra0.

9.

7. The method for synthesizing a nickel-based vanadium carbide composite coating according to any one of claims 3 to 5, characterized in that, The base material of the cast steel brake disc is 24CrNiMo cast steel.

8. A cast steel brake disc, characterized in that, It is obtained by forming a cladding coating on a cast steel brake disc substrate using the method for synthesizing a nickel-based vanadium carbide composite coating as described in any one of claims 3 to 7.

9. The cast steel brake disc according to claim 8, characterized in that, The average surface hardness is greater than 370 HV, and the wear volume is less than 2900 mm². 3 Impact toughness greater than 28 J / cm 2 .

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