CN115058627B

CN115058627B - Preparation method of laser cladding Co-based coating for high-speed train brake disc

Info

Publication number: CN115058627B
Application number: CN202210768603.0A
Authority: CN
Inventors: 陈辉; 胡登文; 刘艳; 吴影; 张振林; 李海舟; 赵永胜; 刘晋
Original assignee: Southwest Jiaotong University
Current assignee: Southwest Jiaotong University
Priority date: 2022-06-30
Filing date: 2022-06-30
Publication date: 2023-03-17
Anticipated expiration: 2042-06-30
Also published as: CN115058627A

Abstract

The invention discloses a preparation method of a Co-based coating for laser cladding of a brake disc of a high-speed train, wherein the Co-based composite alloy powder for the coating comprises a component A and a component B, and the mass ratio of the component A to the component B is 100:0.5 to 1.5; the component A comprises C in percentage by mass: 0.45 to 0.60%, cr:20 to 24%, si:0.8 to 1.2%, fe:3.0 to 4.0%, mo:2.5 to 4.3 percent, and the balance of Co and inevitable trace impurities; the component B is TiN coated Ni core-shell structure nano alloy powder, and the mass percentage of TiN in the component B is 4-6%. The composite alloy powder can be used as laser cladding powder of a brake disc of a high-speed train, and a formed laser cladding layer has the advantages of good high-temperature resistance, excellent thermal fatigue resistance and oxidation resistance, low crack sensitivity, good compatibility with a matrix of a cast steel brake disc, outstanding comprehensive toughness and capability of meeting the harsh requirement of the service of the brake disc.

Description

Preparation method of laser cladding Co-based coating for high-speed train brake disc

Technical Field

The invention relates to the technical field of alloy materials, in particular to Co-based composite alloy powder and a preparation method of a laser cladding Co-based coating of a high-speed train brake disc.

Background

The brake system is a core component for safe operation of the high-speed train, and the disc brake is the last defense line for safe operation of the high-speed train. With the rapid development of high-speed trains, the demand for brake discs is also becoming huge. The brake disc material of the high-speed rail motor train unit is mainly 24CrNiMo cast steel and comprises 0.24% of C, 1.12% of Cr, 0.65% of Mn, 1.0% of Ni, 0.12% of Si, 0.49% of Mo and the balance of Fe.

The existing cast steel brake disc has higher strength and toughness, higher thermal cracking resistance, good wear resistance and thermal fatigue resistance, and the using speed is generally 200-350 km/h. But for high-speed trains with the speed of more than 400km/h, the temperature rise of the disc surface approaches 1000 ℃ during braking, the brake disc is required to have high strength, high heat resistance, large heat capacity, excellent heat conduction, corrosion resistance, wear resistance and other comprehensive properties, and the existing cast steel brake disc does not meet the application requirements. The brake disc after abrasion is repaired by laser cladding aiming at huge brake disc consumption of 200-350 km/h, so that the service life of the brake disc can be effectively prolonged; aiming at the operation requirement of a high-performance brake disc of 400km/h, a coating material which can resist high temperature, has large heat capacity and high toughness and is formed by laser cladding on the surface of the brake disc is urgently needed so as to meet the operation requirement of a high-speed train with higher speed.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

The invention aims to provide Co-based composite alloy powder and a preparation method of a laser cladding Co-based coating of a high-speed train brake disc thereof, so as to improve the technical problem.

The invention is realized by the following steps:

in a first aspect, the invention provides a Co-based composite alloy powder, which comprises a component a and a component B, wherein the mass ratio of the component a to the component B is 100:0.5 to 1.5; the component A comprises C in percentage by mass: 0.45-0.60%, cr:20 to 24%, si:0.8 to 1.2%, fe:3.0 to 4.0%, mo:2.5 to 4.3 percent of Co and inevitable trace impurities as the rest; the component B is core-shell structure nano alloy powder of TiN coated Ni, and the mass percent of TiN in the core-shell structure nano alloy powder is 4-6%.

In a second aspect, the present invention also provides a method for preparing the above Co-based composite alloy powder, comprising: and mixing the components A and B according to the element composition and proportion to obtain the Co-based composite alloy powder.

In a third aspect, the invention also provides application of the Co-based composite alloy powder in preparing a surface coating of a high-speed train cast steel brake disc, and optionally, the material of a steel matrix of the high-speed train cast steel brake disc is 24CrNiMo.

In a fourth aspect, the invention also provides a cast steel brake disc for a high-speed train, which comprises a brake disc steel matrix and a laser cladding layer on the surface of the steel matrix, wherein the cladding raw material of the laser cladding layer is the Co-based composite alloy powder.

Optionally, the material of the brake disc steel substrate is 24CrNiMo; the thickness of the laser cladding layer is 2-4 mm.

Optionally, the laser cladding layer is composed of a plurality of laser cladding layers, and the thickness of a single laser cladding layer is 0.5-0.8 mm.

Optionally, the tensile strength of the cast steel brake disc of the high-speed train is more than or equal to 1150MPa, the yield strength is more than or equal to 940MPa, the elongation after fracture is more than or equal to 11.0, and the impact absorption power KV2 at room temperature is more than or equal to 28J/cm ² The hardness HRC is more than or equal to 29.

In a fifth aspect, the invention also provides a high-speed train, which comprises the cast steel brake disc of the high-speed train.

In a sixth aspect, the invention further provides a preparation method of the cast steel brake disc of the high-speed train, which comprises the following steps: and forming a laser cladding layer on the surface of the brake disc steel matrix by the Co-based composite alloy powder through a laser cladding method.

The invention has the following beneficial effects: the components and the proportion of the Co-based composite alloy powder are selected and regulated, so that the Co-based composite alloy powder can be used as laser cladding powder of a brake disc of a high-speed train, and a formed laser cladding alloy layer has the advantages of good high temperature resistance, excellent thermal fatigue resistance and oxidation resistance, low crack sensitivity, good compatibility with a matrix of a cast steel brake disc, outstanding comprehensive toughness and capability of meeting the rigorous requirements of service of the brake disc. And the brake disc with the cladding coating formed by the Co-based composite alloy powder has high bonding strength with the cladding coating, so that the abrasion of the brake disc can be effectively reduced, the service life of the brake disc is further prolonged, and the braking requirement of a high-speed train with higher speed of more than 400km/h can be met.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.

Fig. 1 is a morphology diagram of a TiN-coated Ni core-shell structure nano alloy powder in embodiment 1 of the present invention, in which (a) is a scanning electron microscope diagram, and (b) is a spectrum scanning result of the powder and a schematic diagram of the core-shell structure;

fig. 2 is a schematic view of laser cladding in example 1 of the present invention, in which (a) is a top view, (b) is a left side view, (c) is a photograph of a brake disc object subjected to laser cladding, and (d) is a photograph after cladding is completed;

FIG. 3 is a diagram showing the effect of liquid penetrant dye-penetrant inspection after laser cladding in example 1 of the present invention, where (a) is a diagram showing the effect of a substance after spraying of a penetrant, and (b) is a diagram showing the effect of a substance after cleaning of a penetrant and after development processing;

fig. 4 is a schematic view of magnetic particle inspection after laser cladding in example 1 of the present invention, in which (a) is a magnetic particle inspection instrument and (b) is a schematic view of magnetic particle inspection;

fig. 5 is a schematic view of ultrasonic flaw detection after laser cladding in example 1 of the present invention, in which (a) is an ultrasonic flaw detection probe, (b) is an ultrasonic flaw detector, and (c) is a schematic view of ultrasonic flaw detection;

fig. 6 is a microstructure diagram of the Co-based coating obtained in example 1 of the present invention, in which (a) is a metallographic diagram of an interface between the Co-based coating and a 24CrNiMo steel matrix of a brake disc, and (b) is a metallographic diagram of the Co-based coating.

Detailed Description

In order to make the objects, 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. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The invention provides Co-based composite alloy powder, a high-speed train cast steel brake disc and a preparation method of the Co-based coating laser-clad on the high-speed train brake disc.

Some embodiments of the present invention provide a Co-based composite alloy powder, which includes a component a and a component B, and the mass ratio of the component a to the component B is 100:0.5 to 1.5; the component A comprises C in percentage by mass: 0.45 to 0.60%, cr:20 to 24%, si:0.8 to 1.2%, fe:3.0 to 4.0%, mo:2.5 to 4.3 percent of Co and inevitable trace impurities as the rest; the component B is core-shell structure nano alloy powder of TiN coated Ni, and the mass percent of TiN in the core-shell structure nano alloy powder is 4-6%.

Through re-compounding of the alloy powder of the two components, a coating formed by the obtained Co-based composite alloy powder has good high temperature resistance, excellent thermal fatigue resistance and oxidation resistance, low crack sensitivity, good compatibility with a matrix of a cast steel brake disc, outstanding comprehensive toughness and capability of meeting the rigorous requirement of service of the brake disc. The Co-based composite alloy powder is cladded on the surface of a cast steel brake disc matrix (such as a 24CrNiMo cast steel brake disc) through laser to form a working coating, so that the abrasion of the brake disc can be effectively slowed down due to high bonding strength, the service life of the brake disc is prolonged, and the braking requirement of a high-speed train with higher speed of more than 400km/h can be met. Through the optimization of the laser cladding process, the brake disc with no crack, high toughness and high performance can be obtained.

Specifically, in some embodiments, component a is prepared essentially by the following steps: vacuum melting is carried out according to the element mass ratio of the component A, and then atomization is carried out to prepare powder, preferably, argon is selected for atomization; preferably, the powder particle size of component A is 150 mesh to 200 mesh. The component B is mainly prepared by the following steps: according to the mass ratio of TiN to Ni of 4-6: mixing the materials in a ratio of 96-94 by high-energy ball milling, and preferably, the ball milling time is 5-8 h. The component A and the component B are obtained by different preparation methods, so that the coating formed after laser cladding of the mixed composite alloy powder has more excellent toughness, and the bonding performance with the matrix also reaches a better state.

It should be noted that the high-speed train mentioned in the embodiment of the present invention refers to a high-speed railway vehicle, in particular, a high-speed railway vehicle with a speed per hour of 400 km/h.

Some embodiments of the present invention also provide a method for preparing the above Co-based composite alloy powder, which includes: and mixing the components A and B according to the element composition and proportion to obtain the Co-based composite alloy powder.

Specifically, the component a and the component B are obtained separately in the manner described above for the preparation method of the component a and the component B, and then the component a and the component B are mixed.

Some embodiments of the invention also provide application of the Co-based composite alloy powder in preparing a surface coating of a cast steel brake disc of a high-speed train. The speed of a high-speed train is high, so the cast steel brake disc needs high strength and toughness and has high requirements on service time, particularly trains with the length of 400 km/h. The Co-based composite alloy powder can have excellent obdurability after forming a coating on the surface of a cast steel brake disc of a high-speed train, has better bonding strength with a matrix, and can meet the performance requirement of long-term service. In some preferred embodiments, the material of the steel substrate of the high-speed train cast steel brake disc is 24CrNiMo.

In summary, some embodiments of the present invention further provide a cast steel brake disc for a high-speed train, which includes a brake disc steel substrate and a laser cladding layer on the surface of the steel substrate, wherein the cladding raw material of the laser cladding layer is the aforementioned Co-based composite alloy powder. The material of the brake disc steel substrate comprises but is not limited to 24CrNiMo.

In order to achieve better performance requirements and service time, in some embodiments, the thickness of the laser cladding layer is 2-4 mm. For example, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, etc. may be selected.

Further, in order to ensure that the coating formed by laser cladding has better uniformity and the bonding performance of the coating meets the expected requirements, in some embodiments, the laser cladding layer is composed of a plurality of laser cladding layers, and the thickness of a single laser cladding layer is 0.5-0.8 mm.

In some embodiments, the tensile strength of the cast steel brake disc with the laser cladding layer of the high-speed train is more than or equal to 1150MPa, the yield strength is more than or equal to 940MPa, the elongation after fracture is more than or equal to 11.0, and the impact absorption power KV2 at room temperature is more than or equal to 28J/cm ² The hardness HRC is more than or equal to 29.

Some embodiments of the invention also provide a high speed train comprising the cast steel brake disc of the high speed train.

Further, some embodiments of the present invention also provide a method for preparing a cast steel brake disc for a high-speed train, which includes: and forming a laser cladding layer on the surface of the brake disc steel matrix by using the Co-based composite alloy powder through a laser cladding method.

In order to optimize the bonding performance of the specific Co-based composite alloy powder with a substrate and further ensure that a coating formed uniformly by the composite alloy powder obtains optimal physical properties such as toughness, the inventors optimize laser cladding process parameters aiming at the component specificity of the Co-based composite alloy powder, for example, the laser cladding process parameters are as follows: the cladding speed is 8-25 mm/s, and the diameter of a laser spot is as follows:

the coaxial powder feeding mode has the powder feeding rate of 13-50 g/min and the carrier gas flow: 20 to 30L/min. Meanwhile, in the cladding process, the brake disc matrix rotates along with the rotating table at the rotating speed of 1.2-2.0 r/min; in some embodiments, the carrier gas is argon.

In some embodiments, the brake disc substrate is preheated to 280 ℃ to 300 ℃ prior to laser cladding, such as 280 ℃, 285 ℃, 290 ℃, 295 ℃, 300 ℃ and the like may be selected. For example, the specific operations may be: preheating a 24CrNiMo steel substrate in a resistance furnace at the temperature of 300 ℃ for 55-65 min. Meanwhile, in order to ensure that the cladding effect of the whole cladding process is better, the temperature of the brake disc is kept within the range of 260-320 ℃ in the cladding process.

In some embodiments, in order to ensure the overall effect of laser cladding, the laser cladding layer needs to be formed by multiple passes of laser cladding, and the overlapping ratio between adjacent passes of laser cladding is 35% to 50%, preferably 40%. Meanwhile, in order to make up for the grooves between the passes, the width of the half pass is deviated in the next pass on the basis of the previous pass. Meanwhile, in order to keep the consistency of the performance of the coating formed in each pass, the laser cladding parameters of each pass are the same.

Specifically, the coating layer is formed by 4 times of laser cladding, namely a first coating layer which is well combined with the surface of the matrix is formed by the first time of laser cladding, and the overlapping rate between passes is 40%; cladding the second layer on the surface of the first layer continuously, wherein the technological parameters are the same as those of the first layer, and the width of a half track is deviated in order to make up for the groove between passes; the parameters of the third layer, the fourth layer and the second layer are the same.

Further, in order to further reduce the residual stress left by laser cladding, the method also comprises the step of carrying out heat preservation treatment at the temperature of 300-400 ℃ for at least 3h, preferably 3-4 h after the laser cladding layer is formed.

Therefore, in some embodiments of the present invention, by performing the preheating treatment, the laser cladding and the post-heat treatment, the difference between the thermal expansion coefficients of the base material and the cladding material can be reduced, so that the cladding material and the base material are effectively metallurgically bonded, the cladding effect is good, and the cladding material is not cracked.

In some preferred embodiments, the cold pressing treatment is carried out on the brake disc after the heat preservation treatment, and the deformation amount is controlled to be less than +/-0.2 mm.

It should be noted that the above various laser cladding parameters do not affect the macroscopic and microscopic quality of the cladding layer independently, but affect each other. The laser cladding material of the brake disc and the selection of various cladding process parameters have great influence on the effect of the brake disc. The cladding material is well matched with the steel matrix, so that cracks and air holes are not generated, and the process performance is good; during laser cladding, the rotating speed of the rotary table is well matched with the laser power and the cladding speed, otherwise, the phenomenon of forming collapse or uneven melting can be caused, and inclusions are generated. The depth of the mutually overlapped areas between the cladding channels is different from the depth of the middle of the cladding channel, thereby influencing the uniformity of the whole cladding layer. And the residual tensile stress of multi-pass lap cladding can be superposed, so that the local total stress value is increased, and the crack sensitivity of the cladding layer is increased. Preheating and tempering reduce the tendency of the cladding to crack.

Some embodiments of the present invention also provide a method for preparing a specific cast steel brake disc for a high-speed train, comprising:

s1, polishing the surface of a steel substrate of a 24CrNiMo brake disc to be flat, wherein the surface roughness is Ra3.2-6.3, removing impurities by using alcohol, and preheating the steel substrate on a resistance preheating plate for 25-30 min at the preheating temperature of 300-DEG C.

And S2, forming 4 layers of coatings on the surface of a matrix of the Co-based alloy powder for 24CrNiMo steel by a laser cladding method, wherein the total thickness is 3-4 mm. The cladding process comprises the following steps: the brake disc matrix is integrally preheated to 300-400 ℃ before laser cladding, 3 methane gas flames are continuously used for heating gas in the cladding process to keep the brake disc temperature at 260-320 ℃, the laser power is 2.5-4 kW, the brake disc rotates along with a rotating table in the cladding process, the actual cladding speed is 8-25 mm/s, the lap joint rate is 40%, and the laser spot diameter is as follows:

adopting a coaxial powder feeding mode, wherein the powder feeding rate is 13-50 g/min, and the argon flow is as follows: 25L/min.

And S3, carrying out heat preservation treatment on the Co-based coating brake disc obtained after cladding in a furnace at the temperature of 300-400 ℃ for 3-4 h.

And S4, taking out the coated brake disc obtained after cladding from the tool, and releasing stress.

And S5, carrying out cold pressing treatment on the coated brake disc obtained after cladding, and controlling the deformation amount to be less than +/-0.2 mm.

And S6, carrying out surface machining on the coated brake disc obtained after cladding, and ensuring that the flatness after turning is Ra0.8.

And S7, flaw detection is carried out on the coated brake disc obtained after cladding, and penetration coloring, magnetic powder and ultrasonic flaw detection are carried out according to corresponding standards.

The features and properties of the present invention are described in further detail below with reference to examples.

The following examples and comparative examples are all based on GB/T15822.1-2005 'magnetic particle testing for nondestructive testing part 1: general rule', magnetic particle testing is carried out on steel-based brake discs, the magnetic particle testing result of the steel-based brake discs meets the requirement of TB/T2980-2014 item 4.6, and the testing conclusion is qualified; according to the part 1 of ultrasonic detection of steel castings, namely general purpose steel castings, GB/T7233.1-2009, the ultrasonic detection of the steel-based brake disc is carried out, the ultrasonic detection result of the steel-based brake disc meets the requirements of the 4.5 th item of TB/T2980-2014, and the detection conclusion is qualified.

Example 1

The Co-based composite alloy powder provided by the embodiment can be mainly used for 24CrNiMo steel of a brake disc and comprises two components, wherein the component A is prepared by the following steps: vacuum melting is carried out according to the following element mass ratio, and special powder is prepared by argon atomization, wherein the special powder comprises the following components in percentage by mass: 0.45%, cr:20%, si:0.8 percent; fe:3.0%, mo:2.5 percent, the balance of Co and inevitable trace impurities, and the granularity of the powder is 150-200 meshes.

The component B is TiN coated Ni core-shell structure nano alloy powder, and the mass ratio of TiN to Ni is 5:95 percent, and is obtained by high-energy ball milling for 5 hours. Scanning electron microscope imaging and energy spectrum scanning are carried out on the TiN coated Ni core-shell structure nano alloy powder, and the result is shown in figure 1. Adding the component A into the component B powder according to the mass percent of 0.5 percent to form mixed powder.

The steel-based brake disc is made of 24CrNiMo, is a wheel-mounted or shaft-mounted brake disc of a high-speed rail motor vehicle set, and is laser-cladded with the Co-based composite alloy powder on the surface.

The process for preparing the laser cladding brake disc comprises the following steps:

1) The surface of a steel substrate of a 24CrNiMo brake disc is polished to be smooth, the surface roughness is about Ra3.2, impurities are removed by alcohol, and the steel substrate is placed into a box-type resistance furnace to be preheated at the preheating temperature of 300 ℃.

2) The 24CrNiMo brake disc steel substrate was mounted on the turntable as shown in fig. 2 and clamped with a clamp. And 3 methane flame spray heads are used for carrying out continuous heat preservation treatment on the alloy, so that the temperature is not lower than 300 ℃ in the cladding process.

3) Laser cladding power 3.8kW, cladding process brake disc rotates along with the revolving stage, and the speed of actually cladding is 20mm/s, and the overlap ratio is 40%, and the laser spot diameter is:

a coaxial powder feeding mode is adopted, the powder feeding rate is 28g/min, and the argon flow is as follows: 25L/min, 4 layers of cladding layers.

4) And (3) carrying out heat preservation treatment on the Co-based coating brake disc obtained after cladding at 350 ℃ in a furnace for 4h.

5) And taking the coated brake disc obtained after cladding out of the tool, and releasing the stress.

6) And (4) carrying out cold pressing treatment on the coated brake disc obtained after cladding, and controlling the deformation to be less than +/-0.2 mm.

7) And (3) carrying out surface machining on the coated brake disc obtained after cladding, and ensuring the flatness of the turned brake disc to be Ra0.8.

8) Flaw detection is carried out on the coated brake disc obtained after cladding, penetration coloring, magnetic powder and ultrasonic flaw detection are carried out according to corresponding standards, the effect picture of the penetration coloring flaw detection is shown as figure 3, the schematic picture of the magnetic powder flaw detection is shown as figure 4, the schematic picture of the ultrasonic flaw detection is shown as figure 5, microscopic imaging is carried out on the obtained coating, and the microscopic structure picture is shown as figure 6.

Example 2

The Co-based composite alloy powder provided by the embodiment can be mainly used for 24CrNiMo steel of a brake disc and comprises two components, wherein the component A is prepared by the following steps: vacuum melting is carried out according to the following element mass ratio, and argon atomization is carried out to prepare special powder C:0.52%, cr:22%, si:1.0 percent; fe:3.5%, mo:3.5 percent, the balance being Co and inevitable trace impurities, and the granularity of the powder is 150-200 meshes.

The component B is TiN coated Ni core-shell structure nano alloy powder, and the mass ratio of TiN to Ni is 5:95 percent, is obtained by high-energy ball milling for 5 hours, and the component B is added into the component A powder according to the mass percent of 1.0 percent to form mixed powder.

The steel-based brake disc is made of 24CrNiMo, is a high-speed rail motor train unit wheel-mounted or shaft-mounted brake disc, and is laser-coated with the Co-based composite alloy powder on the surface.

2) And (3) mounting the 24CrNiMo brake disc steel substrate on a rotary table, and clamping by using a clamp. And 3 methane flame spray heads are used for carrying out continuous heat preservation treatment on the alloy, so that the temperature is not lower than 300 ℃ in the cladding process.

3) Laser cladding power 3.5kW, cladding process brake disc rotates along with the revolving stage, and the actual speed of cladding is 20mm/s, and the overlap ratio is 40%, and laser spot diameter is: phi 10mm, a coaxial powder feeding mode is adopted, the powder feeding rate is 25g/min, and the argon flow is as follows: 25L/min, 4 layers of cladding layers.

5) And taking out the coated brake disc obtained after cladding from the tool, and releasing stress.

6) And (4) carrying out cold pressing treatment on the coating brake disc obtained after cladding, and controlling the deformation amount to be less than +/-0.2 mm.

7) And (3) carrying out surface machining on the coated brake disc obtained after cladding, and ensuring that the flatness after turning is Ra0.8.

8) And (4) flaw detection is carried out on the coated brake disc obtained after cladding, and penetration coloring, magnetic powder and ultrasonic flaw detection are carried out according to corresponding standards.

Example 3

The Co-based composite alloy powder provided by the embodiment can be mainly used for 24CrNiMo steel of a brake disc and comprises two components, wherein the component A is prepared by the following steps: vacuum melting is carried out according to the following element mass ratio, and special powder is prepared by argon atomization, wherein the special powder comprises the following components in percentage by mass: 0.60%, cr:24%, si:1.2 percent; fe:4.0%, mo:4.3%, ni:3.2 percent, the balance being Co and inevitable trace impurities, and the granularity of the powder is 150-200 meshes.

The component B is TiN coated Ni core-shell structure nano alloy powder, and the mass ratio of TiN to Ni is 5:95, performing high-energy ball milling for 5 hours, and adding the component B into the component A powder according to the mass percent of 1.5% to form mixed powder.

3) Laser cladding power is 4kW, and cladding process brake disc rotates along with the revolving stage, and the actual speed of cladding is 25mm/s, and the overlap joint rate is 40%, and laser spot diameter is: phi 10mm, a coaxial powder feeding mode is adopted, the powder feeding rate is 40g/min, and the argon flow is as follows: 25L/min, 4 layers of cladding layers.

Comparative example 1

The comparative example is a 24CrNiMo cast steel brake disc matrix without a laser cladding coating, and the matrix comprises the following chemical components: 0.24% of C, 1.12% of Cr, 0.65% of Mn, 1.0% of Ni, 0.12% of Si, 0.49% of Mo, and the balance of Fe, it being noted that the chemical composition of the 24CrNiMo brake disc steel matrix in the above example is the same as that in the present comparative example.

Comparative example 2

The Co-based alloy powder for 24CrNiMo steel of the brake disc provided by the comparative example is prepared by vacuum melting and argon atomization of the following elements in parts by mass: 0.52%, cr:22%, si:1.0 percent; fe:3.5%, mo:3.5 percent, the balance being Co and inevitable trace impurities, and the granularity of the powder is 150-200 meshes.

The steel-based brake disc is made of 24CrNiMo, is a wheel-mounted or shaft-mounted brake disc of a high-speed rail motor vehicle set, and is laser-cladded with the Co-based alloy powder on the surface.

Comparative example 3

The Co-based alloy powder for the brake disc 24CrNiMo steel provided by the comparative example comprises two components, wherein the component A is prepared by the following steps: vacuum melting is carried out according to the following element mass ratio, and special powder is prepared by argon atomization, wherein the special powder comprises the following components in percentage by mass: 0.52%, cr:22%, si:1.0 percent; fe:3.5%, mo:3.5 percent, the balance being Co and inevitable trace impurities, and the granularity of the powder is 150-200 meshes.

The component B is core-shell structure nano alloy powder of TiN coated Ni, and the mass ratio of TiN to Ni is 5:95, performing high-energy ball milling for 5 hours, and adding the component B into the component A powder according to the mass percentage of 2.0% to form mixed powder.

1) The surface of a steel substrate of a 24CrNiMo brake disc is polished to be smooth, the surface roughness is about Ra3.2, impurities are removed by alcohol, and the steel substrate is placed into a box-type resistance furnace to be preheated, wherein the preheating temperature is 300 ℃.

4) And (3) carrying out heat preservation treatment on the Co-based coating brake disc obtained after cladding in a furnace at 350 ℃ for 4h.

Comparative example 4

The Co-based alloy powder for 24CrNiMo steel of the brake disc provided by the comparative example is prepared by vacuum melting and argon atomization of the following elements in mass ratio to prepare special powder C:0.45%, cr:30%, si: 1.4 percent; fe:2.7%, mo:6.0%, ni:4.0%, mn:0.18%, W:0.48 percent, the balance of Co and inevitable trace impurities, and the granularity of the powder is 150-200 meshes.

The steel-based brake disc is made of 24CrNiMo, is a high-speed rail motor train unit wheel-mounted or shaft-mounted brake disc, and is laser-coated with the Co-based alloy powder on the surface.

Comparative example 5

The Co-based alloy powder for 24CrNiMo steel of the brake disc provided by the comparative example is prepared by vacuum melting and argon atomization of the following elements in parts by mass to prepare special powder C:0.52%, cr:22%, si:1.0 percent; fe:3.5%, mo:3.5 percent, the balance of Co and inevitable trace impurities, and the granularity of the powder is 150-200 meshes.

3) Laser cladding power 2kW, cladding process brake disc rotates along with the revolving stage, and the actual speed of cladding is 30mm/s, and the overlap joint rate is 40%, and the laser spot diameter is: phi 10mm, a coaxial powder feeding mode is adopted, the powder feeding rate is 40g/min, and the argon flow is as follows: 25L/min, 4 layers of cladding layers.

The performances of the examples and the comparative examples are tested by using the standards of GB/T228-2010 metallic material tensile test room temperature test method, TB/T-2980-2014 brake disc for locomotive vehicles, GB/T230.1-2018 metallic material Rockwell hardness part 1 test method, GB/T229-2007 metallic material Charpy pendulum impact test method, YS/T1256-2018 nonferrous metal material specific heat capacity test differential scanning calorimetry and the like.

The effects of examples and comparative examples are shown in the table

In conclusion, the enhanced coating formed by laser cladding of the Co-based composite alloy powder on the surface of the 24CrNiMo cast steel matrix can prolong the service life of the brake disc, meet the service requirements of more severe working conditions, further improve the overall performance of the brake disc, can be effectively applied to high-speed trains of 200-400km/h, and has good economic benefit.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The Co-based composite alloy powder is characterized by comprising a component A and a component B, wherein the mass ratio of the component A to the component B is 100:0.5 to 1.5;

the component A comprises C:0.45 to 0.60%, cr:20 to 24%, si:0.8 to 1.2%, fe:3.0 to 4.0%, mo:2.5 to 4.3 percent, and the balance of Co and inevitable trace impurities; the component B is core-shell structure nano alloy powder with TiN coating Ni, and the mass percentage of TiN in the core-shell structure nano alloy powder is 4-6%.

2. The Co-based composite alloy powder according to claim 1, wherein the component a is prepared mainly by the steps of: vacuum melting is carried out according to the element mass ratio of the component A, and then argon is selected for atomization to prepare powder; the powder granularity of the component A is 150-200 meshes;

the component B is mainly prepared by the following steps: according to the mass ratio of TiN to Ni of 4-6: mixing the materials in a ratio of 96 to 94 by high-energy ball milling for 5 to 8 hours.

3. A method for producing the Co-based composite alloy powder according to claim 1 or 2, characterized by comprising: and mixing the components A and B according to the element composition and proportion to obtain the Co-based composite alloy powder.

4. The method of preparation according to claim 3, characterized in that it comprises: mixing the component A and the component B.

5. The use of the Co-based composite alloy powder according to claim 1 or 2 for preparing a surface coating of a cast-steel brake disc for a high-speed train, wherein the steel matrix of the cast-steel brake disc for a high-speed train is made of 24CrNiMo.

6. A cast steel brake disc of a high-speed train is characterized by comprising a brake disc steel matrix and a laser cladding layer on the surface of the steel matrix, wherein the cladding raw material of the laser cladding layer is the Co-based composite alloy powder as claimed in claim 1 or 2.

7. The cast-steel brake disc of the high-speed train as claimed in claim 6, wherein the material of the steel matrix of the brake disc is 24CrNiMo.

8. The high-speed train cast steel brake disc as claimed in claim 6, wherein the thickness of the laser cladding layer is 2 to 4mm.

9. The high-speed train cast steel brake disc as claimed in claim 6, wherein the laser cladding layer is composed of multiple layers of laser cladding layers, and the thickness of a single layer of laser cladding layer is 0.5-0.8mm.

10. The cast-steel brake disc for the high-speed train as claimed in claim 6, wherein the cast-steel brake disc for the high-speed train has tensile strength of 1050MPa or more, yield strength of 900MPa or more, elongation after fracture of 8.0 or more, room-temperature impact absorption power KV2 of 27J or more, and hardness HBW of 290 or more.

11. A high-speed train, characterized by comprising the cast steel brake disc for the high-speed train as claimed in any one of claims 6 to 10.

12. A preparation method of a laser cladding Co-based coating of a brake disc of a high-speed train is characterized by comprising the following steps: the Co-based composite alloy powder according to claim 1 or 2, which is used for forming a laser cladding layer on the surface of a brake disc steel substrate by a laser cladding method.

13. The preparation method of claim 12, wherein the laser cladding process parameters are as follows: the cladding speed is 8 to 25mm/s, and the diameter of a laser spot is as follows: phi 10mm, a coaxial powder feeding mode, a powder feeding rate of 13 to 50g/min, a carrier gas flow rate: 20 to 30L/min.

14. The preparation method according to claim 13, wherein in the cladding process, the brake disc steel substrate rotates with a rotating table at a rotating speed of 1.2 to 2.0r/min; the carrier gas is argon.

15. The method of claim 13, wherein the brake disc steel substrate is preheated to a temperature of 280-300 ℃ before laser cladding, and the brake disc temperature is maintained at 260-320 ℃ during cladding.

16. The preparation method of claim 13, wherein the laser cladding layer is formed by multi-pass laser cladding, and the overlapping ratio between adjacent passes of laser cladding is 35% -50%; the next pass deviates by the width of a half pass on the basis of the previous pass; the laser cladding parameters of each pass are the same.

17. The manufacturing method according to claim 13, wherein the material of the brake disc steel substrate is 24CrNiMo.

18. The method for preparing the polyurethane foam according to any one of claims 12 to 17, further comprising performing heat preservation treatment at a temperature of 300 ℃ to 400 ℃ for at least 3 hours after the laser cladding layer is formed.

19. The preparation method of claim 18, further comprising performing heat preservation treatment at 300-400 ℃ for 3-4 h after the laser cladding layer is formed.

20. The method for preparing the brake disc, according to the claim 19, further comprises the step of cold pressing the brake disc after the heat preservation treatment, wherein the deformation amount is controlled to be less than +/-0.2 mm.