Laser cladding method and device for preparing composite layer on rail surface

Abstract

The present invention provides a laser cladding method and device for preparing a composite layer on the surface of a rail, and belongs to the technical field of laser surface engineering of large workpieces. Laser cladding technology is used to clad an alloy layer layer by layer in the area to be clad, and the alloy is a second-phase particle-reinforced material. An auxiliary heat source is simultaneously applied to the surface of the cladding layer that has solidified and completed the solid-state phase transformation, and the surface of the cladding layer is heated again. The energy of the auxiliary heat source is adjusted in real time to stabilize the surface temperature of the cladding layer to the optimal temperature range required for reheating the cladding layer. In this temperature range, the nucleation and precipitation of the second-phase particles in the cladding layer can be promoted but not significantly grown, so that the microhardness and mechanical properties of the cladding layer are significantly improved, thereby obtaining a rail surface with excellent wear and rolling contact fatigue performance. The present invention also provides a corresponding device.

Description

Technical Field

[0001] The present invention belongs to the technical field of large-scale workpiece laser surface engineering, and more specifically, relates to a laser cladding method and device for preparing a composite layer on the surface of a rail. Background Art

[0002] With the rapid development of high-speed and heavy-load trains, rail damage has become increasingly prominent, especially in small-radius curves, turnouts and welded joints. Rail maintenance not only causes delays in railway transportation services, but also significantly increases the operating costs of the railway network. Therefore, how to significantly extend the service life of rails has been one of the major technical challenges faced by railway-related departments for many years.

[0003] Laser cladding technology is one of the fastest-growing and most widely used technologies among many surface engineering technologies. It can be used to prepare a variety of functional coatings on the surface of workpieces, significantly extend their service life, or repair or remanufacture worn parts. The relevant technology has received extensive attention from domestic and foreign railway departments and their related research units, and has been applied to the surface strengthening or repair of ordinary rails. However, for rails with harsh service conditions (such as turnouts, small radius curve rails, etc.), the toughness of the material is required to be higher.

[0004] With the increasing requirements for steel toughness in recent years, a large number of high-strength steel grades have been developed, in which second-phase particle strengthening plays an important role. Representative second-phase particle-strengthened steel grades include maraging steel and precipitation-hardening martensitic stainless steel. While precipitation strengthening, lath martensite ensures the strength and toughness of the material. However, the precipitation of second-phase particles in these alloy steels usually requires several hours of solid solution + aging heat treatment. For laser cladding strengthening and repair of rail surfaces, the composition and organization of the matrix and cladding materials are quite different. In addition, the rails are long and large in size, so heat treatment in the workshop can be carried out with difficulty. However, it is impossible to perform overall heat treatment on the railway site, making this technology impossible to apply in engineering.

[0005] To solve the above problems, the patent document (publication number CN101125394A) discloses a laser cladding alloy powder, rail and preparation method. The temperature cycle curve of the cladding layer can be adjusted by adjusting the laser cladding process, that is, the in-situ heat treatment effect of the laser itself is used to precipitate a large number of fine NiAl phases, which significantly improves the hardness and strength of the rail. However, the above process method is only applicable to the materials with a short aging precipitation time mentioned in the document. For the currently common commercial maraging steel (such as 18Ni300) or precipitation hardening stainless steel (17-4PH), the strength improvement mainly depends on the precipitation of intermetallic compounds rich in Mo, Ti or Cu elements, which have a high nucleation barrier and a slower precipitation rate than NiAl and TiAl. It cannot be fully precipitated by relying solely on the transient heat treatment effect during the multi-layer laser cladding process. Therefore, the maraging steel or precipitation hardening stainless steel prepared by conventional multi-layer and multi-pass laser cladding is usually softer and has a lower tensile strength of about 0.9GPa to 1.2GPa, which is not enough to meet the use requirements.

[0006] In the process of laser cladding the second phase particle reinforcement material on the rail surface, induction is used as an auxiliary heat source to perform in-situ heat treatment on the deposited material, which is expected to promote the generation of second phase particles without affecting the performance of the matrix, thereby improving the toughness of the coating. The patent document (publication number CN108456879A) discloses a method for laser-assisted heat source efficient composite cladding to strengthen rails. The laser-assisted heat source efficient composite cladding method is applied to rail strengthening. This method greatly reduces the cooling rate of the heat-affected zone through the synchronous composite action of laser and induction, thereby preventing the heat-affected zone from producing martensitic phase transformation and cracking problems. However, the synchronous action of induction and laser greatly reduces the cooling rate of the molten pool, which easily causes the coating structure to be coarse, which is not conducive to ensuring that the surface cladding layer of large-sized parts has sufficiently high toughness.

[0007] In addition, since the second-phase particle-reinforced steel mainly relies on the precipitation of second-phase particles, and its precipitation temperature is limited, too high an induction heating temperature will cause austenitization of the coating and fail to achieve hardness improvement; too low an induction heating temperature is not conducive to the precipitation of precipitates and also fails to improve the hardness and wear resistance of the cladding layer.

[0008] Therefore, an effective method and device are used to adjust the synergistic mode of induction and laser, and the temperature of auxiliary induction heating can be accurately controlled, which has important engineering value and practical significance for improving the strength and toughness of the laser cladding layer prepared on the surface of the rail. Summary of the invention

[0009] In view of the defects of the prior art, the present invention aims to provide a laser cladding method and device for preparing a high-performance cladding layer on the surface of a rail. First, a second-phase particle-reinforced cladding layer is prepared on the surface of the rail to be repaired by laser cladding, and then the deposited cladding layer is subjected to in-situ aging heat treatment by induction heating to promote the nucleation and precipitation of nano-precipitation phases in the cladding layer without growth. The laser cladding and induction heating aging heat treatment in one design cycle form a cladding layer preparation cycle. Repeating multiple cladding layer preparation cycles can significantly improve the strength and toughness of the cladding layer without affecting the performance of the substrate, thereby greatly improving the comprehensive service performance of the rail.

[0010] To achieve the above-mentioned purpose, the present invention provides a laser cladding method for preparing a composite layer on the surface of a rail, wherein a second-phase particle-reinforced cladding layer is prepared layer by layer on the surface of the rail to be repaired or strengthened by laser cladding, and an induction heat source is simultaneously used to heat the cladding layer that has solidified and completed the phase change. During this process, the actual temperature of the heated surface of the cladding layer is detected in real time to stabilize it to the temperature range where the second-phase particles precipitate.

[0011] Furthermore, a laser cladding method for preparing a composite layer on the surface of a rail comprises the following steps:

[0012] S1: According to the actual working conditions, the easily worn area of ​​the rail is removed by machining, the removal depth is 2mm to 20mm, and then the surface to be clad is cleaned.

[0013] S2: Formulate laser cladding process and determine cladding processing path.

[0014] S3: Design the induction coil and determine the induction heat source heating process, i.e. the induction heating temperature T0 and time t0.

[0015] S4: Start laser cladding and perform induction heating on the solidified cladding layer. Real-time monitoring of the surface temperature T of the cladding layer during the induction heating process k , get the temperature T k The difference between the temperature T0 required for induction heating is used to adjust the induction heating power P according to the difference to perform closed-loop control, stabilize the surface temperature of the cladding layer to the temperature required for the precipitation of the second phase particles, and control the single induction heating time of all solidified cladding layers to t1.

[0016] S5: After completing a cladding layer preparation cycle, determine whether the thickness of the cladding layer meets the requirements. If so, jump to step S6. If not, repeat step S4.

[0017] S6: Complete the strengthening work at the bottom of the cladding layer.

[0018] Furthermore, it also includes strengthening the surface of the cladding layer, that is, step S7, as follows:

[0019] S7: Turn on induction heating to perform aging heat treatment on the surface of the cladding layer, and detect and control the induction heating power P in real time k , so that the surface temperature of the cladding layer is T0, the processing time is t0,

[0020] S8: completing the preparation of the composite layer.

[0021] Furthermore, the relationship between the total induction heating time t0 and the induction heating time t1 of a composite layer preparation cycle is: t0 = t1*D / δ,

[0022] Where D is the temperature of the cladding layer when the surface of the cladding layer is heated to T0, and the temperature of the cladding layer is the minimum effective induction heating temperature T min is the distance from the surface, and δ is the coating thickness of one cladding preparation cycle.

[0023] Furthermore, the induction heating time t0 in step S3 is determined by the following steps:

[0024] S31: Prepare a cladding layer of set thickness on the rail surface.

[0025] S32: Use an induction heat source to heat the cladding layer, use a thermometer to detect the surface temperature of the cladding layer, and control the surface temperature of the cladding layer to be the effective heating temperature T0.

[0026] S33: Detect and record the microhardness of the cladding layer under different heating times, and fit the curve equation of the relationship between the microhardness of the cladding layer and the induction heating time to obtain H=ab*c^t, where H is the microhardness of the cladding layer, t is the heating time, a, b and c are measurement constants, respectively.

[0027] S34: Assuming that the microhardness of the required composite layer is H0, the required induction heating time t0 is calculated according to the relationship between the microhardness of the cladding layer and the induction heating time H=ab*c^t.

[0028] Furthermore, the induction heating temperature T0 needs to be within the effective induction aging temperature range T min -T max When the cladding layer is heated by the induction heat source within this range, the microhardness and yield strength both increase.

[0029] Furthermore, a cladding layer preparation cycle may be less than one cladding pass, and may be a single pass or multiple passes, and may also be a single-layer or multi-layer deposition process.

[0030] Further, the second phase particle-reinforced powder is an iron-based alloy, which includes the following components and the mass percentage of each component: C 0.01%~0.20%, Cr 12.00%~17.50%, Ni 0.60%~5.00%, Cu0.20%~5.00%, Nb 0.10%~0.45%, and Fe as the balance; or the second phase particle-reinforced powder is an iron-based alloy, which includes the following components and the mass percentage of each component: Ni 16%~22%, Co 6%~12%, Mo 3%~7%Mo, Al 0.1%~7%, Ti 0.5%~5%, and Fe as the balance.

[0031] Furthermore, it comprises a rail surface laser cladding unit, an induction heating unit and a temperature detection unit, wherein the rail surface laser cladding unit comprises an optical path component and a powder feeding system.

[0032] The rail surface laser cladding unit is used to clad the alloy powder on the rail surface to form an alloy strengthening layer.

[0033] The induction heating unit includes an induction power supply, an induction coil and a water cooling element. The induction coil is connected to the induction power supply and is placed at a set height from the surface of the cladding layer. A circular temperature measuring through hole is provided at the tail of the induction coil.

[0034] The temperature detection unit includes a pyrometer and an industrial computer, which are used to detect the temperature of the surface of the cladding layer in real time during the induction heating process. The pyrometer detects the surface temperature of the cladding layer through a circular temperature measuring through hole set at the tail of the induction coil, and feeds back the detected surface temperature of the cladding layer to the industrial computer, so as to control the stability of the surface temperature of the cladding layer through the industrial computer.

[0035] In general, the above technical solution conceived by the present invention has the following advantages compared with the prior art:

[0036] Beneficial effects:

[0037] 1. Select the second-phase particle-reinforced alloy material with both strength and toughness as the cladding material, and use the induction heating-assisted laser cladding process to deposit it on the surface of the rail to be processed. On the basis of not damaging the rail substrate, the process of the present invention can promote the nucleation and precipitation of the second-phase particles in the cladding layer, effectively solving the problem that when the second-phase particle-reinforced alloy material is directly laser-clad, the second-phase particles are difficult to precipitate and thus it is difficult to exert its second-phase strengthening mechanism. At the same time, while ensuring the toughness of the rail, its strength can be improved, so that the wear resistance and fatigue resistance of the rail after laser cladding are greatly improved, and the service life is greatly increased. Moreover, in-situ aging heat treatment is performed on the surface of the rail while laser cladding, and there is no need for subsequent overall aging heat treatment, which has high processing efficiency.

[0038] 2. First, laser cladding is used to prepare a coating of the second phase particle reinforced alloy material on the surface area of ​​the rail to be repaired or strengthened, and then the coating surface is subjected to aging heat treatment, which can reduce the deterioration of the transition cladding layer structure caused by element diffusion, making it easier for the rail and the cladding layer to produce metallurgical bonding, inhibiting the generation of interface defects such as cracks and unfusion, and effectively releasing the large internal stress caused by the rapid heating and cooling effect of laser cladding, and reducing the warping deformation of the rail that may be caused by continuous large-area laser cladding. The present invention application better grasps the processability in the time dimension, can truly improve the aging heat treatment effect, and can improve processing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a flow chart of a laser cladding method for preparing a composite layer on the surface of a rail provided by an embodiment of the present invention;

[0040] Figure 2 It is a schematic structural diagram of a laser cladding device for preparing a composite layer rail provided in an embodiment of the present invention;

[0041] FIG3( a ) is a schematic diagram of a cladding layer preparation cycle provided by an embodiment of the present invention, which is a single pass in the vertical direction (synchronous action of induction heat source and laser);

[0042] FIG3( b ) is a schematic diagram of a cladding layer preparation cycle provided by an embodiment of the present invention, which is a single pass in the horizontal direction (synchronous action of the induction heat source and the laser);

[0043] FIG4( a ) is a schematic diagram of a cladding layer preparation cycle with multiple passes in a vertical direction provided by an embodiment of the present invention;

[0044] FIG4( b ) is a schematic diagram of a cladding layer preparation cycle with multiple passes in the horizontal direction provided by an embodiment of the present invention;

[0045] Figure 5 It is a schematic diagram of a cladding layer preparation cycle of a single layer or multiple layers provided by an embodiment of the present invention;

[0046] Figure 6 is a curve diagram showing the relationship between the microhardness of the maraging steel cladding layer and the induction heating time provided by an embodiment of the present invention;

[0047] Figure 7 This is the hardness distribution diagram of the maraging steel / bainite steel core along the depth direction prepared by ordinary laser cladding and induction heating assisted laser cladding;

[0048] Figure 8 is a curve diagram showing the relationship between the microhardness of the martensitic precipitation hardened stainless steel cladding layer and the induction heating time provided by an embodiment of the present invention;

[0049] Fig. 9It is the hardness distribution diagram along the depth direction of the martensitic precipitation hardening stainless steel U75V wing rail prepared by conventional laser cladding and induction heating assisted laser cladding.

[0050] In all drawings, the same reference numerals are used throughout to denote the same elements or structures, wherein:

[0051] 1- industrial computer; 2- induction power supply; 3- pyrometer; 4- induction coil; 5- optical path component; 6- laser; 7- cladding layer; 8- powder feeding system; 9- laser spot. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0053] The present invention proposes an effective induction heating assisted laser cladding process method, in which the deposited material is subjected to in-situ aging heat treatment during the laser cladding process to maximize the toughness of the coating, thereby further improving the service life of the rail. Specifically, in view of the low service life of existing rails (such as small radius curve sections, frogs and joints, etc.) and the various shortcomings of the existing laser cladding rail repair technology, the present invention provides a laser cladding method and device for preparing a composite layer on the surface of the rail, firstly using laser cladding technology to prepare a second phase precipitation strengthened coating layer layer by layer on the surface of the rail to be repaired, and then in-situ aging heat treatment is performed on the deposited coating by induction heating to promote the generation of nano-precipitated phases in the coating, one laser cladding and one induction heating aging heat treatment form a cladding layer preparation cycle, and multiple cladding layer preparation cycles are repeated, which can significantly improve the toughness of the cladding layer without affecting the performance of the substrate, thereby greatly improving the comprehensive service performance of the rail.

[0054] Figure 1 is a flow chart of a laser cladding method for preparing a composite layer on a rail surface provided by an embodiment of the present invention, comprising Figure 1 It can be seen that the laser cladding method for preparing a composite layer on the surface of a rail of the present invention comprises the following steps:

[0055] S1: According to the actual working conditions, the easily worn area of ​​the rail is removed by machining, the removal depth is 2mm to 20mm, and then the surface to be clad is cleaned.

[0056] S2: Formulate laser cladding process and determine cladding processing path.

[0057] S3: Design the induction coil and determine the induction heat source heating process, i.e. the induction heating temperature T0 and time t0.

[0058] S4: Start laser cladding and perform induction heating on the solidified cladding layer. Real-time monitoring of the surface temperature T of the cladding layer during the induction heating process k , get the temperature T k The difference between the temperature T0 required for induction heating is used to adjust the induction heating power P according to the difference to perform closed-loop control, stabilize the surface temperature of the cladding layer to the temperature required for the precipitation of the second phase particles, and control the single induction heating time of all solidified cladding layers to t1.

[0059] S5: After completing a cladding layer preparation cycle, determine whether the thickness of the cladding layer meets the requirements. If so, jump to step S6. If not, repeat step S4.

[0060] S6: Complete the strengthening work at the bottom of the cladding layer.

[0061] Among them, the induction auxiliary heat source acts on the surface of the cladding layer that has solidified and completed the martensitic phase transformation, so that its surface is heated again to the temperature range where the second phase particles precipitate. The pulsed high-temperature induction heating in the multi-layer laser cladding process can promote the nucleation and precipitation of the second phase particles without growing up, so that the microhardness and mechanical properties of the cladding layer are greatly improved, thereby obtaining a rail with excellent wear and rolling contact fatigue performance.

[0062] Figure 2 It is a structural schematic diagram of a laser cladding device for preparing a composite layer rail provided in an embodiment of the present invention. As can be seen from the figure, the device mainly includes a rail surface laser cladding unit, an induction heating unit and a temperature detection unit. The rail surface laser cladding unit includes an optical path component 5 and a powder feeding system 8. An important component of the optical path component 5 is a laser 6. The rail surface laser cladding unit is used to laser clad an alloy strengthening layer on the rail surface. The induction heating unit includes an induction power supply 2 and an induction coil 4. The induction coil is connected to the induction power supply and placed at a certain height from the surface of the cladding layer. A temperature measuring hole is provided at the tail of the induction coil. The temperature detection unit includes a pyrometer 3 and an industrial computer 1. The industrial computer 1 is connected to the pyrometer 3 for real-time detection of the temperature of the surface of the cladding layer during the induction heating process. The pyrometer detects and controls the stability of the surface temperature of the cladding layer through the temperature measuring hole of the induction coil.

[0063] The laser cladding method for preparing a composite rail provided by the present invention is further described below according to a specific embodiment. It should be noted that when the method of the present invention is used, a cladding layer preparation cycle can be less than or equal to one cladding path, wherein FIG3(a) is a schematic diagram of a cladding layer preparation cycle provided by an embodiment of the present invention as a single path in the vertical direction (synchronous action of the induction heat source and the laser), and FIG3(b) is a schematic diagram of a cladding layer preparation cycle provided by an embodiment of the present invention as a single path in the horizontal direction (synchronous action of the induction heat source and the laser), as can be seen from the figure, one cladding layer 7 preparation cycle is approximately half a cladding path, or it can be a whole cladding path, which is determined by the scanning path of the laser spot 9. FIG4(a) is a schematic diagram of a cladding layer preparation cycle provided by an embodiment of the present invention as multiple paths in the vertical direction, and FIG4(b) is a schematic diagram of a cladding layer preparation cycle provided by an embodiment of the present invention as multiple paths in the horizontal direction, as can be seen from the figure, one cladding layer 7 preparation cycle provided by an embodiment of the present invention is a single path or multiple paths, which is determined by the scanning path of the laser spot 9. Figure 5 Schematic diagram of a cladding layer preparation cycle of a single layer or multiple layers provided by an embodiment of the present invention, such as Figure 5 As shown, the cladding layer 7 is one layer or multiple layers, which is determined by the scanning path of the laser spot 9 .

[0064] Example 1

[0065] The material to be clad is a bainitic steel fork core, and the second phase particle reinforcement alloy powder is a maraging steel, which includes the following components and the mass percentage of each component (wt%): 17.0-19.0wt.% Ni, 8.5-10.0wt.% Co, 4.5-5.2wt.% Mo, 0.8-1.2wt.% Ti, 0.1-0.2wt.% Al, and the balance is Fe.

[0066] The present invention provides a laser cladding method for preparing a composite layer on the surface of a rail, the flow chart of which is as follows: Figure 1 As shown, combined Figure 1 It can be seen that this embodiment specifically includes the following steps:

[0067] S1: According to the actual working conditions, the easily worn area of ​​the rail is removed by machining, the removal depth is 7mm, and then the surface to be clad is cleaned.

[0068] S2: Formulate laser cladding process, with a single layer thickness of 0.5 mm, and determine the cladding processing path.

[0069] S3: Design the induction coil to be long and strip-shaped, determine the heating temperature of the induction heat source to be 500°C, and the relationship between the induction heating time and the microhardness of the cladding layer is H=521-156*0.955^t, such as Figure 6 As shown, Figure 6: is a curve diagram showing the relationship between the microhardness of the maraging steel cladding layer and the induction heating time provided by the embodiment of the present invention. When the microhardness of the cladding layer is set to be about HV440, the induction heating time is 5 minutes.

[0070] S4: Start laser cladding. After depositing a cladding layer, the solidified cladding layer is induction heated. Real-time monitoring of the cladding layer surface temperature T during the induction heating process k , get the temperature T k The difference between the induction heating temperature and the required temperature of 500°C is used to adjust the induction heating power P according to the difference to perform closed-loop control, stabilize the surface temperature of the cladding layer to the temperature required for the precipitation of the second phase particles, and control the single induction heating time of all solidified cladding layers to 30s.

[0071] S5: Repeat step S4 to complete the deposition of 14 layers of laser cladding, and the bottom of the cladding layer is strengthened.

[0072] S6: Start aging heat treatment on the surface of the cladding layer, and detect and control the induction heating power P in real time k , so that the surface temperature of the cladding layer is 500℃ and the processing time is 5min.

[0073] The coating prepared in this example has good strength-toughness matching. Figure 7 This is the hardness distribution diagram of the maraging steel / bainite steel fork core prepared by ordinary laser cladding and induction heating assisted laser cladding along the depth direction. It can be seen that the performance of the maraging steel prepared by induction heating assisted laser cladding is significantly better than that prepared by ordinary laser cladding.

[0074] Example 2

[0075] The substrate to be clad is a U75V wing rail, and the alloy powder is a martensitic precipitation hardening stainless steel powder, including the following components (wt%): C: ≤0.07, Si: ≤1.00, Mn: ≤1.00, Ni: 3.00-5.00, Cr: 15.0-17.5, Cu: 3.00-5.00, Nb: 0.15-0.45, and the balance is Fe.

[0076] The present invention provides a laser cladding method for preparing a composite layer on the surface of a rail, the flow chart of which is as follows: Figure 1 As shown, Figure 1 It can be seen that this embodiment specifically includes the following steps:

[0077] S1: According to the actual working conditions, the easily worn area of ​​the rail is removed by machining, the removal depth is 7mm, and then the surface to be clad is cleaned.

[0078] S2: Formulate laser cladding process, with a single layer thickness of 0.5 mm, and determine the cladding processing path.

[0079] S3: Design the induction coil to be long and narrow, determine the heating temperature of the induction heat source to be 600°C, and the relationship between the induction heating time and the microhardness of the cladding layer is H = 424-81*0.908^t, such as Figure 8 As shown, Figure 8 : is a curve diagram showing the relationship between the microhardness of the martensitic precipitation hardened stainless steel cladding layer and the induction heating time provided by the embodiment of the present invention. When the microhardness of the cladding layer is set to be about HV 380, the induction heating time is 5 minutes.

[0080] S4: Start laser cladding. After depositing a layer of cladding layer, perform induction heating on the solidified cladding layer. Real-time monitor the surface temperature Tk of the cladding layer during the induction heating process, obtain the difference between the temperature Tk and the required temperature of 600°C for induction heating, and adjust the induction heating power P according to the difference to perform closed-loop control, stabilize the surface temperature of the cladding layer to the temperature required for the precipitation of the second phase particles, and control the single induction heating time of all solidified cladding layers to 30s.

[0081] S5: Repeat step S4 to complete the deposition of 14 layers of laser cladding, and the bottom of the cladding layer is strengthened.

[0082] S6: Start aging heat treatment on the surface of the cladding layer, detect and control the induction heating power Pk in real time, make the surface temperature of the cladding layer 600°C, and the treatment time is 5 minutes.

[0083] The coating prepared in this example has good strength-toughness matching. Fig. 9 This is the hardness distribution diagram of the martensitic precipitation hardening stainless steel U75V wing rail prepared by induction heating assisted laser cladding along the depth direction. It can be seen from the figure that the performance of the martensitic precipitation hardening stainless steel prepared by induction heating assisted laser cladding is significantly better than that prepared by ordinary laser cladding.

[0084] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser cladding method for preparing a composite layer on the surface of a rail, characterized in that: Laser cladding is used to prepare the second-phase particle-reinforced cladding layer layer by layer on the surface of the rail to be repaired or strengthened. At the same time, an induction heat source is used to heat the cladding layer that has solidified and completed the phase change. During this process, the actual temperature of the heated surface of the cladding layer is detected in real time to stabilize it to the temperature range where the second-phase particles precipitate. It includes the following steps: S1: According to the actual working conditions, the easily worn area of ​​the rail is removed by machining, with a removal depth of 2 mm to 20 mm, and then the surface to be clad is cleaned. S2: Formulate laser cladding process and determine cladding processing path. S3: Design the induction coil, determine the induction heat source heating process, determine the required induction heating temperature T0 and the required induction heating time t0, S4: Start laser cladding and perform induction heating on the solidified cladding layer, and monitor the surface temperature T of the cladding layer during the induction heating process in real time. k , get the temperature T k The difference between the temperature T0 required for induction heating is used to adjust the induction heating power P according to the difference to perform closed-loop control, stabilize the surface temperature of the cladding layer to the temperature required for the precipitation of the second phase particles, and control the single induction heating time of all solidified cladding layers to t1. S5: After completing a cladding layer preparation cycle, determine whether the thickness of the cladding layer meets the requirements. If so, jump to step S6. If not, repeat step S4. S6: Complete the strengthening work at the bottom of the cladding layer. After step S6 is finished, the preparation and strengthening of all layers of cladding layers are completed, and then step S7 is performed. Step S7 is used to strengthen the surface of the entire cladding layer. Step S7 is as follows: S7: Turn on induction heating to perform aging heat treatment on the surface of the entire cladding layer, and detect and control the induction heating power P in real time k , so that the surface temperature of the cladding layer is the required temperature T0 for induction heating, and the processing time is the required induction heating time t0, S8: Complete the preparation of the composite layer on the rail surface. The relationship between the required induction heating time t0 and the single induction heating time t1 is: t0=t1*D / δ, Where D is the temperature of the single-layer cladding layer when the surface is heated to the required temperature T0 for induction heating. The current surface temperature of the single-layer cladding layer is the minimum effective induction heating temperature T min is the distance from the surface, δ is the coating thickness of a cladding preparation cycle, The required induction heating time t0 in step S3 is obtained by the following steps: S31: Prepare a cladding layer of set thickness on the rail surface. S32: Use an induction heat source to heat the cladding layer, use a thermometer to detect the current surface temperature of the cladding layer, and control the surface temperature of the cladding layer to the temperature T0 required for induction heating. S33: Detect and record the microhardness of the cladding layer under different heating times, and fit the curve equation of the relationship between the microhardness of the cladding layer and the induction heating time to obtain H=ab*c^t, where H is the current microhardness of the cladding layer, t is the heating time, a, b and c are measurement constants, respectively. S34: Assuming that the microhardness of the required composite layer is H0, the required induction heating time t0 is calculated according to the relationship between the microhardness of the cladding layer and the induction heating time H=ab*c^t.

2. A laser cladding method for preparing a composite layer on the surface of a rail according to claim 1, characterized in that: The required temperature T0 for induction heating is in the effective induction aging temperature range T min -T max When the cladding layer is heated by the induction heat source within this range, the microhardness and yield strength both increase.

3. The laser cladding method for preparing a composite layer on the surface of a rail according to claim 2, characterized in that: In step S5, one cladding layer preparation cycle is the preparation of a single-pass or multi-pass cladding layer, or one cladding layer preparation cycle is the preparation process of one or more cladding layers.

4. A laser cladding method for preparing a composite layer on the surface of a rail as claimed in claim 3, characterized in that: The second phase particle-reinforced powder is an iron-based alloy, which includes the following components and the mass percentage of each component: C 0.01% ~0.20%, Cr 12.00% ~17.50%, Ni 0.60% ~5.00%, Cu 0.20% ~5.00%, Nb 0.10% ~0.45%, Fe balance, or the second phase particle-reinforced powder is an iron-based alloy, which includes the following components and the mass percentage of each component: Ni 16.0% ~22.0%, Co 6.0% ~12.0%, Mo 3.0% ~7.0%, Al 0.1% ~7.0%, Ti 0.5% ~5.0%, and the balance is Fe.

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